Toxicity, Pathogenicity, and Genetic Differentiation of Five Species of Fusarium from Sorghum and Millet

Abstract

Fusarium isolates recovered from sorghum and millet are commonly identified as F. moniliforme, but with the recognition of new species in this group, the strains given this name are being re-evaluated. We analyzed five strains each from five Fusarium species (F. andiyazi, F. nygamai, F. pseudonygamai, F. thapsinum, and F. verticillioides) often associated with sorghum and millet for their ability to produce fumonisin and moniliformin, their toxicity to ducklings, and their ability to cause disease on sorghum seedlings in vitro. These species can be distinguished with isozymes (fumarase, NADP-dependent isocitrate dehydrogenase, and malate dehydrogenase) and with banding patterns resulting from amplified fragment length polymorphisms. Two species, F. pseudonygamai and F. thapsinum, produced high levels of moniliformin, but little or no fumonisins, and were consistently highly toxigenic in the duckling tests. Two species, F. verticillioides and F. nygamai, produced high levels of fumonisins, but little or no moniliformin, and also were toxigenic in the duckling tests. F. andiyazi produced little or no toxin and was the least toxigenic in the duckling tests. In sorghum seedling pathogenicity tests, F. thapsinum was the most virulent followed by F. andiyazi, then F. verticillioides, and finally F. nygamai and F. pseudonygamai, which were similar to each other. Thus, these five species, which would once have all been called F. moniliforme, differ sufficiently in terms of plant pathogenicity and toxin production profile, that their previous misidentification could explain inconsistencies in the literature and differences observed by researchers who thought they were all working with the same fungal species.

Identification and Characterization of Toxigenic Fusaria Associated with Sorghum Grain Mold Complex in India

“…are dominant within the grain mold complex. Some species of Fusarium (F. andiyazi, F. proliferatum, F. thapsinum and F. sacchari) involved in grain mold complex produce mycotoxins, such as fumonisins, moniliformin, trichothecenes, and fusaproliferin [2]. The secondary invading Aspergillus spp.…”

“…There is a general consensus that Fusarium growing on sorghum belongs mainly to Giberella fujikuroi species complex, which comprises of Fusarium species included in section Liseola [2]. Since several species of Fusarium have been reported to be associated with sorghum grain mold [17], and most of them are morphological similar, it is essential to identify species of Fusarium causing grain mold more precisely.…”

“…Since isolates of the same species of Fusarium have been reported to have >65% genetic similarity [2], it was expected that the isolates representing each group with more than 70% similarity to be the same species. The grouping of each species in distinct cluster was confirmed by α-Elongation factor sequence based species identification.…”

“…Fusarium thapsinum, although identified most commonly associated with sorghum grain mold complex in India, it was atoxigenic for fumonisin production except one isolate F 88. Fusarium thapsinum has been reported to produce high levels of moniliformin, but only traces of fumonisins [2,22,23].…”

Molecular Characterization of Fusarium globosum Strains from South African Maize and Japanese Wheat

“…This technique was first applied by Leissner et al [19] to discriminate between strains of F. graminearum. AFLP has since proven to be a powerful tool for evaluating genetic variation in populations and has resolved many other questions concerning mating type and formae speciales in the genus Fusarium [2,4,11,21,22,36,51].…”