ECOLOGICAL GROUPING OF PLANT NEMATODES

Abstract

Phytonematodes typically infect plants of various ages, but they are especially dangerous to woody plants in the first years of life. Plant infestations with phytohelminths are characterized by stunted growth, deformation of stems and shoots, shoot wilting, and chlorosis. Studying phytonematodes, their species, development conditions, and adaptation processes is important.

The ability of phytonematodes to adapt to specific moisture levels allows them to be divided into the following major ecological groups: xerophylls, mesophills, hygrophiles, and eurybionts. Xerophylls comprise an ecological complex of nematode species confined to strictly arid environments. The mesophilic ecological complex includes nematode species confined to biotopes with moderate moisture levels. Hygrophiles comprise a complex of species confined to areas with excessive moisture due to the close proximity of groundwater. Hygrophila are divided into two subgroups: megathermic and mesothermic. Mesothermic hygrophila are confined to floodplain forests (tugai) of river valleys. Under irrigated agriculture, megathermic hygrophila can migrate to cultivated areas and cause significant damage to agriculture. Mesothermic hygrophila include nematode species confined to biotopes with excessive moisture and moderate or cold temperatures. Some species of mesothermic hygrophila are potentially dangerous parasites of agricultural plants grown under irrigated conditions, but cannot survive in dryland plantings. It should be noted that this unique habitat has a unique set of environmental factors, as well as a unique composition of plant nematodes.

Root gall-forming plant nematodes cause the disease meloidogyna. They are dangerous pests, damaging up to 5% of the world's cultivated plant crops. Plant nematodes, or plant helminths, are microscopic worms belonging to the class Nematoda of the phylum Roundworm. Their bodies are typically filiform or spindle-shaped, typically 0.5–35 mm long, and covered with a dense shell (cuticle). The oral cavity of plant nematodes contains a stele—a piercing, sucking mouthpart with which the nematode pierces plant tissue. The bulbus—a muscular expansion of the middle part of the esophagus—is responsible for nutrient absorption in nematodes. Many species of plant nematodes overwinter in the soil, particularly in the wintering parts of plants (roots, tubers, bulbs, galls). Plant nematode eggs are the overwintering stage, so when the larvae hatch, they infect plants by burrowing into small roots, and some migrate to above-ground parts. Plant nematodes are extremely fecund, laying up to 3,000 eggs per season. Furthermore, many nematodes produce several generations per year, resulting in a single female producing up to several billion offspring.