Showing papers in "Journal of the American Society for Horticultural Science in 1999"

1-Methylcyclopropene Inhibits Apple Ripening

Abstract: ADDITIONAL INDEX WORDS. fruit quality, firmness, ethylene, Malus sylvestris var. domestica, postharvest physiology, storage ABSTRACT. An ethylene action inhibitor, MCP, was applied to preclimacteric and climacteric apple ( Malus sylvestris L. (Mill.) var. domestica Borkh. Mansf.) fruit. Experiments were conducted in North Carolina and Washington State utilizing the following cultivars: Fuji, Gala, Ginger Gold, Jonagold, and Delicious. MCP inhibited loss of fruit firmness and titratable acidity when fruit were held in storage at 0 °C up to 6 months and when fruit were held at 20 to 24 °C for up to 60 days. For all cultivars except 'Fuji', differences in firmness between treated and nontreated fruit exceeded 10 N after 6 months storage. These beneficial effects were seen in both preclimacteric and climacteric fruit. Ethylene production and respiration were reduced substantially by MCP treatment. MCP-treated fruit had soluble solids equal to or greater than those in nontreated fruit. Storage and shelf life were extended for all cultivars tested. Chemical name used: 1-methylcyclopropene (MCP).

Molecular Typing of S-alleles through Identification, Characterization and cDNA Cloning for S-RNases in Sweet Cherry

Abstract: This report identifies S-RNases of sweet cherry (Prunus avium L.) and presents information about cDNA sequences encoding the S-RNases, which leads to the development of a molecular typing system for S-alleles in this fruit tree species. Stylar proteins of sweet cherry were surveyed by two dimensional polyaclylamide gel electrophoresis (2D- PAGE) to identify S-proteins associated with gametophytic self-incompatibility. Glycoprotein spots linked to S-alleles were found in a group of proteins which had Mr and pI similar to those of other rosaceous S-RNases. These glycoproteins were present at highest concentration in the upper segment of the mature style and shared immunological characteristics and N-terminal sequences with those of S-RNases of other plant species. cDNAs encoding these glycoproteins were cloned based on the N-terminal sequences. Genomic DNA and RNA blot analyses and deduced amino acid sequences indicated that the cDNAs encode S-RNases; thus the S-proteins identified by 2D-PAGE are S-RNases. Although S 1 to S 6 -alleles of sweet cherry cultivars could be distinguished from each other with the genomic DNA blot analysis, a much simpler method of PCR-based typing system was developed for the six S-alleles based on the DNA sequence data obtained from the cDNAs encoding S-RNases.

Sensitivity of Continuous and Discrete Plant and Soil Water Status Monitoring in Peach Trees Subjected to Deficit Irrigation

Abstract: To characterize tree responses to water deficits in shallow and deep rooted conditions, parameters developed using daily oscillations from continuously measured soil water content and trunk diameter were compared with traditional discrete monitoring of soil and plant water status in lysimeter and field-grown peach trees ( Prunus persica (L.) Batsch 'O'Henry'). Evaluation occurred during the imposition of deficit irrigation for 21 days followed by full irrigation for 17 days. The maximum daily available soil water content fluctuations (MXAWCF) taken at any of the four monitored root zone depths responded most rapidly to the deficit irrigation. The depth of the MXAWCF increased with time during the deficit irrigation. Differences relative to a fully irrigated control were greater in the lysimeter than the field-grown trees. Minimum daily trun k diameter (MNTD) and maximum daily trunk shrinkage (MDS) responded sooner than midday stem water potential (stem Ψ), predawn or midday leaf water potential (predawn leaf Ψ and leaf Ψ), or photosynthesis (A). Parameters based on trunk diameter monitoring, including maximum daily trunk diameter (MXTD), correlated well with established physiological parameters of tree water status. Statistical analysis of the differences in the measured parameters relative to fully irrigated trees during the first 10 days of deficit irrigation ranked the sensitivity of the parameters in the lysimeter as MXAWCF > MNTD > MDS > MXTD > stem Ψ = A = predawn leaf Ψ = leaf Ψ. Equivalent analysis with the field-grown trees ranked the sensitivity of the parameters as MXAWCF > MNTD > MDS > stem Ψ = leaf Ψ = MXTD = predawn leaf Ψ > A. Following a return to full irrigation in the lysimeter, MDS and all the discrete measurements except A quickly returned to predeficit irrigation levels. Tree recovery in the field-grown trees was slower and incomplete due to inadequate filling of the root zone. Fruit size was significantly reduced in the lysimeter while being minimally affected in the field-grown trees. Parameters only available from continuous monitoring hold promise for improving the precision of irrigation decision-making over the use of discrete measurements.

Suppressing green mold decay in grapefruit with postharvest jasmonate application

Abstract: Jasmonic acid (JA) and methyl jasmonate (MJ), collectively referred to as jasmonates, are naturally occurring plant growth regulators involved in various aspects of plant development and responses to biotic and abiotic stresses. In this study, we found that postharvest application of jasmonates reduced decay caused by the green mold Penicillium digitatum (Pers.: Fr.) Sacc. after either natural or artificial inoculation of grapefruit ( Citrus paradisi 'Marsh Seedless'). These treatments also effectively reduced chilling injury incidence after cold storage. The most effective concentration of jasmonates for reducing decay in cold-stored fruit or after artificial inoculation of wounded fruit at 24 °C was 10 μmol·L -1 . Higher and lower jasmonate concentrations were less effective at both temperatures. MJ at 10 μmol·L -1 also most effectively reduced the percentage of fruit displaying chilling injury symptoms after 6 weeks of storage at 2 °C and 4 additional d at 20 °C. When tested in vitro, neither JA nor MJ had any direct antifungal effect on P. digitatum spore germination or germ tube elongation. Therefore, it is suggested that jasmonates probably reduced green mold decay in grapefruit indirectly by enhancing the natural resistance of the fruit to P. digitatum at high and low temperatures.

Apple Fruit Growth and Maturity are Affected by Early Season Temperatures

Abstract: Container-grown 'Delicious', 'Golden Delicious', 'Braeburn', 'Fuji' and 'Royal Gala' apple ( Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.) trees, on Malling 9 (M.9) rootstock, were subjected to a range of different maximum/ minimum air temperature regimes for up to 80 days after full bloom (DAFB) in controlled environments to investigate the effects of temperature on fruit expansion, final fruit weight, and fruit maturation. Fruit expansion rates were highly responsive to temperature with those at a mean of 20 oC being ≈10 times greater than those at a mean of 6 oC. All cultivars exhibited the same general response although 'Braeburn' consistently showed higher expansion rates at all temperatures compared with lowest rates for 'Golden Delicious' and intermediate rates for both 'Delicious' and 'Fuji'. The duration of cell division, assessed indirectly by measuring expansion rate, appeared to be inversely related to mean temperature (i.e., prolonged under cooler conditions). Subsequently, fruit on trees from the coolest controlled temperature treatment showed greater expansion rates when transferred to the field and smaller differences in fruit size at harvest than would have been expected from the measured expansion rates under the cool treatment. Nonetheless, mean fruit weight from warm postbloom treatments was up to four times greater at harvest maturity than that from cool temperature treatments. Postbloom temperature also markedly affected fruit maturation. Fruit from warm postbloom temperature conditions had a higher soluble solids concentration, more yellow background color, lower flesh firmness, and greater starch hydrolysis than fruit from cooler temperatures. complicated by development phase. The apple fruit grows in two distinct phases: an early exponential phase of cell division that

