Identification of rhizospheric microorganisms that manages root knot nematode and improve oil yield in sweet basil (Ocimum basilicum l.)

Sweet basil (Ocimum basilicum), a highly valuable medicinal crop, is extremely susceptible to Meloidogyne incognita infestation, leading to severe losses in yield and chemo-pharmaceutical quality. Currently, chemical nematicides are the only effective option for the disease management. However, high toxicity to non-target organisms and adverse impact on soil health motivated the look for ecofriendly alternatives. Here, bioinoculants (Bacillus megatarium (“BM”), B. subtilis (“BS”)) were isolated from the rhizosphere of various medicinal and aromatic plants growing in Lucknow region, India. Their biocontrol effects were studied in O. basilicum plants that were invaded by M. incognita either in single or in consortium with Trichoderma harzianum (“TH”) and their efficiency compared to chemical nematicide (carbofuran) and a microbial reference strain (Pseudomonas fluorescens). The results show that all bioinoculants enhanced the growth and oil yield production and increased the nutrient content of O. basilicum by significantly reducing M. incognita infestation by 46 to 72%. Among the strains, a consortium of BM and TH was the most potent treatment. The efficiency of these bioinoculants was not restricted to sterile soil condition but remained high also in natural soil conditions, indicating that enriching soils with rhizospheric microbes can be an effective alternative to chemical nematicides.