Distinctive metabolites of Alternaria, Fusarium and Microdochium fungi as a tool for assessing their relationship in micobiota of wheat grain

Fungal contamination of 17 winter wheat varieties grown in the Krasnodar region under the natural infections was analyzed. In addition to the traditional mycological analysis of infection with fungi, methods based on the quantitative detection of metabolites inherent in fungi and absent in the host plant were used. For this purpose, the ranges of DNA contents of Alternaria, Fusarium and Microdochium fungi, as well as mycotoxins produced by these fungi were characterized in the grain. Abundant presence of Alternaria fungi was detected without a significant difference between the varieties. A quantitative detection of the Microdochium fungi in grain was carried out at the first time in Russia and it was shown that the content of M. nivale DNA was significantly exceeds the content of M. majus DNA. The dominant of F. graminearumin the complex of Fusarium fungi in comparison to other species and the significant range of the content of the metabolites produced by this pathogen were shown. The high variation of contents of marker metabolites inherent in highly aggressive species of fungi and the stability of these parameters for saprotrophic organisms can be of fundamental importance in the selection of objective for quantitative measurements of plants resistant to pathogens. The maximum amount of F.graminearum metabolites was found in the grains of susceptible Brigada. The minimum content of Fusarium metabolites was established in the grain of Adel and Kurs varieties, which are the relatively resistant to pathogenic Fusarium fungi. The proportion of F.graminearum DNA as a percentage of the DNA of Fusarium group forming trichothecene mycotoxins ranged from 6.1% to 100.9%. This value is an indicator of plant resistance to infection by pathogens. According to our observations, values above 30% are characteristic of susceptible varieties. A positive correlation was found between DNA contents of M.nivale and F. sporotrichioides fungi. Any significant relations between the most abundantly present fungi of Alternaria and the parameters of grain contamination by other analyzed fungi have not been revealed. Diversity of the reactions of wheat genotypes to the invasion of various heterotrophic fungi and the possibility of using objective quantitative assessment of resistance were shown.