Selection for High and Low Harvest Index in Three Winter Wheat Populations1

Abstract

Low heritability of grain yield in wheat (Triticum aestivum L.) often results in a slow response to selection. Selection criteria other than grain yield per se are being sought by wheat breeders. Harvest index (HI), the ratio of grain yield to total biomass yield, may be a useful selection trait for yield improvement. A study was undertaken to estimate the heritability of HI and to determine the response to selection for high and low HI in three genetically diverse populations of winter wheat. Selections were made in the F3 generation and selected progenies were evaluated in replicated tests in the F4 generation. Realized heritability estimates for HI were intermediate in magnitude (0.44 to 0.60). Selection in F3 for high and low HI was effective in identifying F4 lines with high and low HI, respectively. Also, selection for high HI resulted in shorter plants with earlier heading dates and lower biomass yield. Genotypic correlations (rG) between HI and grain yield were low (rG = 0.04 to 0.23). Phenotypic correlations between HI and grain yield were relatively high in the F3 but much lower in the F4. Harvest index was negatively correlated with plant height and days to heading, while correlations between HI and biomass yield were mostly nonsignificant. Simple correlation coefficients between F3 and F4 means were higher for HI than for grain yield. Results indicated that HI in the F3 generation was a good predictor of HI in the F4, but a poor predictor of grain yield in the F4.