SELECTION RESPONSE FOR GRAIN YIELD AND ITS COMPONENTS SEED NUMBER AND SEED SIZE IN SORGHUM

Abstract

The objective of the present work was to compare direct, indirect and combined selection indexes in the improvement of grain yield and its grain number and grain weight components in sorghum (Sorghum bicolor L. Moench). Four F₂ populations and one F₃ progeny involving parents differing in seed size and seed number, were used. The study was carried out at the University of Nebraska, USA. The F₂ populations were evaluated in 1997 at one location, while the F₃ progeny (99 S₁ families) in 1998 at two locations. Traits measured were grain yield (GYP), 100-grain weight (GW), and grain number (GNP) recorded in the main panicle of individual plants. Expected gain per cycle from single plant selection for GYP in the four F₂ populations varied from 9.5 to 13.6 %, and was of 13.5 % from S₁ family selection in the F₃ progeny. Direct selection for GYP was more advantageous to improve GYP, GW, and GNP than indirect selection for highest GW or GNP. The efficiency of three selection indexes involving grain yield and one or both yield components, ranged from 0.16 to 7.21 % in relation to direct selection for GYP. The contrast between seed number and seed size of parents involved in the populations were not an important factor in increasing genetic gains of GYP and its components.