Genetic variation within maize population GT-MAS:gk and the relationship with resistance to Aspergillus flavus and aflatoxin production

Aspergillus flavus (Link:Fr.) infection and aflatoxin contamination of maize (Zea mays L.) grain are an extremely serious problem. Maize genotypes resistant to A. flavus attack are needed. Maize breeders and plant pathologists must identify resistance sources and incorporate resistance into adapted breeding material. Maize population GT-MAS:gk has been released for use as a resistance source. In this study, we surveyed the genetic variation in this population and made the breeders/plant pathologists aware of the heterogeneous nature in this maize population by using RAPD analysis and correlated the RAPD marker association with the resistance to A. flavus and aflatoxin production. Of 40 RAPD primers, only 15 gave sufficient numbers of reproducible and readily scored polymorphic bands suggesting that this population was highly homogeneous. However, genetic distances, ranging from 0.08 to 0.28 and averaging 0.17, suggest that there is variation within the population. Cluster analysis distinguished three major polymorphic groups. Laboratory bioassay revealed that group I contained the most resistant individuals, i.e., those with less aflatoxin production. Group Il had the least resistance, and group III was intermediate. This study showed that the maize population GT-MAS:gk is heterogeneous and individuals are different in resistance to A. flavus and aflatoxin production. Resistance should be confirmed through progeny testing before further development. The RAPD marker OPX-04, which may be associated with the resistance trait, has been cloned and further characterization will be pursued.