QTL Mapping For Adult-Plant Resistance To Powdery Mildew In Bread Wheat

Powdery mildew, caused by Blumeria graminis f sp. tritici, is a major wheat disease in China, resulting in a great deal of loss of wheat grain yield. Mapping of QTLs for adult-plant resistance to powdery mildew (or slow mildewing ) is of great importance in molecular marker-assisted selection (MAS) for breeding resistant wheat cultivars.Up to date, QTL analysis of adult-plant resistance (APR) against powdery mildew has not been reported in China. In the present study, QTL mapping of APR was conducted using a doubled-haploid (DH) population derived from the cross (Fukuho-komugi × Oligoculm) and a F_2:3 population from the cross (Bainong64 × Jingshuang16). The methods and main results are described as follows:1. A doubled-haploid (DH) population from an intervarietal cross between the Japannese cultivar Fukuho-kumugi and the Israeli wheat line Oligoculm was prouduced by means of wheat × maize crosses. One hundred and seven DH lines were genotyped with 313 SSR markers and 37 RFLPs. Field trials were conducted in Beijing and Anyang, respectively, in 2003-2004 crop season. 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 leaves was evaluated for 5 times with an interval of 7 days. The maximum disease severity on penultimate leaf was scored in Anyang under natural inoculation around May 18, 2004. Linkage analysis indicated that the genetic map consisting of 313 SSR and 37 RFLP markers covered 21 wheat linkage group with a total genetic distance of 3101cM. Four QTLs for adult-plant resistance to powdery mildew were detected on 1A, 2B, 4B and 7D, explaining 13.6%, 6.6%, 8.9% and 12.7% of phenotypic variance, respectively.2. A total of 218 F_2:3 families were derived from the cross between Bainong 64 and a susceptible line Jingshuang16. Field test for powdery mildew resistance at the adult plant stage was carried out under artificial inoculation in Beijing with highly virulent isolate E20 of Blumeria graminis f. sp. tritici in 2004, and the powdery mildew severity on penultimate leaves was evaluated for 5 times with an interval of 7 days. The population was genotyped with 100 SSR and 58 AFLP markers. Linkage analysis indicated that the genetic map consisting of 100 SSR and 58 AFLP markers covered 21 wheat linkage group with a total genetic distance of 3114 cM. With the method of composite interval mapping (CIM), 3 QTLs for adult-plant resistance to powdery mildew were detected on 2BS, 2BS and 5AL, explaining 22.4%, 39.5% and 31.8% ofphenotypic variance, respectively.