Selection of Superior Biological Control Agents with Genetic and Cultural Criteria
U.S. Arid Land Agricultural Research Center
2013 Annual Report
1a.Objectives (from AD-416):
Determine selection criteria for next generation atoxigenic biological control agents through development of laboratory and population based assays and criteria. Delineate both association of specific fungal groups with target crops and genetic characteristics of value in monitoring fungi of interest and in selecting elite biocontrol fungi.
1b.Approach (from AD-416):
Apply genetic methods to identify unique biological control agents and to associate specific fungal genetic groups with target crops and regions. Develop pyrosequencing assays to monitor specific fungi in the environment and during host infection. Utilize genomic approaches to identify traits of potential value in selecting next generation biological control agents for aflatoxin mitigation. Use crop based assays to rank relative desirability of atoxigenic strains for use in target agroecosystems.
This project directly contributes to Objective 1, Advance biocontrol technologies through strain selection, formulation, and adaptation to agronomic practices, and Objective 2, Characterize adaptive differences among Vegetative Compatibility Groups and strains of Aspergillus flavus including adaptation to host, environment, and ecosystem, of the inhouse parent project. Laboratory studies aimed at selecting next-generation atoxigenic biocontrol strains continue to be conducted. Pyrosequencing assays developed to differentiate biological control fungi from other members of the fungal community were developed for use in assessment of variation among biocontrol fungi in competition on crops. These assays will be employed by other projects seeking to optimize biocontrol. A population based study was undertaken to evaluate the genetic stability of an atoxigenic genetic group of Aspergillus flavus used in biological control and to determine the suitability of members of this group for biological control over an expanded area. Multiple isolates of the genetic group from each of four states in Mexico, Tamaulipas, Nayarit, Sonora, and Sinaloa, were compared with isolates from Arizona and Texas. Several deoxyribonucleic acid (DNA) characteristics suggest the isolates belong to a single genetic population that contains variation but is distinct from other genetic groups of Aspergillus flavus. The results suggest the investigated genetic group will have value across a broad geographic area and that population studies can be used to identify additional, similar, potentially valuable, genetic groups. A previously characterized genetic defect known to prevent aflatoxin production by this genetic group was found in all the examined isolates. In addition, further deterioration in the genes used to produce aflatoxins was also detected indicating both stability of atoxigenicity and further evolution of this atoxigenic genetic group. The overall project is making significant contributions to designing processes through which optimal biological control agents may be select and, as a result, optimizing biological control with atoxigenic strains.