Development of white-grain pre-harvest sprouting tolerant and pyramided protein-rich leaf rust resistant wheats using molecular breeding

The present study was undertaken for developing pre-harvest sprouting tolerant (PHST) wheat genotypes using marker-assisted backcross breeding (MABB). A major QTL for PHST was introgressed into an elite Indian wheat cv. Lok1 that is PHS susceptible. These PHST lines were also pyramided with one gene each for high grain protein content (Gpc-B1) and leaf rust resistance (Lr24). For introgression of PHST QTL, initially Lok1 was separately crossed with each of the two donors (PHS tolerant white-grained AUS1408 and CN19055). Backcrossing in each generation was followed by foreground and background selections using SSR markers. In advanced lines, KASP assay was also carried out for the candidate gene TaMKK3-A underlying the PHST QTL. The MAS derived lines homozygous for PHST QTL were screened for PHS using simulated rain chambers resulting in the selection of 10 PHST lines. For pyramiding of three QTL/genes (PHST QTL, Gpc-B1, and Lr24), MABB derived BC4F2 plants (from the cross Lok1/CN19055) were crossed with a MAS derived BC2F5 line [Lok1 (Gpc-B1 + Lr24)] developed earlier by us in the same background of Lok1. After foreground MAS followed by PHS screening, four advanced lines carrying all the three QTL/genes in homozygous condition were selected. These lines exhibited high level of PHST (PHS score 2–3) associated with significant improvement in GPC with no yield penalty and resistance against leaf rust under artificial epiphytotic conditions.