Resistance inAegilops squarrosato Wheat Leaf Rust, Wheat Powdery Mildew, Greenbug, and Hessian Fly

Gill, B. S., Raupp, W J , Sharma, H. C., Browder, L. E., Hatchett, J. H., Harvey, T. L., Moseman, J. G., and Waines, J G 1986. Resistance in Aegilops squarrosato wheat leafrust, wheat powdery mildew, greenbug, and Hessian fly. Plant Disease 70:553-556. Sixty accessions of Aegilops squarrosa (= Triticum tauschii Schmal) were evaluated for resistance to leaf rust (Paccinia reconditaf. sp. lrirlci) culture PRTUS6; powdery mildew (Erysiphe graminis f. sp. tritici),composite cultures ABK, 127, YUMA CC, and Asosan; greenbug (Schizaphis graminum) biotype E; and Hessian fly (Mayetiola destructor) biotype D. Thirty-two accessrons were resistant to the leaf rust pathogen, 3l to the powdery mildew pathogen, and 34 to the greenbug; 24 were homozygous and I 6 were segregating for resistance to the Hessian fly. Multiple resistance was widespread and six accessions were resistant to both pathogens and both insects Resistance varied from immune to moderate reactions. Because A. squarrosaisthe donor ofthe D genome in common wheat, this species can be readily exploited in breeding wheats for pest resrstance Common or bread wheat (Triticum aestivum L. emend. Thell) is an allohexaploid (AABBDD) of recent origin (about 8,000 yr) between a tetraploid wheat ?i turgidum L. (AABB) and Aegilops squarrosa L. e f. Muschii [DD]) (14). Presumably, initial hybridization was restricted to a narrow range of genotypes of each species, thus the genetic diversity of today's wheats primarily accumulated during the culture and spread of bread wheat into the Mediterranean region, Africa, India, China, and elsewhere. During this expansion. further introgression may have occurred with il, turgidum but not with A. squarrosa because of the latter's strong cross-incompatibility with bread wheat.