Lycopersicon esculentum (tomato) plants, grown in sterilised clay pots, were inoculated with 50, 500, 1000, and 3000 second-stage juveniles (J2) of the rootknot nematode (Meloidogyne incognita) and were kept in a greenhouse. A nonsignificant reduction in plant growth and yield was noticed in T1 plants. Significant reductions in plant growth and yield were found in T2, T3, and T4 plants. Highest reductions, in growth and yield, were observed in T5 plants. Transverse and longitudinal sections revealed that M. incognita traversed through the cortical tissues of the root, caused infection in the differentiating vascular tissues and successfully established in the infected roots. The post-infection changes in the affected parts were hypertrophy and hyperplasia, around the head of the nematodes. Five to 10, among the hypertrophied cells, developed into very large, multinucleate, prominent, and highly specialised giant cells. The nuclei in each giant cell enclosed one or more nucleoli. Xylem and the phloem strands were found to be disoriented. Abnormal xylem and phloem comprised a substantial portion near the giant cells. The metabolic changes in the affected part led to the formation of galls, characteristic of the root-knot infection.

The effects of plant growth-promoting rhizobacteria (PGPR) (Bacillus pumilus and Pseudomonas putida) and antagonistic fungi (Aspergillus awamori, Aspergillus niger and Trichoderma harzianum) were studied alone and in combination in glasshouse experiments on the growth, chlorophyll catalase and peroxidase activity and on the Fusarium root-rot of pea caused by Fusarium solani f. sp. pisi. Application of PGPR and antagonistic fungi caused a significant increase in growth, chlorophyll, catalase and peroxidase activities of both root-rot fungus inoculated and un-inoculated pea plants. Use of P. putida was more effective in reducing disease severity and improving the growth of root-rot fungus-inoculated plants than A. niger and T. harzianum. The greatest increase in growth, chlorophyll, catalase and peroxidase activities of root-rot fungus-inoculated plants and reduction in disease severity was achieved when A. awamori or B. pumilus was used with P. putida compared to other tested combinations.

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