Abstract
In this study, the possibility of sexual reproduction in sampled Aspergillus flavus strains was evaluated by assessing the distribution of mating type (MAT) genes, which are known to control sexual character among fungi, for two counties in Kenya. Forty-four isolates from Nandi and Makueni counties were genotyped by MAT using a multiplex polymerase chain reaction assay. The primer pair for the MAT1-1 amplified a 396 base pair (bp) fragment containing an α-box motif, and MAT1-2 primers targeted a 270 bp segment with a high mobility group protein. The MAT1-2 genes dominated in both regions although the frequency was higher in Nandi (75%) than in Makueni (54.17%). There were no MAT1-1 genes sampled in Nandi, and in Makueni their proportion was 15.91%. The percentage of isolates that amplified for both MAT genes in Makueni was 9.09%, while in Nandi it was 11.36%. Currently, use of aggressive aflatoxin non-producing A. flavus strains as biocontrol is the most promising preharvest aflatoxin control strategy in Kenya. However, we address the possibility of introduced biocontrol strains to breed with existing aflatoxin producing strains in nature, which could lead to the generation of A. flavus offspring capable of aflatoxin production while also being aggressive colonizers and possibly increasing the burden of aflatoxin exposure in food.
Highlights
Aspergillus spp. belongs to phylum Ascomycota and family Trichocomaceae
In this study, sampled A. flavus strains from Makueni and Nandi include those that contain at least fragments of both mating type (MAT) genes and those that contain a single MAT gene
This study underscores the importance of investigating the mating type distribution in the field, prior to biocontrol selection and release, to minimize the potential for sexual recombination while promoting efficacy of the biocontrol strain
Summary
Aspergillus spp. belongs to phylum Ascomycota and family Trichocomaceae. Species in the fungus genus’ section Flavi have potential to infect maize, peanuts, cotton, and tree nuts among other crops and may contaminate with aflatoxins, which are Group 1 carcinogens according to International Centre for Cancer Research [1, 2]. Successful sexual reproduction requires the presence of functional and compatible mating type genes (MAT - and MAT - genes). Selffertility is possible when both mating type genes are present and functional within the same organism, either on different chromosomes or adjacent to the same chromosome. Only one mating type gene is present in a strain, so it is considered self-infertile and requires the presence of a compatible strain having a functional gene representative of the opposite mating type [4, 5] (Horn et al, 2013). Aspergillus flavus is considered functionally heterothallic, and it is uncommon for strains to contain both MAT genes. Horn et al [6] reported A. nomius strain that contained both MAT genes, which were self-infertile but functionally bisexual, meaning they could mate with both MAT - and MAT - strains
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