Identification of Aspergillus flavus Isolates as Potential Biocontrol Agents of Aflatoxin Contamination in Crops

Abstract

Aspergillus flavus, a haploid organism found worldwide in a variety of crops, including maize, cottonseed, almond, pistachio, and peanut, causes substantial and recurrent worldwide economic liabilities. This filamentous fungus produces aflatoxins (AFLs) B1 and B2, which are among the most carcinogenic compounds from nature, acutely hepatotoxic and immunosuppressive. Recent efforts to reduce AFL contamination in crops have focused on the use of nonaflatoxigenic A. flavus strains as biological control agents. Such agents are applied to soil to competitively exclude native AFL strains from crops and thereby reduce AFL contamination. Because the possibility of genetic recombination in A. flavus could influence the stability of biocontrol strains with the production of novel AFL phenotypes, this article assesses the diversity of vegetative compatibility reactions in isolates of A. flavus to identify heterokaryon self-incompatible (HSI) strains among nonaflatoxigenic isolates, which would be used as biological controls of AFL contamination in crops. Nitrate nonutilizing (nit) mutants were recovered from 25 A. flavus isolates, and based on vegetative complementation between nit mutants and on the microscopic examination of the number of hyphal fusions, five nonaflatoxigenic (6, 7, 9 to 11) and two nontoxigenic (8 and 12) isolates of A. flavus were phenotypically characterized as HSI. Because the number of hyphal fusions is reduced in HSI strains, impairing both heterokaryon formation and the genetic exchanges with aflatoxigenic strains, the HSI isolates characterized here, especially isolates 8 and 12, are potential agents for reducing AFL contamination in crops.

Endophytic Fungi as Potential Biocontrol Agents against Rhizoctonia solani J.G. Kühn, the Causal Agent of Rice Sheath Blight Disease

“…In the present study, A. fumigatus and A. awamori showed great in vitro and greenhouse biocontrol potentials against the pathogenic fungi. This finding concurs with the results obtained by Rosada et al [ 50 ] and Cook and Baker [ 7 ]. Rosada et al [ 50 ] identified isolates of A. flavus Link with good biocontrol potential against aflatoxin-producing agents in crops.…”

“…This finding concurs with the results obtained by Rosada et al [ 50 ] and Cook and Baker [ 7 ]. Rosada et al [ 50 ] identified isolates of A. flavus Link with good biocontrol potential against aflatoxin-producing agents in crops. In the present study, A. fumigatus ranked the second most effective in controlling the rice sheath blight fungal agent in the dual culture and greenhouse methods, and first in the volatile metabolite method.…”

A Shotgun Metagenomic Sequencing Exploration of Cabernet Sauvignon Grape Must Reveals Yeast Hydrolytic Enzymes

“…Aspergillus spp. has been previously reported as potential biocontrol agent (Tiwari et al, 2011;Rosada et al, 2013) and also shown to secrete β-glucosidase (Watanabe et al, 1992;Vaithanomsat et al, 2011) that are beneficial for the wine production . Talaromyces sp.…”

Heterokaryosis and diploid formation among Brazilian isolates of Macrophomina phaseolina

“…In the present analysis, the inability of isolate 1 to form viable heterokaryons between its genetically complementary nit mutants, and its reduced count of hyphal fusions compared with its HSC counterparts (isolates 4 and 13), led it to be characterized as having an HSI phenotype. Although statistically nonsignificant variations in the number of hyphae anastomoses were observed among HSC isolates 4 and 13 of M. phaseolina , significant variations in the frequency of hyphal anastomosis among HSC isolates of Aspergillus flavus and Fusarium solani have been previously demonstrated (Hawthorne & Rees‐George, ; Rosada et al ., ). In the present study, hyphal anastomosis in HSI isolate 1, under laboratory conditions, was found on average to be about six times less common when compared to HSC isolates 4 and 13.…”

“…Lack of complementation between the two complementary nit mutants may mean: (i) their original wild isolates are in different VCGs, or (ii) one or both of their wild isolates are unable to form a heterokaryon in which complementation can occur. Such isolates are designated heterokaryon self‐incompatible (HSI; Rosada et al ., ).…”