Species Composition and Structure of the Communities of Plant-Parasitic and Free-Living Soil Nematodes in the Greenhouses of Botanical Gardens of Ukraine. Gubin, A. I., Sigareva, D. D. — In greenhouses of botanical gardens of Ukraine 81 species of nematodes were found. The richest by the number of species was Tylenchida order that was presented by 25 species (31 % of species composition). The dominant group of nematodes was plant-parasitic (most frequent was Rotylenchus robustus (de Man, 1876) Filipjev, 1936 and Meloidogyne incognita (Kofoid et White, 1919) Chitwood, 1949). The group of saprobiotic nematodes, which was presented by 52 species (64 %), appeared to be the richest by the number of species. It is shown, that formation of nematode communities in greenhouses of botanical gardens was caused by the interaction of many related factors, crucial of which is the composition of plant collections. The structure of communities is quite constant and almost independent of the quantity of nematodes species. Plant-parasitic species dominate by the number and frequency of detection, and represent a kind of a core of nematode communities.
A survey for entomopathogenic nematodes (EPNs) of the Steienernematidae and Heterorhabditidae in soils of different crop types of agricultural lands (household plots, commercial fields) in the forest (Polissya) and forest-steppe (Lisostep) zones of Ukraine was carried out in spring, summer and autumn months from 2016 to 2018. In total, 205 soil samples and 92 live-traps were processed. In addition, 98 samples of soil-living larvae and adults of insect crop pests, including cockchafer beetles, click beetle larvae, darkling beetle larvae, caterpillars of the scoops were collected. It is shown that the EPNs distribution and frequency of occurrence depends on the natural geographical features (regional characteristics) and habitat types. EPNs were found in 46 (15.4 %) out 297 samples. The incidence (% of samples) of the entomopathogenic nematodes, and their diversity varied depending on the location-based sampling, the type of agrocenosis, and the predominant agricultural plant species or typical species-edificators. The proportion of entomopathogenic nematodes (Steinernema spp., Heterorhabditis spp.) recovery from regions of Lisostep zone was 16.9 %, and 13.6 % from regions of Polissya zone. The highest number among all positive samples was recorded from the apple trees, Malus domestica Borkh., 1803 (10 samples). The least number of positive samples (one sample) was obtained from sweet cherry trees, Prúnus cérasus L., 1753, junipers, Juniperus communis L., 1753, alfalfa, Medicago sativa L., 1753, common beans, Phaseolus vulgaris L., 1753, and common pumpkin, Cucurbita pepo L., 1753. The steinernematid nematodes were noticeably dominant over heterorhabditid nematodes: 60.8 % vs 39.2 % respectively. Steinernema spp. is widespread in different regions and plots, whereas Heterorhabditis spp. are common in fruit orchards and coniferous decorative perennial plantings.
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.