Inheritance And QTL Analysis For Slow Mildewing Resistance In Wheat Cultivar Lumai 21

Powdery mildew is one of the most serious wheat diseases in China. The use of resistant cultivars has been proven to be an effective and environmentally safe strategy for controlling the disease. Since slow-mildewing is more durable than race-specific resistance, it is very important to study the inheritance and QTLs of slow-mildewing resistance in wheat breeding.Both parents and F1,F2,BC1P1,BC1P2,F2:3 and F2:4 derived from the cross Lumai 21 (resistant)×Jingshuang 16 (susceptible) were used for genetic analysis. A total of 1375 molecular markers were used to map QTL for slow-mildewing resistance in F2:3 and F2:4 populations. Bulked segregant analysis (BSA) was used to facilitate the identification of molecular markers associated with slow-mildewing resistance. Field trials were conducted in Beijing and Anyang during 2005-06 and 2006-07 cropping seasons, respectively. The parents and lines were planted in a randomized complete block design with two to three replications. Artificial inoculation was carried out in Beijing with highly virulent isolate E20 of Blumeria graminis f. sp. tritici and the powdery mildew severity on penultimate leaf was evaluated from one to three times after heading.The results showed that the inheritance of slow mildewing resistance in the population from the cross Lumai 21×Jingshuang 16 was fit to the additive-dominant genetic model and additive effect was higher, and at least three to four resistance genes were detected. Transgressive segregation indicated that Jingshuang 16 might have contributed one minor gene for resistance. Therefore, Lumai 21 holds at least two to three slow resistance genes to powdery mildew. The broad-sense heritability of resistance was from 0.53 to 0.78, and the narrow-sense heritability of resistance was 0.41.With the method of composite interval mapping (CIM), two quantitative trait loci (QTL) for slow mildewing resistance were detected on chromosomes 2BS and 2DS, respectively. The QTL on chromosome 2BS is located between the microsatellite markers Xbarc98 and Xbarc18 with 6.0 cM away from Xbarc98, explaining 11.2 to 28.4% of the phenotypic variation across two environments. The other QTL on chromosome 2DS is located at the marker interval Xbarc168-Xwmc18, with 12.7 cM away from Xwmc18, accounting for 7.1 to 15.9% of the phenotypic variance. The two QTLs associated with slow mildewing resistance were derived from Lumai 21.The QTL on chromosome 2DS may be a new gene for powdery mildew resistance.