Showing papers in "Seed Science and Technology in 2002"

The influence of priming on germination of rice (Oryza sativa L.) seeds and seedling emergence and performance in flooded soil

Abstract: The effects of priming treatments (CaCl 2 , CaCl 2 + + NaCl (1:1.4 mol/mol), CaCl 2 + NaCl (1:1.4 mol/mol)+10, 100, or 1000 ppm GA 3 , at -1.25 MPa for 2 d and polyethylene glycol (PEG 8000) at -1.25 MPa for 3 d at 20°C) were investigated on rice seeds (Oryza sativa L. cv 'Zhenongda 454') in germination tests in the laboratory. Priming did not improve rice seed germination, but significantly increased germination energy and germination index and slightly reduced mean germination time (MGT). Seeds primed with salt solutions had a significantly higher germination index and lower MGT than those primed with PEG8000. There were no significant differences in energy of germination and germination percentage among seeds primed with salt solutions and those primed with PEG8000. The addition of GA 3 to CaCl 2 + NaCl solution did not significantly improve the rate of germination or germination percentage as compared with CaCl 2 + NaCl priming solution. In a greenhouse trial, priming improved the seedling vigour index and seedling and stand establishment in flooded soil. The addition of GA 3 to CaCl 2 + NaCl did not significantly increase either the speed of emergence or stand establishment as compared with CaCl 2 + NaCl priming solution. It is suggested that priming of rice seeds may contribute to improved seedling establishment in anaerobic soil.

What is seed quality

Abstract: If quality is defined as degree or standard of excellence, then seed quality can be viewed as a standard of excellence in certain characters or attributes that will determine the performance of the seed when sown or stored. In practice the expression seed quality is used loosely to reflect the overall value of seed for its intended purpose; the performance of seed must measure up to the expectations of the end user of that seed. This review examines seed quality from five different perspectives: seed quality as a misused biosecurity tool; seed quality as a marketing tool; seed quality as a nonsense; seed quality as a specific requirement for modern crop production; and seed quality needs in non-temperate environments.

Germination, seed reserve utilization and seedling growth of chickpea as affected by salinity and seed size

Abstract: Experiments were conducted to determine the effects of seed size (large, medium and small), salinity (osmotic potentials of 0, -0.3, -0.6 and -0.9 MPa) and their interaction effect on germination and heterotrophic seedling growth of two chickpea (Cicer arietinum L.) cultivars, Jam and Kaka. Total (G mx ), rate (R50), uniformity (GU) and time lag (D10) of germination, were not affected by seed size, but all of the traits were affected by salinity to differing extents. G mx was the most tolerant and GU was the most sensitive in response to salinity. Seedlings from large seeds had greater root (RTL) and shoot (STL) lengths and seedling growth rate (SLGR) than those from small seeds. These seedlings utilized seed reserves at a faster rate; however, conversion efficiency of seed reserves into plant tissue (SRUE) was the same regardless of seed size. The advantage of large seeds was a result of their ability to provide energy more rapidly to the growing seedlings. Decreasing osmotic potential (OP) progressively decreased RTL, STL and SLGR. Decrease in SLGR was a result of a progressive decrease in seed reserve utilization rate (SRUR) as affected by OP, but SRUE was decreased only at -0.9 MPa. The cultivar x OP interaction was significant for G mx , R50, D10, RTL, STL and SRUR; Kaka was more susceptible to salinity than Jam. There was a significant OP x seed size interaction for RTL, STL and SLGR. Under non-saline conditions, large seeds were superior, but declining OP exhausted this advantage, so that there was no significant difference between large, medium and small seeds at OPs of -0.6 and -0.9 MPa. It was concluded that the use of large seed would be an advantage in producing more vigorous seedlings of chickpea in non-saline condition. Under saline conditions, seed grading does not result in more vigorous seedlings.

