VIEW ARTICLE

Antagonistic Interaction between Heterodera glycines and Rhizobium japonicum on Soybean. K. R. Barker, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27607; D. Huisingh(2), and S. A. Johnston(3). (2)(3)Associate Professor, and Honors-Research Undergraduate, respectively, Department of Plant Pathology, North Carolina State University, Raleigh 27607. Phytopathology 62:1201-1205. Accepted for publication 1 May 1972. DOI: 10.1094/Phyto-62-1201.

Greenhouse experiments and histological investigations were conducted to determine the basis for the antagonistic interaction between the soybean cyst nematode, Heterodera glycines (SCN), and Rhizobium japonicum (R). Treatments included inoculation of 5- to 7-day-old Lee soybean plants with 200 crushed cysts or 20,000 eggs of SCN and/or 200 mg of commercial inoculum of R, in the following combinations: SCN with R added simultaneously and at 2 to 14 days later; R with SCN added simultaneously and at 2 to 14 days later; R or SCN alone at the above time intervals; and noninoculated controls. Greatest inhibition of nodule development occurred with simultaneous inoculations of R and race 1 of SCN. A 14-day delay in introducing SCN resulted in only slight to moderate inhibition of nodulation. Race 1 of SCN, which inhibits nodulation, penetrated nodular tissues at a much greater rate than race 4, which has little effect on nodulation. Nodular tissue, however, was unfavorable for the development of larvae of either race. Most nematodes that matured in nodules were males. Histological studies also showed nodular tissues to be unsuitable for development of race 1. Infection of nodules by race 1 of SCN produced necrosis in the area around the nematode. Although a few mature cysts developed on nodules, most infections of these tissues by larvae failed to induce syncytia.