INHERITANCE OF PHOSPHORUS RESPONSE IN WHITE CLOVER (TRIFOLIUM-REPENS L)

Genotypes of white clover that exhibited divergent responses to P were identified in a glasshouse pot trial. Six high P-responding genotypes were selected from previously identified high P-responding cultivars and 5 low P-responding genotypes were selected from previously identified low P-responding cultivars. These were crossed in a full diallel design without selfing and reciprocals were kept separate. The P-response of progeny lines was compared with parents. High P-response was dominant over low P-response with progeny from crosses between high and low P-response genotypes being similar to the high P-response parent. Reciprocal effects were not significant. The general combining abilities of high P-response genotypes were generally greater than that of the low P-response genotypes, although there were significant specific combining abilities. Narrow sense heritabilities for P response were moderate, 0.46 based on the linear coefficient and 0.33 based on the quadratic coefficient of the fitted response curves. The mode of inheritance, feasibility of manipulating differences in P response by breeding and future directions of this work are discussed.