Effects of priming on germination and health of rice (Oryza sativa L.) seeds

Abstract: The effects of priming treatments, including CaCl 2 , NaCl, KNO 3 and polyethylene glycol (PEG 8000) at -1.25 MPa for 2, 3, or 4 d at 20°C, were assessed on rice seeds (Oryza sativa L. cv 'Zhenongda 454'). Primed and nonprimed control seeds were then germinated at 25°C. The blotter method was used for mycological analysis of primed and nonprimed seeds. None of priming treatments significantly increased germination capacity of rice seed compared with control. A significantly higher energy of germination was observed after seven priming treatments and mean germination time decreased and germination index increased after three treatments. Priming caused an increase in the number of genera or species of fungi detected in rice seeds, Although there was no significant effect on the total infestation of rice seed. Primed seeds had significantly higher incidence of Fusarium spp. and lower incidence of Cladosporium spp. than nonprimed ones. Pre-treatment with sodium hypochlorite had no effect on the total infestation of rice seed. Pre-treatment caused decrease in the incidence of Fusarium spp. in primed rice seeds and increase in the incidence of Curvularia spp.

A controlled deterioration test for Arabidopsis thaliana reveals genetic variation in seed quality

Abstract: Several ecotypes (Landsberg erecta, Enkheim, Cape Verde islands and C24) and mutants (abal-1, abi3-7, gal-1 and tt4-1) of Arabidopsis thaliana L. were subjected to a variety of seed quality tests to assess genetic variation. The wild type (Landsberg erecta) and two mutants (abi3-7, tt4-1) gave close to 100% germination at 25°C whilst other genotypes and mutants showed varying degrees of dormancy. A controlled deterioration assay was developed to compare genotypes with regard to their storability. Equilibration of the seeds at 85% relative humidity and subsequent hermetic storage at 40°C was more discriminatory in identifying differences in storability than was equilibration at 75% relative humidity followed by storage at 40 or 50°C. With longer deterioration treatments, germination was reduced and average germination time and frequency of abnormal seedlings increased. This test revealed clear differences in seed stress tolerance amongst genotypes. Additional differences in seed quality were observed in germination tests performed at sub-optimal conditions, such as low temperatures (10 and 15°C) or under osmotic stress (-0.25 MPa and -0.50 MPa). The observed differences in seed quality and the assays developed can be used to identify genes involved in different aspects of seed quality.

Effect of osmoconditioning upon seed germination of sorghum (Sorghum bicolor (L.) Moench) under low temperatures

Abstract: The response of germination to temperature and to seed osmopriming among ten sorghum genotypes of diverse genetic background was examined in order to assess the genetic variability and the possibility of improving germination performance by means of seed water manipulation. Genotypes were tested in combination with seven germination temperatures (ranging from 4° to 25°C) and two seed treatments (no treatment (control) and osmopriming (250 g 1 -1 of PEG at 15°C for two days)). The response of germination rate to temperature among genotypes and the thermal time to 50% germination, for each seed treatment were examined. The treatment of the seeds in osmotic solution was effective on promoting higher germination percentages at lower temperatures (ranging from 8° to 10°C). Osmotic treatment reduced base temperature by almost one degree centigrade compared to control. Differences among genotypes on the base temperature for germination have been found, which is promising for the development of cold tolerant sweet and fibre sorghum genotypes.

Effects of salinity and temperature on the germination and early seedling growth of Atriplex cordobensis Gandoger et Stuckert (Chenopodiaceae)

Abstract: Experiments were conducted to determine the effect of salinity and temperature on the germination and early seedling growth of Atriplex cordobensis. Germination recovery under optimum conditions after exposure to salinity was also studied. Seeds were exposed to 0, 100, 200 and 300 mM NaCI and temperature regimes of 10, 20 and 30°C. Our data indicate that seed germination of A. cordobensis is significantly affected by the interaction of salinity and temperature. The seeds of A. cordobensis at 10 and 20°C behave in the same way as other halophyte seeds, with the ability to tolerate hyper-saline conditions or to stay dormant until appropriate conditions appears. However, at 30°C seeds are very sensitive to salt stress, which acts as a selective factor favoring vigorous seeds. On the other hand, seedlings have the ability to take up Na + and probably use it for osmotic adjustment allowing them to growth under water stressing conditions. Thus the mechanisms of tolerance to salt stress in seeds and seedling contribute to explain the distribution of A. cordobensis in the semiarid region of central Argentina.

