Pathotyping Puccinia triticina and resistance of wheat cultivars to leaf rust in India during 2019-2022

The surveys for the occurrence of leaf rust (Puccinia triticina) in wheat-growing areas of India were conducted from 2019-2022. The leaf rust appeared sporadically late in the season, and major outbreaks were not recorded. Twenty-nine pathotypes were identified in 963 wheat leaf rust samples analyzed. Pathotype 52 (121R60-1; MHTKL) comprised 55.7% of the population, followed by 77-5 (121R63-1; THTTM), and 52-4 (121R60-1,7; MHTKL) in 19.4 and 10.1% of the samples, respectively. The remaining 30 pathotypes were observed in 14.8% of the pathotyped samples only. The field population of P. triticina was avirulent on Lr9, Lr19, Lr24, Lr25, Lr29, Lr32, Lr39, Lr45, Lr47, and Lr80. A considerable genetic diversity for leaf rust resistance was found in 42 wheat varieties recommended for cultivation from 2020-2022. Twelve Lr genes (Lr1, Lr2a, Lr3, Lr10, Lr13, Lr23, Lr24, Lr26, Lr34, Lr37, Lr46, and Lr68) were inferred in 37 varieties. Among these Lr13, and Lr23 were observed in 13 varieties each followed by Lr10 in 11 varieties, and Lr26 and Lr1 in 5 varieties each. The presence of Lr24, Lr34, Lr37, Lr46, and Lr68 was confirmed through molecular markers. In controlled polyhouse studies, the slow-leaf rusting was observed in five wheat varieties (DBW327, HD3293, HD3298, HD3369, and VL2041) whereas 26 of the 31 varieties conferred race-specific adult plant resistance. These findings would help to further streamline the future resistance breeding program in the Indian subcontinent and strategic management of wheat leaf rust.