Genetics of Weed Competitiveness in Sweet Corn (Zea mays L).

Weeds are a major issue for sweet corn farmers. If crop varieties can compete well against weeds, yields may be improved and weed management expenses reduced. To develop weed-competitive sweet corn varieties, we need to know what heritable traits affect weed competitiveness. To do this, we are evaluating a sugary1 diallel for heritable differences in plant morphology and phenology, weed tolerance and suppressive ability. These are first year results from a two year experiment. In 2007, we planted 22 sugary1 sweet corn hybrids at Madison and Arlington WI. 21 hybrids were from a Griffing’s Method 4 diallel plus one check. The trials were planted in a split-block RCBD with 3 replicates, each split block having all of the sweet corn hybrids and either planted normally or interplanted with sorghum. We measured plant height, leaf area, leaf height, leaf angle, number of tillers, heights of tillers, growing degree days to tasseling, and yields of dried ears. Yield loss was determined by comparing yields of entries between the sorghum and non-sorghum plots. We additionally measured sorghum height, density and biomass. There were significant (p<0.05) hybrid effects at both locations for: plant height, leaf area and leaf height, tiller number and tiller height, GDD to tasseling, yield and sorghum biomass. At both locations, GDD to tasseling and early leaf area were negatively correlated (r2=-0.71 and r2=-0.79 ) with sorghum biomass. At at least one location, we found significant (p<0.05) differences in GCA for: plant height, leaf area and height, leaf angle, tiller number, GDD to tasseling, yield and sorghum biomass. There were differences between hybrids for traits thought to affect weed competitiveness. Two traits, earliness and early leaf area suppressed sorghum growth. Many traits vary based on parentage. Data from 2008 trials will help clarify our results.