RESISTANCE TO KARNAL BUNT (TILLETIA-INDICA MITRA) IN SYNTHETIC HEXAPLOID WHEATS DERIVED FROM TRITICUM-TURGIDUM X T-TAUSCHII

Synthetic hexaploids (SH) developed at the International Maize and Whe at Improvement Center (CIMMYT), involving four Triticum turgidum and n ine T. tauschii parents, were evaluated for resistance to Karnal bunt (KB) (Tilletia indica Mitra) during three crop seasons over three year s at Ciudad Obregon, Sonora, Mexico. Ten tillers of each SH at boot st age, taken at random, were injected with a suspension of sporidia in w ater (10,000 spores/ml of water). At maturity the inoculated spikes we re threshed individually and evaluated for the percentage KB-infected grains. Based on the mean KB score of each entry for three seasons, 49 % of the SH were immune (0 % infection) to KB. Highly resistant expre ssions characterized the SH which appeared to be influenced by the res istance of their T. turgidum and/or T. tauschii parents. The overall m ean infection of the SH wheats was 0.24 % compared to 56.14 % in the s usceptible bread wheat check cultivat 'WL711'. Transfer of K.B resista nce genes from SH wheats into bread wheat is currently underway at CIM MYT.