SPECIFIC AND POPULATION ADAPTATION OF CIRCULAR NEMATODES

Abstract

The seasonal and perennial age structure of the population was studied in detail using the example of an oat nematode. The release of larvae from cysts into the soil with different intensities occurs practically throughout the entire vegetation period of host plants. Therefore, the age structure of the population changed with a certain cyclical nature and successive dominance of individual phases of development. At the beginning of May, diapausing larvae of the second age dominated in the age structure. In the first decade of June, a significant part of the population remained in anabiosis (36%) with a high proportion of parasitic larvae of the third (21%) and fourth (16%) ages, and later in the structure of the population an increase in the number of adult individuals: females and males occurred. After the formation of eggs, females eventually died off and turned into cysts - a stage of rest. It was also established that despite the optimal abiotic conditions and the presence of forage plants, part of the oat nematode population remained in diapause for many years, remaining an insurance fund for the survival of the species. The cyst nematode diapause should be divided into physiological — genetically fixed adaptation of the organism to experiencing cyclical adverse conditions and physical — induced by the short-term effect of meteorological factors. In whole, the general patterns of seasonal dynamics of the release of larvae from cysts were also observed when growing unresponsive crops of the crop rotation or keeping the experimental plots under clean steam. However, when activated by optimal hydrothermal conditions, and when growing insensitive crops with root secretions, the second instar larvae emerge from cysts, on average, 1.5–2 times less than the stimulating effect of typical host plants.