Narrow sense heritability of number of spikes per plant, number of grain per spike, 100 grain weight and grain yield as well as the environmental, phenotypic and additive genetic correlations between those characteristics, were estimated based on data collected for crosses between the tall cultivar IAC-227 (P1) and short Mexican lines: CMH 78.390/ CMH 77A.917// CMH 79.215 (P2), CMH 79.959/2* CNO 79 (P3), CMH 79.481/ CMH 77A.917 (P4) and CMH 80A. 747 (P5). Parental, F1, F2 and reciprocal backcross generations were evaluated, on an individual plant basis. Narrow sense heritability of number of grains per spike in the cross P1 x P2 was 0.717. This value indicated that the selection for this trait could be efficient in F2 or F3 generations. Medium to low narrow sense heritability of number of spikes per plant (0.157 - 0.547), number of grains per spike (0.047 - 0.321), except for the cross P1 x P2, 100 grain weight (0.125 - 0.476) and grain yield (0.421 - 0.550) suggested that selection for these caracteristics should be delayed to more advanced generations, when progeny tests would be made. The additive genetic correlations suggested that it would be possible to select plant types, which combine high yield potential with large number of spikes per plant and grain per spike and heavy grains. However, large F2 populations would be required to ensure the frequency of the desired recombinants. Considering the positive additive genetic correlations for all traits evaluated in the hybrid P1 x P4, selections of desirable plants could be made using small segregating population.
wheat; grain yield; yield components; heritability; correlations