Inheritance and epistasis studies of chlorophyll deficiency in lettuce

Abstract: Three mutant traits for chlorophyll deficiency in lettuce ( Lactuca sativa L.), bleached bud, calico-2, and pale green, are inherited as single recessive alleles. Bleached bud is epistatic to another recessive allele, dappled. Calico-2 is epistatic to dappled. Pale green is hypostatic to chlorophyll deficient-3. The Vanguard cd mutant is the same as chlorophyll deficient-3. The light green mutant 8744-1 is the same as light green. Independent inheritance is shown for bleached bud and dappled, calico-2 and dappled, and pale green and chlorophyll deficient-3, respectively. Vanguard cd has yellow leaves, which are similar in appear- ance to those of 80-1277 (cd-3). The inheritance of Vanguard cd was studied in the cross Vanguard cd x 'Salinas 88'. Vanguard cd was found in a greenhouse population of 'Vanguard', a crisphead lettuce. The cross 80-1277 x Vanguard cd was made to test for allelism. Calico was selected from a field population of mutants derived from treatment with EMS. It was used in the following crosses for genetic analysis: Calico x 'Prizehead', Calico x Pseudo-tipburn, Calico x GL 77, Calico x 'Oakleaf', 92-163 x Calico, Calico x 80- 1277 and reciprocal, and Calico x Vanguard cd and reciprocal. Pseudo-tipburn is a mutant type not reported here. GL 77 is a leaf type lettuce line from Korea. 'Oakleaf' is a leaf type cultivar. Calico has green cotyledons with white margins. The true leaves show a mosaic of dark and light green, yellow-green, and white. Later appearing leaves, including the cauline leaves, are green with no mosaic effect. The involucres are white when immature, turning light green with maturity; this phenotype is very similar to bleached bud. Pale green also was derived from a population treated with the mutagen and was originally called EMS yellow. It was studied in the cross 80-1277 x EMS yellow. Cotyledons are green. True leaves on young plants are very light green with a yellowish cast, becoming greenish-yellow on new leaves forming on older plants. Involucres on the seed head are greenish-yellow. Pedicels are short, giving the seed head a compressed appearance. 'Australian' and 8744-1 are both light green in color, with no apparent color change as the plant matures. 'Australian' is a leaf lettuce with lobed leaves. Leaf color is controlled by light green (lg) (Lindqvist, 1960; Ryder unpublished; Thompson, 1938). 8744-1 is a mutant derived from seeds treated with thermal neutrons. The cross 8744-1 x 'Australian' was made to study gene identity. Genetic mapping in lettuce proceeds on two fronts. One is the generation of genetic markers of various types from a single cross by means of several molecular technologies (Kesseli et al., 1994). This enables the establishment of linkage between DNA-based markers and previously identified character genes (Waycott et al., 1999). The other is identification of new character genes, link- ages, and epistatic effects by study of numerous crosses each involving relatively few traits. This report is of the latter type, and describes the inheritance of three new genes for chlorophyll deficiency, the epistatic relationship among these and other previously reported chlorophyll deficiency genes, and clarifica- tion of the identity of similar mutants. The most recent publication on chlorophyll deficiency in lettuce described six mutants and their epistatic relationship to each other and to previously described mutants (Ryder, 1996). Of these, chlorophyll deficient-3 (cd-3) is recessive and epistatic to light green (lg); chlorophyll deficient-4 (cd-4 ) is recessive, hypo- static to virescent (vi), and linked to an anthocyanin gene; and chlorophyll deficient-5 (cd-5), chlorophyll deficient-6 (cd-6), and chlorophyll deficient-7 (cd-7) are unlinked recessive genes. It was shown that cd-5 and cd-6 are both epistatic to cd-7. The sixth gene, dappled (dap), is recessive, lethal in combination with sickly (si), epistatic to lg, and hypostatic to vi.

Postharvest Application of Calcium and Magnesium to Honeydew and Netted Muskmelons: Effects on Tissue Ion Concentrations, Quality, and Senescence

Abstract: Muskmelon senescence is directly associated with a decline in hypodermal mesocarp membrane integrity and its Ca concentration, but infusing Ca into melons has been a problem. Fully ripened and abscised hybrid honeydew (Cucumis melo L. (Inodorus Group) 'Honey Brew') and netted muskmelon ( Cucumis melo L. (Reticulatus Group) 'Explorer') fruit were submerged (dipped) 20 min at 25 ± 3 °C in a solution containing a Ca-chelate, a Mg-chelate, a combination of both chelates, or no mineral chelate. Following 10 or 24 days of cold storage (4 °C for 'Explorer' and 10 °C for 'Honey Brew'), fruit were analyzed for mineral content and various senescence-related parameters. Abscised 'Honey Brew' fruit dipped in either Ca-chelate or (Ca+Mg)-chelate and abscised 'Explorer' fruit dipped in (Ca+Mg)- chelate, followed by 10 days cold storage, had hypodermal mesocarp Ca concentrations of at least 6.0 mg·g -1 dry weight. Maintaining hypodermal mesocarp tissue Ca concentrations at this level during postharvest storage, especially for fully ripe 'Honey Brew' fruit, maintained membrane integrity and fruit firmness, and extended storage life 2.4-fold (i.e., to 24 days). The senescence regulatory effect of postharvest Ca-chelate treatments on abscised 'Explorer' was highly variable, compared to 'Honey Brew', which appeared to be due to the surface netting interfering with movement of Ca into the hypodermal mesocarp. Thus, postharvest Ca-chelate application to abscised 'Honey Brew' fruit could delay fruit senescence in commercial storage, and open up new markets for fully ripened honeydew melons.

Effects of Plant Tissue and DNA Purification Method on Randomly Amplified Polymorphic DNA-based Genetic Fingerprinting Analysis in Carrot

Abstract: ADDITIONAL INDEX WORDS. marker-assisted selection, polymerase chain reaction, PCR, RAPD ABSTRACT. Seven plant genomic DNA purification protocols were evaluated for genetic fingerprinting analysis using six tissues obtained from inbred carrot (Daucus carota L.) lines. Evaluations included 1) DNA yield, 2) DNA purity, 3) DNA cleavage with HindIII, 4) DNA integrity, and 5) DNA suitability for amplification in a random amplified polymorphic DNA (RAPD) system. Significant differences were observed among tissues and purification methods for the total amount of DNA. An extraction method using CTAB buffer + organic solvents gave the best results in DNA yield, purity, and HindIII cleavage when compared with the other six nonorganic extraction methods. Of the tissues examined, flowers yielded the most DNA (average value = 115 ng of DNA/mg of fresh tissue); followed by seeds (54 ng·mg -1 ), fresh leaves (48 ng·mg -1 ), lyophilized leaves (40 ng·mg -1 ), calli (22 ng·mg -1 ), and tap roots (4 ng·mg -1 ). For most of the preparations, the DNA showed no traces of degradation. However, DNA preparations were not consistently accessible to HindIII cleavage in all tissue-extraction method combina- tions. Uncut DNA was observed chiefly in extractions from flowers and fresh leaves suggesting a tissue-specific adverse effect on restriction endonuclease activity. Differences in RAPD band (amplicon) intensity and number were observed across tissues and DNA extraction methods using identical PCR conditions for RAPD. Callus was the best type of tissue for RAPD-based fingerprinting yielding a consistently higher number of more intense amplicons when compared to the other tissues. In flowers and seeds, only DNA obtained with the CTAB extraction method could be amplified. Polymorphisms deviating from genetic expectations were mainly observed in root and fresh leaf DNA, indicating that some RAPD markers may not present satisfactory levels of reproducibility. Judicious and uniform selection of DNA purification method as well as tissue source for DNA extraction are, therefore, important considerations for reliable RAPD-based DNA fingerprinting analysis in carrot. In addition, our studies allowed the identification of a better combination of procedures for use in routine manipulations of carr ot DNA such as RFLP-RAPD-based cultivar fingerprinting, molecular mapping, screening of transgenic plants, construction of genomic libraries, and gene cloning.

