Molecular introgression of leaf rust resistance gene Lr34 validates enhanced effect on resistance to spot blotch in spring wheat

The adult plant leaf rust resistance gene Lr34 was introduced using marker assisted selection (MAS) into an Indian wheat cultivar HUW510. Lr34 is associated with enhanced resistance to spot blotch. However, this effect has not been validated previously via introgression from one genetic background into another using MAS. The donor parent was the CIMMYT breeding line Picaflor#1. The morphological marker leaf tip necrosis (LTN+) and co-dominant STS marker csLV34 were used to track Lr34. Background selection was made with 90 simple sequence repeat (SSR) loci. BC3F3 to BC3F5 progenies were tested for spot blotch resistance. The results showed that the introgression of Lr34 can lead to enhanced resistance to spot blotch. Eleven selections retained in the cv. HUW510 background carried Lr34 and had a genetic background estimated to be as high as 95% that of the recurrent parent. The mean AUDPC for spot blotch in BC3F5 lines of Picaflor#1 × HUW510 was substantially lower (917 at timely sown conditions and 1015 under late sown conditions) than the recipient parent HUW510 (1332 at timely sown conditions and 1412 under late sown conditions). The results showed that introgression of Lr34 can lead to enhanced resistance to spot blotch.