Seed testing for endophytes by microscopic and immunoblot procedures

Abstract: Hill, N S, Hiatt, E E, De Battista, J P, Costa, M C, Griffiths, C H, Klap, J, Thorogood, D, Reeves, J H (2002) Seed testing for endophytes by microscopic and immunoblot procedures Seed Science and Technology, 32, 347-355

Salt stress-induced cytosolute accumulation, antioxidant response and membrane deterioration in three rice cultivars during early germination

Abstract: Salt resistant (Hamilton and SR26B) and salt sensitive (Ratna) rice cultivars when exposed to 100mM NaCl treatment, showed differential salinity stress response in respect to cytosolute accumulation (free proline, total soluble carbohydrate and reducing sugars) during early germination. Antioxidant response was measured in terms of free radical scavenging enzymes (catalase, CAT; peroxidase, POD and superoxide dismutase, SOD) and the reactive oxygen species, H 2 O 2 accumulation. Extent of membrane damage due to involvement of oxyfree radicals was assessed from membrane lipid peroxidation (accumulation of malon dialdehyde, MDA), leakage of UV-absorbing substances and membrane permeability status. Hamilton and SR26B produced higher amount of proline and reducing sugars. Also, higher specific activities of POD, CAT and SOD were evident in above cultivars when compared with cultivar Ratna under identical conditions. When compared, the salt resistant cultivars (SR26B and Hamilton) which are also high cytosolute producers experienced lower degree of free radical induced membrane damage during early germination period under salinity.

Varietal differences in seed germination and seedling vigor of Korean rice varieties following dry heat treatment

Abstract: Five rice varieties with different grain characteristics were exposed to various dry-heat temperatures (70, 75, 80, 85 and 90°C) for 24 hours and then seed germination and seedling vigor were investigated. The dry heat tolerance of 32 Korean rice varieties was also evaluated after exposure to 90°C for 24 hours. At higher temperatures (85°C and 90°C), percentage germination, percentage emergence, seedling height and dry weight were significantly reduced compared with the control. The treatment at lower temperatures (70°C - 80°C) had no adverse effects. Varietal differences in seed germination, seedling emergence, plant height and dry weight were revealed at 90°C. The 32 varieties were classified into two groups by cluster analysis based on percentage germination and emergence. Tongil varieties, which were developed by crossing indica and japonica, were classified as highly tolerant, whereas most of japonica varieties including four glutinous varieties fell into the sensitive group. The percentage germination of hulled seeds was significantly reduced relative to that of intact seeds at 75°C for 24 hours. This indicated that rice hull had a very important role in dry heat tolerance. The germinability of japonica varieties completely disappeared after exposure of 90°C for 96 hours. The critical temperature of rice seeds was 100°C under 24 hours of exposure.

Separation of viable and non-viable filled Scots pine seeds by differentiating between drying rates using single seed near infrared transmittance spectroscopy

Abstract: Single seed near infrared (NIR) transmittance spectroscopy showed high potential to classify and separate viable seeds from non-viable filled seeds of Scots pine (Pinus sylvestris L.). Multivariate calibration models based on NIR transmittance spectroscopy in the range 850-1048 nm had high prediction accuracy (98-99%) for the characterisation and separation of viable and non-viable filled Scots pine seeds. Viable and non-viable filled seeds were imbibed to 30% moisture content for 4 days at 15°C and nearly 100% relative air humidity. Utilising the phenomenon of different drying rates of imbibed viable and non-viable filled seeds, calibration models were fitted based on single seed spectra collected after 0.8-3.8 h of drying time at ca 20°C and ca 25% relative air humidity. The high prediction accuracy of classifying viable and non-viable filled seeds in the test set, dried for 2 h, was achieved using PLS regression modelling of NIR spectra collected within the calibration set.

