Nematode Diversity and the Effects of Bacillus and Rhizobium on the Management of Plant Parasitic Nematodes in Common Bean 

Karanja, N., Mutua, G. K., Ayuke, F., Ndukhu, H. and Kimenju, J. W.



Nematode losses in vegetable crops have contributed to significant loss in yield reducing food security. Assessment of the potential of dual inoculation of Bacillus subtilis and Rhizobium leguminosarum biovar phaseoli strain USDA 2674 on plant parasitic nematodes in common bean was carried out on farmers’ fields which were at varying cultivation period since conversion from forest as follows; 1-10, 10-20, 20-40 and >40 years. Bean seeds of variety Rose Coco, were treated with three B. subtilis isolates namely K158, K194 and K263 singly or in combination with Rhizobium and then planted in nematode infested fields. Plant parasitic nematodes in the genera Meloidogyne, Pratylenchus and Scutelonema were dominant. Nematode diversity assessed by Shannon (4.10-1.70), Simpson’s (5.23-3.74), Trophic (2.84-1.26) and Maturity indices (3.92-2.31) declined with increased length of cultivation since conversion from forest. Plant parasitic index was 63% higher in the cultivated farms than in the control plots. The dual innoculant enhanced nodulation variably depending on the length of cultivation and increased bean yields compared to the control. Bacillus subtilis isolates K194, K158 and K263 suppressed plant parasitic nematodes by 42, 36 and 28%, respectively. The potential of dual inoculation of Bacillus and Rhizobium in addressing nematode and soil fertility challenges was demonstrated in this study.

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