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Soil amendment with biochar is widely used to improve soil fertility and crop productivity. However, its effect on plant nematodes has not been examined properly. The present study investigates the effects of biochar on root knot nematode, Meloidogyne incognitaunder in planta conditions. In pots experiment, biochar (45 g) when paired with oil cakes (15 g) suppressed the M. incognitaand improved the plant growth of tested plant. Significant suppression in nematode infestation in terms of egg masses and eggs by (56.0 and 52.7%) and maximum improvement in plant growth in plant length and dry weight by 74.1 and 63.8%, respectively was observed when combined soil application of biochar and mustard cake was applied in the soil. The effect was least when biochar was applied alone. The study has suggested that biochar amendment along with mustard oil cake can control root knot nematode infestation in lentil.

Induced resistance techniques for plant disease management are one of the robust and constructive approaches against plant pests. The present study conducted to trigger the plant-mediated resistance in tomato cv. “K-21” against Meloidogyne incognitaby the involvement of dl-β aminobutyric acid (BABA) under salt stress conditions. Results indicate that seedlings elicitors (dl-β aminobutyric acid) strongly suppressed multiplication of nematode population. At the same time, we could not observe this effect in an inoculated control. Additionally, treated tomato roots with BABA and BABA, coupled with NaCl, showed significant improvement in growth parameters and phenolic compounds. Application of BABA (1.21 mM) + NaCl (100 mM) in combination significantly reduced the root-knot index by 48%. Whereas the same combination significantly improved the phenolic compounds and dry weight content up to 75% and 64% respectively. The minute amount of BABA, in combination with salt stress, resulted in greater efficacy as compared to the higher quantity of BABA (2.42 mM) that might be the cause of synergistic interaction. However, the lowest % increase in phenolic compounds by 60% and decrease of the root-knot index by 40% as we observed in the highest dose of BABA (4.84 mM). Findings of our study suggest that the application of BABA alone and in combination with salt is a promising tactic to inflate the tomato resistance against M. incognitathat might be associated with the enhanced defence response in tomato. Moreover, the stress modulation reaction of BABA under salt stress would be linked with resistance in plants.

To evaluate the 13 carrot cultivars against Meloidogyne incognitaunder green house conditions; different levels of susceptibility were observed in all the examined cultivars. Cultivar Golden Rosy was resistant to nematode attack with a low root gall index (1.2) while cultivar Kamini was found highly susceptible showing the highest root gall index (5.0). Similarly, the cultivars Rose Red, Noorie, Lali, Sindhuri, and Selection 80 were susceptible; the cultivars Pearl Red, Super Red, Surbhi, and Kamboj were moderately susceptible and the cultivars Desi Red and Red King were found moderately resistant against the nematode damage. A negative and significant correlation was found between root-knot nematode infestation and plant growth parameters.