Faunistic complex and ecology of phytoparasitic nematodes of vine agrocenoses in the south of Uzbekistan

ABSTRACT

The article analyzes the faunistic complex of phytoparasitic nematodes of grapes collected in the period from 2018 to 2020. from 14 districts and 28 farms of the Surkhandarya Valley. During the study period, 49 species of parasitic nematodes belonging to 2 subclasses, 3 orders, 5 suborders, 8 superfamilies, 15 families, 18 subfamilies and 22 genera were found on grape agrocenoses. The degree of dominance of registered phytonematodes in the roots and root soil of grapes, as well as the ecological classification based on the trophic relationships of nematodes with plants, has been studied.

АННОТАЦИЯ

В статье анализируется фаунистический комплекс фитопаразитических нематод винограда, собранных в период с 2018 по 2020гг. из 14 районов и 28 хозяйств Сурхандарьинской долины. В период исследования на виноградных агроценозах всего обнаружено 49 видов паразитических нематод, относящихся к 2 подклассам, 3 отрядам, 5 подотрядам, 8 надсемействам, 15 семействам, 18 подсемействам и 22 родам. Изучена степень доминирования зарегистрированных фитонематод в корнях и прикорневой почве винограда, а также, экологическая классификация, основанной на трофических связях нематод с растениями.

Keywords: parasitic nematodes, grapes, agrocenosis, ecological classification, degree of dominance.

Ключевые слова: паразитические нематоды, виноград, агроценоз, экологическая классификация, степень доминирования.

Introduction

Viticulture in Uzbekistan is constantly improving, thanks to the improvement of agricultural technology, the selection of the best varieties, the creation of new farms, where grapes are the leading highly profitable crop. Grapes occupies a special place among other crops cultivated in the south of Uzbekistan. The climatic and soil conditions favor the growth of varieties here with strong growth of bushes, large clusters and berries, high sugar accumulation and good taste. The demand of the population is increasing from year to year and this imposes a great responsibility on the workers of the vineyards. But unfortunately, like other agricultural crops, there are various pests in the vineyards that cause great damage to viticulture. In this regard, special attention should be paid to diseases and pests from different systematic groups, among which phytonematodes from the class of roundworms occupy a special place. Phytonematodes, being the main members of the soil biogeocenosis, play an important role in metabolism. The qualitative and quantitative composition of plant nematodes is diverse; they are found in all biotopes of the planet [6, 9, 10, 11].

Among phytonematodes, herbivorous nematodes are very dangerous. They are microscopic in size, very fertile, can live in any part of the plant, and most importantly, they are difficult to get rid of. The grape is host to many parasitic nematode species. The grape parasitic nematodes mainly feed on the roots of grapes or inside the roots. They slow down the growth and development of young grape seedlings, inhibit mature bushes, and also lead to a decrease in yield. In addition, some nematodes found on grapes can carry dangerous viruses, bacteria and fungi. Most of these nematodes are found all over the world where grapes are grown [4, 7, 13, 15].

Analysis of the main phytohelminthological studies carried out around the globe shows that at present about 250 species of endoparasitic and ectoparasitic phytonematodes are registered on grapes [1,2,3]. Among them, Xiphinema wittenezi, X. coxi, X. mediteranium, X. brevicolae, X. americanum, X. index, X. diversicaudatum, X. paсhtaicum, X.elongatum, Meloidogyne, Longidorus elongatus, Bitylenchus dubius, Pratylenchus pratensis, P. neglectus, P. crenatus, P. penetrans, P. thornei, P. fallax, Helicotylenchus dihystera, Ditylenchus dipsaci and other species. The greatest harm from endo and ectoparasitic plant nematodes is mainly the species of the genera Xiphinema, Longidorus, Meloidogyne, Pratylenchus and Ditylenchus. The Xiphinema index species is especially dangerous [12, 14].

