Characterization of bacterial endophytes of King chilli for biocontrol potential and plant growth promotion

Bacterial endophytes associated with host plants provide various beneficial effects. This study assessed the diversity of bacterial endophytes in King chilli, focusing on their biocontrol potential and plant growth-promoting (PGP) activities. The survey was carried out in King chilli-growing regions and identified anthracnose and fruit rot diseases as significant contributors to economic yield loss. A total of 20 bacterial endophytic isolates were obtained using the sterility check method and identified as Pseudomonas through 16S rRNA gene sequencing. In in-vitro studies, isolates P. fluorescens KEB15, P. putida KEB5, and P. putida KEB7 exhibited notable mycelial growth inhibition rates of 66.67 %, 69.26 %, and 66.30 % against Pythium, Fusarium, and Colletotrichum, respectively. Of the 20 isolates, 5, 16, and 17 isolates demonstrated positive production of hydrogen cyanide (HCN), ammonia (NH3), and indole-3-acetic acid (IAA), respectively. The efficacy of crude antibiotics from the best-performing antagonistic endophytes was tested against the linear growth of Fusarium, with KEB11 showing the largest inhibition area of 35.14 mm. Sequence analysis using the maximum likelihood method revealed close relationships among the potent Pseudomonas isolates, identifying KEB5 and KEB7 as P. putida and KEB15 as P. fluorescens. Field evaluations indicated that KEB7 was most effective in controlling bacterial wilt, anthracnose, and dieback diseases, achieving a maximum plant height of 85.10 cm and a yield of 3683.67 kg/ha. This study demonstrates that bacterial endophytes can effectively exhibit antifungal activity and promote plant growth in King chilli.