QUANTITATIVE INHERITANCE OF CREEPING-ROOT IN ALFALFA

Abstract

Creeping-root scores of two alfalfa populations developed by breeding were statistically analysed to estimate the heritability, and to detect non-additive genotypic variance. Genotypic variation was found to be predominantly additive but some non-additivity was present. Heritability of individual plant scores for creeping-root was estimated as 20 and 26% for the two populations for the first time of scoring, and 28 and 31% for the scores recorded in the second year after the character was first expressed. The extent of creeping-root development in plants actually scored as being creeping-rooted, was weakly inherited (10 and 2%) but considerable non-additive genotypic variation was evident. It was concluded that non-additive genotypic variation of the order observed in creeping-root scores is unlikely to bias progeny tests sufficiently to impair breeding progress by much more than 5% provided the progenies from at least 5 different crosses are used to evaluate selected clones.