Differential Gene Expression of Maize and Teosinte Varieties Demonstrating Differences in Weed Tolerance.

Weeds negatively impact crop growth and future yields.  The literature suggests that sweet corn (Zea mays convar. saccharata var. rugosa) and some modern dent variants (field corn, Zea mays indentata) have varying degrees of weed tolerance (or weed suppressive ability).  These variants were derived from teosinte, the ancestor to all corn varieties, which is a weedy plant that still grows wild in southern ranges.  Understanding what genes and mechanisms are involved in weed tolerance and yield loss, and what untapped genetic resources may exist in teosinte, are keys to reaching the goal of increasing crop tolerance of weeds.  Determining which gene expression patterns and growth parameters correlate with yield differential while under weed pressure is a first step in determining genetic mechanisms available for increasing or building upon pre-existing crop tolerance abilities in corn and other crops.  Eleven corn varieties and five teosinte lines in a three-year study were evaluated to determine correlations between corn or teosinte variety, crop height, leaf area, stem diameter, and mid-season biomass differentials and yield differentials between weedy and non-weedy treatments. No single parameter measured in weedy plots correlated with yield loss or gain in weedy plots compared with controls.  Further research is needed to determine which, if any, morphological traits in corn and teosinte are clearly related to weed tolerance and the ability to maintain yield under weedy conditions.