Raúl E. Avendaño1, Fred L. Patterson2 y Ralph L. Davis2

Studies of general and specific combinin ability (GCA and SCA) were performed on six alfalfa clones. Also, yield of all possible 4-5-6 clones Syn-1 combinations were considered.
Although additive and non-additive gene action appear to be responsible for the expression of yield in winter, spring and summer, mean square ration indicated thar GCA was more important than SCA, which substantiates suggestions made for genotypes of less wide genetic diversity. Fall growth was controlled mainly by additive gene action.
The analysis of the Syn-1 combinations did not suggest a clear superiority for 4-5 or 6 clones synthetics. Yields were quite uniform probably due to the low SCA effects and the limited genetic diversity of the parents.
Phenotypic correlation and simple linear regression analysis performed between excepted and actual Syn-1, showed a significant correlation and regression only when additive gene action was predominant.

1Ing.Agr., Ph. D., Instituto de Investigaciones Agropecuarias (INIA). Casilla 5427, Santiago, Chile.
2Professor of Agronomy, Purdue University, Lafayette, Indiana, USA.