Sugar-beet seed quality and DNA synthesis in the embryo in relation to hydration-dehydration cycles

Abstract: Two samples of sugar-beet seed of one cultivar, that differed in vigour, were hydrated in distilled water for two, four and eight hours for up to 14 times, with each hydration being followed by two days of drying (dehydration), all at room temperature. Seed quality parameters such as seedling length vigour index (SLVI) and germination capacity, as well as the cell cycle status (the G 2 /G 1 ratio) in the embryo were estimated at the end of each hydration-dehydration cycle. The greatest improvement in seed quality was achieved after hydration (and subsequent dehydration) three times for four hours. This was especially true for the low vigour seeds, which after such treatment reached a quality level close to that of the high vigour seeds. The G 2 /G 1 ratio increased upon hydration-dehydration treatment, faster when longer periods of hydration were applied. Regardless of the hydration time (two, four or eight hours), the quality parameters under study significantly decreased if the seeds were hydrated and dehydrated more than four or five times. This was a consequence of the transition of most of the seeds from a reversible stage of germination to an irreversible one, in which dehydration caused death of the embryo. The results are discussed from the point of view of the improvement of commercial seed lots.

Development of a PCR-based diagnostic assay for detecting pathogenic Alternaria species in cruciferous seeds.

Abstract: Alternaria brassicae, A. brassicicola and A. japonica are the causal agents of the blackspot disease of crucifers. To limit the propagation of this worldwide occurring disease by infected seeds it is necessary to guarantee the absence of the three pathogenic Alternaria species in seed shipments. The actual detection method which relies on culture and morphological identification of the pathogens is long and not always reliable. A polymerase chain reaction (PCR) based diagnostic technique has been developed for the detection of the three seed-borne Alternaria species. Specific primers were designed from DNA sequence in the internal transcribed spacer (ITS) region of nuclear rDNA and used in PCR reactions containing DNA extracted from seed macerates. The assay successfully reveals after only two days of incubation, the presence of A. brassicicola and A. japonica in seeds of crucifers even at levels of infection as low as 10%.

Germination strategies of Strandveld Succulent Karoo plant species for revegetation purposes: I. temperature and light requirements

Abstract: Optimum germination requirements of 28 Strandveld Succulent Karoo species (representing 31 seed types) were examined. Of these species, light had a negative effect on the germination of c. 50% of the species, although in several cases this was only evident at sub-optimal temperatures. Most of these were perennial species. Light promoted the germination of seven species (c. 29%), most of them annual species, while the germination of five species was not affected by light. Most species were characterised by intermediate mean optimum temperatures for germination. Alternating incubating temperatures significantly increased germination percentage above that of the control in only one species, however, there were 13 instances where alternating temperatures gave lower germination than the control. In only 16.7% of the species did the optimum germination temperature exceed 20°C. Seeds of most species produced shortest mean times to germination at intermediate temperatures, irrespective of light conditions. An understanding of the germination requirements of these species will allow the local mining industry to maximize their revegetation efforts on post-mining areas.

Chlorophyll fluorescence sorting as a method for improvement of barley (Hordeum vulgare L.) seed health and germination

Abstract: Important factors which determine seed quality, include the maturity and viability, expressed as percentage and uniformity of germination, as well as the presence of certain diseases in a seed lot. Although the physiological aspects of germination are of utmost importance, the impact of the seed-borne pathogens should not be ignored. In the present study the chlorophyll fluorescence (CF) technique was used to measure differences in the chlorophyll contents in barley grains (Hordeum vulgare L.), as a quality factor for maturity and germination. Sorting a barley seed lot into six subsamples varying in CF values resulted in an optimal seed quality for the subsamples with low and intermediate CF signals. The amount of chlorophyll was related to the germination performance and the health status of the seeds. The percentage of seeds contaminated with Fusarium spp. and Cochliobolus sativus, both known to affect germination, showed a relation with CF value - the subsample with the highest CF signals was always the most heavily infected. CF sorting of the barley seeds improved their germination quality not only on the basis of removing less mature grain, but also due to removing the seeds with the heaviest fungal infection levels.

Relationships between physical, morphological, and physiological characteristics of seeds developed at different positions of the ear of two maize (Zea mays L.) hybrids

Abstract: Maize seeds developed at different portions of the ear of two hybrids (one, a large seeded, and the other a small seeded hybrid) were compared as to physical positions, morphological, and physiological characteristics viewing to gain information to be used during seed conditioning. The number of positions in the ear were 10, starting at the proximal and ending at the distal end. For the sake of simplification, the data were combined to refer to seeds of the proximal, the central and the distal sectors of an ear. Measurements made of the seeds as to shape (length, width, and thickness) and as to size (1,000 seeds weight) indicated that the round seeds growing at the distal sector are significantly smaller (mainly when thickness is considered) and lighter than those growing at the proximal sector. On the other hand, determinations of the physiological quality indicated that the round-proximal and the central seeds are equivalent and both significantly superior to the round-distal ones. Considering these significant differences as to size, shape, and physiological quality, a proposition of suppressing part of the round-distal from the totallity of the round seeds during the operations of seed conditioning is made.

