Effects of Seeding Rates on Harvest Index, Grain Yield, and Biomass Yield in Winter Wheat1

Abstract

Harvest index (HI) is considered a potential selection criterion for improving grain yield in cereals. Selections are usually made in thinly seeded populations. Therefore, effective selection is dependent upon expression of the traits under selection being consistent in different crop stands. The literature indicates differences in results from selection using HI vs. selection for grain yield per se in thin crop stands. This study was conducted to examine the effects of two seeding rates, standard (67.2 kg ha−1)) and low (16.8 kg ha−1), on HI, grain yield, and biomass yield and to compare the relationship of HI and biomass yield to grain yield in winter wheat (Triticum aestivum L.). Ten hard red winter wheat genotypes were evaluated in replicated field tests in three environments. The field plot design was a split plot with genotypes as main plots and seeding rates as subplots. Results indicate that effects of seeding rate and genotype ✕ seeding rate interactions were significant for grain and biomass yields but not for HI. However, environmental effects and seeding rate ✕ environment interactions were significant for all three traits. The simple and rank correlation coefficients between genotypes grown at the two seeding rates were higher for HI and biomass yield compared to grain yield, which suggests that HI and biomass yield each could have merit as a selection criterion in different crop stands. However, HI and biomass yield in thin crop stands appear to be less effective than grain yield for identifying high grain yielding genotypes.