The impact of selection and breeding for above-ground vigour on below-ground traits associated with weed competitiveness in wheat

Weeds are a critical pest management issue for wheat producers. The weed competitiveness of wheat has typically been reduced through a century of selection for dwarf genotypes to prevent lodging and increase the harvest index. Many of the cultural and chemical strategies employed to manage weeds are costly and some may lead to the development of herbicide resistance. Therefore, novel and cost-effective integrated approaches for weed management in cereals are needed. One approach to enhance competitiveness without reducing harvest index is through selection for early shoot vigour. However, the impact of above-ground vigour on below-ground root traits and competitiveness has not been well characterised to date. Competitive root traits in wheat were evaluated against commercial cultivars and parent genotypes using a collection of wheat genotypes generated by recurrent selection at CSIRO. In field and controlled environments, shoot and root traits were evaluated in a series of experiments. Historic cultivars, triticale or cereal rye were included as positive weed suppressive controls for enhanced competitiveness. Genotypic differences in root traits and the allelopathic potential from root exudation were noted among selected early vigour and commercial lines. Their weed suppressiveness was quantified in field and controlled environments