GENETIC-STUDIES OF LEAF AND STEM RUST RESISTANCE IN 6 ACCESSIONS OF TRITICUM-TURGIDUM VAR DICOCCOIDES

Six accessions of Triticum turgidum var. dicoccoides L. (4x, AABB) of diverse origin were tested with 10 races of leaf rust (Puccinia recond ita f.sp. tritici Rob. ex Desm.) and 10 races of stem rust (P. gramini s f.sp. tritici Eriks. and Henn.). Their infection type patterns were all different from those of lines carrying the Lr or Sr genes on the A or B genome chromosomes with the same races. The unique reaction patt erns are probably controlled by genes for leaf rust or stem rust resis tance that have not been previously identified. The six dicoccoides ac cessions were crossed with leaf rust susceptible RL6089 durum wheat an d stem rust susceptible 'Kubanka' durum wheat to determine the inherit ance of resistance. They were also crossed in diallel to see whether t hey carried common genes. Seedlings of F-1, F-2, and BC1F2 generations from the crosses of the dicoccoides accessions with RL6089 were teste d with leaf rust race 15 and those from the crosses with 'Kubanka' wer e tested with stem rust race 15B-1. The F-2 populations from the diall el crosses were tested with both races. The data from the crosses with the susceptible durum wheats showed that resistance to leaf rust race 15 and stem rust race 15B-1 in each of the six dicoccoides accessions is conferred by a single dominant or partially dominant gene. In the diallel crosses, the dominance of resistance appeared to be affected b y different genetic backgrounds. With one exception, the accessions ca rry different resistance genes: C17181 and PI197483 carry a common gen e for resistance to leaf rust race 15. Thus, wild emmer wheat has cons iderable genetic diversity for rust resistance and is a promising sour ce of new rust resistance genes for cultivated wheats.