VIEW ARTICLE

Physiology and Biochemistry

Responses of Nodulation to Various Combinations of Bradyrhizobium japonicum Strains, Soybean Cultivars, and Races of Heterodera glycines. M. P. Ko, Former graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616, Current address: Department of Plant Pathology, University of Hawaii, Honolulu 96822; Pi-Yu Huang, Jeng-Sheng Huang, and K. R. Barker. Research cooperator, and professors, respectively, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Phytopathology 81:591-595. Accepted for publication 26 December 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-591.

Nodulation efficiency of various combinations of bradyrhizobial strains, races of Heterodera glycines, the soybean cyst nematode (SCN), and soybean cultivars were investigated. Suppression of nodulation by SCN was influenced by the nematode race/soybean cultivar interaction but not by bradyrhizobial strains. Nodulation of susceptible Lee 68 soybeans was suppressed by race 1, regardless of the bacterial strain. In contrast, nodulation of resistant soybeans was less affected despite comparable penetration rates of juveniles and subsequent necrosis in the roots. Nodules from race 3-infected Lee 68 soybean had similar ultrastructures of bacteroid-containing cells and uninvaded cells and protein patterns in sodium dodecyl sulfate (SDS)-polyacrylamide gels, but reduced heme contents and nitrogen-fixation efficiency, as compared with those from the controls. Emerging nodules from race 1-infected plants accumulated phytoferritin and starch granules and had altered protein patterns in SDS-polyacrylamide gels, when compared to nodules of similar size from control or race 3-infected plants. Such differences were indicative of differentially altered nodule physiology and function as a result of infection by these two SCN races.