RELATIONSHIPS AMONG ATTRIBUTES OF PURE LINES OF BREAD WHEAT DERIVED FROM HETEROTIC F1 HYBRIDS

Measurements were made of the number of spikes per unit area, the numb er of kernels per spike, kernel weight and plant weight in four hetero tic hand-made hybrids and the commerical hybrid Comet, together with t he parents of the hand-made hybrids, and 75 pure lines derived from ea ch hybrid by single seed descent. Kernel weight exhibited the stronges t heterosis, while the incidence of positive heterosis for the remaini ng yield components varied between crosses. Mid-parent heterosis for p lant height was significant for all hand-made hybrids. In both hybrids and pure lines, high yield was associated with intermediate kernel we ight and intermediate plant height, but for each trait higher values w ere observed in the hybrids and pure lines compared with their parents . In terms of both plant height and the major components of yield, viz . kernel number per unit area and kernel weight, the highest yielding pure lines and the hybrids were similar, demonstrating that it is poss ible to recover homozygous genotypes with the same basic characteristi cs as the heterotic hybrids from which they were derived. The absence of any consistent pattern on how the best lines obtained their yield s uggests that selection for yield based on its components would be unre warding, except for selection against extremes of kernel weight and pl ant height.