MOLECULAR GENETIC APPROACHES FOR INVESTIGATION OF TAXONOMY AND SPECIFIC IDENTIFICATION OF TOXIN-PRODUCING Fusarium SPECIES: ACHIEVEMENTS AND PROBLEMS (review)

Abstract

A b s t r a c tAscomycetous fungi of the genus Fusarium, which was separated as a single taxonomic group in 1809 by Heinrich Friedrich Link, are distributed worldwide and have different ecological niches. They have been found in soil and plants as endophytes, saprotrophs and parasites. Infections of agricultural plants, caused by Fusarium fungi, lead to annual damage, estimated in hundred million dollars. In addition to decrease harvest quality and quantity, Fusarium fungi are able to produce toxic metabolites (fusariotoxins). The consumption of fusariotoxin-contaminated winter grain led to deaths of tens of thousands of people in Volga and Ural regions in 1930s-1940s. These factors make necessary investigation of morphology, biochemistry and genetics of those organisms. Nowadays there is no universal taxonomic system of the genus Fusarium, so it is not possible to identify an isolate to species level in many cases. The high variability of morphological structures, and, on the other side, their similarity for closely related species, are major problems for researchers which use classical methods for identification and systematization of this group of fungi. Today, the molecular methods, based on the use of specific DNA sequence, are playing an increasingly important role in Fusarium systematics. The application of this approach has led to establishment of a number of new species in the genus. T. Yli-Mattila et al. (2009, 2011 used multilocus phylogenetic analysis to describe the novel species F. sibiricum and F. ussurianum which were found in Siberia and Far East and proved to be morphologically similar to F. graminearum and F. langsethiae, respectively. The authors of this paper identified the species F. torulosum (morphologically similar to F. avenaceum) in Russia for the first time based on the use of DNA markers. It is no less important that the analysis of interand intraspecific polymorphism makes possible the development of highly-specific assays for molecular detection of Fusarium fungi, including ones which infect plants and produce mycotoxins. The use of these assays (for example, ones described by M. Nicolaisen et al., 2009 and A.A. Stakheev et al., 2011) allows not only to detect the contamination of plants by mycotoxin producers, but also to estimate the quantity of their content in a probe. At the same time, a lot of questions are still unanswered: particularly, simultaneous application of different species concepts (morphological, biological and phylogenetic) makes it difficult to develop universal taxonomic system of the genus; also the most informative and reliable marker, which would reflect the evolutionary history of the genus, has not been found. The main achievements and problems of Fusarium phylogenetics, and perspectives of the application of molecular approach for studies of this group of organisms are discussed in this review.

An evolutionary view of the Fusarium genome

“…These toxins are produced by the fungus on stored agricultural products, or even directly on the growing plant (12). In the period 1930-1940 in the Volga and Ural regions, the presence of fusariotoxins in winter cereals claimed the lives of tens of thousands of people (13).…”

“…With the scienti c and technological developments at the end of the XX century, genetic and biochemical features were added to solve morphological disagreements. Nevertheless, is not until recent years, using modern phylogenetic methods, that evolutionary approaches started to clarify the chaotic taxonomic assignment of Fusaria (3,11,13,16,17). Several of these rst phylogenetic works were based on multilocus sequence analysis of conserved genes, or partial genes like cmdA, rpb1, rpb2, tef1, and tub2 (11,16).…”

Mycotoxin contamination of fresh berries and fruits marketed in the central region of Russia

“…Наряду с известными и контролируемыми МТ могут выявляться ранее не учитываемые токсичные грибные метаболитыэмерджентные МТ (ЭМТ) [6][7][8], нуждающиеся в дальнейшем изучении и оценке опасности их присутствия в пищевых продуктах. Появление новых и малоизученных штаммов плесеней в сельскохозяйственных ареалах [9][10][11], недостаточность данных о характере контаминации МТ отечественных плодов и ягод обосновывают необходимость изучения характера и уровней загрязненности МТ и ЭМТ этой группы растительных продуктов массового потребления.…”

Mycotoxin contamination of fresh berries and fruits marketed in the central region of Russia

“…These emergent MTs [6][7][8] should be investigated and hazards posed by their occurrence in foods should be assessed. Occurrence of new and poorly explored mold strains in agricultural areas [9][10][11] and insufficient data on MT contamination in domestically grown fruits and berries justify the necessity to explore the nature and levels of MT and EMT contamination in this plant group of mass consumer products.…”