Studies on the agronomy, genetics and interrelationships of yield and its morphological components in a diallel set of families ofLolium perenneL.

Abstract

SummaryFive selected clones ofLolium perennewere selfed and diallel crossed without reciprocals to produce 15 families. These families were grown in a replicated field trial for 2 years at four rates of applied nitrogen – 0, 225, 450 and 675 kg N/ha – per annum. The data recorded included dry-matter yield, number of fertile and sterile tillers per plant, mean dry weight per fertile and sterile tiller and total dry weights of fertile and sterile tillers. Conventional analyses of variance and diallel analyses were applied to the data as well as path analyses, used to examine the interrelationships between yield and the tiller characters.The main effect ofyearswas significant only for mean dry weights per tiller and dry-matter yield. Increasing the rate of applied nitrogen increased the number of tillers and yields but decreased mean tiller dry weights. Differences betweenprogenieswere due to both general and specific combining ability for most characters. Relatively high narrow-sense heritabilities were obtained for the tiller characters although there were differences between the two years.The progenies achieved their yield through different combinations of tiller characters, some having large numbers of fertile tillers with medium dry weights and others having numerous sterile tillers with high dry weights. Although there was inconsistency in the interrelationships between characters, number of tillers was always more important in determining yield than mean dry weight per tiller.The results are discussed in relation to the predictive value of tiller characters on yields and the implications for breeding programmes.