GENETIC VARIABILITY AND HERITABILITY OF ALFALFA (MEDICAGO SATIVA L.) SEED YIELD AND ITS COMPONENTS.

A better understanding of the inheritance of new genes and its influence on the seed yield traits is necessary to develop alfalfa populations with the genetic capacity for high seed yield. Therefore, the objective of the present research was to identify the inheritance mode of seed yield and its components. The present study was conducted at Institute of Plant Breeding and Acclimatization, located in Radzikow, Warsaw, Poland, from April, 1999 to July, 2003. • Both δ 2 A and δ 2 D were responsible for the expression of flowering date and seed yield at BC1F2-generation level, shoots number plant -1 at BC2F2-generation level, flowering date, number of shoots and racemes per plant as well as seeds number pod -1 across two-generations. The presence of both additive and dominance effect for these traits led to moderate estimates of narrow-sense heritability. • Because, the proportional contribution of male variance was larger than male vs. female interaction variance for the raceme traits in all evaluated generations, the additive variance contributed most of the genetic variance for these components. The lack of dominance effects suggests that raceme traits behave additively. Consequently, selection for raceme characters can be performed using breeding methods designed to exploit additive genetic variance. • The negative value of narrow-sense heritability observed in BC2F2-generation for number of pods raceme -1 reflected absence of genetic variance in relation to the examined trait; where, the effect of males, females and their interactions was nonsignificant. The other reason for negative heritability is that highly adapted parents produced weakly adapted progeny, because, the environment was completely different in the two generations. High estimates of heritability were obtained for some seed yield components indicating that, the response to selection with any breeding program could be expected. In general, the broad sense-heritability was moderate to high. • The raceme traits seem to be a reasonable breeding goal for improving seed yield in alfalfa. These traits showed high narrow-and broad-sense heritability, in addition, they were strongly influenced by the experimental populations carrying the long raceme peduncle-type.