Inhibition of Pythium ultimum and Rhizoctonia solani by Shredded Leaves of Brassica Species

Abstract: The U.S. Clean Air Act bans the use of methyl bromide after 2005. Consequently, the development of alternative methods for control of soilborne pathogens is imperative. One alternative is to exploit the pesticidal properties of Brassica L. species. Macerated leaves (10 g) from 'Premium Crop' broccoli ( B. oleracea L. (Botrytis Group)), 'Charmant' cabbage (B. oleracea L. (Capitata Group)), 'Michihili Jade Pagoda' Chinese cabbage (B. rapa L. (Pekinensis Group)), 'Blue Scotch Curled' kale (B. oleracea L. (Acephala Group)), Indian mustard (B. juncea (L.) Czerniak, unknown cultivar) or 'Florida Broadleaf' mustard (B. juncea (L.) Czerniak) were placed in 500-mL glass jars. Petri dishes with either Pythium ultimum Trow or Rhizoctonia solani Kuhn plugs on potato-dextrose agar were placed over the jar mouths. Radial growth of both fungi was suppressed most by Indian mustard. Volatiles were collected by solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry. Allyl isothiocyanate (AITC) comprised >90% of the volatiles measured from 'Florida Broadleaf' mustard and Indian mustard whereas (Z)-3-hexenyl acetate was the predominant compound emitted by the other species. Isothiocyanates were not detected by SPME from 'Premium Crop' broccoli and 'Blue Scotch Curled' kale although glucosinolates were found in freeze-dried leaves of all species. When exposed to AITC standard, P. ultimum growth was partially suppressed by 1.1 μmol·L -1 (μmol AITC/headspace volume) and completely suppressed by 2.2 μmol·L - 1 R. solani was partially suppressed by 1.1, 2.2, and 3.3 μmol·L -1 AITC. Use of Brassica species for control of fungal pathogens is promising; the presence of AITC in both lines of B. juncea suppressed P. ultimum and R. solani but some Brassicas were inhibitory even when isothiocyanates were not detected. Tomato (Lycopersicon esculentum Mill.) production systems in the United States depend on the use of methyl bromide soil fumiga- tion for control of soilborne pests. In accordance with the U.S. Clean Air Act, the use of methyl bromide as a fumigant will be banned in the United States by 2005 (U.S. Dept. of Agriculture, 1999). This regulation and public concern with environmental and health effects of other synthetic chemical pesticides have prompted increased interest in the development of alternative pest control strategies. One alternative approach has been the use of macerated tissues of Brassica species to reduce disease incidence. The incidence of Aphanomyces euteiches Drechs. root rot of peas ( Pisum sativum L.) was decreased when soil was amended with residues from cabbage (Brassica oleracea (Botrytis Group)), kale ( B. oleracea (Acephala Group)), and rapeseed (B. napus L.) (Chan and Close, 1987; Muehlchen, 1990). When chopped broccoli (B. oleracea (Italica Group)) was incorporated into soil, the number of Verticillium dahliae Kleb propagules was lower than in nontreated control plots and was similar in plots fumigated with methyl bromide + chloropi- crin (Subbarao et al., 1994). Pesticidal activity associated with Brassica residues is often attributed to release of isothiocyanates (ITCs) from the plant tissue. ITCs are breakdown products of glucosinolates (GLs), a class of plant compounds containing a thioglucose moiety, a sulphonated oxime, and a side chain (R-group). In laboratory studies, canola and Indian mustard (B. juncea) roots released methyl ITC and phenylethyl ITC respectively, both of which were inhibitory to Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker grown in pure culture (Angus et al., 1994). Another in vitro study found that allyl ITC (AITC), p-hydroxybenzyl ITC, and 4-methylsulphinylbut-3- enyl ITC completely inhibited conidia germination of Botrytis cinerea Pers.: Fr., Monilinia laxa (Aderhold & Ruhland) Honey, Mucor piriformis E. Fisch., Penicillium expansum Link, and Rhizo-

Inheritance of Phytophthora Root Rot and Foliar Blight Resistance in Pepper

Abstract: The inheritance of resistance to Phytophthora capsici Leonian root rot and foliar blight was compared in two different Capsicum annuum L. var. annuum pod types. The seedling was screened for phytophthora root rot, while a genetically identical stem cutting was screened for phytophthora foliar blight to determine if the same gene(s) confer resistance to both disease syndromes. The susceptible parents were 'Keystone Resistant Giant #3' ('Keystone'), a bell pepper type, and 'Early Jalapeno', while 'Criollo de Morelos-334' was the resistant parent. Resistance was observed in both F1 populations screened for phytophthora root and foliar infection indicating dominance for resistance. Reciprocal effects were not detected. To determine if the same gene(s) conferred root rot and foliar resistance, root rot screening results were matched to the corresponding foliar blight stem cutting reaction. The segregation of resistance in the F 2 generations was dependent on the susceptible parent. In the F 2 generation derived from 'Early Jalapeno', root rot resistance and foliar blight resistance segregated in a 9:3:3:1 (root resistant/foliar resistant : root resistant/foliar susceptible : root susceptible/foliar resistant : root susceptible/foliar susceptible) ratio. One independent, dominant gene was necessary for root rot resistance, and a different independent, dominant gene was needed for foliar blight resistance. In the F2 generation derived from 'Keystone', root rot and foliar blight resistance segregated in a 7:2:2:5 (root resistant/ foliar resistant : root resistant/foliar susceptible : root susceptible/foliar resistant : root susceptible/foliar susceptible) ratio. This segregation ratio is expected when one dominant gene is required for root resistance, and a different dominant gene is required for foliar resistance. In addition to these two genes, at least one dominant allele of a third gene must be present for expression of root rot and foliar blight resistance.

Water stress and crop level interactions in relation to nectarine yield, fruit size distribution, and water potentials

Abstract: ADDITIONAL INDEX WORDS. nectarine, crop load, fruit size distribution, water potential, water stress, irrigation ABSTRACT. The interactions between irrigation and crop level with respect to fruit size distribution and soil and stem water potentials were investigated in a nectarine ( Prunus persica (L.) Batsch. 'Fairlane') orchard located in a semiarid zone. Irrigation treatments during stage III of fruit growth ranged from 0.62 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (200 to 1200 fruit/tree in the 555-tree/ha orchard). Total yield did not increase with increasing irrigation rate above 0.92 ETp in 1996 and maximum yield was found at 1.06 ETp in 1997. Fruit size distribution was shifted towards larger fruit with increasing irrigation level and with decreasing crop level. The two highest irrigation treatments had similar midday stem water potentials. Our findings indicate that highest yields and highest water use efficiency (yield/water consumption) are not always related to minimum water stress. Total yield and large fruit yield were highly and better correlated with midday stem water potential than with soil water potential. This confirms other reports that midday stem water potential is an accurate indicator of tree water stress and may have utility in irrigation scheduling.

