Quantitative genetic analysis in Phalaris and its breeding implications.

The genetic variation for a number of important agronomic characters within a widely based breeding population of Phalaris tuberosa has been analysed, and the interrelationships among the variables characterized.Estimates of heritability for flowering date, seed retention and seed weight were higher than those for cool season growth measured in spaced plants or swards, but all characters showed appreciable additive genetic variation, which offers considerable scope for further selection. There was no evidence of any general loss of adaptation in the widely based population, though flowering date and seed weight tended to show increased environmental variability by comparison with the adapted Australian cultivar.One of the most important changes in the genetic relationship between characters in the breeding population has been the elimination of undesirable ecotypic correlations which were present in the parental material prior to hybridization and recombination.In the advanced breeding population significant intra-population correlations existed between the various estimates of growth made on single plants, but in general, estimates of growth made under these conditions were not significantly correlated with the performance of the same families in swards. Of particular interest, however, were the significant genetic correlations between seedling growth of full-sib families measured in controlled environments, and the growth of the same families as spaced plants and in swards.The predicted response to either direct or indirect selection indicates considerable potential for improvement in a number of important characters including seedling growth, seed retention, and winter growth in swards. Of particular interest is the possibility of increasing sward production as a correlated response to intensive selection for seedling growth.A selection procedure is described involving simultaneous selection in full-sib families grown as swards and spaced plants. This technique provides a useful compromise when progress is desired in a number of characters which are best assessed under one or the other regime.