Identifying chromosome regions conferring Karnal Bunt resistance in wheat using deletion stocks and source of resistance in winter wheat

Karnal bunt of wheat (Tilletia indica) is a disease of global importance. Resistance breeding is the main option for combating the disease in endemic areas. The disease appearance is highly dependent upon the environmental conditions prevailing at heading to flowering stage of the crop. As such, resistance has been identified and incorporated in elite germplasm by way of screening a large number of wheat genotypes. However, the whole system of developing high yielding KB resistance wheat is highly cumbersome due to artificial inoculations which are labour intensive, time consuming and prone to environmental variations. Therefore, use of molecular markers may provide rapid and reliable evaluation of the germplasm. KB resistance has been shown to be associated with chromosome number 5B, 4B, 3, 6A, 1AL,4BL,5D and 3BL using WH 542 x HD 29, WH 542 x W485 (RILs) and micro RIL population from the cross KBRL 22/5*PBW343. Evaluation of deletion stocks provides direct evidence of the chromosome regions linked with resistance. Such stocks developed for all the chromosomes in the background of Chinese spring (received from Dr. B S Gill, Director, Wheat Genomic Research Centre, Kansas State University, United States under a collaborative project) were evaluated against Karnal bunt under artificial inoculation conditions. The stocks showing deletions on 1AS, 2AS, 6AS, 4AL, 4BS, 6BS, 6BL, 7BL, 1DS, 1DL, and 6DS have shown very high disease during the last 3 years of evaluation (2005–06 to 2007—08) as compared to Chinese spring, indicating their association with KB resistance. Another set of 792 winter wheat lines received from Dr. R L Bowden and Art Clatt, KSU US under the collaborative project with USDA, was evaluated against KB in the year 2006–07 and 2007–08. Two methods were followed to synchronize the heading stage with the suitable inoculation time (Feb-March) i.e. i) vernalization for a period of 28 days and ii) early sowing, combined with increased photo period by providing flood lights. Out of the lines tested, 8 lines (NI98414/WESLEY, OGALLALA/TX92D7960//BIG, DAWG/TX92U2317, 700-2, 701-14, 703-9, U5237(2)-16, U5240(1)-19) in 2006–07 & 2007–08 and 83 lines in 2007–08 showed less than 1% KB infection in the Winter Wheat Karnal Bunt Nursery (WWKBSN). The promising winter wheat lines are being utilized in the breeding programme.