In a recent investigation, while studying the transmission of rye chromosome in the plants of 20_IIW+1_IW+1_IR (W: wheat chromosome, R: rye chromosome) constitution, it was found that nullisomic gametes (20W) and rye substitution gametes (20W+1R), though largely eliminated, were equally efficient in the male gametophyte. Four types of gametes were expected to be formed in 19(20W): 3(20W+1R): 6(21W): 1(21W+1R) ratio (GUPTA 1967, 1968). As shown in Table 1, while the nullisomic gametes were transmitted in 4.5% cases, the substitution gametes were transmitted in 0.75% cases. Since they were formed in 19:3 ratio, their transmission indicated that rye chromosome did not put any extra burden on the already deficient nulli gametes. If the percentage of substitution gametes was increased by using the plants of 20_IIW+1_IIR+1_IW constitution, disomic rye substitutions could be obtained in good number. This method was practiced by JENKINS (1966) and RAY (1962) for systematic substitution of rye chromosomes in common wheat. The non-compensating rye substitutions obtained thus, would be at least as good as, if not better than, the 19 non-compensating nullisomic-tetrasomic lines obtained by SEARS (1966) in wheat. The availability of such non-compensating alien substitutions would lend further support to the concept of homoeology between specific wheat chromosomes and those of alien species. How many of the total possible 147 wheat rye substitutions can be obtained, is to be seen. Work in this direction is in progress at the Department of Plant Science, the University of Manitoba, Winnipeg, Canada.

Literature

GUPTA, P. K. 1967. Ph. D. Thesis. The University of Manitoba, Winnipeg. 1-62.

GUPTA, P. K. 1968. Wheat Information Service 27: 13-15.

HALLORAN, G. M. 1966. J. Hered. 57: 233-235.

JENKINS, B. C. 1966. Proc. 2nd Int. Wheat Genet. Symp. 1963. Lund. 301-321.

JOHNSON, R. 1966. Can. J. Genet. Cytol. 8: 279-292.

JOHNSON, R. & G. KIMBER 1967. Genet. Res. 10: 63-72.

KNOTT, D. R. 1964. Can. J. Genet. Cytol. 6: 500-507.

RAY, M. 1962. Ph.D. Thesis. The University of Manitoba, Winnipeg. 1-67.

RILEY, R. 1964. Proc. 11th Int. Cong. Genet. The Hague 3: 681-688.

RILEY, R.,V. CHAPMAN & R. C. F. MACER 1966. Can. J. Genet. Cytol. 8: 616-630.

SEARS, E. R. 1966. In "Chromosome manipulations & Plant Genetics". 29-45.

WEINHUES, A. 1960."Vortrage fur Pflanzenzuchter" D. L. G. Verlag. Frankfurt.

WEINHUES, A. 1966. Proc. 2nd Int. Wheat Genet. Symp. 1963. Lund. 328-341.

(Received November 21, 1968)