Ecological Niches of Fungi of the Genus Fusarium Link. on Plants of Different Varieties of Spring Wheat in Western Siberia
The ecological niches implementation by soil phytopathogens in the underground organs of host plants is a complex process that determines the species composition of pathogenic complexes. The purpose of the research was to determine the dynamics of the ecological niches implementation by phytopathogens from the genus <i>Fusarium</i> in the system of spring wheat varieties underground organs. The studies were carried out on 20 spring wheat varieties in 2019–2021 in the northern forest-steppe of the Ob region according to generally accepted and author's methods. The main phytopathogens were <i>Bipolaris sorokiniana</i> Sacc. Shom. and fungi of the genus <i>Fusarium</i> Link., the occurrence of which on underground plant organs reached 100%. The species composition of <i>Fusarium</i> fungi was represented by 10 main species, the biological diversity of which was maximal in the flowering phase on secondary roots in 50% of varieties. <i>F. poae</i> was the dominant in pathogenic mycocenosis of spring wheat root rot, <i>F. oxysporum</i> was a subdominant species, <i>F. sambucinum</i>, <i>F. equiseti</i>, <i>F. graminearum</i>, and <i>F. solani</i> were additional species; <i>F. sporotrichioides</i>, <i>F. culmorum</i>, <i>F. heterosporum</i> and <i>F. acuminatum</i> were rare species. The genus <i>Fusarium</i> fungi succession manifested itself in the confinement of <i>F. equiseti</i> to the stems bases at the germination phase, <i>F. graminearum</i> and <i>F. sporotrichioides</i> to the plants root system at the heading-flowering phase of varieties, <i>F. solani</i> and <i>F. culmorum</i> to the end of the growing season, regardless of plants underground organs. The maximum (93.1%) degree of the realized ecological niches overlapping in terms of the joint parasitism frequency was found in the dominant species <i>F. poae</i> and <i>F. oxysporum</i>. More than half less the niches overlapping was found in the dominant species with <i>F. sambucinum</i> and <i>F. equiseti</i>, the overlapping of the same niches with <i>F. culmorum</i>, <i>F. graminearum</i>, <i>F. solani</i> was 25.6–31.2%. The almost complete absence of the realized niches overlapping in <i>F. equiseti</i> with <i>F. acuminatum</i>, <i>F. heterosporum</i>, and <i>F. culmorum</i> was due to temporary divergence, as well as the confinement of <i>F. equiseti</i> to the bases of plant stems.