Antagonistic Interaction Between Meloidogyne incognita and Rhizobium leguminosarum on Cowpea. M. A. Ali, Associate Professor, Plant Protection Department, College of Agriculture, Riyadh University, Riyadh, Saudi Arabia. I. Y. Trabulsi, Assistant Professor, and M. E. Abd-Elsamea, Lecturer, Plant Protection Department, College of Agriculture, Riyadh University, Riyadh, Saudi Arabia. Plant Dis. 65:432-435. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-432.

Greenhouse experiments and histologic investigations were done to determine interactions between cowpea root-knot nematodes (Meloidogyne incognita) and root-nodule bacteria (Rhizobium leguminosarum). Cowpea plants inoculated with both rhizobia and nematodes showed more severe nitrogen deficiency and retarded growth than plants inoculated with nematodes only or uninoculated plants. Nematode invasion reduced the numbers of nodules and inhibited nitrogen fixation by about 63% in nodular tissue. Infected nodules contained the different developmental stages of the nematode. Histologic studies indicated that nematodes developed in nodular tissue, and they were found inside vascular bundles. Many giant cells with thickened walls were produced and exhibited the morphologic characteristics of transfer cells. The nematodes did not alter the structure of nodules, but bacteriodes did not develop adjacent to nematodes. Infected nodules deteriorated earlier than uninfected ones.