Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/6/2006
Publication Date: 11/6/2006
Citation: Rowland, D., Dorner, J.W., Sorensen, R.B., Holbrook Jr, C.C. 2006. Variation Among Peanut Cultivars in Pod Water Uptake and Its Effect on Pre-harvest Aflatoxin Contamination. Aflatoxin Elimination Workshop Proceedings. Interpretive Summary: none required
Technical Abstract: The ability to withstand drought stress appears to be a critical crop physiological characteristic impacting pre-harvest aflatoxin contamination. This is especially true in peanut production where dryland peanuts exposed to late season drought are extremely vulnerable to aflatoxin contamination. However, very little is known about the link between peanut physiological drought tolerance and aflatoxin resistance. One key physiological response may be the ability to maintain the water status of the kernel, either through adequate water flow from the plant or direct uptake of water through the hull during pod development. The objectives of this research were to determine the differences in pod water uptake between aflatoxin resistant and susceptible genotypes by: 1) quantifying the relative contribution of water to the developing kernel both from the plant and from the soil directly; 2) determining differences in pod water uptake patterns between genotypes during late season drought; and 3) determining the correlation between water movement through the hull and eventual aflatoxin contamination at harvest. These questions were addressed utilizing labeled water applied to the soil surrounding developing peanuts in enclosed pans, thereby isolating the labeled pod soil from non-labeled rooting soil. These pans were installed next to the developing crop and deuterium was applied at 90 days after planting, just prior to subjecting the crop to complete drought until harvest. The deuterium signal was quantified in pods, attached pegs, and attached stems as the drought progressed. Evidence was found of passive movement of water across the hull during drought as well as differences between cultivars in the amount of water movement. Aflatoxin contamination at harvest was correlated with water movement in a positive direction such that the more water movement, the greater the aflatoxin contamination. This suggests that the movement of water across peanut hulls may indicate a more permeable hull that allows for greater fungal invasion of intact pods, or allows for a moist microclimate within the pods that is conducive to fungal growth and eventual aflatoxin production.