Postulation of leaf rust resistance genes in Indian and exotic wheat germplasm using near-isogenic lines (NILs) and molecular markers

Leaf rust caused by Puccinia triticina Eriks. (Pt) is one of the most devastating fungal diseases affecting wheat (Triticum aestivum L.) production worldwide. Deployment of resistant cultivars is a prominent eco-friendly approach to manage this disease. But major constraint in this case is emergence of new pathotypes of pathogen due to faster evolution. Widening the gene pool by gene mining from diverse panel is the key strategy to keep pace with the ever-evolving pathogen. So, in this study attempts were made to identify leaf rust resistance genes in a selected set of 149 germplasm lines by seedling reaction test against two most prevalent Pt pathotypes, 77-9 (MHTKL) and 77-5 (THTTM) and for field resistance at Ludhiana and Gurdaspur during 2018-2021. Based on seedling infection type (IT) data, 88 lines were found resistant (low IT; 0-2) and 39 lines were susceptible (high IT; >= 3). Under field conditions, 77 lines showed highly resistance response across the locations and years. Gene postulation in the test germplasm was done by gene matching technique and further confirmed by linked molecular markers; which revealed the presence of 11 Lr genes singly or in combinations. Leaf rust resistance gens; Lr9, Lr19, Lr24, Lr34, Lr37, Lr42, Lr45, Lr52, Lr57, Lr58 and Lr76 were detected in 4, 7, 10, 1, 7, 33, 41, 44, 2, 24 and 6 lines respectively. The present study's resistant germplasm lines can be utilised as resistant parents in crosses intended for pyramiding and the deployment of leaf rust resistance genes.