| Thus chromosome 6B of both varieties possesses a dominant gene, Sr11,
for resistance. As no susceptible segregants were obtained in F2 populations
of crosses Gabo x Yalta, it is assumed that the same gene at the same position
on the chromosome is involved in the two varieties. The segregation ratios of the totals of the other twenty F2 families were 1,220 res. : 561 sus. (i.e., 2.17 : 1) and 695 : 529 (1.31 : 1) for Gabo and Yalta respectively. The departures from a 3 res. : 1 sus. ratio and the difference in the ratios involving Gabo and Yalta may be the result of differential transmission rates of gametes as discussed by LUIG (1960, 1964), SEARS and LOEGERING (1961) and LOEGERING and SEARS (1961, 1963). The wide range of reaction types in the resistant group of F2 segregates compared with the reaction type of the resistant parent in crosses involving Kenya 744 and particularly Eureka is presumably due to segregation of modifying genes effecting reaction type. References GREEN, G. J., KNOTT, D. R., WATSON, I.A. & PUGSLEY, A.T., 1960, Can. J. Pl. So., 40: 524- 538. LOEGERING, W.Q. & SEARS., E.R., 1961, 53rd Annual Meeting, Agron. Soc. Amer. Abstr., p.53. LOEGERING, W.Q. & SEARS, E.R., 1963, Can. J. Genet. Cytol., 5: 65-72. LUIG, N.H., 1960, Nature, 185 (4713): 636--637. LUIG, N.H., 1964, Nature, 204 (4955): 260-261. SEARS. E.R. and LOEGERING, W.Q., 1961, Genetics, 46: 897 (Abstr.). STAKMAN, E. C., LEVINE, M. N. & LOEGERING, W. Q., 1944, Sc. J. Series of Minnesota Agr. Exp. Stat. Paper 2148. WATSON, I. A. & LUIG, N. H., 1961, Conference Cereal & Pasture Plant Breeders, C.S.I.R.O., Vol. 1. WATSON, I.A. & LUIG, N.H., 1963, Proc. Linn. Soc. N.S.W. 88: 235-258. |
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