Response To Powdery Mildew And Analysis Of Resistance Genes In Wheat Cultivars

Wheat powdery mildew, which is caused by Blumeria graminis (DC.) E.O. Speer (Bgt, syn.Erysiphe graminis DC. f. sp. tritici Em. Marchal), is one of the most epidemic diseases worldwide. Thefungus B. graminis can cause severe yield reductions in wheat. At present, this disease occurs in nearlyall the wheat production regions in China. Although fungicides are routinely used to control powderymildew, application of resistant wheat cultivars is one of the important measures in controlling powderymildew. Understanding of inheritance of powdery mildew resistance in wheat commercial cultivars is ofgreat importance for controlling of this disease with host resistance. In this study, reactions to differentisolates of Bgt were tested in the commercial wheat cultivars, wheat lines involved in the national yieldtrials, and core collections. The presence of known powdery mildew resistance genes was detectedusing the gene-specific markers.1. Seedling reactions to 11 Bgt isolates in 446 wheat cultivars recently released or breeding linesinvolved in the national yield trials from 2008 to 2012 were tested. The presence of known powderymildew resistance genes Pm2, Pm3, Pm4a, Pm8, and Pm21 was detected using gene-specific markers.Seven cultivars were resistant to all the isolates with different spectra of resistance, and 227 cultivarswere resistant to at least 1 isolates, accounting for 50.9%. Based on the origin of the wheat cultivars,resistance of the wheat cultivars from the Yangtze River region appeared to be superior to the cultivarsfrom other regions, the frequency of resistance to 1-11 isolates in the cultivars from this region was42.4%. A few cultivars that were resistant to more than 7 isolates were detected in some cultivars fromthe irrigation regions of the Southern and Northern parts of Yellow-Huai River groups. However, mostcultivars from the Yellow-Huai River Dryland group of cultivars were able to resistant to one or twoisolates. The frequencies of cultivars from various regions without resistance to any isolates rangedfrom 27.3% to 67.8%. The results of adult resistance test indicated that the cultivars from the YangtzeRiver group had higher percentage of resistance than those from other groups. Molecular detectiondemonstrated that genes Pm4a and Pm21 were detected mainly in the cultivars originated from YangtzeRiver region. Although genes Pm2 and Pm8 were present in the cultivars from all the regions, Pm8 wasdetected mainly in the cultivars originating from Yellow-Huai River groups region.2. Out of 1160 entries in the core collection, the proportions of entries resistant to isolate E09were 3.4% and 4.2% in the landrace and improved cultivars, respectively. The SouthwesternAutumn-Sown Spring Wheat Zone and the Xinjiang Winter-Spring Wheat Zone had higherpercentages of E09-resistant cultivars than other wheat zones. None of the cultivar from the SouthernAutumn-Sown Spring Wheat Zone, Northeast Winter Wheat Zone, and Northern Spring Wheat Zonewas resistant. This indicates that there is a need to select resistant entries as recurrent parents forefficient use of existing core collection and to construct applied core collection for resistance topowdery mildew.3. Seedling reactions to 17 Bgt isolates in 12 wheat cultivars recently released or breeding linesinvolved in the national yield trials were tested. The presence of known powdery mildew resistance genes was detected using gene-specific markers. These cultivars were resistant to at least 11 isolateswith different spectra of resistance. Isolates E09, E20, and Bg2 were used to test the F2populations foranalyzing genetic control of powdery mildew resistance in these cultivars. The results demonstrated thatsingle dominant gene(s) in these cultivars was responsible for the resistance against these Bgt isolates.Based on the reactions to different isolates and molecular marker analysis, Pm2 was most likelyassociated with the resistance to powdery mildew in Liangxing 66, and powdery mildew resistance inother cultivars may arise from unknown resistance genes. The powdery mildew-resistant cultivarsidentified in the present study not only diversify resistant cultivars in wheat production, but also provideuseful resistant resources for developing wheat cultivars against powdery mildew.