EARLY GENERATION SELECTION FOR GRAIN-FILLING PERIOD IN WHEAT

Grain-filling period (GFP) may be a useful physiological selection tra it that could influence grain yield of cereals. This study was conduct ed to estimate heritability of GFP and to determine the response to se lection for long and short GFP in six genetically diverse populations of spring wheat (Triticum aestivum L. emend. Thell.). Selections were made in the F-2 generation and selected progenies were evaluated in re plicated field tests in the F-3 generation. The tests were seeded unde r normal and late conditions at Rampur, Nepal, in 1990. Date of seedin g had a significant effect on GFP, grain and biomass yield, harvest in dex, and hundred kernel weight. Selection in the F-2 for long and shor t GFP was effective in identifying F-3 lines with long and short GFP, respectively. Also, selection for long GFP usually resulted in higher grain and biomass yield. Average harvest index and hundred kernel weig ht of the long GFP lines were higher than those of the short GFP lines . Realized heritability estimates for GFP were intermediate to high in magnitude (0.52-0.86). Duration of GFP had a high positive genotypic correlation with grain yield (0.52-0.79), harvest index (0.50-0.80), a nd hundred kernel weight (0.53-0.72). Results indicated that selection for long GFP in early segregating generations should bring about posi tive improvements in these yield components.