Differences in seedling vigor among diverse cotton genotypes
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Stand establishment and early vigor are critical to the successful production of cotton. However, there is a lack of information on the genetics and the physiological mechanisms determining early vigor. Physiological and genetic aspects of resource allocation by cotton plants in the time period between emergence and first bloom need to be examined. As an initial step, early vigor among modern cultivars and advanced breeding lines were compared. In addition, the effect of seed source (parent plants grown in Arkansas or Arizona) on seedling vigor were compared. Various traits, including leaf area development and shoot dry weight, root dry weight (greenhouse only) were measured under field and greenhouse conditions. In two field seasons, seeds produced in AZ had greater shoot dry weight early in development than seeds produced in AR, which may have been caused by differences in seed weight. Advanced breeding lines, regardless of seed source, exhibited greater shoot dry weight than commercial seeds. However, the differences in seedling biomass between seed source were reduced as plants developed. Several genotypes had consistently superior or inferior shoot dry weights in both years despite different environmental conditions. Characteristics closely associated with seedling biomass were seed dry weight, cotyledon area and dry weight, and area and dry weight of the first leaf. As expected, the associations of cotyledon and first leaf area with traits measured at later harvests were reduced. These data suggest that the area of the cotyledons and the first leaf are important drivers for early growth in cotton.
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