Relationships between genetic distance measured by RAPD-PCR and heterosis in inbred lines of white clover (Trifolium repens L.)

The RAPD-PCR technique has been used to generate DNA amplification profiles from a set of advanced generation inbred lines of white clover ( Trifolium repens L.). The genetic distances between lines have been estimated and ha ve been compared with the extent of positive heterosis for dry matter yield in hybrid crosses. The analysis clearly separated the four major groups (H , J, R and S), with little within group variation. Heterosis, previously sh own to be positively correlated with the extent of phenotypic variation bet ween parental lines, was greatest between lines from groups showing the lea st genetic distance. The lack of correlation between heterosis and genetic divergence is discussed in the context of results from other systems. Addit ionally, the data allow a comparison of the extent of phenotypic variation for a trait under selective pressure with the degree of variation at the DN A level detected with the RAPD technique.