Endophytic bacteria isolated from medicinal plants induce plant growth promotion and southern blight disease suppression in tomato

Sanjit Baran Hari, Preangka Saha Briste, Ashiya Akter Sumi, Md Khaled Mosharaf, Sulav Indra Paul, Md. Mahidul Islam Masum & Rayhanur Jannat

Abstract:

In this study, endophytic bacteria isolated from three medicinal plants, namely Cantella asiatica, Ocimum sanctum, Solanum sisymbriifolium were evaluated for their plant growth-promoting (PGP) activity and antagonistic potential against tomato southern blight pathogen Sclerotium rolfsii. Three isolates namely PLPKb, PLPTw, PLPTu showed a varied level of antagonism against S. rolfsii. The isolate PLPTu showed impressive mycelial growth inhibition of S. rolfsii which was recorded as 91.11%, while the extracellular metabolite produced by the three isoates inhibited 100% growth of S. rolfsii. All the three isolates were positive in indole-3-acetic acid and biofilm production. However, only PLPTw and PLPKb were positive for phosphate solubilization, with a phosphate solubilization efficiency of 4.05% (PLPTw) and 3.16% (PLPKb) respectively. Phylogenetic analysis of the isolates PLPTw and PLPTu identified them as Burkholderia contaminans and PLPKb as Bacillus velezensis. Soil amendments and seed treatment with the three isolates considerably increased the growth characteristics of tomato plants, including germination percentage, root length, shoot length, fresh weight, and dry weight. In addition, the percent disease incidence (DI) and percent disease index (PDI) of southern blight disease decreased significantly and yield of the tomato improved significantly. For ensurimg bacterial colonization inside the plants, tomato seeds were treated with bacterial suspension and allowed to grow in water agar. Colonies with similar morphology were chosen for re-isolation, and further phylogenetic analysis verified the presence of the three isolates. Our study highlights the efficiency of endophytes of medicinal plants for the development of suitable bioformulation to improve plant growth of tomato including yield and to control southern blight disease which is a malignant soil borne disease of tomato.

https://link.springer.com/article/10.1007/s42161-022-01248-2