'Hass' Avocado Carbohydrate Fluctuations. II. Fruit Growth and Ripening

Abstract: Persea americana, perseitol, soluble sugar, starch ABSTRACT. Changes in soluble sugar and starch reserves in avocado ( Persea americana Mill. on 'Duke 7' rootstock) fruit were followed during growth and development and during low temperature storage and ripening. During the period of rapid fruit size expansion, soluble sugars accounted for most of the increase in fruit tissue biomass (peel: 17% to 22%, flesh: 40% to 44%, seed: 32% to 41% of the dry weight). More than half of the fruit total soluble sugars (TSS) was comprised of the seven carbon (C7) heptose sugar, D-mannoheptulose, and its polyol form, perseitol, with the balance being accounted for by the more common hexose sugars, glucose and fructose. Sugar content in the flesh tissues declined sharply as oil accumulation commenced. TSS declines in the seed were accompanied by a large accumulation of starch (≈30% of the dry weight). During postharvest storage at 1 or 5 °C, TSS in peel and flesh tissues declined slowly over the storage period. Substantial decreases in TSS, and especially in the C7 sugars, was observed in peel and flesh tissues during fruit ripening. These results suggest that the C7 sugars play an important role, not only in metabolic processes associated with fruit development, but also in respiratory processes associated with postharvest physiology and fruit ripening. The avocado fruit is characterized by a high respiration rate throughout growth and also during postharvest ripening (Blanke and Whiley, 1995; Bower and Cutting, 1988; Whiley et al., 1992). However, little is known concerning the nature of the carbon substrates which support respiratory processes. Varying storage temperatures and durations may result in different changes in carbohydrate storage and use and affect fruit quality (Eaks, 1990; Kikuta and Erickson, 1968; Luza et al., 1990; Spalding, 1976). The aim of the present study was therefore to quantify changes in major nonstructural carbohydrates (individual soluble sugars and starch) which occur during important developmental stages, and also during storage and ripening, in 'Hass' avocado fruit.

Scoparone and Scopoletin Accumulation and Ultraviolet-C Induced Resistance to Postharvest Decay in Oranges as Influenced by Harvest Date

Abstract: ADDITIONAL INDEX WORDS. Citrus sinensis, cold storage, decay, phytoalexins, 6,7-dimethoxycoumarin, 7-hydroxy 6- methoxycoumarin ABSTRACT. 'Washington Navel', 'Biondo Comune', 'Tarocco', and 'Valencia Late' orange ( Citrus sinensis (L.) Obsek) fruit, harvested at various periods of time, were subjected to ultraviolet-C (UV-C) irradiation at 0.5, 1.5, or 3.0 kJ·m -2 doses and then stored at 7 °C and 90% to 95% relative humidity (RH) for 4 weeks plus one additional week at 20 °C and ≈80% RH. Following UV-C treatment, there was varying amounts of rind browning and necrotic peel damage, depending on cultivar, treatment dose, and harvest date. 'Tarocco' fruit were damaged more easily by UV-C treatment than the other cultivars. 'Valencia L.' were the most resistant to UV-C irradiation, showing no adverse effects at the lowest dosage and having the lowest percentages of damaged fruit at higher dosages. 'Washington Navel' and 'Biondo Comune' oranges showed an intermediate susceptibility to UV-C treatment, with negligible differences between these cultivars. The percentage of damaged fruit after irradiation at the higher UV-C dosages decreased in most fruit samples as the season progressed. UV-C irradiation at 0.5 kJ·m -2 effectively reduced decay development compared with nontreated fruit. Irradiation with 1.5 kJ·m -2 was more effective compared with 0.5 kJ·m -2 only in early harvested fruit. In 'Washington Navel' and 'Biondo Comune' oranges in the later harvests, treatment with 3.0 kJ·m -2 improved decay control further, compared with 0.5 kJ·m -2 . Following UV-C treatments the phytoalexins, scoparone and scopoletin, accumulated in flavedo tissue depending on the cultivar, fruit age, and UV-C treatment. Both phytoalexins displayed a similar accumulation pattern, however, the levels of scopoletin were very low compared with scoparone. Concentrations of phytoalexins rose as the irradiation dose increased. No scoparone and scopoletin could be detected in nontreated fruit. The highest concentration of phytoalexins among cultivars was recorded in 'Valencia Late' oranges, the lowest in 'Tarocco', with similar intermediate accumulations in 'Washington Navel' and 'Biondo Comune'. In 'Washington Navel', 'Biondo Comune', and 'Tarocco' oranges, the rate of scoparone accumulation was significantly higher in fruit harvested earlier in the season while 'Valencia late' oranges exhibited an opposite trend.

Seven MADS-box Genes in Apple are Expressed in Different Parts of the Fruit

Abstract: To study the role of MADS-box genes in developing apples ( Malus ×domestica Borkh.), clones corresponding to seven different genes, MdMADS5 to MdMADS11, were isolated from a 2-day-old apple cDNA library. Through DNA sequence comparison, six genes were classified into the APETALA1 (AP1) group and one gene, MdMADS10, into the AGAMOUS (AG) group. Six of the genes, MdMADS5 to MdMADS10, were found to be preferentially expressed in fruit following pollination. These genes also showed differential expression patterns in core, cortex and skin of young fruit. For instance, MdMADS5, which is highly homologous to AP1, showed preferential expression in the cortex and skin tissues while MdMADS10, which is highly homologous to AGL11, showed exclusive expression in the core tissues. The gene MdMADS11 showed a similar expression level and pattern in flowers, fruit at several early developmental stages, and for different fruit tissues. The range of expression patterns suggests that the genes play different roles in apple development.

Comparison of softening-related changes during storage of 'honeycrisp' apple, its parents, and 'delicious'

Abstract: Many studies of apple (Malus ×domestica Borkh.) softening have been done using cultivars that eventually become mealy. We wanted to determine whether observations in these studies would be seen in a cultivar that maintains its crispness. In this paper, we compared the texture, ultrastructure, and some physiological parameters of Honeycrisp, an apple cultivar introduced in 1991 by the Minnesota Agricultural Experiment Station, with its parents and Delicious. Sensory evaluations and instrumental texture measurements showed that 'Honeycrisp' maintained a crisp texture from harvest through 6 months of cold storage, whereas its parents, 'Macoun' and 'Honeygold', softened over the same time period. Turgor potential, cell wall composition, and ultrastructural comparisons of the fruit were made. Cell turgor potentials of 'Honeycrisp' and 'Delicious' were similar and greater than those of 'Macoun' and 'Honeygold', and clearly correlated with firmness. There were no differences in cell wall neutral sugar composition, except for arabinose, which was not highly correlated with crispness. 'Honeycrisp' fruit maintained cell wall integrity after 6 months of storage, while cell walls of 'Macoun' and 'Honeygold' deteriorated. These data show that it is important to compare more than one cultivar when studying crispness. Honeycrisp is a cultivar that maintains its crispness through long storage without controlled atmosphere conditions. After 6 months of storage, this crispness can be attributed to a maintenance of high turgor potential and cell wall integrity. 'Calville de San Sauveur' apples as "dissolution of the middle lamella," although areas containing plasmodesmata retained their structure. In one of the few studies comparing several apple cultivars differing in their firmness, Lapsley et al. (1992) concluded that mechanical forces applied to firm apples causes structural failure through cells, while in mealy apples, the failure is between cells. The structure of firm apples used in this study was similar to that of

Allelism Found between Two Common Bean Genes, Hilum Ring Color (D) and Partly Colored Seedcoat Pattern (Z), formerly Assumed to Be Independent

Abstract: Inheritance of two phenotypes, the virgarcus pattern of partly colored seedcoats and the margo d seedcoat pattern, were studied in common bean (Phaseolus vulgaris L.) materials that segregated jointly for genes controlling the two phenotypes to test the hypothesis of allelism of two genes, D and Z. The F2 progeny from the cross j margo BC3 5-593 x t z virgarcus BC3 5-593 produced an unexpected phenotypic class, margo d, suggesting possible allelism of D and Z. The F2 also produced another unexpected phenotypic class, white seedcoat, for which the genetic hypothesis t j z was made. The F2 from the cross t j marginata BC3 5-593 x t z virgarcus BC3 5-593 provided supporting evidence for the new genotype, t j z, for a white seedcoat. Analysis of the F2 and F3 progenies of 80 random F2 plants from the cross t z virgarcus BC3 5- 593 x d j (margo d) BC3 5-593 provided support for the hypothesis that the D and Z loci are allelic. Production of two different phenotypes (white vs. white with two tiny pale gray dots, one each at the raphe and micropyle) for t J/j z in two different genetic and cytoplasmic backgrounds is discussed. The F2 from the crosses d j (margo d) BC2 5-593 x j v margo BC2 5-593 and d j (margo d) BC3 5-593 x j margo BC3 5-593 segregated for d (vs. D) phenotypes, which were found not to be independent of a randomly amplified polymorphic DNA (RAPD) marker (AM10560) associated (1.4 cM) with the Z locus. Because the Z gene symbol has priority, we propose to retain Z for the locus.