Despite the presence of a significant number of works on nematodes on grapes abroad and in the northern part of the republic, in the territory of the southern part of Uzbekistan, until that time, no comprehensive studies were carried out. The importance of this culture in the national economy of the republic, as well as the poor knowledge of their phytohelminths and the harmfulness of certain groups of species on the territory of the Surkhandarya Valley served as the basis for this study.

Methods

Field studies were conducted from 2018 to 2020. Faunistic studies were carried out by the generally accepted route method [19, 20]. The material for phytohelminthological studies was the root and soil samples of grape plants (from the sarts of taifi, Khusayne white, grape and black raisins) collected in 14 regions (Termez, Angora, Sherabad, Muzrabad, Kizirik, Bandykhansky, Baysunsky, Zharkurgan, Shurchkurgan, Altynsai, Sariassi, Uzun) and 28 farms of the Surkhandarya valley. During the phytohelminthological study, 1280 samples of soil and root system of grape plants were collected and analyzed. For this reason, in each surveyed farm, two plots with similar soil conditions were selected for collecting plant and soil samples. To identify the phytohelminthological situation, 12 samples from the root system and arable (0-50 cm) layer of the root soil were taken from each site for analysis. In the field, each soil sample, along with the roots, was placed in a separate cellophane bag and labeled.

The collected samples were analyzed in the phytohelminthological laboratory. First, the roots of the plant were carefully examined for infestation by parasitic nematodes. Then, the root soil and root system were examined separately. To isolate nematodes from the soil and root system of plants, a modified Berman funnel method was used [16, 18]. Exposure at room temperature + 250C was 20-28 hours, at a temperature of +300 + 350C - 10-12 hours. Soil samples for the presence of cyst nematodes were usually analyzed by the Decker method [17]. For fixation of nematodes, 4-6% formalin or TAF (a mixture of triethanolamine + water + formalin) was used. Enlightenment of nematodes was performed in a mixture of glycerol with alcohol (1: 3), and permanent preparations on glycerol were prepared for in-office processing of the material according to the Seinhorst method [5]. Preparations for determining the species of root gall nematodes were prepared according to the well-known method of E.S Kiryanova, E.L Krall [8].

The species composition of parasitic nematodes was studied under an MBR-3 microscope using light filters and a phase contrast device. When determining the species belonging of plant nematodes, the works of domestic and foreign authors were used, as well as the atlas of plant nematodes compiled at the Institute of Problems of Ecology and Evolution named after A. N. Severtsov of the Russian Academy of Sciences. To determine the species, we used morphometric parameters obtained according to the generally accepted de Mann formula modified according to Micoletzky [5].

The degree of dominance of phytoparasites in roots and soil samples was determined by the percentage state of individuals of certain species to the number of all found [19]. In this case, the dominant or eudominants are species that make up more than 10% of all detected species, dominants - 5.1-10%, subdominants - 2.1-5%, sub-precedents less than 2.1% of individuals.

Results

During the study, in the roots and root soil of grape plants, we registered 49 species of phytoparasitic nematodes belonging to 2 subclasses, 3 orders, 5 suborders, 8 superfamilies, 15 families, 18 subfamilies, and 22 genera (Table 1).

In our material, the Adenophorea subclass is represented by the Dorylaimida order. The order Dorylaimida is represented by one family as Xiphinematidae and three species.

The subclass Secernentea includes the orders Aphelenchida and Tylenchida. The Aphelenchida order is represented by 4 families: Aphelenchidae, Paraphelenchidae, Aphelenchoididae and 19 species, 14 of which belong to the Aphelenchoididae family, 3 to Aphelenchidae and two Paraphelenchidae.

The order Tylenchida includes 27 species belonging to 8 families: Tylenchidae (4 species), Dolichodoridae (3), Psilenchidae (1), Hoplolaimidae (3), Rotylenchulididae (1), Pratylenchidae (4), Meloidogynidae (2), Paratylenidae (2), Neotylenchidae (1), Anguinae (4), Sychnotylenchidae (2).

Table 1.

