Characterizing phenotypic variation, physiological costs, and global gene expression associated with shade avoidance in selected crop species

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The shade avoidance response of plants is considered to be an adaptive, plastic response that increases the probability of successful reproduction in natural environments. Within an agricultural environment, this shade avoidance response should also enable crop species to be more competitive with weeds. However, shade avoidance may be expressed at a cost to reproductive fitness. No study has been conducted previously to associate shade avoidance as a mechanism to explain the outcome of crop and weed competition. Therefore, to explore the role of shade avoidance in crop-weed interactions, we propose the following three objectives: (1) to mathematically define a plasticity index of phenotypic variation within selected crop germplasm in response to changes in light quality; the intent of this objective is to predict crop field performance under weedy conditions, (2) to determine the cost of shade avoidance, as measured by crop yield or as a loss of phenotypic plasticity to subsequent abiotic stresses, and (3) to discover key metabolic and signaling pathways associated with weed-induced shade avoidance in corn. These objectives will be addressed under field and laboratory conditions. This project will generate new knowledge pertaining to the physiological and molecular response of selected crop species to stress caused by early weed competition. This new knowledge will be of direct use to public and private crop breeding programs throughout Canada and North America. We anticipate that knowledge generated from these studies will be used to develop new, more weed tolerant crop hybrids and varieties. The commercialization of this technology will improve net on-farm income, reduce pesticide loading into the environment, and thereby be of direct benefit to the rural economy of Canada.