Seed Increase Problems in Synthetic Cultivars of Elymus junceus Fisch.1

Abstract

Polycrosses and Syn‐ls, produced in 3 consecutive years (1959, 1960, and 1961) in a recombination block composed of the parent clones of ‘Vinall’ Russian wildrye (Elymus junceus Fisch.), were evaluated for seed yield in two replicated tests. The polycrosses were composed of equal weights of seed of 20 replications of each parent. The Syn‐ls were equal‐weight composites of five polycrosses. The 1959 polyerosses and the 1959 Syn‐1 were compared with their 1960 counterparts in 1962 and 1964.Counterparts for 1960 and 1961 were compared in 1966 and 1967.In the first test, the 1960 Syn‐1 yielded significantly higher (P<.05) than the 1959 Syn‐1, demonstrating superiority of the 1960 seed. Differential performances of three polycrosses accounted for the difference. In the second test, yields of the 1960 and 1961 Syn‐ls, as well as combined averages for the 1960 and 1961 polycrosses, were closely similar. However, one 1961 polycross yielded significantly higher (P<.05) than its 1960 counterpart. The reverse was true of three other polycrosses, but the differences were not significant (P<.05). These opposing effects, although balanced in the Syn‐1, could cause divergence in later generations.In the recombination block, large clone‐by‐year differentials were evident in seed production and seed size. if pollen production paralleled seed production, as seems likely, there were inequities of male parentage in all 3 years. Relative differences in seed size gave rise to both over‐ and under‐representation of females in the equalweight Syn‐I for each year. Inequalities of parentage were greatest in 1959.Where these conditions exist, simple practices offering Where these conditions exist, simple practices offering Where these conditions exist, simple practices offering Where these conditions exist, simple practices offering more effective control of synthetic parentage are (a) imposing a uniform limit on number of spikes per plant to equalize male parentage, and (b) compositing on the basis of seed size to equalize female parentage. more effective control of synthetic parentage are (a) imposing a uniform limit on number of spikes per plant to equalize male parentage, and (b) compositing on the basis of seed size to equalize female parentage.