Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2001
Publication Date: 1/1/2002
Citation: Guo, B.Z., Butron, A., Li, H., Widstrom, N.W., Lynch. R.E. 2002. Restriction fragment length polymorphism assessment of the heterogeneous nature of maize population GT-MAS:GK and field evaluation of resistance to aflatoxin production by Aspergillus flavus. Journal of Food Protection. 65(1):167-171. Interpretive Summary: Aflatoxin is a byproduct of mold growth in a wide range of commodities. It is considered to be the most potent naturally-occurring carcinogen. Aflatoxin is produced from the molds pre-harvest in the field, and post- harvest in storage. In both cases, damage due to insects, mishandling or environmental stress can enable the molds to invade the seeds. Thus, they are of major concern, especially in the Southeastern U.S. The development of strategies to reduce or eliminate aflatoxin contamination in food and fiber is a research priority in ARS. Our efforts on this problem have focused on increasing natural resistance in the host such as corn. We have released GT-MAS:gk, a corn population, for use as a resistance source to the mold. To utilize the resistance traits, inbreedng with selection for resistance is needed. In the present study, we assessed the genetic variation in this corn population using molecular technique. Considerable variation was detected with moledular markers. Three groups were distinguished and the aflatoxin concentration among the lines were different in the field evaluation. The maturity was also different. Because of the genetic variation existing in this germplasm, the most resistant lines should be inbred to increase homogeneity and resistance should be confirmed through testing.
Technical Abstract: Aflatoxin, produced by Aspergillus flavus, is one of the most toxic and carcinogenic substances known and contaminates many agricultural commodities such as corn, peanuts, cottonseed, and tree nuts. The challenge to breeders/plant pathologists is to identify lines that have resistance to aflatoxin production. Maize population GT-MAS:gk has been identified and released as a germplasm with resistance to aflatoxin contamination. In the present study, we assessed genetic divergence in the GT-MAS:gk population using RFLP DNA markers to survey 11 selfed inbred lines and conducted field evaluations for the dissimilarities in aflatoxin production among these inbred lines in comparison with a sister population, GT-MAS:pw,nf. The 11 selfed inbred lines were assayed for DNA polymorphism using 113 restriction fragment length polymorphism (RFLP) markers in 10 linkage groups covering 1518.2 cM. Considerable variation among the inbreds was detected with RFLP markers of which 42 probe-enzyme combinations gave 102 polymorphic bands. Cluster analysis based on genetic similarities revealed associations and variations among the tested lines. Three polymorphic groups were distinguished by cluster analysis. A two-year field evaluation data showed that aflatoxin concentration among the lines were significantly different in both years (P<0.001). The maturity data were also different. Thus, this study demonstrated that the maize population GT-MAS:gk is heterogeneous and individuals may be different in resistance to A. flavus infection and aflatoxin production. Therefore, the most resistant lines should be inbred to increase homogeneity and resistance should be confirmed through progeny testing.