Genetic analysis of adult plant resistance to powdery mildew in pea (Pisum sativum L.)

Summary An analysis of adult plant resistance of powdery mildew in 15 F₁, F₂ and F₃ populations of pea derived from crossing 15 diverse and susceptible lines with one resistant line revealed that resistance to powdery mildew is controlled by duplicate recessive genes. The genes were designated as er₁ and er₂.Disease reaction showed independent segregation with three known markers in the resistant parent, namely, af (afila, chromosome 1), st (stipule reduced, chromosome 3) and tl (clavicula, chromosome 7).Contribution form the Department of Genetics and Plant Breeding Banaras Hindu University, Varanasi-221005, India.     

Reactions of Hordeum spontaneum to infection with two cultures of Puccinia hordei from Israel and United States

Summary The reactions to infection with two cultures of Puccinia hordei were determined for 292 Hordeum spontaneum (syn. H. vulgare ssp. spontaneum) accessions, collected at 16 sites which encompassed the ecological range of H. spontaneum in Israel. Culture Tel-Aviv was from Israel and culture 57.19 was from the United States. Fifty-two percent of the accessions were resistant to culture Tel-Aviv and 67% were resistant to culture 57.19. Forty-three percent of the accessions were resistant to both cultures. The average infection type (IT) of accessions within sites ranged from 2.7 to 7.5 on a 0–9 rating scale. The results showed that the presence of Ornithogalum species, the alternate hosts of P. hordei, may increase the percentage of H. spontaneoum accessions resistant to P. hordei. More accessions were resistant at sites where humidity at 1400 was higher, the annual evaporation was lower, and where the glumes were shorter. Kernel weight and annual rainfall was not correlated with resistance. A lower percentage of H. spontaneum accessions were resistant to P. hordei culture Tel-Aviv from Israel than to culture 57.19 from the United States. In a previous study a lower percentage of H. spontaneum accessions also was found to be resistant to a culture of Erysiphe graminis hordei from Israel than to cultures from other countries. Previous studies also have shown that cultures of P. hordei and E. graminis hordei from Israel have many genes for virulence on barley, and that H. spontaneum accessions from Israel have many genes for resistance to these two pathogens. Previous results and the results reported in this paper support the hypothesis of coevolution of resistant host genes and virulent pathogen genes where hosts and pathogens have coexisted for many thousand years.     

Short Communication Comparison between QTL analysis of powdery mildew resistance in barley based on detached primary leaves and on field data

A quantitative trait loci (QTL) analysis of quantitative powdery mildew resistance was performed on 216 doubled haploid lines derived from a cross between the winter-barley varieties ‘Igri’ and ‘Danilo’ using 67 RFLP loci. Resistance to powdery mildew was determined in the field with natural infection and on detached primary leaves with a specific isolate. The major QTL found in both sets of analysis mapped to the same chromosomal region. No further QTL could be found in the analysis based on detached leaves and one additional minor QTL was found in the analysis based on field data.     

Powdery-mildew-resistance genes Mla29 and Mla32 in H. spontaneum derived winter-barley lines

Allelism to the highly polymorphic Mia locus was demonstrated for the powdery-mildew resistance of two Hordeum spontaneum derived winter–barley lines, ‘110-4 × Sonja’ and ‘142–29 × Dura’, by testing the F2 progeny of crosses between these lines and the winter-barley cv. ‘Triton’ (Mlal3) with two appropriate isolates. The results were confirmed by RFLP analysis, using the probe MWG 1H036, which is very closely linked to the Mia locus. The designations Mla29 and Mla32 are proposed for the genes identified in the two lines.     

