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Differential Suppression of Stripe Rust Resistance in Synthetic Wheat Hexaploids Derived from Triticum turgidum subsp. dicoccoides and Aegilops squarrosa. Gert H. J. Kema, DLO-Research Institute for Plant Protection, IPO-DLO, P.O. Box 9060, NL-6700 GW, Wageningen, the Netherlands; Wouter Lange(2), and Cor H. Van Silfhout(3). (2)DLO-Centre for Plant Breeding and Reproduction Research, CPRO-DLO, P.O. Box 16, NL-6700 AA, Wageningen, the Netherlands; (3)DLO-Research Institute for Plant Protection, IPO-DLO, P.O. Box 9060, NL-6700 GW, Wageningen, the Netherlands. Phytopathology 85:425-429. Accepted for publication 12 December 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-425.

The expression of resistance to stripe rust of wheat, conditioned by four Aegilops squarrosa (DD, 2n = 14) and 11 Triticum turgidum subsp. dicoccoides (AABB, 2n = 28) accessions, was studied by testing 22 synthetic hexaploids (AABBDD, 2n = 42) with five stripe rust races in the seedling stage and two races in the adult plant stage. Resistance in one or both parents was frequently suppressed in the synthetic hexaploids, indicating the presence of suppressor genes on the AB and D genomes. Specificity was apparent because the putative suppressor genes affected the expression of specific resistance genes, although not with all races nor in all growth stages. The results and data from F1 and F2 populations derived from crosses between two synthetic hexaploids with the same T. t. dicoccoides parent but with different A. squarrosa parents revealed that several recessively inherited suppressor genes on the D genome seemed to be involved. A possible mechanism explaining these results and the variable mode of action of suppressors are discussed.

Additional keywords: gene expression, race specificity, resistance mechanism, wild emmer wheat.