Investigating Early Growth and Development Response of Corn to Weed Competition Using Transcriptome Analysis.

Corn-weed competition studies indicate that resource limitation slows normal corn growth and development and often results in lower yields.  However there is minimal information on the physiological basis of crop competition, especially at the early growth stages when resources would be expected to be plentiful based on plant size.  The research objectives of this study were to determine if gene expression and physiological responses of corn at the V2 and V4 growth stages differed when grown under optimal vs stress conditions.  Stress treatments were 1) low N; 2) 40% shade applied at crop emergence and removed fromV2 toV8, and 3) canola planted in rows close to corn (to mimic weed stress) at corn planting and removed from VE to V8.  At V2 and V4, corn height, leaf area, plant biomass, and chlorophyll content were measured and leaf tissue sampled for microarray analysis.  Preliminary results show that corn plants under 40% shade had the least leaf area, biomass, chlorophyll content, and were shorter than corn grown alone or with canola.  When shade was removed at V2, plants analyzed at V4 had less leaf area, biomass, and were shorter than nonstressed plants. Corn plants grown with canola was removed from VE to V6 were similar in height and chlorophyll content as corn grown alone. At harvest, corn yield losses compared to the optimal treatment were measured in two treatments; canola removed at V8 or low N conditions. Based on transcriptome analysis from V2 leaf samples, corn gene expression differed among the optimal, shade, and canola treatments.  Corn stressed with canola, multiple genes regulating early light inducible proteins (ELIP) were induced whereas shaded corn had several genes that regulate Photosystem II proteins induced.  These data indicate that the physiological responses of corn to weed and light stress differ.