INHERITANCE OF SEED WEIGHT AND ASSOCIATED TRAITS IN BROMEGRASS, BROMUS INERMIS LEYSS.

Abstract

Among 71 S0 and S2 clones of diverse origin in a space-planted, replicated polycross nursery the range in mean seed weight was 0.71 to 1.30 grams per 300 seeds. A correlation of 0.25 was noted between seed weight and open-pollinated seed set for these clones. Their polycross progenies exhibited a range of only 0.74 to 0.94 grams per 300 seeds in a solid-planted test. The progeny-parent regression value was non-significant (b = 0.09) while the correlation (r = 0.56) was significant at the 1 per cent level.Inbred segregates of 10 representative clones were evaluated in a replicated test for seed weight, fertility, seed yield and bloom date. In each family, segregates showed significant differences in performance for the former three traits which is indicative of genetic segregation. These three traits all exhibited substantial inbreeding depression, averaging 21, 20 and 53 per cent for seed weight, fertility and seed yield, respectively, from S0 to S1 for seven families, and 19, 24 and 66 per cent, respectively from S2 to S3 for three families. Inbreeding resulted in a delay of 1 to 2 days in bloom date, on the average.Progeny-parent regression and correlation values for the four traits were all significant. The regression value for seed weight, 0.39, was equal to that for yield but lower than that of fertility, 1.19, or bloom date, 0.78. Correlations ranged from 0.83 to 0.94. Seed weight, fertility index and seed yield all were positively associated in intercharacter correlation studies, indicating no adverse relationships from a selection standpoint.