Scholarly record

TAXONOMIC AND ECOLOGICAL STRUCTURE OF FREE-LIVING AND PLANT PARASITIC NEMATODES IN POTATO FIELDS IN KHULO (AJARA, EASTERN GEORGIA)

Lali Jgenti, Eka Tskitishvil, Tengiz Vadachkoria

Abstract

The aim of this study is to determine the prevalence of plant parasitic nematodes in the main potatoe growing area in Ajara and to show whether altitu-dinal gradient affects nematode diversity and community structure along three contrasting altitudinal localities of Ajara: Kobuleti (10 m.a.s.l), Shuakhevi (450 m.a.s.l) and Khulo (950 -1800 m.a.s.l). The first part of this study is to assess for the first time the taxonomic and ecological structure of plant parasitic and free-living nematodes in agroecosystems of Khulo in this territory. Fauna of soil nematodes was studied in three villages of Khulo municipality: Dekanashvilebi, Okhropilauri and Uchkho. Sampling was conducted in six sites in early spring, in middle summer and in late fall. The 3 composite soil samples collected from each field (weighing 300-500g) consist of 50 individual sub-samples of soil and roots. Nematodes were extracted by a modified Baermann-s method from a sample of 50 g, and exposition time was 48 h. The fauna consists of 109 forms of free-living and phytoparasitic nematodes, with up to species identified. The majority of the unidentified nematodes are in larval forms. 2 forms have been identified down to the family level. Registered nematodes belong to 8 orders and one suborder (Enoplida; Filipjev, 1929, Araeolaimida De Coninck & Schuurmans Stekhoven 1933, Dorylaimida; Pearse, 1942, Mononchida Jairajpuri, 1969, Rhabditida; Chitwood, 1933, Tylenchida Thorne, 1949; Aphelenchida; Siddiqi, 1980), encompassing 33 families and 53 genera. The largest abundance of nematodes was observed in the village Uchko, with 86 specimens/ 50 g soil, and the smallest was in the village Dekanashvili, with 37 specimens/50g. Plant-parasitic nematodes from 7 genera (Ditylenchus, Xiphynema Tylechus, Tylenchorhynchus, Helicotylenchus, Pratylenchus, Aphelenchus) were found in soil and (or) potato root samples. All these nematodes can be divided into five groups according to their feeding habits. The omnivore group, with 23 species (45,9%) in Spring, 38 species (34,2%) in Summer and 41 species (40,2%) in Autumn, constitut the core of nematode community. Investigations reveal that nematode populations and communities vary seasonally, with their maximum numbers observed during harvest. The number of identified phytoparasitic nematodes does not exceed a certain limit, which causes measurable economic damage. The obtained data are very significant for studying the biodiversity of the nematode population in Georgia.

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