TAXONOMIC STRUCTURE OF THE NEMATODE COMMUNITIES IN AGROECOSYSTEMS OF SHUAKHEVI (AJARA, GEORGIA)

Potatoes is the fourth important food crop worldwide after maize, wheat, and rice and are grown in more than 100 countries worldwide under temperate, subtropical and tropical conditions, however, they are considered as cool temperature crop. Potato is one of the most important food crops in Georgia and potato growing has always been the subject of great importance for settlement of food supply problems in country. Potato crops are severely affected by approximately forty soil borne diseases worldwide including those caused by soil inhabiting fungi, bacteria and nematodes. Plant-parasitic nematodes are among the important pests of potato production, they can cause serious yield losses but remain unnoticed, in most cases. Above ground symptoms of nematode damage are rarely observed since most nematodes cause damage on roots and tubers. The aim of this study is to determine the prevalence of plant parasitic nematodes in the main potatoe growing area in Ajara. Fauna of soil nematodes was studied in three villages of Shuakhevi municipality: Dgvani, Dabadzveli and Okhropilauri. Sampling was conducted in nine 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. From a total of 83 species of nematodes were found. The richest by the number of species was Dorylaimida order that was presented by 26 species (32 % of species composition). The registered nematodes belong to 2 subclasses, 7 orders, 63 genus and 27 families. The largest abundance of nematodes was observed in the Dgvani village with115 specimens/ 50g soil , and the smallest was in Okhropilauri, with - 37 specimens/50g. Plant-parasitic nematodes from 6 genera (Ditylenchus, 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. Plant parasitic nematodes does not exceed a certain limit, which causes measurable economic damage.