Thursday, November 16, 2006 - 10:15 AM
312-9
Physiological Response of Maize Grown with Velvetleaf using Microarray Analysis.
Weeds compete with crop plants for light, water, and nutrients. However, the specific mechanisms for weed-crop interactions have not been well elucidated due to a dearth of tools to assess the physiological state of the plant. Microarray analysis was used to identify changes in gene expression in maize leaves collected from plants at the V11-14 growth stage that resulted from competition with velvetleaf. The plants were grown in field plots under adequate N (addition of 220 kg N ha-1) and irrigation. Consequently only differences due to light competition and perhaps allelopathic stress were anticipated. N amounts were 7% less and δ15N values were greater in maize leaves competing with velvetleaf. Leaf 13C discrimination also was affected by velvetleaf competition indicating differences in 13CO2 fixation. Maize growing with velvetleaf expressed 253 of the 19,200 scanned genes differently (false discovery rate (q value) <0.15) than maize growing in weed-free conditions. Of these differentially expressed genes, 240 were down-regulated in the presence of velvetleaf. Genes involved in carbon (34) and nutrient utilization (10), growth and development (31), oxidative stress (17), protein catabolism (23), signal transduction (38), responses to auxin (19) and ethylene (6), and zinc transport were repressed in maize growing in competition with velvetleaf. Only 13 genes were induced due to competition with velvetleaf, and those that were provided little indication of the physiological response of maize. No significant differences were observed in multiple genes responsive to water stress or genes involved in sequestering/transporting most micronutrients indicating that these stresses were not a major component of velvetleaf competition with maize at the developmental stage tested.
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