Genetic control of flowering time in subterranean clover

Abstract

The quantitative inheritance of flowering time in autumn-sown subterranean clover (Trifolium subterraneum L. ssp. subterraneum) was studied in a 13 x 13 diallel cross in a Mediterranean-type environment. Flowering time was shown to be highly heritable with a low average degree of dominance, which was predominantly in the direction of earliness. Covariance/variance ( Wr/Vr) regression analysis indicated early flowering to be conditioned mostly by dominant alleles, and lateness mostly by recessives. The alleles were slightly asymmetrically distributed among the parents, with recessives marginally in excess. Inadequacy of the additive-dominance model, on which the Birmingham diallel analysis is based, was detected by a significant departure from unity of the joint regression coefficient and the heterogeneity among arrays of (Wr Vr) values, which could be ascribed to and overcome by omitting two late-flowering parents from the diallel cross.