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

Giovanni Beccari,Francesco Valente,Andrea Onofri,Łukasz Stępień,Biancamaria Ciasca,Monika Urbaniak,Sally I Abd-El Fatah,Lorenzo Covarelli,Veronica M T Lattanzio

doi:10.3390/microorganisms8020241

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 B1, fumonisin B2 and fumonisin B3 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.

Highlights

Fusarium verticillioides (Sacc.) Nirenberg is a member of the Gibberella fujikuroi species complex, called Fusarium fujikuroi species complex (FFSC), a group of 40 closely related Fusarium species defined by morphological traits, sexual compatibility and DNA-based phylogenetic analysis [1,2].In particular, F. verticillioides belongs to the “African” clade of the FFSC [3], and it is the main causal agent of Fusarium ear rot of maize (Zea mays L.) [4,5]
Total fumonisins biosynthesized by all positive strains (n = 71) varied from 0.03 to 69.84 μg/g, with fumonisin B1 (FB1) being the most abundant analogue followed by fumonisin B2 (FB2) and fumonisin B3 (FB3)
The three fumonisin analogues analyzed in this study (FB1, FB2 and FB3) were simultaneously produced by 81% of positive strains (n = 58), while two analogues, FB1 and FB2 as well as FB1 and FB3, were simultaneously biosynthesized by 7% (n = 5) and 1% (n = 1) of positive strains, respectively

Summary

Introduction

F. verticillioides belongs to the “African” clade of the FFSC [3], and it is the main causal agent of Fusarium ear rot of maize (Zea mays L.) [4,5]. This fungus has been reported worldwide and, in particular, it prevails in drier and warmer climatic regions [6,7] such as those present in temperate, semitropical and tropical regions including European [4], Mediterranean [8], African [9] and Middle Eastern [10] maize-growing areas. Fumonisin accumulation in maize grains can occur in the field, following preharvest infections, and possibly continue during grain storage [28]

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