Showing papers on "Plant disease resistance published in 1989"

Protection Against Potyvirus Infection in Transgenic Plants: Evidence for Broad Spectrum Resistance

Abstract: Protection Against Potyvirus Infection in Transgenic Plants: Evidence for Broad Spectrum Resistance

The Genetic Engineering of Two Commercial Potato Cultivars for Resistance to Potato Virus X

Abstract: We efficiently transformed the commercial cultivars of potato (Solanum tuberosum) Bintje, Desiree and Escort after optimizing the conditions for regeneration from potato tuber discs. For transformation, tuber discs were cocultivated with Agrobacterium tumefaciens using a disarmed binary vector system. This system allowed the introduction of a chimaeric gene encoding the coat protein (CP) of potato virus X (PVX) into two cultivars most susceptible to this virus, Bintje and Escort. Five transgenic plant lines with expression levels of CP higher than 0.1% of soluble leaf protein were analyzed for resistance to a challenging inoculation with PVX (1 μg/ml). We observed a delay in symptom development as well as a drastic reduction in the accumulation of virus. Furthermore, we found a correlation between the expression level of the CP–gene and the reduction in virus accumulation. Cytogenetic analysis of 62 independently obtained transgenic lines showed the normal tetraploid number of chromosomes (2n = 4x = 48) in 97 percent of the examined plants. Phenotypically all these plants appeared normal. One plant line exhibited an abnormal phenotype and contained about the octaploid number of chromosomes (4n ≈ 8x = 96). These results and preliminary data on morphological characteristics, as these are determined in the official variety registration procedure, indicate that potato cultivars can be genetically engineered to contain new desirable traits with preservation of their intrinsic properties.

An experimental field study of anther-smut disease of Silene alba caused by Ustilago violacea: genotypic variation and disease incidence.

Abstract: Twenty cloned genotypes of Silene alba differed greatly (0-100%) in the percentage of flowering plants that became diseased by the anther-smut fungus Ustilago violacea following natural spore dispersal in a two-year field experiment. Male genotypes with the highest percentage of disease had high rates of flower production; this trait may increase the probability of spore deposition on flowers, a common site of infection. Because of this relationship, male genotypes with the highest percentage of disease also produced the most healthy flowers in the two-year period. Flowering early in the season was also a predictor of high disease levels for male genotypes in the first year. Variation among female genotypes in disease levels was not correlated with either flower production or phenology, suggesting that the sexes differ in their interaction with the pathogen. Plants of both sexes that remained nonreproductive the first year but flowered the second year could become diseased due to infection of vegetative tissue. Disease levels of the genotypes following natural spore dispersal were not correlated with disease levels of the genotypes following inoculation of vegetative tissue. This discrepancy points out that the methodology used to investigate genetic variation in disease resistance may affect the results obtained.

An isozyme marker for resistance to race 3 of Fusarium oxysporum f. sp. lycopersici in tomato.

Abstract: The inheritance and the linkage relationship of resistance to race 3 of Fusarium oxysporum f. sp. lycopersici derived from Lycopersicon pennellii (LA 716) were analyzed in an interspecific backcross to L. esculentum. Progeny from each backcross (BC1) individual were in-oculated with race 3 and their response was measured according to a visual rating system; progeny responses were used to calculate a mean disease rating for each BC1 individual. The frequency distribution of the disease ratings was bimodal, indicating that resistance to race 3 was controlled by one major locus. Linkage analysis of this locus proceeded in two steps. Initially, disease ratings were compared between homozygotes and heterozygotes at each of 17 segregating marker enzyme loci. Highly significant differences were detected for the chromosome segment marked by the Got-2 locus on chromosome 7. This indicated that Got-2 was linked to the race 3 resistance gene, designated I-3; this gene accounted for the observed bimodal distribution of BC1 disease ratings. In the second step, the genotype of each BC1 individual at the I-3 locus was determined using cluster analysis of the disease ratings; a test for independent assortment between I-3 and Got-2 revealed strong linkage, with an estimated map distance of 2.5 centiMorgans. Additional evidence for this linkage was obtained from the analysis of five breeding lines previously selected for resistance to race 3 solely on the basis of inoculations; all five showed co-selection for Got-2. The Got-2 locus is proposed as a selectable marker to expedite the transfer of race 3 resistance to commercial tomato cultivars.

