Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2006
Publication Date: 5/17/2007
Citation: Xu, W., Odvody, G., Williams, W.P. 2007. Improving drought-tolerance and earworm resistance to reduce aflatoxin in corn [abstract]. In: Proceedings of the 2006 Multicrop Aflatoxin/Fumonisin Elimination & Fungal Genomics Workshop, October 16-18, 2006, Ft. Worth, Texas. p. 67. Interpretive Summary:
Technical Abstract: Aflatoxin contamination of corn by A. flavus is a chronic problem in the southern United States where a hot and dry environment favors aflatoxin production, stresses the plants, and increases aflatoxin production. Producers need new hybrids that are adapted to the southern environments and resistant to aflatoxin contamination. The corn breeding program at the Texas Agricultural Experiment Station (TAES) at Lubbock has been developing drought tolerant corn hybrids by introgressing tropical corn germplasm. We have observed that under drought conditions, drought tolerant corn hybrids produced a higher yield and had much less grain mold than susceptible hybrids. The objective of this study was to identify lines and hybrids with improved stress tolerance and low aflatoxin. Twenty-one experimental and four commercial hybrids (Pioneer hybrid 31B13, Garst 8285, Triumph 1416, and DKC66-80) were grown under replicated trials in Lubbock, Halfway, Dumas, Corpus Christi, and Beeville in Texas and Mississippi State, MS in 2005 and 2006. The Lubbock and Halfway locations had optimum and limited irrigation treatments. The experimental hybrids are developed by the corn-breeding program of the Texas Agricultural Experiment Station (TAES) in Lubbock, TX. They were chosen for improved drought tolerance and earworm resistance. In Lubbock and Halfway, plants were inoculated one week after silking by injecting 3-ml A. flavus conidia (1.5 x 106 conidia/ml) into silk channels. In Corpus Christi, Beeville, and Mississippi State, corn kernels colonized by A. flavus were distributed between all rows when the first hybrid was at the mid-silking stage to provide the increased and uniform aerial dissemination of conidia. In all cases, the inocolum was from a high aflatoxin-producing A. flavus strain (NRRL3357). A limited late planting date was used in Corpus Christi, Beeville, and Mississippi State to encourage severe drought stress at later stages of maturity. The tests used a randomized complete block design with nine replications at Corpus Christi and Beeville, three replications in other locations. Ears from each plot were hand-harvested. All ears were threshed and agronomic data were recorded including grain yield. Corn earworm feeding damages were measured on 10 ears. All grain from each composite replicate was initially ground in a Romer mill at the coarse grind setting. After thoroughly mixing the ground kernels, a 200 g sub-sample was ground again at the finest grind setting on the mill. Aflatoxin B1 assay was done on 50 g sub-samples of the finely ground material for each composite replication using the Vicam immunoassay/fluorometer system. Standard ANOVA was performed to test the differences among hybrids. Natural log transformation of aflatoxin data was made before data analysis. The aflatoxin level was low and not significantly different among hybrids in Lubbock and Halfway, but it was high and different among hybrids at Corpus Christi, Beeville, and Mississippi State. At the three locations, the average aflatoxin of six TAES hybrids (C2A554-1 x B110, S2B73BC x NC300, CUBA117:S15-1A x Tx205, WQ22W x S1W, Tx202 x CML343, and S1W x CML343) was at least 50% lower than the mean of four check hybrids. The aflatoxin S2B73BC x NC300 and S1W x CML343 was 501 and 1060 ppb, equivalent to 13% and 28% of check means (3806 ppb). The samples from 2006 trials have not been analyzed for aflatoxin. The average grain yield in eight environments in 2005 and 2006 was 156 bu/a for S2B73BC x NC300 (ranging 78 to 204 bu/a) and 137 bu/a for S1W x CML343 (ranging from 40 to 191 bu/a) as compared to the 154 bu/a average yield of commercial checks (ranging from 71 to 209 bu/a). These results indicate that new hybrids such as S2B73Bc x NC300 have comparable yield yet significantly low aflatoxin in comparison to the commercial hybrids.