Species and quantitative composition of parasitic nematodes found in the root and root soil of vineyards

The above analysis shows that among the orders in terms of species composition, the order Tylenchida occupies the first place, which is 55.1% of all detected species of nematodes of grape plants. Then the order Aphelenchida (38.8%) and the order Dorylaimida (6.1%).

In terms of the number of individuals among the orders, the first place is occupied by the order Tylenchida, which is 71.1% of the total number of detected phytonematodes. The second place is occupied by the Aphelenchida detachment (27.3%), followed by the Dorylaimida detachment (1.6%).

Phytonematodes are (inoculators) carriers of microorganisms. A.A. Paramonov proposed an ecological classification based on the trophic relationships of nematodes with plants [15] and divides all parasitic species of plant nematodes into two ecological subgroups:

a) phytohelminths of nonspecific pathogenic effect or potential parasites; b). phytohelminths of a specific pathogenic effect or real parasites.

The first group includes such types of plant nematodes that feed with plant juices, but do not specifically cause disease in plants. They are called semi-parasites or potential parasites. Real parasites are those species that not only feed with plant juices, but also specifically cause disease in plants as called phytohelminthiases.

Conclusion

In our studies, the group of potential parasites in the roots and root soil of grapes is represented by 30 species from the genera Aphelenchus, Paraphelenchus, Aphelenchoides, Bursaphelenchus, Tylenchus, Filenchus, Aglenchus, Lelenchus, Psilenchus, Ditylenchus, Neotylenchus, Neodtylenchus, Neodtylenchus, Neodtylenchus Common species include Aphelenchus avenae, Aphelenchoides parietinus, Filenchus filiformis, and Ditylenchus myceliophagus. The faunal complex can include 3 more species: Tylenchus davainei, Neotylenchus abulbosus and Ditylenchus intermedius.

Real parasites in the root soil are represented by 19 species. This includes species of the genera Xiphinema, Tylenchorhynchus, Bitylenchus, Helicotylenchus, Rotylenchus, Pratylenchus, Pratylenchoides, Meloidogyne, Paratylenchus, Ditylenchus. There are no massive parasitic species in the soil. Common species include Bitylenchus dubius, Helicotylenchus dihystera, Pratylenchus pratensis, Pratylenchus neglectus and Ditylenchus dipsaci. For grape plants, ectoparasites from the genus Xiphinema can have a serious threat and a certain value, but they are few in the root soil. On the one hand, they feed with plant juices, partially harming the plants, on the other hand, they do harm by piercing the roots of plants with their spears and at the same time will open the way for various microorganisms (inoculator). They are carriers of viral plant diseases. Currently, dozens of viral diseases have been recorded that are carried by Xiphinems.

Phytoparasites in the roots are represented by 18 species, of which species such as Bitylenchus dubius, Helicotylenchus dihystera, Pratylenchus pratensis and Ditylenchus dipsaci were often found.

The degree of dominance or frequency of occurrence of the found species of phytoparasitic nematodes in root and soil samples are absent from dominant or eudominant species. The roots and root soil of grapes are dominated by 4 species: Aphelenchus avenae, Helicotylenchus dihystera, Pratylenchus pratensis and Ditylenchus dipsaci. Of the subdominants in the roots and rhizosphere of the plant, 10 species were found: Aphelenchoides parietinus, Tylenchus davainei, Filenchus filiformis, Tylenchorhynchus brassicae, Bitylenchus dubius, Helicotylenchus multicinctus, H. erythrina. The rest of the registered phytoparasitic species (35 species) are sub-precedents.

Despite certain successes in the study of phytoparasitic nematodes in vineyards, it should be noted that phytohelminthological studies were carried out in an insignificant part of the republic. We carried out extensive phytohelminthological research only in the Surkhandarya region. Research in other regions of the republic is sporadic or has not been carried out at all. Nevertheless, the pathogenic significance of most species for the culture under consideration is poorly understood. In this respect, Uzbekistan is no exception. This involves carrying out large-scale research in specific regions that grow berry crops, in particular, like grapes.

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