Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/1995
Publication Date: N/A
Interpretive Summary: Aflatoxin, produced by certain molds that infest grain crops, is one of the most potent animal poisons known. Contamination of grains and grain products with this toxin before or after harvest at levels exceeding 20 parts per billion can cause significant economic losses to growers and processors since the products may have to be discarded. In the current study, a resistance mechanism in corn kernels against attack by the aflatoxin producing mold was identified that was found to be dependent on relative humidity. Corn kernels held at certain relative humidities for 3 days and then inoculated with the aflatoxin producing mold accumulated significantly less aflatoxin than those not subjected to prior incubation. The resistance mechanism may be related to substances being produced during the initiation of kernel germination or sprouting at certain relative humidity levels. All corn varieties were not equally responsive to the humidity treatments and therefore may have different genetic capacities to ward off aflatoxin producing molds. The current study expands our knowledge of corn kernel resistance mechanisms effective against aflatoxin producing molds which could lead to manipulation of these resistance traits to control aflatoxin contamination on a practical basis.
Technical Abstract: Kernels of maize population GT-MAS:gk, resistant to aflatoxin B1 production by Aspergillus flavus, and susceptible Pioneer hybrid 3154 were tested for aflatoxin when incubated under different relative humidities (RH). High aflatoxin levels were not detected in either genotype at RH<91 percent. Resistance in GT-MAS:gk was consistent across all RH levels (91-100 percent) at which significant aflatoxin accumulation was detected. Aflatoxin levels in GT-MAS:gk averaged about 2 percent of those in susceptible Pioneer 3154, which suggests that storage of this or other genotypes with similar resistance mechanisms may be possible under moisture conditions less exacting than are required with susceptible hybrids. Results for fungus growth and sporulation ratings on kernel surfaces were similar to those for aflatoxin levels. When kernels of both genotypes were incubated 3 d at 100 percent RH prior to inoculation with A. flavus, germination percentages increased to very high levels compared to kernels that were not preincubated. Aflatoxin levels remained consistently low in GT-MAS:gk, but decreased markedly (61 percent) in Pioneer 3154. When eight susceptible hybrids were evaluated for aflatoxin accumulation in preincubated kernels, seven of these supported significantly lower toxin levels. Average reduction across hybrids was 83 percent, and reductions within hybrids ranges from 68-96 percent. Preincubated kernels of one susceptible hybrid (Deltapine G-4666) supported aflatoxin levels comparable to those in resistant GT-MAS:gk.