In Vitro Fumonisin Biosynthesis and Genetic Structure of Fusarium verticillioides Strains from Five Mediterranean Countries

Abstract

Investigating the in vitro fumonisin biosynthesis and the genetic structure of Fusarium verticillioides populations can provide important insights into the relationships between strains originating from various world regions. In this study, 90 F. verticillioides strains isolated from maize in five Mediterranean countries (Italy, Spain, Tunisia, Egypt and Iran) were analyzed to investigate their ability to in vitro biosynthesize fumonisin B 1 , fumonisin B 2 and fumonisin B 3 and to characterize their genetic profile. In general, 80% of the analyzed strains were able to biosynthesize fumonisins (range 0.03-69.84 µg/g). Populations from Italy, Spain, Tunisia and Iran showed a similar percentage of fumonisin producing strains (>90%); conversely, the Egyptian population showed a lower level of producing strains (46%). Significant differences in fumonisin biosynthesis were detected among strains isolated in the same country and among strains isolated from different countries. A portion of the divergent FUM1 gene and of intergenic regions FUM6-FUM7 and FUM7-FUM8 were sequenced to evaluate strain diversity among populations. A high level of genetic uniformity inside the populations analyzed was detected. Apparently, neither geographical origin nor fumonisin production ability were correlated to the genetic diversity of the strain set. However, four strains from Egypt differed from the remaining strains. 2 of 17 semitropical and tropical regions including European [4], Mediterranean [8], African [9] and Middle Eastern [10] maize-growing areas. For example, F. verticillioides was the species isolated more frequently from maize kernels harvested in Italy [11-13], Spain [14-16], Egypt [17-21] and Iran [22]. This is also one of the species able to biosynthesize the secondary metabolites fumonisins [23]. Specifically, F. verticillioides is considered the main fumonisin producer; therefore, this is the most important species associated with fumonisin contamination of maize grains [24]. Fumonisins occur worldwide in maize, including Mediterranean [4,8,24,25] farming areas, where this is one of the most widely cultivated crops [26,27]. Fumonisin accumulation in maize grains can occur in the field, following preharvest infections, and possibly continue during grain storage [28].Contaminations strongly impair maize grain quality because of the negative impact on animal and human health [29]. Fumonisin mycotoxins can be divided into four main groups, with the most abundant fumonisins found in nature included in the B group: fumonisin B 1 (FB 1 ), fumonisin B 2 (FB 2 ) and fumonisin B 3 (FB 3 ). Among B analogues, FB 1 is the most detected fumonisin in maize as well as the most toxicologically active [24,30]. In fact, after ingestion, fumonisins may cause a wide range of toxic effects, especially towards liver and kidneys [31][32][33][34][35]. For this reason, the European Commission has established maximum limits for the sum of FB 1 and FB 2 in maize for human consumption [36,37].The amount of fumonisins found in maize kernels is a...

Aspergillus niger Environmental Isolates and Their Specific Diversity Through Metabolite Profiling

“…Fumonisins are synthesised with great predominance by Fusarium spp. ( Beccari et al, 2020 ; Stępieñ, 2020 ). A. niger is able to form mainly fumonisin B2 (FB2), especially on the cultivation media RC (reinforced clostridial agar), CYA (Czapek yeast extract agar) and YES (yeast extract sucrose medium), while usually not on the vast majority of plant-based media, such as MEA (malt extract agar base w/mycological peptone), OA (oat agar), or PDA (potato-dextrose agar).…”

Fusarium: Mycotoxins, Taxonomy, Pathogenicity

“…In general, there is no correlation between the efficiency of the metabolite synthesis and geographical origin of the strains studied. Nevertheless, there are reports of significant differences in the toxin production that occur despite the genetic uniformity of the population over a large area [ 11 ]. The chemotypes emerging in unexplored geographic areas could be a serious threat.…”