Development And Characterisation Of Wheat Germplasm Resistant To Cereal Cyst Nematode And Powdery Mildew

Cereal cyst nematode(CCN, Heterodera spp.) has occurred in major wheat(Triticum aestivum L.) producing regions in China. Developing wheat cultivars resistant to CCN is limited due to the shortage of effective sources of resistance. Madsen, a winter wheat cultivar released in the Pacific Northwest Region of the USA, is highly resistant to certain CCN populations from China. However, it is difficult to use this cultivar in breeding programs because of its late heading and maturity. Additionally, it is necessary to improve resistance to powdery mildew when Madsen is used. In the present study, wheat germplasm lines that were resistant to CCN and powdery mildew were developed by means of crossing and backcrossing strategy using Madsen as the source of resistance to CCN.1. A number of lines were developed from the crosses between Madsen and the Chinese wheat commercial cultivars Yannong 21, Jimai 19, Yanzhan 4110, and Xumai 856. Results of field test indicated that out of 172 lines tested 83 were resistant to the Xingyang population of H. avenae(pathotypes H43), accounting for 48.25%, and 89 lines(51.74%) were susceptible. Among the 132 lines tested in Xuchang, Henan province, where H. filipjevi(pathotypes Hfc-1) occured, 111 lines(84.09%) were resistant and 21 line were susceptible. Using 3 Blumeria graminis f. sp. Tritici(Bgt) isolates, 139 lines were tested against powdery mildew at the seedling stage, resulting in 29 lines that were resistant to these isolates and the remaining 110 lines were susceptible, 64 lines were tested against powdery mildew at the adult plant stage, 120 lines were tested against powdery mildew at the adult plant stage of maximum disease sevenity sevennity.2. Lines H3714 and H4058 were developed from BC1F4 progenies. Tests under both natural infestation and artificial inoculation conditions indicated that resistance of H3714 and H4058 to the H. avenae Xingyang population(pathotype Ha43) and the H. filipjevi Xuchang population(pathotype Hfc-1) from Henan province was superior to that of Yannong 21 and Jimai 19. Results of the field test inoculated with a mixture of Bgt isolates demonstrated that both lines showed adult plant resistance to powdery mildew, and line H4058 was also resistant to different Bgt isolates at the seedling stage. The heading date of these lines was comparable to that of Yannong 21 and Jimai 19, and obviously earlier than that of Madsen. The fragments of chromosome 2NS from Aegilops ventricosa were detected in lines H3714 and H4058 using a pair of chromosome-specific primers VENTRIUP-LN2 and the molecular markers Vlr2.6-3′-Vlr2.4-5′ and VRGA-F11-VRGA-R5 that were specific for Vrga1 D gene from Ae. ventricosa. Results of Illumina ISelect 90 K SNP assay showed that the two lines differed in their chromosome constitutions. Two thirds of the polymorphic SNPs were identical and the remaining one third was different among 4918 polymorphic SNPs between the two sib lines. The newly developed wheat lines H3714 and H4058 can be used as effective sources of resistance in developing CCN-resistant wheat cultivars.