ALLELIC FREQUENCY CHANGE OF P1 GENE IN A MAIZE POPULATION AFTER RECURRENT SELECTION FOR GRAIN-YIELD

Full-sib family recurrent selection for grain yield was conducted for four cycles in maize (Zea mays L,), The source population was the F-2 of A632 (with red cob) x Mu195 (with white cob). Objectives of this re search were to evaluate the change in allelic frequency at the PI gene (determining cob color), to assess whether this change was due to ran dom drift only, and to detect whether allelic frequencies were correla ted with grain yield responses. The source and the four selected popul ations were crossed to two inbred lines with white cob (recessive trai t). The frequency of red cob allele increased with selection following a highly significant linear trend (b = 0.066 cycle(-1)), suggesting t he effect of directional selection. Correlation between allelic freque ncy and grain yield was significant for populations as S-2 generation (r = 0.938), and as testcrosses (r = 0.886), and could be ascribed to tight linkage, to pleiotropy, or both.