Molecular Mapping of Disease Resistance Genes for Halo Blight, Common Bacterial Blight, and Bean Common Mosaic Virus in a Segregating Population of Common Bean

Abstract: Diseases of beans (Phaseolus vulgaris L.) are primary constraints affecting bean production. Information on tagging and mapping of genes for disease resistance is expected to be useful to breeders. The objectives of this study were to develop a random amplified polymorphic DNA (RAPD) marker linkage map using 78 F9 recombinant inbred (RI) lines derived from a Middle-American common bean cross Great Northern Belneb RR-1 (resistant to common bacterial blight (CBB) and halo blight (HB)) x black A 55 (dominant I gene resistance to bean common mosaic potyvirus) and to map genes or QTL (quantitative trait loci) for resistance to CBB, HB, BCMV (bean common mosaic virus), and BCMNV (bean common mosaic necrosis virus) diseases. The RI lines were evaluated for resistance to leaf and pod reactions to Xanthomonas campestris pv. phaseoli (Xcp) (Smith Dye) strain EK-11, leaf reactions to two Pseudomonas syringae pv. phaseolicola (Psp) (Burkholder) Young et al. (1978) strains HB16 and 83-Sc2A, and BCMV strain US-5 and BCMNV strain NL-3. The linkage map spanned 755 cM, including 90 markers consisting of 87 RAPD markers, one sequence characterized amplified region (SCAR), the I gene, and a gene for hypersensitive resistance to HB 83-Sc2A. These were grouped into 11 linkage groups (LG) corresponding to the 11 linkage groups in the common bean integrated genetic map. A major gene and QTL for leaf resistance to HB were mapped for the first time. Three QTL for leaf reactions to HB16 were found on linkage groups 3, 5, and 10. Four regions on linkage groups 2, 4, 5, and 9, were significantly associated with leaf reactions to HB strain 83-Sc2A. The gene controlling the hypersensitive reaction to HB 83-Sc2A mapped to the same region as the QTL on LG 4. The I locus for resistance to BCMV and BCMNV was mapped to LG 2 at about 1.4 cM from RAPD marker A10.1750. Five and four markers were significantly associated with QTL for resistance to CBB in leaves and pods, respectively, with four of them associated with resistance in both plant organs. A marker locus was discovered on LG 10, W10.550, which could account for 44% and 41% of the phenotypic variation for CBB resistance in leaves and pods, respectively. QTL for resistance in pod to CBB, leaf resistance to HB, and the I gene were linked on LG 2.

'Hass' Avocado Carbohydrate Fluctuations. I. Growth and Phenology

Abstract: Seasonal fluctuations in nonstructural carbohydrates (starch and soluble sugars) were studied in 'Hass' avocado (Persea americana Mill.) trees on 'Duke 7' rootstock over a 2-year period in southern California. On a dry weight basis, total soluble sugar (TSS) concentrations ranged from 33.0 to 236.0 mg·g -1 dry weight and were high compared to starch concentration (2.0 to 109.0 mg·g -1 dry weight) in all measured organs (stems, leaves, trunks and roots). The seven carbon (C7) sugars, D-mannoheptulose and perseitol, were the dominant soluble sugars detected. The highest starch and TSS concentrations were found in stem tissues, and in stems, a distinct seasonal fluctuation in starch and TSS concentrations was observed. This coincided with vegetative growth flushes over both sampling years. Stem TSS and starch concentrations increased beginning in autumn, with cessation of shoot growth, until midwinter, possibly due to storage of photosynthate produced during the winter photosynthetic period. TSS peaked in midwinter, while starch increased throughout the winter to a maximum level in early spring. A second peak in stem TSS was observed in midsummer following flowering and spring shoot growth. At this time, stem starch concentration also decreased to the lowest level of the year. This complementary cycling between stem TSS and starch suggests that a conversion of starch to sugars occurs to support vegetative growth and flowering, while sugars produced photosynthetically may be allocated directly to support flowering and fruit production.

Potassium Requirements for Maximum Yield and Fruit Quality of Processing Tomato

Abstract: ADDITIONAL INDEX WORDS. mineral nutrition, magnesium, Lycopersicon esculentum ABSTRACT. A survey of 140 processing tomato (Lycopersicon esculentum Mill.) fields in central California was conducted in 1996-97 to examine the relationship between K nutrition and fruit quality for processing. Quality parameters evaluated were soluble solids (SS), pH, color of a blended juice sample, and the percent of fruit affected by the color disorders yellow shoulder (YS) or internal white tissue (IWT). Juice color and pH were not correlated with soil K availability or plant K status. SS was correlated with both soil exchangeable K and midseason leaf K concentration ( r = 0.25 and 0.28, p < 0.01) but the regression relationships suggested that the impact of soil or plant K status on fruit SS was minor. YS and IWT incidence, which varied among fields from 0% to 68% of fruit affected, was negatively correlated with K status of both soil and plant. Soil exchangeable K/√Mg ratio was the measure of soil K availability most closely correlated with percent total color disorders (YS + IWT, r = -0.45, p < 0.01). In field trials conducted to document the relationship between soil K availability and the fruit color disorders, soil application of either K or gypsum (CaSO 4, to increase K/√Mg ratio) reduced YS and total color disorders. Multiple foliar K applications were effective in reducing fruit color disorders at only one of two sites. In no field trial did K application improve yield, SS, or juice color. California is a leader in processing tomato production, growing nearly 40% of world supply. Most fruit is processed into concen- trated paste, but an increasing percentage of the crop is being used for products using peeled fruit, either whole or diced. Important fruit quality attributes for paste production are soluble solids content (SS) and color of the blended product. Uniformity of color is more important for peeled fruit; even a small area of poorly colored tissue is problematic. Uneven ripening of processing tomatoes is a common problem in California. The typical external symptom is a ring of tissue around the stem scar that upon ripening remains yellow; this symptom, called yellow shoulder (YS), can range in severity from only a few mm wide to discoloration of the top third of the fruit. Internal white tissue (IWT), which can occur throughout the pericarp, is often severe enough to render affected fruit unsuitable for use in peeled, diced products. The occurrence of these disorders has been frequent, but unpredictable.

