Skip to main content
ARS Home » Southeast Area » Dawson, Georgia » National Peanut Research Laboratory » Research » Publications at this Location » Publication #293403
Title: Clonality and sex impact aflatoxigenicity in Aspergillus populations

Author
item CARBONE, IGNAZIO - North Carolina State University
item Horn, Bruce
item OLARTE, RODRIGO - North Carolina State University
item MOORE, GEROMY - North Carolina State University
item WORTHINGTON, CAROLYN - North Carolina State University
item MONACELL, JAMES - North Carolina State University
item SINGHI, RAKHI - North Carolina State University
item STONE, ERIC - North Carolina State University
item HELL, KERSTIN - International Institute For Tropical Agriculture
item CHULZE, SOFIA - National University Of Argentina
item BARROS, GERMAN - National University Of Argentina
item WRIGHT, GRAEME - Department Of Primary Industries
item NAIK, MANJUNATH - College Of Agriculture

Submitted to: Fungal Genetics Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2013
Publication Date: 3/12/2013
Citation: Carbone, I., Horn, B.W., Olarte, R.A., Moore, G.G., Worthington, C.J., Monacell, J.T., Singhi, R., Stone, E.A., Hell, K., Chulze, S.N., Barros, G., Wright, G., Naik, M.K. 2013. Clonality and sex impact aflatoxigenicity in Aspergillus populations. Fungal Genetics Conference. Pacific Grove, CA. March 12-17, 2013.

Interpretive Summary: none required.

Technical Abstract: Species in Aspergillus section Flavi commonly infect agricultural staples such as corn, peanuts, cottonseed, and tree nuts and produce an array of mycotoxins, the most potent of which are aflatoxins. Aspergillus flavus is the dominant aflatoxin-producing species in the majority of crops. Populations of aflatoxin-producing fungi may shift in response to: (1) clonal amplification that results from strong directional selection acting on a nontoxin- or toxin-producing trait; (2) disruptive selection that maintains a balance of extreme toxigenicities and diverse mycotoxin profiles; (3) sexual reproduction that results in continuous distributions of toxigenicity; or (4) female fertility/sterility that impacts the frequency of sexual reproduction. Population shifts that result in changes in ploidy or nuclear DNA composition (homokaryon versus heterokaryon) may have immediate effects on fitness and the rate of adaptation in subsequent fungal generations. We found that A. flavus populations with regular rounds of sexual reproduction maintain higher aflatoxin concentrations than predominantly clonal populations and that the frequency of mating-type genes is directly correlated with the magnitude of recombination in the aflatoxin gene cluster. Genetic exchange within the aflatoxin gene cluster occurs via crossing over between divergent lineages in populations and between closely related species. During adaptation, specific toxin genotypes may be favored and swept to fixation or be subjected to drift and frequency-dependent selection in nature. Results from mating experiments in the laboratory indicate that fertility differences among lineages may be driving genetic and functional diversity. Differences in fertility may be the result of female sterility, changes in heterokaryotic state, DNA methylation, or other epigenetic modifications. The extent to which these processes influence aflatoxigenesis is largely unknown, but is critical to understand for both fundamental and practical applications, such as biological control. Our work shows that a combination of population genetic processes, especially asexual/sexual reproduction and fertility differences coupled with ecological factors, may influence aflatoxigenicity in these agriculturally important fungi.