Neupane R B, Sharma R C, Duveiller E, Ortiz-Ferrara G, Ojha B R, Rosyara U R, Bhandari D, Bhatta M R
Institute of Agriculture and Animal Science, Rampur, Chitwan, Nepal.
CIMMYT, South Asia Regional Office, P.O. Box 5186, Kathmandu, Nepal.
Plant Dis. 2007 Jun;91(6):692-697. doi: 10.1094/PDIS-91-6-0692.
A number of exotic wheat (Triticum aestivum) genotypes resistant to spot blotch caused by Cochliobolus sativus are being used to improve the resistance of commercial cultivars in the warm regions of South Asia. The objective of the present study was to determine the inheritance of field resistance to spot blotch in two resistant (R) wheat genotypes, 'Chirya.3' and 'Milan/Shanghai #7' (MS#7), which were crossed to a susceptible (S) commercial cultivar, 'BL1473.' The two resistant genotypes also were crossed to determine allelic relationships for resistance between them. Spot blotch severity was recorded on the parents and on F, F, and F progenies. The F plants from the two crosses between susceptible and resistant genotypes had low disease severity like the resistant parents, indicating that resistance in Chirya.3 and MS#7 is conditioned by dominant gene action. The F plants segregated in 3R:1S ratios, and the F families showed the ratio of 1R:1S:2S, segregating for R and S, suggesting that resistance in the two resistant parents is conditioned by a single, dominant gene. The F plants from the cross between the two resistant genotypes were resistant, whereas their F progenies segregated in 15R:1S, suggesting that the resistance genes in MS#7 and Chirya.3 are nonallelic. These simply inherited sources of resistance could be useful for improving spot blotch resistance in the warm regions of South Asia and also may offer useful diversity to breeding programs for developing spot-blotch-resistant wheat cultivars in other regions.
一些对小麦根腐平脐蠕孢引起的叶斑病具有抗性的外来小麦（普通小麦）基因型正被用于提高南亚温暖地区商业品种的抗性。本研究的目的是确定两个抗性（R）小麦基因型“Chirya.3”和“米兰/上海#7”（MS#7）对叶斑病田间抗性的遗传方式，这两个基因型与一个感病（S）商业品种“BL1473”进行了杂交。这两个抗性基因型也进行了杂交，以确定它们之间抗性的等位基因关系。在亲本以及F1、F2和F3后代上记录叶斑病严重程度。感病和抗性基因型之间两个杂交组合的F1植株病害严重程度较低，与抗性亲本相似，表明Chirya.3和MS#7中的抗性受显性基因作用控制。F2植株以3R:1S的比例分离，F3家系表现出1R:1S:（2S）的比例，R和S发生分离，表明两个抗性亲本中的抗性受单个显性基因控制。两个抗性基因型杂交组合的F1植株具有抗性，而它们的F2后代以15R:1S的比例分离，表明MS#7和Chirya.3中的抗性基因是非等位的。这些简单遗传的抗性来源可能有助于提高南亚温暖地区对叶斑病的抗性，也可能为其他地区培育抗叶斑病小麦品种的育种计划提供有用的多样性。
