Communities of Ditylenchus Destructor Satellite Species of Nematodes in Infected Potato Tubers: Species Composition of Phytonematode Complex and the Structure of their Infracommunities

Within September–April 2016–2017 potato tubers affected by the potato rot nematode Ditylenchus destructor were selected in the potato storage facilities of the Institute of Potato Production of NAAS. 18 species of phytonematodes were identified, including an edificator species of microparasitocenosis and 17 satellite species of this pathogenic phytohelminth, mycohelminths (6 species) and saprobiotic nematodes (11 species). These phytonematodes are representatives of two orders, Rhabditida (11 species from 4 families) and Tylenchida (7 species from 4 families). Nematodes that are part of the group formed by D. destructor and its satellite species are divided into five groups according to quantitative indicators (the prevalence of invasion P and intensity of invasion I). The dominant is one species — D. destructor. Satellite species of D. destructor are divided into four groups, these are subdominants (4 species) and common species (3 species), which together with the dominant species form the core of the group, as well as rare (6) and accidental (4). It was shown that in the course of the disease a regular succession occurs, the species composition of phytonematodes, the grouping structure, the relationship between the number of species of various trophic groups, and the number of certain species change. There are five stages in the course of the disease, from D. destructor colonisation of the tuber, the penetration of the mycohelminths and saprobionts into the focus of the disease, and the disappearance of D. destructor. The maximum number of D. destructor occurs at stage III, mycohelminths — at stage IV, and saprobiotic nematodes — at stage V. Infracommunities consist of from two to seven species. The distribution of all the studied tubers by the number of species in the infracommunity is close to normal, most often 3–4 species of nematodes were found, several species of nematodes of the same genus are extremely rare in a particular infracommunity