Characterization of non-aflatoxigenic strains of Aspergillus flavus as potential biocontrol agent for the management of aflatoxin contamination in groundnut

Abstract

In the present study, nine non-aflatoxigenic Aspergillus flavus strains were evaluated for their potential to reduce A. flavus infection and aflatoxin contamination in groundnut. Genetic characterization of these strains revealed six different deletion patterns (A-F) for thirteen examined genes from the aflatoxin biosynthesis pathway. Strain AFGS5 recorded maximum number of gene deletion (F) which included 12 out of 13 tested genes. Our findings indicated that aflR was the most frequently absent gene among the observed deletion patterns. A dendrogram inferred from combining random amplified polymorphic DNA and microsatellite data showed three of the non-aflatoxigenic strains segregating from other sampled isolates (aflatoxigenic and non-aflatoxigenic) tested. Greenhouse experiments, involving non-aflatoxigenic strains as biocontrol agents resulted in two strains, AFGS5 and AFGS12, which significantly reduced the population of aflatoxigenic fungi and the level of total aflatoxins in the rhizosphere/geocarposphere of soil samples as well as in groundnut seeds. Based on our findings, the use of these native non-aflatoxigenic strains; AFGS5 or AFGS12 in particular, as biopesticides could offer efficacious mitigation of aflatoxin contamination.

Present Status and Perspective on the Future Use of Aflatoxin Biocontrol Products

“…Research programs at UC Davis and collaborating universities in Argentina and Spain have identified through laboratory tests, atoxigenic A. flavus isolates with potential as biocontrol agents for use on those nations, but the efficacy of those isolates has not been tested under field conditions [68][69][70]. Similarly, studies for identifying potential A. flavus biocontrol isolates are being conducted in other countries including, China [71], India [72], Thailand [73,74], and Serbia [75].…”

Control of Aflatoxigenic Molds by Antagonistic Microorganisms: Inhibitory Behaviors, Bioactive Compounds, Related Mechanisms, and Influencing Factors

“…However, as Ehrlich [111] reviewed, there were a lot of challenges to using nontoxigenic Aspergillus species. Primarily, due in part to inherent diversity of Aspergillus species and genetic complexity, genetic mutations may happen in nontoxigenic Aspergillus spp., which potentially leads atoxigenic strains to mutate to aflatoxigenic strains; therefore, from a long-term security, nontoxigenic Aspergillus strains were also suggested to be cautiously used [112][113][114].…”

Biological Control of Mycotoxigenic Fungi and Their Toxins: An Update for the Pre-Harvest Approach

“…However, competition of other mycotoxigenic pathogens such as F. pseudograminearum through nutrient competition [50] and F. culmorum and F. graminearum [51] were also reported. It has been demonstrated that atoxigenic A. flavus strains are powerful BCAs to control the toxigenic strains of A. flavus in cottonseed [52][53][54], maize [27,[55][56][57] and various types of nuts [58][59][60][61]. Currently, different strains of atoxigenic A. flavus are being used depending on the endemic area and sometimes a mixture of strains is used in the field.…”

“…Doster et al used A. flavus strain AF36 as a BCA to control AFs in pistachio orchards for four consecutive seasons (2008-2011) and he could diminish AFs level by 20-45% [114]. In groundnuts, more trials in vitro [61,66] and in the field [58][59][60] have been done. Zhou et al 2015 found a positive correlation between AFs reduction rate and inoculum dose while Hulikunte Mallikarjunaiah et al 2017 measured total AFs in rhizospheric and geocarpospheric soil and groundnut seeds after he treated them with two strains isolated from India.…”

“…Zhou et al 2015 found a positive correlation between AFs reduction rate and inoculum dose while Hulikunte Mallikarjunaiah et al 2017 measured total AFs in rhizospheric and geocarpospheric soil and groundnut seeds after he treated them with two strains isolated from India. A significant reduction of mycotoxin concentration below the maximum permissible levels for ground nuts was obtained [61]. Field trials in Argentina were designed to control AFs in groundnut.…”