Uncovering novel sources for Karnal bunt resistance in bread wheat using multi-environment phenotyping

Karnal bunt caused by Tilletia indica remains a significant constraint to global wheat trade due to its detrimental impact on grain quality. Developing and deploying resistant cultivars is the most effective and sustainable management strategy, given the impracticality of large-scale chemical control and the limited efficacy of cultural practices. Two hundred fifty-nine diverse wheat genotypes, including genetic stocks, released varieties, advanced breeding lines, and exotic introductions, were evaluated for resistance to Karnal bunt under artificial inoculation in nine environments over two crop years (2022–23 and 2023–24). Syringe inoculation method was employed, and genotypes were classified into five resistance categories based on Coefficient of Infection (CI) values. CI ranged from 0.0% (highly resistant) to over 58% (highly susceptible). Significant variation was observed among genotypes and locations, highlighting genetic variability and strong influence of environmental factors on disease development. Across years, a consistent trend highlighted the importance of phenotyping in understanding the potential stability of resistance under different conditions. A core set of 28 stable resistant lines with an average CI below 1.0 was identified, including three genotypes TAB368.25//BUL//TURAACO, MRNG/BUC’S’CLD’S’PLN’S’X12, and HD29 that consistently showed complete resistance across all environments. The predominance of genetic stocks in this core set reinforces their critical role as reservoirs of durable resistance. These promising genotypes hold strong potential for incorporation into breeding programs to develop Karnal bunt-resistant wheat cultivars, thereby contributing to sustainable disease management and safeguarding wheat production and trade.