Seed storage behaviour in Madhuca indica J.F. Gmel.

Abstract: Desiccation and storage experiments were performed on mahua (Madhuca indica J.F. Gmel.) seeds to determine their storage behaviour. The mature seeds, which were shed at relatively high moisture content (53%), exhibited 100% viability initially. Drying of seeds to 39.4% moisture content (natural drying) had no adverse effect on germination but further drying to 37.7% moisture content (silica gel drying) reduced germination by 11%. Almost 90% loss in germinability was registered when dehydrated below 16.8% and 14.8% moisture content after 29 (natural drying) and 10 days (silica gel drying). Seeds became non-viable when desiccated below 9.4% moisture content in both the drying conditions (natural drying and silica gel drying). The strong positive correlation obtained between decline of viability and rate of dehydration; natural drying (R 2 =0.97) or silica gel drying (R 2 =0.98) strengthens the case of desiccation induced loss of viability in M. indica seeds. Storage experiments carried out with undried (53 ± 2.6) and silica gel dried seeds (moisture contents: 48 ± 0.4, 37.7 ± 3.6 and 28.4 ± 4%) at range of temperatures (-20, 0, 15 and 25°C) showed maximum survival of undried seeds for 30 days with 35% viability at 15°C. The undried and dried seeds of M. indica could not tolerate cold temperatures and were killed when exposed to 0°C and -20°C. Our results suggest that the storage behaviour of M. indica seeds is true tropical recalcitrant.

Accelerating ageing test for comparing wheat seed vigour

Abstract: The objective of this study was to evaluate various combinations of temperature and time for the accelerated ageing vigour test for wheat seed. In the first experiment, three aging temperatures (41, 43, 45°C) were compared across three time intervals (24, 48, 72 h) for three soft red winter wheat seed lots. In the second experiment several ageing time/temperature combinations (41°C/72 h, 45°C/48 h, 43°C/72 h, 41°C/96 h and 45°C/72 h) were evaluated for six seed lots and compared to standard germination and conductivity. Three accelerated ageing regimes, 43°C/72 h; 41°C/96 h; 45°C/72 h provided better separation of wheat seed lots into vigour levels than the 41°C/72 h presently suggested by ISTA. The three methods were highly correlated (r ≥ 0.95), but either 43°C/72 h or 45°C/72 h are suggested because of the shorter time interval for testing. Germination after ageing regardless of time/temperature regime was poorly correlated with standard germination and showed no relationship with seed leachate conductivity.

Effect of essential plant oils on storage fungi, germination and emergence of cowpea seeds

Abstract: The antifungal activity of plant essential oils on storage fungi commonly associated with cowpea (Vigna unguiculata (L.) Walp) seed was investigated. The antifungal activity of the essential oils of thyme, clove, peppermint, soybean and peanut were tested against Aspergillus flavus, A. niger, Fusarium oxysporum, F. equiseti and Penicillium chrysogenum in vitro. Only thyme and clove significantly inhibited growth of all five fungi at 500 and 1000 ppm whereas peppermint oil successfully inhibited growth at 2000 ppm. Thyme, clove and peppermint were tested in vivo against storage fungi on naturally infected (cultivars PAN 325 and PAN 311) and artificially infected (cultivar CH 14) cowpea seed. Only thyme oil (1000 ppm) showed antifungal activity against storage fungi associated with PAN 325 cowpea seeds. In the PAN 311 cultivar, clove and thyme at 1000 ppm and peppermint at 2000 ppm exhibited antifungal activity against the storage fungi. In cultivar CH 14, thyme, clove and peppermint significantly reduced growth of P chrysogenum whilst thyme and peppermint inhibited growth of F. oxysporum. Only thyme had an antifungal effect on F. equiseti. No treatment showed antifungal activity against A. flavus and A. niger. None of the oils showed harmful effects on the germination and emergence of cowpea seeds. The storage fungi significantly reduced percentage germination and emergence of the white (IT 93K452-1) seed but had little or no effect on the brown (CH 14) seed. Furthermore, all three oils significantly inhibited the storage fungi on the white seed thereby increasing the percentage germination and emergence.

