Canola Interference for Weed Control

Abstract

The increased incidence of herbicide-resistant weed species, and the related biological repercussions, poses a major threat to sustainable crop production. Integrated weed management, which involves greater reliance on non-chemical weed management tactics such as crop interference, needs to be included in canola production systems. Crop interference comprises both competition and allelopathy which favour the growth of the crop. This review examines canola plant traits associated with competitiveness and allelopathy. Competitive ability is evaluated by the ability of plant morphological traits to improve access to scarce light, nutrients and water in a limited space. Allelopathy refers to the harmful or beneficial effect of crop biochemicals on neighbouring weed species. Allelochemicals are a subset of secondary metabolites produced from intact living roots and crop residues that differ between cultivars and have specific defensive functions in the rhizosphere. Elite allelopathic cultivars can be identified by screening canola germplasm. The identification of the allelochemicals involved and their effects in the field also need to be explored. The impact of genetic variation, the mechanisms of allelopathic action, the source and fate of allelochemicals and associated biota in the rhizosphere all need to be considered in new cultivar development. The breeding of weed-suppressive allelopathic canola cultivars needs to be in the context of good agronomic performance. Although allelopathic canola cultivars are unlikely to eliminate all weed pressures in the field, the extent to which they contribute in weed management is worthy of exploration. It remains to be known whether combined competitive and allelopathic cultivars can be developed to maximise overall interference. The integration of agronomic practises with canola interference also needs to be developed.