FORMATION OF SORGHUM HYBRIDS FOR GRAIN. ll. BEHAVIOR per se OF THE LINES AND THEIR GENERAL COMBINATORY FITNESS

Abstract

The general combining ability (GCA) of a line is the averaqe response of all hybrids involved in that line. Furthermore GCA evaluations also require to form the desired hybrids, so time, land and other resources are consumed in this process. lt has been suggested the per se  behaviour of lines as a good estímate of the GCA. At Tepalcingo, State of Morelos, 294 (sorghum  bicolor L. Moench) hybrids were evaluated along with 18 R y 13 B of their parental lines. Correlation coefficients of 0.68** and 0.61** between GCA and l ines yield per se, were obtained for female and male lines, respectively. Grain yield of hybrids formed with parental lines both of them being high yielders or having a high GCA, exceeded from 52 to 91% the yield of hybrids formed with low yielding or low GCA lines. Similarly, high yielding hybrids were three of five times more frequent in the first group than in the second one. lt is concluded that the yield per se  test is a good criterion for screening parental lines in a hybrid sorghum program.