Alcohol Dehydrogenase Expression and Alcohol Production during Pear Ripening

Abstract: ADDITIONAL INDEX WORDS. Pyrus communis, controlled atmosphere, acetaldehyde, ethanol, methanol, pyruvate decarboxylase ABSTRACT. Regulation of alcohol dehydrogenase (ADH), activity of pyruvate decarboxylase (PDC) and accumulation of acetaldehyde and ethanol in 'Packham's Triumph' pears ( Pyrus communis, L.) subsequent to different storage regimes were investigated. Pears were stored for two months at -1 °C either in air (Air) or under hypoxia at 3 kPa O 2 (Hyp) and subsequently warmed and allowed to ripen in air at 20 °C. One set of fruit stored in air at -1 °C was subjected to 3 days of hypoxia at -1 °C (Air+Hyp) before ripening in air. Acetaldehyde, ethanol and methanol levels increased in all fruit in a similar fashion during ripening and did not reflect differences in storage treatments. During ripening, ADH activities in posthypoxic samples were generally twice that of air samples. PDC activities increased for ≈6 days during ripening then declined slightly but did not differ significantly among treatments. Upon transfer to 20 °C in air, slightly higher levels of Adh mRNA were observed in samples treated with hypoxia than in air controls. Over the following 2 days at 20 °C, the Adh transcription was markedly induced in Air and Air+Hyp samples. Although all Adh mRNAs returned to control levels within 4 days, ADH activities remained higher in hypoxia-treated fruit than in controls for up to 18 days. These results suggest that, in ripening pears, ADH does not limit ethanol production, and that the expression of this enzyme comprises post-transcriptional regulations. GenBank accession numbers of the Adh cDNAs are AFO 31899 and AFO 31900. Pears, like many other fruit, produce acetaldehyde and ethanol during the ripening phase (Janes and Frenkel, 1978; Nanos et al., 1992). The ethanol pathway branches from pyruvate, through decarboxylation of the pyruvate by PDC to form acetaldehyde which is then reduced to ethanol by ADH. In the pome fruit industry controlled atmospheres (CA) and/or low temperature regimes are commonly used to increase shelf life and maintain fruit quality. But they have also been reported to be detrimental to aroma (Yahia, 1994). ADH, which is induced by CA in pears (Nanos et al., 1992), may play various roles leading to aroma changes by i) producing alcohols, which are precursors of esters (themselves important aroma compounds, Yahia, 1994) or ii) maintaining the fruit tissues in a reduced state, while many oxidation processes are necessary to aroma production (Yahia, 1994, and references therein). Some work has been undertaken to examine the effects of controlled atmospheres on the physiology of stored pear fruit. 'Bartlett' pears stored under a hypoxic regime (0.25 kPa O2 at 20 °C) (Ke et al., 1994; Nanos et al., 1992) have increased levels of ethanol together with increased ADH activity, the latter being retained during subsequent ripening in air. To extend these studies and to investigate the apparent retention of ADH activity in hypoxic-treated fruit, we have examined 'Packham's Triumph' pear fruit stored under two different re- gimes of combined low temperature and hypoxia (one with long term and one with short term hypoxic induction). Levels of ethanol were determined and were compared with the activity of ADH in the fruit. As PDC activity is a limiting factor in ethanol formation in hypoxic tobacco leaves (Bucher et al., 1994), we also monitored PDC activity as well as acetaldehyde levels. To examine further whether the activity of the ADH enzyme was a direct function of gene activity, cDNAs to two ADH mRNAs were prepared from pear fruit mRNA and were used as hybridiza- tion probes to measure mRNA abundance in the ripening fruit subsequent to the various storage treatments. The mRNA abun- dance was compared with ADH activities in the fruit. Materials and Methods PLANT MATERIAL. 'Packham's Triumph' pears were obtained from a local grower on the day of harvest and were stored for 2 months under either air (Air) or 3 kPa O 2 (Hyp) or air followed by 3 d at 3 kPa O2 (Air + Hyp), all at -1 °C, before the ripening trials. In the hypoxic treatments, the oxygen level was set at 3 kPa (CA storage of Packham's pears in Australia commonly uses O 2 levels of between 2 and 3 kPa). The CO2 level was kept under 0.2 kPa over the whole storage period, in all treatments, as the object of the experiments was to study the effects of hypoxia, not those due to high CO2 levels. Ripening was induced by transferring the fruit to 20 °C in air (day 0 for all three treatments). At various times during the ripening phase, peeled and cored fruit were diced into liquid nitrogen. Samples were kept frozen in freezer bags at -75 °C until analysis.

Ice Nucleation and Propagation in Cranberry Uprights and Fruit Using Infrared Video Thermography

Abstract: Infrared video thermography was used to study formation of ice in leaves, stems, and fruit of cranberry (Vaccinium macrocarpon Ait. 'Stevens'). Ice formed on the plant surface at -1 or -2 °C by freezing of a droplet of water containing ice nucleation-active bacteria ( Pseudomonas syringae van Hall). Samples were then cooled to a minimum of -8 °C. Observations on the initiation and propagation of ice were recorded. Leaves froze only when ice was present on the abaxial surface. Once initiated, ice propagated to the stem and then readily to other leaves. In both unripe and ripe fruit, ice propagation from the stem to the fruit via the pedicel was not observed. Fruit remained supercooled for up to 1 hour after ice was present in the stem. Fruit could only be nucleated when ice was present at the calyx (distal) end. Red (ripe) berries supercooled to colder temperatures and for longer durations than blush (unripe) berries before an apparent intrinsic nucleation event occurred. These observations provide evidence that leaves are nucleated by ice penetration via stomata. The ability of fruit to supercool appears to be related to the presence of barriers to extrinsic ice propagation at both the pedicel and fruit surface. Stomata at the calyx end of the fruit in the remnant nectary area may provide avenues for extrinsic ice nucleation.

Transformation of `Beurre Bosc' Pear with the rolC Gene

Abstract: Beurre Bosc' pear ( Pyrus communis L.) was transformed with Agrobacterium tumefaciens (E.F. Smith & Townsend) Conn strain EHA101 containing the binary vector pGA-GUSGF into which the rolC gene had been inserted. Leaf explants from in vitro shoot tip cultures were wounded, Agrobacterium-inoculated, and cultured on kanamycin selection medium. Regenerating shoots were transferred to proliferation medium without antibiotics. Three clones tested positive for GUS and nptII enzyme activity. Transformation with the rolC gene was confirmed by DNA, RNA, and protein blot analyses. The number of copies of the rolC transgene varied from one to three. Plantlets of the three transgenic clones were acclimated and transferred to the greenhouse. Preliminary observations of phenotype indicate that the rolC gene reduced height, number of nodes, and leaf area of transgenic 'Beurre Bosc'. under the control of the CaMV 35S promoter, which has generally produced more extreme effects than the native promoter. The purpose of our research project was to transform pear with the rolC gene, and to determine the potential of the rolC gene under the control of its native promoter for producing trees of reduced stature and improved production efficiency.

Relationship of Seasonal Changes in Carbohydrates and Cold Hardiness in Canes and Buds of Three Red Raspberry Cultivars

Abstract: Canes of three field-grown cultivars of red raspberry ( Rubus idaeus L. 'Maurin Makea', 'Ottawa', and 'Muskoka') were sampled from October to April. Carbohydrate contents of canes and flower buds were analyzed, and cold hardiness (LT50) was determined by controlled freezing. Starch, sucrose, glucose, fructose, and minor amounts of raffinose and stachyose were present in both cane and bud tissues. Glucose and fructose were the predominant sugars in buds. In canes, the proportion of sucrose of all sugars was greater than in buds. Seasonal changes in carbohydrates were related to changes in cold hardiness and mean air temperature during a 5-day period preceding sampling. Starch decreased during fall and was barely detectable in midwinter. Soluble carbohydrates accumulated to 73 to 89 mg·g -1 dry weight in canes and 113 to 131 mg·g -1 dry weight in buds in midwinter. The most striking increase occurred in the concentration of sucrose, but glucose, fructose, raffinose, and stachyose also accumulated. There was a positive correlation between LT50 and the amount of starch, but a negative correlation between LT 50 and the amounts of total soluble carbohydrates, sucrose, glucose, and fructose. High levels of sucrose, total soluble carbohydrates, and a high ratio of sucrose to glucose plus fructose were characteristic of a hardy cultivar. Results are evidence of the importance of carbohydrate reserves, especially sucrose, on winter survival of red raspberry.