Seed maturity affects the uniformity of cherry (Prunus avium L.) seed response to dormancy-breaking treatments

Abstract: Cherry seeds are deeply dormant and require at least 15 weeks of low temperature treatment to break dormancy. More complex dormancy-breaking treatments that interrupt the time at low temperature with periods of warm (20°C) temperature can be more effective. However, seed lot response to treatment remains variable in practice. The results presented indicate that differences in seed response to treatment both between and within seed lots can result from different degrees of maturity at harvest. Differences in seed maturity were also linked to differences in their requirement for warm temperature interruptions during cold treatment to remove dormancy. For example, drying of prematurely harvested seeds increased the proportion of the population that had an absolute requirement for this period of higher temperature before germination could take place. A period of moist storage at 15°C immediately following harvest and before drying, induced changes in seed response to treatment like those in late seed development on the tree. Moist storage therefore minimised the requirement for warm temperature interruptions during low temperature treatment. Moist storage may therefore allow continued seed development, however, physical changes in the seed coat and endocarp during moist storage cannot be discounted as possible causes. The relevance of these results to horticultural practice is discussed.

Storability of cotton seeds predicted by vigour tests

Abstract: The ability of different vigour tests to predict the storage potential of cotton seeds was assessed. Chemically delinted seeds from one seed lot of the cultivars IAC-20 RR, CS-50, DP-20 and DP-90 were stored for 12 months under ambient environmental conditions at the Seed Laboratory of the Federal University of Vicosa. Seed quality was assessed before storage by the following tests: standard germination, seedling vigor classification, early primary root emission, accelerated ageing, cool germination, field emergence and electrical conductivity. Standard germination was performed after every three months of storage. The generalized Mahalanobis distances procedure was used to assess the relationship between vigour test and standard germination test results obtained in the different storage periods. Seed viability decreased linearly during the storage period. There was the greatest similarity or smaller and no significative Mahalanobis distances between standard germination and accelerated ageing results. The accelerated ageing test carried out before storage best estimated seed viability after nine months storage.

Application of chlorophyll fluorescence in sorting controlled deteriorated white cabbage (Brassica oleracea L.) seeds

Abstract: Chlorophyll fluorescence (CF) method has been applied for improvement of white cabbage seed quality after a controlled deterioration treatment (cd). Two sets of experiments, in which seeds were sorted before or after a cd treatment, were carried out. Median CF signal, seed number, germination percentage, T 10 , U 90-10 , mean germination time and seed leachate electrical conductivity for each obtained subsample were determined. Increasing median CF signal was correlated with the change in germination parameters and seed leachate electrical conductivity, confirming a decrease in seed quality. CF sorting was more effective after the cd treatment. Seeds first subjected to a cd treatment and subsequently sorted in the low CF subsample showed comparable germination parameters as seeds belonging to the low CF subsample and without a cd treatment. However, control seeds showed a dramatic decrease in quality after the cd treatment. CF method could be useful for a better understanding of the distribution of seed sub-groups with different vigour patterns within a deteriorated seed population and for the related application in sorting a highly viable seed subsample from a deteriorated seed lot after storage in a genebank.

Effect of dry-heat, soaking in distilled water and gibberellic acid on the germination of Cistus clusii, C. monspeliensis and C. salvifolius seeds

Abstract: Different pretreatments for promoting germination of Cistus clusii, C. monspeliensis and C. salvifolius, Cistaceous species widely distributed in Mediterranean region, were investigated. Pretreatments applied were: dry-heat, seed soaking in distilled water and gibberellic acid. Germination tests were performed under controlled conditions at 15°C in darkness. Dry-heat treatments were shown to break dormancy. The highest germination percentages in the three species studied were obtained with dry-heat at 100°C for five minutes. Dry-heat at 80°C for a longer exposition times was only effective for C. clusii and C. salvifolius. These results indicated that hardness and impermeability of seed coats to water uptake might be the most important cause of the dormancy present in seeds of C. clusii, C. monspeliensis and C. salvifolius, as in other Cistus species. The soaking of seeds in distilled water and exogenous gibberellic acid applications did not significantly increase germination over untreated seeds.

