Pathogenicity and Population Increase of Paratrichodorus Minor as Influenced By Some Environmental Factors

Abstract

The relative importance of the effect of soil temperature, soil texture and host species on the increase and the pathogenicity of a population of Paratrichodorus minor from Israel was studied. Populations increased fastest at 26° C, followed by 30°, 22° and 18°, approaching the host-specific equilibrium density after 90 days. In the presence of a host, populations thrived better in sand and sandy loam than in clay, but were obviously sensitive to moisture fluctuations. Host species affected population increase more than soil temperatures and soil types. In fallow, survival was better in clay and sandy loam than in sand. In vitro, P. minor fed vigorously on epidermal cells in the elongation and meristematic zone of wheat and eggplant roots, causing browning and collapse of the epidermis and cessation of growth. After detaching itself from the feeding site, the nematode left a small tube attached to the cell wall. In pathogenicity trials, two good hosts - eggplant and cotton - showed different responses: growth of eggplant was drastically inhibited at an inoculation level of 200 nematodes per plant, while populations of up to 800 nematodes per plant stimulated growth of cotton roots and tops. Infested eggplant seedlings exhibited a severely thinned and shortened lateral root system and stunted tops.