Phenotypic and molecular confirmation of durable adult plant leaf rust resistance (APR) genesLr34+,Lr46+ andLr67+ linked to leaf tip necrosis (LTN) in select registered Indian wheat(T. aestivum)genetic stocks

Abstract

Nearly twenty thousand wheat lines were phenotyped for the presence of leaf tip necrosis (LTN), a phenotypic trait linked to adult plant leaf rust resistance (APR) genes, viz. Lr34, Lr46 and Lr67 having pleiotropic association with multiple disease resistance genes. Thirty-six lines showed varied expression of LTN and moderate level of leaf rust severity at adult plant stage with slow rusting (disease progress at a retarded rate). Seedling resistance test (SRT) revealed susceptible and mixed infection types, a characteristic of adult plant resistance (APR) genes. Further molecular confirmation for the presence of these genes using available microsatellite markers revealed that of the 36 lines, five lines carried Lr46 + alone and five other lines carried Lr67 + alone. Seven lines carried the combination of Lr34 + and Lr67 + while six lines confirmed to carry the combination of Lr46 + and Lr67 +. Remarkably three lines carried all the three APR genes, viz. Lr34 +, Lr46 + and Lr67 +. All these stocks can be a source of APR multiple disease resistance genes. Ten lines were not confirmed to carry any of the genes but still had LTN and SRT results showing an infection type typical of APR genes and these can be the source of identifying newer APR genes. The resistance based on minor APR genes when combined with a few additional minor genes in the background of high yielding cultivars is expected to have high level of race non-specific resistance and to be durable.