Diversity for Disease Resistance in Barley Landraces from Syria and Jordan

Abstract: A number of barley landraces collected in Syria and Jordan were evaluated for resistance to yellow rust, powdery mildew, scald and covered smut by inoculating single-head progenies with local pathogen strains during two years of field tests. A large diversity in resistance was observed for each pathogen both between populations of different collection sites as well as between head progenies within collection sites. The level of resistance varied from absolute and partial resistant types up to highly susceptible lines. No consistent association between the environmental conditions of the collection site and the level of resistance of the landrace-lines could be found.

Response of wheatgrasses and wheat wheatgrass hybrids to barley yellow dwarf virus

Abstract: Resistance to barley yellow dwarf virus (BYDV), manifested by low enzyme-linked immunosorbent assay (ELISA) values in plants exposed to viruliferous aphids, was identified in several wheatgrasses (Agropyron spp.). ELISA results were similar for root and leaf extracts of infested plants. No difference in reaction to BYDV was found between plants grown in the field and those in the growth chamber. Interspecific hybrids were generated using pollen from single resistant plants of Agropyron spp. to pollinate soft red winter wheat spikes. Resistance in hybrids appeared to be at the level of virus replication rather than at the level of vector inoculation. The hybrids varied in their reaction to BYDV. Expression of BYDV resistance in hybrids was influenced not only by wheat genotype and Agropyron species but, in some cases, reaction varied even among hybrids between the same wheat genotype and Agropyron plant. Implications of these results are discussed.

Monogenic resistance in tomato to Fusarium oxysporum f. sp. lycopersici race 3

Abstract: Resistance to fusarium wilt, incited by Fusarium oxysporum (Schlecht.) f. sp. lycopersici (Sacc.) Snyder & Hansen race 3 in tomato (Lycopersicon esculentum Mill.) was discovered in LA 716, a L. pennellii accession. A resistant BC1F3 breeding line, E427, was developed from LA 716. E427 was crossed with the susceptible cv. Suncoast and F1, BCP1, BCP2 (to Fla 7155, a susceptible parent) F2, F3, and BCP2S1 seeds were obtained. Segregation for resistance following root dip inoculation over three experiments indicated a single dominant gene controlled resistance. Five of the 12 BCP1S1's segregated more susceptible plants, whereas one of the 12 segregated more resistant plants than expected (P<0.05). Three of 23 F3 lines segregated more susceptible plants than expected while 1 of the 23 had more resistant plants than expected (P<0.05). Segregation in all other lines fit expected ratios. Five of the 23 F3's were homozygous resistant which was an acceptable fit to expectations (P=0.1−0.5). The gene symbol I 3 is proposed for resistance to race 3 of the wilt pathogen. Deviations from expected ratios in data reported here and for other breeding lines indicate an effect of modifier genes and/or incomplete penetrance. Plant age at inoculation and seed dormancy did not affect results.

Cytoplasmic male sterility and maternal inheritance of disease susceptibility in maize

Abstract: Mendelian inheritance of traits of higher plants, including disease resistance, forms the foundation of successful plant breeding. Segregation for disease resistance, including multigenic inheritance patterns, is assumed to result from recombination of genes from both male and female parents, and results in progeny from which breeders and pathologists choose desirable pheno­ types. Plant pathogens need not adhere to these simple humankind-imposed behavioral rules because they indeed represent "shifty enemies" (80), and can be expected to exploit any niche provided, advertantly or inadvertantly. During the 1969 maize growing season, southern com leaf blight and yellow com leaf blight became epidemic in the U.S. com belt. The subse­ quent spread of the pathogens in 1970 resulted in epidemics of the two diseases that were unusually virulent on maize hybrids produced in the T, (Texas) source of cytoplasmic male sterility (ems), then used in about 85% of U.S. hybrid maize production. The determinants of susceptibility were mater­ nally inherited, and thus in spite of nuclear genetic diversity among hybrids, maize was generally susceptible because of the probable identical cytoplasms

Origins of resistances to rust and late leaf spot in peanut (Arachis hypogaea, Fabaceae)

Abstract: The cultivated peanut (Arachis hypogaea, Fabaceae) is believed to have originated along the eastern slopes of the Andes in Bolivia and northern Argentina The crop is now grown throughout tropical and warm temperate regions Among diseases attacking peanuts, rust caused byPuccinia arachidis and late leaf spot caused byPhaeoisariopsis personata are the most important and destructive on a worldwide scale Both pathogens, restricted in host range to Arachis, probably originated and coevolved in South America along with their hosts In recent years there has been much emphasis on screening of peanut germplasm for resistance to these diseases At the International Crops Research Institute for the Semi-Arid Tropics (ICRISA T), India, some 10,000 peanut germplasm accessions were screened for resistance to rust and late leaf spot during 1977–1985 and sources of resistance indentified for either or both pathogens Of the resistant genotypes, about 87% belonged to A hypogaea varfastigiata and 13% to varhypogaea; 84% originated in South America or had South American connections A high percentage (75%) had their origin in Peru (believed to be a secondary gene center for varhirsuta and varfastigiata,), suggesting that resistance to rust and late leaf spot diseases might have evolved in that country

