Chromosomal location of genes for resistance to Karnal bunt in wheat

Karnal bunt (Tilletia indica Mitra) infestation of wheat (Triticum aestivum L.) kernels reduces grain quality. Deployment of genetic resistance would be preferable to chemical applications for control of the disease. Inoculation studies were carried out in a wheat mapping population with the aim of locating genes for resistance. Recombinant inbred (RI) lines from a cross between a resistant synthetic wheat (Triticum turgidum 'Altar 84' x T. tauschii) and the susceptible common wheat cultivar (Opata 85' were inoculated with Karnal bunt sporidial suspension and evaluated for symptom development in the field for three seasons and in the greenhouse, Based on restriction fragment length polymorphism (RFLP) analyses, regions on chromosome arms 3BS and 5AL carrying marker alleles from the Altar durum parent were consistently associated with reduced kernel disease. Main marker effects accounted for up to 32% of disease variation in the field but only 15% in the greenhouse, where the level of disease was higher, suggesting an environmental component of resistance. The tagging of these Karnal bunt partial-resistance genes in tetraploid and hexaploid backgrounds may facilitate the accumulation of resistance via marker-assisted transfer to susceptible durum and common wheat cultivars. This practice should reduce laborious disease screening requirements.