Taxonomic Diversity of Micromycete Complexes in the Root Zone of a Perennial Wild Species of Sunflower Helianthus Grosseserratus

The aim of our research was to determine the peculiarities of the formation of the taxonomic structure of micromycete complexes in the root zone of the perennial wild species of sunflower Helianthus grosseserratus when grown in the South of Ukraine. Soil samples taken from the root zone of two samples of perennial wild sunflower Helianthus grosseserratus 1630 and H. grosseserratus 1201, which were grown for more than 20 years in one place in the collection nursery of the Institute of Oilseed Crops of NAAS of Ukraine, were studied. Areas where plants are grown have not been treated with herbicides. Samples of fallow soil served as a control. Soil - chernozem ordinary low-humus leached. Soil samples for analysis were taken at the end of the growing season. To isolate microscopic fungi from the soil, the generally accepted method of serial dilutions was used, followed by sowing of the soil suspension on a dense nutrient medium Chapek-Dox. The method of sowing - deep, dilution of the suspension - 1: 1000. Duration of fungi cultivation - 7-14 days in a thermostat at a temperature of 28оС. The experiment was repeated five times. The complex of fungi-micromycetes in soil samples was determined using determinants and original works. The similarity of the species composition of the soil mycobiota of the fallow and the root zone of wild sunflower was determined by the Sorensen coefficient. Reliable indicators of similarity when comparing the species composition of two different associations were considered those in which the Sorensen coefficient was more than 50%.The analysis of the taxonomic structure of the studied mycocenoses revealed qualitative differences in the genus and species composition of micromycete fungi in the rhizosphere of wild sunflower species and fallow soil. In total, of the 29 species of micromycetes we isolated, 11 were found only in the soil of the fallow. According to our data, only 4 species (A. alliaceus, Paecilomyces lilacinus, F. oxysporum var. orthoceras, M. racemosus) were common species in the soil samples of fallow and root zone Helianthus grosseserratus 1630 and H. grosseserratus 1201. The species diversity of micromycetes of the root zone of H. grosseserratus 1201 was wider, and, accordingly, more similar to the soil of the fallow - 15 common species. Micromycetes that were typical for both fallow soil and sunflower are saprotrophs of A. niveus, P. canescens, P. crustosum, P. nigricans, P. thomii, as well as opportunistic species Verticillium album and V. lateritium. A comparative analysis of the lists of species composition of micromycete complexes revealed significant differences between the mycocenoses of the root zone of wild sunflower and fallow soil, as evidenced by the calculated Sorensen coefficients. The data indicated that the similarity of the species composition of the mycobiota H. grosseserratus 1201 with fallow was 66.7% (Cs = 0.67), and Helianthus grosseserratus 1630 - only 35.8% (Cs = 0, 35). The coefficient of similarity of the species composition of the mycobiota of the root zone of wild sunflower was 0.47, which is apparently due to the peculiarities of the composition of the root exudates of plants and their selection zones, which affect the formation of microbial complexes of the rhizosphere and edaphosphere.