Effect of Rhizobium phaseoli and Meloidogyne incognita on Black gram

The association of rhizobia with plant nematodes in soil rhizosphere on plant nutrition and growth led to investigations into the potential role of nematode parasitism on nodulation. It was observed that root-knot nematode multiplied 24.8 times in both Rhizobium and nematode treated plant and 15.6 times in absence of rhizobium treated plant. Further, the nematode significantly reduced all plant growth characters like length of shoots (25.9%), roots (22.4%), fresh weight of shoots (41.7%) and roots (27.9%), dry weight of shoots (35.6%) and roots (42.2%) than uninoculated control. However, maximum increase in these characters i.e. up to 15.7% in shoot length, 69.8% in root length, 33.7% in fresh shoot weight, 42.6% in fresh root weight and 8.6% in dry shoot weight, 22.5% in dry root weight were recorded from Rhizobium treated plants. Addition of M. incognita to Rhizobium treated plants, adversely affected the nodulation process to the extent of 31.8% which clearly indicated that, M. incognita acted as a limiting factor in nodule formation process.