Submitted to: American Peanut Research and Education Society Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 31, 2003
Publication Date: March 1, 2004
Citation: Guo, B., Sobolev, V., Holbrook, Jr., C.C., Lynch, R.E. 2003. Impact of phytoalexins and lesser cornstalk borer damage on resistance to aflatoxin contamination [abstract]. Proceedings of the American Peanut Research and Education Society, July 8-11, 2003, Clearwater, Florida. 35:65. Technical Abstract: In peanut, the mechanism of resistance to Aspergillus flavus has been reported as the capacity to synthesize phytoalexins, the antibiotic secondary metabolites. The lesser cornstalk borer (LCB) is one of the most destructive insects in peanut production area. Penetration of peanut pods by insects enhances infection of pods by A. flavus/parasiticus and aflatoxin contamination in peanut. Water activity is a measurement of the energy status of the water in a system, indicating how tightly water is bound. We use water activity in a pod to explain the drought stress placed on the plants and drought tolerance. Field experiments were carried out in the rainout shelters to study the influence of phytoalexins on resistance to aflatoxin formation in peanut lines and determine if damage to the peanut by lesser cornstalk borer compromises the resistance. We compared two peanut cultivars, Georgia Green (popular commercial cultivar) with a small root system and Tifton 8 (drought tolerance) with a large root system. Rainout shelter was moved over 90 days after planting. We measured water activity, phytoalexins, and aflatoxin concentrations in all samples. The preliminary analyses of 2001 samples indicate that peanut cultivar Tifton 8 has higher water activity under drought stressed condition than Georgia green. Three phytoalexins have been measured, trans-resveratrol, trans-arachidin-3, and trans-3-isopentadienyl-4,3',5'-trihydroxystilbene. Damaged pods of Tifton 8 had higher concentrations of all three phytoalexins than Georgia Green. The total aflatoxin levels were lower in Tifton 8 than in Georgia Green. LCB damage significantly increased aflatoxin concentrations in all samples, but Tifton 8 had lower total aflatoxin contamination, which might be correlated with the concentrations of phytoalexins in the damaged pods.