New sources of resistance to southern corn leaf blight from tropical hybrid maize derivatives

Abstract: Three selected inbred lines were intercrossed and topcrossed to a known resistant (NC250) and a known susceptible (B73) inbred. Several sources of resistance roughly equivalent to the high level of resistance available from NC250 were identified. Inheritance studies suggest that different genetic systems are involved, with a range of additive and recessive types of gene action. Resistance in these sources appears to be controlled by relatively few genes that combine in a positive epistatic fashion with the resistance genes in NC250

The exploration of genetic resources of Portuguese cabbage and kale for resistance to several Brassica diseases

Abstract: Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris).

The effect of transfers of alien genes for leaf rust resistance on the agronomic and quality characteristics of wheat

Abstract: Nine transfers of leaf rust (Puccinia recondita Rob. ex Desm.) resistance to wheat (Triticum aestivum L.) from Agropyron elongatum Host. Beauv., Triticum speltoides Tausch and rye (Secale cereale L.) were backcrossed up to 10 times to commercial wheat cultivars. The objective was to study the effect of the transfers on agronomic and quality characters and to make them available in desirable genetic backgrounds. The results varied greatly for different transfers. In four cases no promising material was obtained even after nine backcrosses. However, for the remaining five transfers material with potential as a new cultivar was obtained.

Incidence of endogenous viral genes in two strains of white leghorn chickens selected for egg production and susceptibility or resistance to Marek's disease.

Abstract: Endogenous viral (ev) genes related to the avian leukosis virus were classified in two differentially selected strains of Leghorns in order to investigate whether such genes affect production traits. Strain K had been selected for resistance to Marek's disease (MD) and for high egg production and egg weight, whereas strain S had been selected only for MD susceptibility. Except that founders of strain K included a few commercial birds, both strains were derived from a common genetic base. DNA restriction fragment length analyses of 110 strain K and 94 strain S birds revealed the presence of 8 different ev-genes, 6 of which were identical to previously identified loci. This result was confirmed by assays for group specific antigen (gs-antigen), the product of the gag region of the ev-genes. The levels of gs-antigen in the birds closely followed what had been predicted from data obtained from previously described ev-genes. Both strains had a similar average number of ev-genes per bird (3.5 and 3.2 for strains S and K, respectively). However, strain K carried only five different ev-genes while strain S carried seven. Four of these loci were present in both strains. Among the ev-genes absent or occurring less frequently in strain K were those that code either for infectious endogenous virus (ev-10 and possibly ev-19) or for the internal viral gag-proteins (ev-3). Only those ev-genes which are transcriptionally silent or which code for the viral envelope gene were present in increased frequencies in strain K. The results indicate that selection for egg traits and/or Marek's disease resistance reduces the frequency of ev-genes which produce endogenous virus or the viral gag-proteins.

Nuclear and cytoplasmic gene control of resistance to loose smut (Ustilago tritici (Pers.) Rostr.) in wheat (Triticum aestivum L.)

Abstract: Using disomic chromosome substitution lines based on the susceptible wheat cultivar ‘Chinese Spring’, loose smut resistance of wheat cultivars ‘Hope’ and ‘Thatcher’ was shown to be conferred in each case by a single dominant major gene carried on chromosome 7 A (‘Hope’) or 7 B (‘Thatcher’). Partial resistance was determined by genes on an additional eight ‘Hope’ or seven ‘Thatcher’ chromosomes, and similarities were evident between the partial resistance genotypes of‘Hope’ and ‘Thatcher’. ‘Chinese Spring’ exhibited a mean infection value of approximately 50%, indicating a significant level of partial resistance, which was found to be due, in part, to genes on the homoeologous chromosome arms 1 As, 1 Es and 1 Ds, and to cytoplasmic genes. Substitution of the ‘Chinese Spring’ nucleus into the cytoplasm of Aegilops squarrosa, Ae. variabilis or Ae. mutica resulted in increased susceptibility to Ustilago tritici. Several alloplasmic lines of the resistant wheat cultivars ‘Selkirk’ and ‘Chris’ exhibited race-specific susceptibility to U. tritici.

