Differential competitive ability of morphologically diverse spring wheat genotypes
Sixteen genotypes of common spring wheat (T. aestivum) were grown under conditions of simulated weed competition at Saskatoon in 1991 and 1992. Weeds consisted of cultivated oat (Avena sativa cv. Waldern) and Oriental mustard (Brassica juncea cv. Cutlass) sown at two densities (48 and 96 seeds m2 per weed species), and a weed free control. Seedling establishment, % ground cover, and seed yield for all three species was recorded as was wheat tiller number, spike number, maximum height, LAI (Ieaf area index), leaf orientation, and flag leaf length and size. Significant (p =0.01) weed rate by genotype interactions involving changes in genotype rank were detected for grain yield, indicating differences in competitive ability existed among the wheat genotypes. The highest yielding genotypes under weed free conditions were not necessarily the highest yielding under weedy conditions. Yield reductions averaged over two weed densities ranged from 36 to 52 %. Genotypes which exhibited lower yield reductions also showed greater suppression of weed growth. Although competitive genotypes were generally taller than non-competitive genotypes, other traits such as tillering capacity and leaf length were important determinants of competitive ability.
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