Eggplant Roots Research Articles

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

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.

EFFECTS OF TRANSPLANT INJURY AND NEMATODES ON INCIDENCE OF VERTICILLIUM WILT OF EGGPLANT

The fungus Verticillium dahliae apparently utilizes injured cortical tissue to reach the vascular elements in eggplant roots. The two major sources of such root injury in sandy soils of Ontario are the damage caused mechanically in the transplanting of the seedlings to the field and the root lesions caused by the nematode Pratylenchus penetrans. Transplant injury may be the more important factor early in the season and nematode injury later in the season. The effect of either of these two factors, acting independently, on incidence of disease, however, appears to be about the same.

Effect of Verticillium Dahliae On the Population of Pratylenchus Penetrans 1)

Verticillium dahliae, added to a field soil heavily infested with Pratylenchus penetrans, increased the relative rate of reproduction of the nematode in the roots of eggplant and tomato, but not pepper. Reproduction of the nematode was higher in the roots of eggplant than in the roots of tomato, whereas in the roots of pepper reproduction was very limited. The ectoparasitic nematode Tylenchorhynchus capitatus was also present in the soil and its rate of reproduction increased on tomato roots with the fungus added. The reason for the increased rate of reproduction was not established.

SYNERGISM BETWEEN PRATYLENCHUS PENETRANS (COBB) AND VERTICILLIUM ALBO-ATRUM R. & B. IN EGGPLANT WILT

Studies conducted in steam-sterilized soil inoculated with Verticillium alboatrum and Pratylenchus penetrans demonstrated a synergistic relationship between fungus and nematode. At low and intermediate levels of Verticillium inoculum, the nematode increased wilt and the increase may be a function of the number of nematodes present. Except at the high inoculum levels of Verticillium, significantly larger numbers of P. penetrans occurred in eggplant roots in the presence than in the absence of the fungus. The nematode alone had no adverse effect on root condition or growth of eggplant.