Tomato resistance to Alternaria stem canker: localization in host genotypes and functional expression compared to non-host resistance.

Abstract: The Alternaria stem canker resistance locus (Asc-locus), involved in resistance to the fungal pathogen Alternaria alternata f. sp. lycopersici and in insensitivity to host-specific toxins (AAL-toxins) produced by the pathogen, was genetically mapped on the tomato genome. Susceptibility and resistance were assayed by testing a segregating F2 population for sensitivity to AAL-toxins in leaf bioassays. Linkage was observed to phenotypic markers solanifolium and sunny, both on chromosome 3. For the Asc-locus, a distance of 18 centiMorgan to solanifolium was calculated, corresponding to position 93 on chromosome 3. This map position of the resistance locus turned out to be the same in three different resistant tomato accessions, one Dutch and two American, that are at least 40 years apart. AAL-toxin sensitivity in susceptible and resistant tomato genotypes was compared with AAL-toxin sensitivity in a non-host Nicotiana tabacum during different levels of plant cell development. In susceptible and resistant tomato genotypes, inhibitory effects were demonstrated at all levels, except for leaves of resistant genotypes. However, during pollen and root development, inhibitory effects on susceptible genotypes were larger than on resistant genotypes. In the non-host Nicotiana tabacum, hardly any effects of AAL-toxins were demonstrated. Apparently, a cellular target site is present in tomato, but not in Nicotiana tabacum. It was concluded that three levels of AAL-toxin sensitivity exist: (1) a susceptible host sensitivity, (2) a resistant host sensitivity, (3) a non-host sensitivity, and that the resistance mechanism operating in tomato is different from that operating in Nicotiana tabacum.

The resistance of Hordeum bulbosum and its hybrids with H. vulgare to common fungal pathogens

Abstract: Two tetraploid and two diploid clones of Hordeum bulbosum were screened for resistance to five isolates of powdery mildew which are virulent on cultivated barley. All were resistant and this resistance was also expressed in hybrids with H. vulgare. The tetraploid genotypes were also resistant to isolates of yellow rust and brown rust. These results show that H. bulbosum contains useful genes for resistance to these diseases and that there is a potential to transfer these into cultivated barley.

Resistance to tomato spotted wilt virus in lettuce

Abstract: Tomato Spotted Wilt Virus (TSWV), a thrips-transmitted virus disease, has become a limiting factor in lettuce (Lactuca sativa L.) production throughout Hawaii and several other areas of the world. In this study, two partially resistant lettuce cultivars, Tinto and PI 342517 («Ancora»), were crossed with the susceptible check cultivar Green Mignonette and to each other. Results of resistance tests of the F 1 and F 2 plants suggest that «Tinto» and PI 342517 have the same genes for resistance and that this resistance is partially dominant

Field and Greenhouse Analysis of Variation for Disease Resistance in Tobacco Somaclones

Abstract: Daub, M. E., and Jenns, A. E. 1989. Field and greenhouse analysis of variation for disease resistance in tobacco somaclones. Phytopathology 79:600-605. A total of 854 somaclones of two flue-cured tobacco cultivars were parent cultivar in black shank resistance, but many had greater resistance generated from protoplast cultures, and their progeny analyzed in to bacterial wilt than did NC2326. Most cultivar Coker 319 somaclones greenhouse and field tests for yield, leaf chemistry, and resistance to black were more susceptible than the parent cultivar to black shank but had shank, bacterial wilt, tobacco mosaic virus, and root knot (Meloidogyne bacterial wilt resistance similar to that of Coker 319. Variation in black incognita). Under the culture conditions established in this study, shank and bacterial wilt resistance was slight, and few somaclones had approximately 55% of the somaclones were not self-fertile. Progeny of the responses equivalent to those of the susceptible and resistant control somaclones had normal phenotype and did not differ significantly from the cultivars. However, conditions used in this study reduced the amount of parent cultivars in yield and leaf chemistry. Significant variation was found potential variation. No somaclones were identified with resistance to in resistance to black shank and bacterial wilt, two diseases for which the tobacco mosaic virus or M. incognita. We conclude that genetic variation parent cultivars have low levels of resistance. The variation that was occurred in the somaclones, that the magnitude of variation was slight, and observed in response to these diseases depended on the disease as well as the that the variation depended on both the genotype of the parent cultivar and genotype of the parent. Somaclones of cultivar NC2326 were similar to the the trait. Additional keywords: Nicotiana tabacum, Phytophthora parasitica var. nicotianae, Pseudomonas solanacearum, tissue culture.

