Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/7/2009
Publication Date: 6/1/2009
Citation: So, Y.F., Williams, M.M. II, Pataky, J.K., Davis, A.S. 2009. Principal Canopy Factors of Sweet Corn and Relationships to Competitive Ability with Wild-proso Millet (panicum miliaceum). Weed Science. 57:296-303. Interpretive Summary: Large canopy differences exist among commercial sweet corn hybrids, and these differences have practical implications to weed management. Unfortunately, drawing inferences about crop competitive ability is often limited by the study of a relatively small number of crop cultivars or traits. The purpose of this work was to obtain a more comprehensive analysis of cultivar-weed interactions, with to goal of advancing sweet corn's ability to compete with weeds. The large number of hybrids tested in this work showed that commercial sweet corn hybrids exhibit greater variation in traits important to crop-weed interactions than previously reported. Consequently, the crop’s ability to tolerate weed interference or provide weed suppression is highly cultivar-specific. Three crop canopy factors derived from 18 traits accounted for much of the variation in canopy development and competitive ability with weeds. Relationships between crop canopy factors and competitive ability revealed that rapid canopy closure and a large, late-maturing canopy were positively associated with competitive ability. The data also reveal more work is needed to fully understand the role of endosperm type and seedling growth on early competitive ability. This work's impact is an improved mechanistic understanding of crop-weed competition, thereby providing better clues on how to exploit crop competitive ability to improve weed management.
Technical Abstract: A more complete analysis of cultivar-weed interactions is needed before advances in sweet corn competitive ability can be realized. Twenty-three commercially available sweet corn hybrids from nine seed companies were grown in the presence and absence of wild-proso millet to 1) quantify the extent to which phenomorphological traits vary among a large number of sweet corn hybrids, 2) identify the underlying principal factors that describe variation in crop canopy development, and 3) determine functional relationships between crop canopy factors and competitive ability with weeds. Eighteen weed-free crop traits measured from emergence to maturity showed greater variation in canopy properties than previous research on two to four hybrids. A principal component factor analysis revealed that seven of the eighteen weed-free crop traits measured at silking loaded highly (0.65 to 0.90) into the first factor, including plant height, shoot biomass, per plant leaf area, leaf area index, and intercepted photosynthetically active radiation, as well as thermal time from emergence to silking and emergence to maturity. All seven factors were highly correlated (0.38 to 0.93) and were interpreted as a ‘late canopy and maturity’ factor. Another seven traits formed two additional principal factors that were interpreted as an early ‘seedling quality’ factor and a mid-season ‘canopy closure’ factor. Relationships between principal factors and competitive abilities were quantified using least-square linear regression. Cultivars with greater loadings in the ‘late canopy and maturity’ and ‘canopy closure’ factors were more competitive with wild proso-millet. In contrast, crop competitive ability declined with plants that loaded highly into the ‘seedling quality’ factor. The analyses showed that cultivar differences in ability to endure weed interference and suppress weed fitness are driven by complex, yet consistent, mechanisms from emergence to harvest. Significant variation in competitive ability among hybrids and relationships to principal canopy factors could be exploited to improve weed management systems in sweet corn.