RESISTANCE TO FOLIAR DISEASES IN A COLLECTION OF TRITICUM-TAUSCHII GERM PLASM

The wild diploid wheat Triticum tauschii (syn. Aegilops squarrosa) is a valuable genetic resource for improvement of pest resistance in hexaploid wheat (T. aestivum). A collection of 219 T. tauschii accessions, obtained from Kyoto University, Japan, and representing most of the species' geographic range, was screened for reaction to four diseases: leaf rust (caused by Puccinia recondita f. sp. tritici), stem rust (caused by P. graminis f. sp. tritici), powdery mildew (caused by Blumeria graminis f. sp. tritici [syn. Erysiphe graminis f. sp. tritici]), and tan spot (caused by Pyrenophora tritici-repentis). Accessions were classified by region of origin, by botanical group, and by genetic group. Genetic groups were assigned based on previously determined molecular-marker genotypes. Resistance to rusts was concentrated in accessions collected near the Caspian Sea and in those classified as subspecies strangulata. Most such accessions belonged to genetic group A. Resistance to powdery mildew and tan spot was more dispersed but more common in accessions collected from regions ranging from the Caspian Sea eastward to Pakistan. Over 30% of 108 accessions that were screened for all diseases were classified as resistant to two or more, and 12% were resistant to three or more. Because disease resistance genes can readily be transferred from T. tauschii to T. aestivum, this collection is proving very useful for wheat improvement.