Inhibition of Catalase by Antisense RNA Increases Susceptibility to Oxidative Stress and Chilling Injury in Transgenic Tomato Plants

Abstract: ADDITIONAL INDEX WORDS. catalase, chilling injury, Lycopersicon esculentum, hydrogen peroxide ABSTRACT. Transgenic tomatoes (Lycopersicon esculentum Mill. 'Ohio 8245') expressing an antisense catalase gene (ASTOMCAT1) were used to test the hypothesis that modification of the reactive oxygen species scavenging mechanism in plants can lead to changes in oxidative stress tolerance. A 2- to 8-fold reduction in total catalase activity was detected in the leaf extracts of transformants. A 2-fold increase in levels of H 2O2 was observed in the transgenic plants with reduced catalase activity. Electrophoretic characterization of multiple catalase isoforms revealed the specific suppression of CAT1 in transgenic plants. Homozygous plants carrying the antisense catalase transgene were used to study the effect of alteration in the expression of catalase on stress tolerance. Transgenic plants treated with 3% H 2O2 showed visible damage within 24 hours and subsequently died. In contrast, wild-type and azygous control plants recovered from the treatment. Transgenic plants did not survive 4 °C chilling stress compared to control wild-type and azygous lines. Physiological analysis of these plants indicated that suppression of catalase activity in transgenic tomato led to enhanced sensitivity to oxidative stress. Our data support a role for catalase in oxidative stress defense system in tomato.

Characterization of 'Gala' Apple Aroma and Flavor: Differences between Controlled Atmosphere and Air Storage

Abstract: Aroma and flavor characters of 'Gala' apples ( Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. 'Gala') were identified by 10 trained panelists. A vocabulary of 13 aroma descriptors and 16 flavor descriptors were used to characterize changes in controlled atmosphere (CA) and air, or regular atmosphere (RA) storage over 20 weeks. When compared with RA storage, the intensity of fruity (pear, banana, and strawberry) and floral descriptors decreased after 10 weeks in CA for whole and cut fruit aroma and flavor. During the entire storage period under CA, aroma of cut apples retained high vegetative and citrus characters but had a less intense anise aroma. Sourness and astringency were significantly higher for CA-stored apples, and sweetness was significantly lower. A musty note was perceived in whole apples stored in CA for 20 weeks. Aroma of whole fruit stored for 16 weeks in CA followed by 4 weeks in RA was higher in fruitiness, banana, floral, and anise characters when compared with apples stored 20 weeks in CA. There was no difference between fruit stored in CA followed by RA versus CA stored apples for flavor and aroma of cut fruit. Changes in descriptor ratings during storage are discussed in relation to gas chromatography and olfactometry data obtained with the Osme method. Consumer opinion determines the success or failure of new products (Williams, 1981). Typically, consumers are vague and not consistent in the vocabulary they use to explain their acceptance or rejection of a product (Williams and Knee, 1977). Through descrip- tive sensory analysis (DSA), product characteristics are identified and variations are measured by trained panelists. Changes in some attributes may explain consumer acceptance of or preference for a product (Williams and Knee, 1977). Instrumental measurements may then be used to understand the physicochemical stimuli neces- sary to induce a response from the sensory receptors. Williams and collaborators have used all three approaches (DSA, consumer tests, and instrumental analysis) to understand the quality of apples (Malus sylvestris var. domestica, 'Cox's Orange Pippin'). They developed a lexicon with 95 descriptive terms (Williams and Carter, 1977). Then, aroma descriptors were corre- lated with gas chromatographic data (Williams and Knee, 1977). DSA data for 'Cox's Orange Pippin' were also used to interpret a consumer survey where panelists were asked to rate acceptability of apples that had been stored under different atmospheres and tem- peratures (Williams and Langron, 1983). Following those studies, Williams (1979) identified texture to be important for consumer acceptance. When optimum texture was present in apples, con- sumer preference was increased by better aroma and flavor. Controlled atmosphere (CA) storage is used commercially to prolong apple shelf life. While low O 2 and high CO2 significantly reduce acidity and firmness loss (Smock, 1979), volatile production

Distribution and Transport of Foliar Applied Zinc in Pistachio

Abstract: The distribution and transport of foliar applied Zn were determined for pistachio ( Pistachio vera L.) seedlings and mature trees using stable 68 Zn isotope. In seedlings, ≈5.4% of Zn adsorbed by the leaf was transported out of the treated leaves and this Zn was detected in all other plant parts to varying extent. In mature trees, the transport of Zn occurred both acropetally and basipetally within the leaflets with more basipetal movement; however, no significant amount of Zn was transported out of the treated leaflets during the first 10 days after application. The total percentage of Zn transported to other plant parts 20 days after application was significantly greater when Zn was applied to immature leaflets (6.5%) than to mature leaflets (2.1%), though the majority of the absorbed Zn remained within the treated leaflets. The limited mobility of foliar-absorbed Zn in pistachio may partially be attributed to the high binding capacity of leaf tissue for Zn. volume of 0.1 N H2SO4. The sample was heated at 75 °C to near dryness and rediluted to the desired volume with double deionized (DDI) water. The pH of the solution was adjusted to 5.3 with 0.5 N KOH. TRANSLOCATION AND DISTRIBUTION OF FOLIAR ABSORBED ZINC IN PISTACHIO SEEDLINGS. Since previous reports on the transport of foliar-applied Zn were contradictory (Bukovac and Wittwer, 1957; Wadsworth, 1970; Wallinhan and Heymann-Herschberg, 1956), experiments were designed to test if the inconsistency is partly due to the effect of plant or leaf age. Pistachio seeds were germinated and grown in medium grade vermiculite in shallow flats and fertilized with 1/4 strength Hoagland's nutrient solution (Hoagland and Arnon, 1950) twice a week. Irriga- tion was provided as necessary. Seedlings were allowed to grow in the greenhouse until they had five to six leaves. To study the distribution of Zn within the plant after foliar application, sixteen seedlings were chosen for uniformity. Two drops, each 40 μL of 7.5 mM 68 Zn solutions, were applied onto the adaxial surface of the third leaf from base. Treatment drops were applied to each side of the midvein in the mid section of the leaf. Treatments were replicated four times with 3 individual seedlings per replicate. At 2 and 10 d after application the plants were harvested and separated into treated leaves, leaves above and below the treated leaves, stems, and roots and prepared for Zn isotope analysis as described below. TRANSLOCATION AND DISTRIBUTION OF FOLIAR ABSORBED ZINC IN MATURE TREES. During May and June, the transport of foliar absorbed Foliar supply of nutrients is commonly practiced in fruit trees and vegetable crops, but its effectiveness is not consistent due to limited rates of leaf absorption and translocation. The initial absorption phase involves penetration through the cuticle and epidermal cells, while the subsequent transport of the foliar absorbed nutrients generally occurs via the phloem (Bidulph, 1954; Swanson and Whitney, 1953). The extent of redistribution of the applied nutrient is an important consideration in the use of foliar fertilization to satisfy the nutrient needs of plants. Foliar applied micronutrients generally exhibit a low mobility (Chamel, 1988; Ferrandon and Chamel, 1988) and Zn mobility varies with species (Bukovac and Wittwer, 1957; Loneragan et al., 1976). The effectiveness of foliar sprays of Zn varies greatly among species. Wallihan and Heymann- Herschberg (1956) reported that Zn was readily absorbed by, and transported from, the leaves of citrus, while Wadsworth (1970) found only 0.2% of total applied Zn was absorbed and translocated out of the treated leaves of pecan. Although various treatments including chelating molecules have been used to improve the efficiency of foliar nutrient treatments (Alexander, 1986), the effec- tiveness of foliar sprays of Zn remains limited in many species. The purpose of this study was to determine the distribution and the extent of transport of foliar absorbed Zn in 'Kerman' pistachio and to optimize Zn application techniques. Previous studies of foliar Zn uptake and translocation were conducted using radioactive 65 Zn as a tracer. In this study we demonstrate that the accuracy and precision of the measurements using inductively coupled plasma- mass spectrometry (ICP-MS) make it possible to utilize stable isotope tracers of Zn in studies of foliar Zn uptake.

