Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/13/2007
Publication Date: 3/18/2008
Citation: Timper, P., Holbrook, Jr., C.C., Wilson, D. 2008. Roos vs pod infection by root-knot nematodes on aflatoxin contamination of peanut [abstract]. Communications in Agricultural and Applied Biological Sciences. 72:655-658. Interpretive Summary:
Technical Abstract: Aflatoxins are potent carcinogens produced by some Aspergillus spp. Infection of peanut (Arachis hypogaea) by root-knot nematodes (Meloidogyne arenaria) can lead to an increase in aflatoxin contamination of kernels when the plants are subjected to drought stress during pod maturation. It is not clear whether the increased aflatoxin contamination is primarily due to greater invasion of the galled pods by toxigenic Aspergillus spp. or whether root galling is also involved. Our objective was to determine the contribution of root and pod galling caused by root-knot nematodes to the increase in aflatoxin contamination in peanut. A greenhouse experiment was conducted in which pods and roots were physically separated. Pod set was restricted to soil-filled pans (41 cm dia. x 10 cm depth), while the roots grew underneath the pan into a pot. The experiment had a factorial arrangement of treatments: pod zone with and without nematodes, and root zone with and without nematodes. The four treatment combinations were replicated 10 to 13 times. Conidia Aspergillus flavus/A. parasiticus was added to the soil surface (pods zone) at mid bloom. Plants were subjected to drought stress 40 days before harvest. Adding nematodes to the pod zone had no effect on aflatoxin concentrations in the peanut kernel. However, the lack of an effect may have been to due to the low occurrence of galling on the hulls. In pots where nematodes were added to the root zone, 50 to 80% of the root system was galled. Adding nematodes to the root zone increased (P = 0.003) aflatoxin concentrations in the peanut kernels from 37 ppb in the control to 67 ppb. In summary, infection of peanut roots by M. arenaria increases aflatoxin contamination of the kernels. Nematode damage to the roots results in greater drought stress which may result in greater susceptibility to aflatoxin contamination. The contribution of pod galling on the increase in aflatoxin levels in nematode-infected peanut is still unclear.