The incidence and distribution of seed-transmitted viruses in pea and lentil seed lots in Ethiopia.

Abstract: The incidence of seed-transmitted viruses was determined in 270 lentil and 219 pea seed samples collected in 1998 and 1999 from farmers' seed lots in Ethiopia. Seedlings obtained from 400 seeds from each sample were serologically tested for infection with six viruses. In lentil, 43.7% of the samples had at least one virus. Pea seed-borne mosaic virus (PSbMV, genus Potyvirus, family Potyviridae) was detected in 31.1% of the samples, whereas bean yellow mosaic virus (BYMV, genus Potyvirus, family Potyviridae), broad bean stain virus (BBSV, genus Comovirus, family Comoviridae), alfalfa mosaic virus (AMV, genus Alfamovirus, family Bromoviridae), and cucumber mosaic virus (CMV, genus Cucumovirus, family Bromoviridae) were detected at very low rates. The highest incidence in a single lentil seed sample was 16.8% for PSbMV. Seventy two out of the 158 samples from central Ethiopia (45.6%) were infected with PSbMV, whereas only 12 out of 112 from northern Ethiopia (10.7%) were infected. Of 219 pea seed samples tested for PSbMV, BYMV, CMV, AMV and pea early browning virus (PEBV, genus Tobravirus), only five were infected with PEBV and two with BYMV at a very low rate and none was infected with PSbMV, AMV and CMV. Testing of 40 lentil and 228 pea germplasm accessions from the National Pulse Improvement Program for PSbMV revealed that 15 lentil and 4 pea lines were contaminated.

Effects of dry storage on germination and survivorship of seeds of four Lonicera species (Caprifoliaceae)

Abstract: Effects of dry storage under ambient laboratory conditions on germination and survivorship was tested for seeds of four Lonicera species. Fresh seeds of L. fragrantissima and L. japonica were dormant, whereas those of L. maackii and L. morrowii germinated to about 30% at 25/15°C in light. Seeds of L. fragrantissima remained dormant during the entire 24 months of storage. Highest germination for seeds of L. japonica, L. maackii, and L. morrowii were 47, 68, and 50%, respectively, in light after 6 months storage. Decrease in germinability between 6 and 12 months storage for L. japonica and L. maackii, and between 6 and 15 months for L. morrowii was greater than decrease in viability; thus, some seeds reentered dormancy. However, for seeds of L. japonica and L. maackii stored longer than 12 months, decrease in viability was greater than decrease in germinability, indicating that more seeds afterripened than lost viability. Survivorship curves for seeds of all four species were approximately Deevey Type II. A graphical model is presented for the roles of reentrance into dormancy, loss of viability, and afterripening in determining germinability of seeds.

Influence of dormancy regulating compounds and salinity on the germination of Zygophyllum simplex L. seeds

Abstract: The role of dormancy regulating compounds (ethephon, fusicoccin, nitrate and thiourea) in alleviating the inhibitory effects of salinity on seed germination of an annual forb, Zygophyllum simplex, was studied. In the non-saline controls only 60% of the seeds germinated and germination decreased with an increase in salinity, with no seeds germinating at 125 mM NaCl. All dormancy regulating compounds significantly promoted germination in the non-saline control. Nitrate and thiourea had some promotive effect at 25 mM NaCl, but no stimulation of germination was detected at either 75 or 125 mM NaCl. Ethylene application significantly promoted germination at all salinities. Fusicoccin completely reversed the inhibitory effects of all salinity treatments on the germination of Z. simplex.

