Aegilops-derived specific genes in common wheat and their introgression into Indian bread wheat cultivars

Abstract

Nine diverse wheat stocks carrying Aegilops-derived known genes conditioning resistance to rusts and 39 accessions of Aegilops, viz., Ae. squarrosa (18), Ae. speltoides (17), Ae. umbellulata (3) and Ae. comosa (1) were evaluated for adult plant resistance to stem rust, leaf rust and stripe rust and seedling resistance to powdery mildew. The study revealed that the genes Lr9, Lr28, Lt32, Lt37, 5132 and Yt8 conditioned a high degree of resistance whereas Lr21, Lr22a, 5133, 5138 and Yt17 conferred moderate resistance. Aegilops comosa derived gene 5134 was ineffective against stem rust in the Nilgiris. The dominant leaf rust resistance genes Lr9, Lr28, Lt32 and Lt37 were introgressed into 16 bread wheat cultivars through a backcross programme. The improved cultivars carrying Lr28 were observed to be moderately resistant to powdery mildew (score 2) whereas the backcross derivatives carrying Lr9 and Lt37 showed enhanced susceptibility to powdery mildew (score 4) as compared to the recurrent parents (score 3). Accessions of Ae. speltoides, a suspected donor of B genome, exhibited a high degree of resistance to rusts and powdery mildew whereas the accessions of Ae. squarrosa, the donor of the D genome, were found susceptible to rusts but showed moderate to high degree of seedling resistance to powdery mildew. In general, the accessions of Ae. umbellulata and Ae. comosa carried high resistance to rusts and powdery mildew although the former showed high susceptibility to stem rust. Five wheat stocks were found to be non-carriers of genes for hybrid necrosis (nel ne2) whereas four stocks carried a weak allele for progressive hybrid necrosis.