Spontaneous and Induced Mutations of Barley for the Reaction to Mildew

HE genetics of resistance in barley to the two pathogenic races of T mildew (Erysiphe graminis DC) hitherto found in Argentina has been already studied (FAVRET, 1949(FAVRET, , 1953(FAVRET, , 1956) ) in about twenty varieties.Summarizing the results, fourteen factors for resistance are distributed in nine loci located on only one chromosome.This chromosome corresponds to the second linkage group and very probably to that named as a or 5, the smallest chromosome of barley without a satellite (BURNHAM and HAGBERG, 1956).Other loci for resistance to other races of mildew have been located on the same chromosome (SCHALLEH and BRIGGS, 1955, HIURA et nl., 1956).Of the eighteen factors for resistance distributed on 14 loci, at least seventeen are in chromosome 5 and one in chromosome 4, corresponding to the fourth linkage group.According to SCHALLER and BRIGGS (1955), SMITH (1951) and my own data, the second linkage group would show diagramatically the following sequence: 13 2 10 1 4 12 16 -4-+-+ +++-+ + +units trtl , I ' M l ' C ~ *1tP / I \ !*MI' in I" ,W I R MI" plus MI', MI"", MI"'"', Ml""', ,ltl9,j;G , ml"', in!'.One of the loci, M P , has at least 3 or 4 alleles for resistance.Three other loci form a genic complex (FAVRET, 1953) being very closely linked and involving six or perhaps seven different alleles or pseudo-At present at the Swedish Seed Association, Svalof, as a fellow of the Rockefeller Foundntion.