Germination strategies of Strandveld Succulent Karoo plant species for revegetation purposes: II. dormancy-breaking treatments

Abstract: The requirement of an after-ripening period was investigated in 27 plant species from the Strandveld Succulent Karoo, South Africa. The seeds of seven species were examined for the presence of endogenous germination patterns, while the effect of other dormancy-breaking treatments on germination percentage and rate was examined in ten species. The germination of 14 species (including annuals and perennials) was promoted by a summer after-ripening period, indicating that the seeds of these species are characterised by non-deep physiological dormancy. Strong evidence for the presence of a clear endogenous germination rhythm in the species investigated was lacking. Chemical or mechanical scarification of the seeds of several annual and perennial species improved germination percentage and rate. The germination of two annual species increased after a hydration/dehydration treatment, or when seeds were given a cold or a heat+cold treatment. Contrary to what was expected, a heat treatment did not improve germination and only one out of ten species showed an increase in germination percentage after a cold+heat treatment. Leaching improved the germination of only one species. In areas where topsoil replacement and sowing have been completed, irrigation should not be applied prior to the start of the rainy season, as the seeds of most species present in the seed bank will be in a state of dormancy or conditional dormancy.

Seed storage and viability of Myristica malabarica Lam. an endemic species of Southern Western Ghats (India)

Abstract: Myristica malabarica Lam. seeds remain viable only for a week under natural conditions. Fresh seeds exhibit 27% moisture content and 100% germination. On natural drying, the critical moisture content value was found to be between 14 and 11% as the germination percentage decreased from 70 to 0% respectively. Sensitivity of seeds to temperatures below 10°C is an indication of recalcitrant nature. Seeds with 27% moisture content stored in polyethylene bags at 30°C / 80% RH retained their viability up to one year.

The effects of high temperature on dormancy and hypocotyl-root growth of wild common bean (Phaseolus vulgaris L.)

Abstract: The aim of this study was to investigate the effects of scarification and high temperature on dormancy and initial hypocotyl-root growth of two wild common bean (Phaseolus vulgaris L.) samples differing in geographic origin and in the domesticated common bean. The wild common bean samples exhibited large differences in the proportion of dormant seeds (ranging from 20 to 70%), depending on their size and origin, with noticeable differences in their rates of imbibiton. In addition, mechanical scarification broke the wild seed dormancy. High temperatures (30-45°C) also broke dormancy in some wild subsamples but killed some seeds in others, particularly those of small size. High temperatures also induced a small but significant increase in water uptake during imbibition. Initial hypocotyl-root growth from small wild seeds was not affected with the increase of temperature, except at 45°C when the growth fell sharply. In contrast, initial hypocotyl-root growth from large wild seeds increased at exposure of 30 to 40°C, but at 45°C the growth was also diminished. Although high temperatures did not affected water uptake in domesticated common bean, especially at 35-45°C, germination and initial hypocotyl-root growth were severely affected. Therefore, the data suggest that high temperature during germination has a positive relationship with the breaking of dormancy of wild common bean, but deteriorated the seed of domesticated common bean.

The effect of seed quality (seed colour variation) on storability, germination temperature and field performance of radicchio

Abstract: The possible role played by seed colour (uniformly light-L, slightly black variegated-LB, widely black variegated-BL, uniformly black-B, purple-P) in the seed quality of 'Rosso di Treviso precoce' and 'Rosso di Chioggia' radicchio was investigated. The effect of seed-storage length (two, seven months) was also studied in 'Rosso di Treviso precoce'. For better evaluation of seed quality, germination tests were carried out at 12, 20 and 28°C. The influence of seed characteristics on crop yield was then investigated in the field. Germinability and seed vigour were linked to colour. Reduced germination was observed with L seeds. Moreover, when germinated, L seeds gave rise to plants with reduced ability to form heads, thus reducing the marketable yield. As colour became increasingly darker, seeds germinated faster and more uniformly, and germinability was higher. The differences apparently resulted from incomplete seed development, as shown by the close relationship between germinability and seed weight, and by the smaller embryos of lighter seeds. Sensitivity to temperature changed with seed colour and radicchio type. The L seeds of both types germinated poorly whatever the temperature. The other lots germinated best at 28°C, excluding the LB and P seeds of 'Rosso di Chioggia' which gave better results at 20°C. The negative effect of 12°C was more evident in P seeds of 'Rosso di Chioggia'. Only germinability at 12°C decreased during storage but, whatever the temperature, germination rate decreased with time.