Host-parasite Relationship and Pathogenicity of Root Knot Nematode, Meloidogyne incognita in Noni

摘要

Investigations were carried out to study the host-parasite relationship and pathogenicity of root knot nematode, Meloidogyne incognita in noni, Morinda citrifolia under pot and micro plot conditions. M. incognita induced feeding sites consisting of three to four hypertrophied giant cells near the head of each adult female of root knot nematode. Infection of feeder roots by the nematode resulted in larger galls which contained atleast one mature female and an egg mass. The giant cell contained granular cytoplasm and several hypertrophied nuclei. Studies on pathogenicity of M. incognita in noni revealed a significant reduction in plant growth parameters viz., plant height, shoot and root weight and number of leaves I plant in plants inoculated with 1,000 and 10,000 juveniles/kg soil in both under pot and microplot conditions. The root knot nematode gall index, number of adult females, number of egg masses and nematode population in soil increased with an increase in the inoculum level. Highest gall indices of 4.8 and 5.0 under pot and 4.7 and 5.0 under micro plot conditions were recorded at inoculum levels of 1,000 and 10,000 juveniles/kg soil respectively. Decrease in the multiplication rate of the nematode in terms of reproduction factor (Rf) wasfound with increase in the inoculum level.