小麦白粉病抗源材料的有效抗病基因分析

采用携带有不同毒性基因的白粉菌菌株进行苗期接种，通过与已知抗病基因材料抗谱的相似性比较分析，对３０多个小麦抗白粉病材料的有效抗病基因进行了测定，其中１份抗源材料具Ｐｍ２＋６；７份具Ｐｍ４ａ；１０份具Ｐｍ４ｂ；２份具Ｐｍ５；４份与小白冬麦的抗性相同，小白冬麦含有一特定的抗病基因；另外有８份材料的抗谱异于所供试的所有已知基因系，从中可能鉴定出新的抗病类型     

Identification of new sources for resistance to powdery mildew in H. spontaneum-derived winter barley lines

Twenty four barley lines derived from the F ₇generation of crosses between two winter barley cultivars and different accessions of Hordeum spontaneum Koch collected in Israel were tested against a set of ten European and five Israeli powdery mildew cultures, possessing virulence genes which completely match the spectrum of known mildew resistance genes. The comparison of reaction patterns justified the conclusion that new genes for resistance have been conferred from H. spontaneum which also differ from genes previously identified in other wild barley accessions from Israel. Participation in the expression of the resistance reaction of one of the two barley cultivars used in the development of the lines is well documented in some cases. The majority of the lines was found to be highly resistant against all or almost all European isolates, while various kinds of reactions were observed against the Israeli cultures. The effective transfer of novel mildew resistance from H. spontaneum into winter barley confirms similar results with spring barley, indicating natural wild barley populations in Israel as a significant gene pool for yet unexploited mildew resistance in barley.     

Genetic differentiation in the French population of Erysiphe cichoracearum, a causal agent of powdery mildew of cucurbits

The relative incidence of Erysiphe cichoracearum and Sphaerotheca fuliginea , both agents of powdery mildew of cucurbits, was determined from 275 samples of mildewed leaves of cucurbits collected in 1994 from five regions of France. E. cichoracearum was identified in 9 to 39% of the mildewed leaf samples from four of the regions but was not detected in samples from the Mediterranean island of Corsica. The genetic structure of the French population of E. cichoracearum was examined using RFLPs of the ribosomal internal transcribed spacers amplified by PCR, random amplified polymorphic DNA (RAPD) markers, pathogenicity and mating-type tests. Forty-one isolates, including one from England, were analysed. Cluster analysis from 147 RAPD fragments using 16 primers revealed the existence of three distinct genetic lineages corresponding to three rDNA haplotypes (designated groups A, B and C). Bootstrap, genetic diversity, gametic disequilibrium and private allele analyses supported this differentiation. The genetic differentiation observed in the French population was not related to the geographical origin of the isolates. Group A isolates may be more specialized on melon as, with one exception, they were of race 1 (growth on four of the five melon cultivars tested) in comparison with group B and C isolates, which were of race 0 (growth on IranH only). Thus, the genetic differentiation observed may indicate a host-specialized subdivision within the French population of E. cichoracearum from cucurbits. Gametic disequilibrium analysis among RAPD loci and biological observations suggest that the sexual stage is of minor importance for epidemics of E. cichoracearum on cucurbits.     

沙打旺白粉病流行规律及化学防治初探

白粉病是沙打旺的一种主要病害，高温、潮湿季节发病率较高，危害较严重。发病初期用粉锈宁喷雾防治，可以有效地控制病害的扩散蔓延，防治效果达到74.9%。     

Identification by genetic analysis of two races of Erysiphe polygoni DC. causing powdery mildew disease in mungbean

Powdery mildew disease is one of the important foliar diseases of mungbean. Earlier, resistance sources have been identified and their genetic nature studied, but there is no information on race identification of Erysiphe polygoni so far. Different genotypes having combinations of the host resistance genes Pm₁Pm₁Pm₂Pm₂‘TARM‐1’, Pm₁Pm₁pm₂pm₂ (S‐158‐16) and pm₁pm₁Pm₂Pm₂ (S‐2‐4‐1) and no resistance genes pm₁pm₁pm₂pm₂ (TPM‐1) were used in the present investigation. The genotypes were screened with four isolates from Akola, Trombay, Jabalpur and Gauribidanur centres in India. The interactions of resistant differentials with the Akola isolate were different from the other three isolates. The inheritance patterns of different resistance genes in various crosses also differed with respect to the Akola isolate. The variation observed in the Akola isolate could be explained as the result of mutation of the dominant avirulence Avr₁Avr₁ genes to virulence avr₁avr₁ genes corresponding to host resistance Pm₁Pm₁genes. Therefore, the Akola isolate is identified as a second race of E. polygoni.