Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2000
Publication Date: 2/1/2001
Citation: Guo, B., Li, R.G., Widstrom, N.W., Lynch, R.E., Cleveland, T.E. 2001. Genetic variation within the maize population GT-MAS:GK and its relationship with resistance to Aspergillus flavus. Theoretic and Applied Genetics. 103:533-539. Interpretive Summary: Aflatoxins are a major group of toxins produced by the fungi Aspergillus flavus and A. parasiticus. They are of major concern, especially in the Southeastern U.S., because they have been shown to cause cancer of the liver. Thus, 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 natural resistance in the host such as corn. We have released GT-MAS:gk, a corn population, for use as a resistance source to A. flavus. To utilize the resistance traits in this population, inbreeding with selection for resistance is needed. In the present study, we surveyed the genetic variation among individual plants from the GT-MAS:gk population using molecular technique. The analyses revealed three major groups. Group one contains the most resistant individuals with less aflatoxin contamination. This study showed that the molecular markers may be linked with the resistance traits that will assist in the selection of resistant corn types.
Technical Abstract: Aspergillus flavus infection and subsequent aflatoxin contamination of maize grain is an extremely serious problem. Maize genotypes resistant to A. flavus attack are desperately needed. The challenge to maize breeders and plant pathologists is to identify resistance sources and to incorporate the improved resistance traits into adapted breeding material. GT-MAS:gk, identified as germplasm resistant to A. flavus, was released for use as a resistance source. This population has been maintained by bulk sibbing without selection and consequent variation in resistance has been observed. To utilize the resistance traits in this population, inbreeding with selection for resistance is needed. In the present study, we surveyed the genetic divergence for DNA polymorphism among individual plants from the GT-MAS:gk population using 40 primers. Only fifteen primers gave sufficient numbers of reproducible and readily scored polymorphic bands and suggested that this population was highly homogeneous based on a low frequency of polymorphic bands (37.5%) with 40 primers. Genetic distance, ranging from 0.079 to 0.276 and averaging 0.164, suggests that there is genetic varation within the population. The average genetic distance between population GT-MAS:gk and the counter population GT-MAS:pw,nf, a susceptible sister population, was 0.293. Cluster analysis revealed three major polymorphic groups. Group one contains the most resistant individuals, i.e. those with less aflatoxin. Group two likely has the least resistance, and group three is intermediate. This study showed that the RAPD markers and the polymorphic bands may be linked with the resistance traits.