The Effect of Hydraulic Characteristics of Volcanic Materials on Yield of Roses Grown in Soilless Culture

Abstract: Rose (Rosa sp.) plants ('Mercedes') were grown in yellow tuff (YT) (volcanic ash, scoria) and pumice from Italy (PI) and Greece (PG) for which physical and hydraulic characteristics were determined. The differences among the measured retention curves of these materials result in significant differences among their relative hydraulic conductivity functions. Th e hydraulic conductivity of YT is much higher than that of PI, which is higher than that of PG. The plants were subjected to optimal growth and nutrition conditions. Irrigation was controlled using electronic tensiometers, at suction values well within the range of easily available water: 13 cm for YT and 8 cm for the two pumice types. Nonetheless, yields were significantly higher in YT than in PI; yields were even lower in PG. We suggest that the limiting factor was the dynamic water availability to the plants, which is affected mainly by the unsaturated hydraulic conductivity. The relative hydraulic conductivity of YT at 13 cm is more than an order of magnitude higher than that of PI at 8 cm. The relative hydraulic conductivity of PG at 8 cm is two orders of magnitude lower than that of YT at 13 cm. It seems that the current concept of easily available water, base d on a predetermined suction range, independent of the hydraulic characteristics of the media, is not an appropriate parameter for irrigation management in soilless culture. The unsaturated hydraulic conductivity, being a characteristic function of the medium and highly sensitive to moisture variation, indicates better the actual availability of water to the roots. Therefore, i t should be used for irrigation control in containers filled with porous substrates. The simultaneous and continuous supply of easily available water (EAW) and oxygen to the whole plant root system is an essential prerequisite for optimal production of plant material. In well-aerated soilless media, oxygen is usually in adequate supply even under conditions of continuous or very frequent irrigation. Matching water flow from irrigation emitters—through the root medium to the plant—with the transpirational demand, is neces- sary to enable high stomatal conductance. This, in turn, enables uninterrupted CO2 fixation, efficient transpirational cooling of the plant canopy and translocation of ions (including essential nutri- ents) and organic molecules into, within and out of the living plant, driven by the transpirational stream. As media differ in their physical characteristics , optimal irriga- tion scheduling should be formulated specifically for each medium type. Such scheduling should enable water flow from the medium to the roots, synchronously with the transpirational demand, as determined by the climatic conditions, i.e., solar radiation, vapor pressure deficit and air velocity, and plant variables such as leaf area and stomatal conductance. Quantification of the hydraulic processes that take place within the container during and between irrigations is essential for the

Efficiency of Randomly Amplified Polymorphic DNA to Sequence Characterized Amplified Region Marker Conversion and their Comparative Polymerase Chain Reaction Sensitivity in Cucumber

Abstract: The conversion of randomly amplified polymorphic DNA (RAPD) markers to sequence characterized amplified region (SCAR) markers, and the effects of differing polymerase chain reaction (PCR) conditions were studied in cucumber (Cucumis sativus L.). Attempts were made to clone and sequence 75 RAPD PCR products to produce SCAR primers (16 to 22 nucleotides) designed to amplify original RAPD PCR products. The influence of template DNA source, purity, and concentration, MgCl2 concentration, Taq polymerase source, and type of thermocycler upon RAPD and SCAR marker performance was evaluated. Conversion of RAPD to SCAR markers was not universally successful, and SCAR primers reacted differently to varying PCR conditions. Only 48 (64%) of 75 RAPD markers were successfully converted to SCAR markers and 11 (15%) of these reproduced the polymorphism observed with the original RAPD PCR product. Moreover, some SCAR primer pairs produced multiple polymorphic PCR products. The band intensity of SCAR markers were brighter (P = 0.05) than their corresponding RAPD markers with only one exception. The SCAR markers examined were less influenced (P = 0.05) by MgCl2 concentration than their corresponding RAPD markers. However, some SCAR markers were more sensitive to reaction impurities than their RAPD counterparts and SCAR markers tended to be less readily visualized (decrease in frequency of visible PCR product) with low concentrations (1 and 2 m M) of template DNA than their corresponding RAPD markers. Neither the source of Taq nor the type of thermocycler used affected the performance of SCAR and RAPD markers. These data suggest that although SCAR markers may demonstrate enhanced performance over the RAPD markers from which they are derived, careful consideration must be given to both the costs and potential benefits of SCAR marker development in cucumber.

Flavonoid Composition of Three Genotypes of Dry Bean (Phaseolus vulgaris) Differing in Seedcoat Color

Abstract: Three dry bean (Phaseolus vulgaris L.) genotypes differing in seedcoat color, mineral brown ( P C D J G B v), yellow brown (P C D J G b v), and pale greenish yellow (P C D J g b v), were analyzed phytochemically. Kaempferol 3-O-β-D-glucoside (astragalin) was isolated and identified by nuclear magnetic resonance spectroscopy from all three genotypes, and was the main flavonoid monomer present. Flavonoid polymers (condensed tannins) were detected by thin layer chromatography, but anthocyanins were not detected in the three genotypes. High pressure liquid chromatography analyses indicated that astragalin was present at similar concentrations in pale greenish yellow and mineral brown genotypes, but was significantly lower in yellow brown. Presently, we do not know the functions of the G and B color genes, although the presence of astragalin in the three genotypes studied indicates these genes do not appear to act in a qualitative manner with regard to astragalin production, but may control the amount of astragalin present. Subtle differences in color between these genotypes may be due to the amount and type of tannins which have secondarily polymerized with phenolics and flavonoid monomers.

Coexpression of potato PVYo coat protein and cryV-Bt genes in potato.

Abstract: o (PVY o ), virus coat protein, Bacillus thuringiensis ABSTRACT. The codon-modified cryV-Bt gene (cryV-Bt) from Bacillus thuringiensis subsp. kurstaki Berliner, which is specifically toxic to Lepidoptera and Coleoptera insects, and a potato virus Y o coat protein gene (PVY o cp), in which the aphid transmission site was inactivated, were cotransformed into potato ( Solanum tuberosum L.) 'Spunta' via Agrobac- terium tumefaciens Conn. We demonstrated the integration and expression of both genes by molecular analysis and bioassays. All cryV-Bt/PVY o cp-transgenic lines were more resistant to potato tuber moth ( Phthorimaea operculella Zeller) and PVY o infection than nontransgenic 'Spunta'. Four cryV-Bt/PVY o cp transgenic lines were equal in potato tuber moth mortality to a cryV-Bt transgenic line, but of these four only two lines were equivalent in PVY o titer levels to a PVY o cp- transgenic line. We identified two transgenic lines, 6a-3 and 6a-5, which showed greater resistance to potato tuber moth and PVY o than the other cryV-Bt/PVY o cp transgenic lines. This study indicated that multiple genes, conferring insect pest