Twenty-nine bacterial endophytes were isolated from healthy rice plants of most popular varieties i.e., ADT-37, MTU-1010, BPT-5204 and RNR-15048 of the Nellore and Chittoor districts and tested for their antagonistic activity against the bacterial leaf blight (BLB) pathogen Xanthomonas oryzae pv. oryzae (Xoo) using the in vitro agar well diffusion method. Inhibition zones among the isolates ranged from 0.0 to 14.5 mm. Four isolates - EYK-3, ECP-1, ESR-5, and ECT-3 demonstrated significant antagonistic activity, with inhibition zones of 14.3 mm, 12.3 mm, 11.43 mm, and 10.53 mm, respectively, exceeding 10.0 mm, and were deemed effective antagonistic endophytic bacterial isolates. Rice plants treated with these four isolates (EYK-3, ECP-1, ECT-3, and ESR-5) showed elevated expression levels of defense-related enzymes—Peroxidase (PO), Polyphenol oxidase (PPO), and Phenylalanine ammonia lyase (PAL)—upon challenge with Xoo compared to untreated controls. Among these isolates, EYK-3 exhibited the highest expression levels of PO, PPO, and PAL. These findings suggest that the endophytic bacterial isolate EYK-3 could be effectively utilized for managing bacterial leaf blight and promoting plant growth for sustainable rice cultivation

Endophytic bacteria, Antagonism, Xanthomonas oryzae pv. oryzae, Plant defense enzymes

The application of endophytic bacterial isolates significantly enhanced the activity of defense-related enzymes such as PO, PPO, and PAL in rice plants, with peak expression observed at 72 hours post-pathogen inoculation. Among the isolates, EYK-3 was the most effective in inducing enzyme activity. These biochemical changes played a vital role in strengthening plant defense responses against Xoo

B. Rajyalakshmi, P. Nagamani, K. Viswanath, P. Madhu Sudhan, P. Latha and G. Jesudasu (2025). Biochemical Changes in Rice Plants Treated with Endophytic Bacteria Against Bacterial Leaf Blight. Biological Forum, 17(8): 09-14