Germination and appressorium formation of wheat leaf rust on susceptible, partially resistant and resistant wheat seedlings and on seedlings of other Gramineae

Abstract: Germination and appressorium formation of wheat leaf rust urediospores were studied in two experiments. No consistent differences could be detected between 11 genotypes of wheat (Triticum aestivum), two of barley, one ofTriticum dicoccum, one ofT. dicoccoides, one ofT. boeoticum and one ofAegilops squarrosa. Host genotypes and non-hosts gave similar results, suggesting that the phases before penetration of the host leaf are not affected by the resistance mechanisms operating in hosts and non-host genotypes.

Identification and characterization of resistance to yellow rust and powdery mildew in wild emmer wheat and their transfer to bread wheat

Abstract: In wild emmer wheat three different kinds of genes for resistance to yellow rust were found, namely genes causing overall resistance, genes causing adult-plant resistance and genes which induce resistance detectable at higher temperatures. At least eleven different and probably novel major genes for overall resistance to yellow rust were detected. The inheritance of overall resistance genes and temperature-sensitive genes was found to be mainly dominant, while the latter showed an additive gene action as well. Several new sources of resistance to powdery mildew were found. These include overall resistance, true seedling resistance, adult- plant resistance and partial resistance. There proved to be no serious crossing barrier between tetraploid wild emmer and hexaploid bread wheat. It was shown that genes for resistance as well as other positive traits are readily transferable to bread wheat, while the negative traits of wild emmer can be easily removed. Two or three consecutive crosses with bread wheat appeared to be optimal for developing wild emmer-derived germplasm or varieties.

Apium wild species: novel sources for resistance to late blight in celery.

Abstract: Screening of 144 varieties of celery A. graveolens L. for late blight (Septoria apiicola Speg.) resistance resulted in the detection of significant differences for disease reaction. However, each accession displayed greater than 25 % leaf necrosis area due to the disease pathogen. Hence the magnitude of infection in the least susceptible plants was still too great to use them as a valuable source for resistance. The wild species A. chilense and A. panul exhibited a few discrete yellow spots with very little, if any, pycnidial development. This type of resistance was not observed in any accession of celery screened. The degree of resistance was intermediate in the F1 hybrids between A. graveolens × A. chilense and A. graveolens×A. panul, indicating incomplete dominance. The resistance to late blight found in these wild species and their ability to cross with celery provides a novel germplasm source for breeding celery lines with improved resistance to late blight.

Oxalic acid induced cytological alterations differ in beans tolerant or susceptible to white mould

Abstract: summary Leaf tissues of two white bean (Phuscolus vulgaris L) cultivars, one susceptible and one tolerant to white mould [Sclerotinia sclerotinrum (Lib) de Bary], were treated for different times with oxalic acid Tissues were prepared by both thin sectioning and freeze-fraeture techniques for electron microscopy The plasma membrane of the resistant cultivar appeared more tolerant to damage induced by oxalic acid than that of the susceptible cultivar At the same concentration of oxalic acid the plasma membrane and chloroplasts of the susceptible cultivar were affected more, and ruptured more quickly, than those of the tolerant one In thin sections, the ruptured organelles were partially or completely disorganized In replicas of freeze-fractured preparations of the plasma membrane, increased protrusions, wrinkles, breakages and ruptures were associated with increasing exposure to oxalic acid Damage was more severe in the plasma membrane of the susceptible cultivar than in that of the tolerant one Measurements of the conductivity of water bathing leaf discs of the two cultivars showed that the susceptible cultivar led to a higher conductivity than the resistant one, indicating that the injury and rupturing of the plasma membrane were closely related to membrane stability

Infection and control of stripe rust in wheat spikes

Abstract: The levels of resistance to stripe rust (Puccinia striiforrms f. sp. tritici) in the leaf and in the spike were related in most wheat (Triticum aestivum L.) cultivars. Cultivars with seedling resistance to stripe rust were not infected in the spike. However, two cultivars, Otane and Advantage, with adult plant resistance on the flag leaf, were infected in the spike. In a susceptible cultivar, Takahe, infection of florets occurred from ear emergence until flowering. In susceptible cultivars, pustule formation began at flowering, approximately two weeks after infection, with the maximum percentage of florets with pustules occurring during milk development. A single application of triadimefon to heavily infected ‘Takahe’ wheat at full ear emergence reduced floret infection from 75% to 20% and increased crop yield by 34%.