Combined Application of Biochar and Biocontrol Agents Enhances Plant Growth and Activates Resistance Against Meloidogyne incognita in Tomato

Biochar (BC) is known to enhance plant growth and may activate plant resistance to various soil borne pathogens. In this experiment, the rice husk (RH) BC was combined with biocontrol agents (BCAs), Bacillus subtilis and Trichoderma harzianum against Meloidogyne incognita in tomato and the efficacy of BC and BCAs in boosting overall plant biomass assessed side by side. BCAs along with 3% RH BC were applied to potting soil, tomato plants were transplanted, and then the soil was inoculated with second stage juveniles of Meloidogyne incognita. Bacillus subtilis +3% RH BC improved overall plant growth and reduced M. incognita damage. To unravel the resistance at the molecular level, root samples were taken 6‑ and 12-days post inoculation (dpi) to measure the expression of two resistance genes, PR-1b and JERF3, with the help of quantitative real-time polymerase chain reaction (qRT-PCR). The expression of PR-1b was upregulated 6 dpi for only BCAs while JERF3 remained unchanged except in only Bacillus subtilis treated plants. Similarly, the expression of both genes was found to be upregulated in some combined treatments at 12 dpi. The results suggested that the 3% BC application with BCAs effectively manages root-knot nematode, enhances overall plant biomass, and triggers defense related genes in tomato plants.