Endophytic bacterial flora in root and stem tissues of black pepper (Piper nigrum L.) genotype: isolation, identification and evaluation against Phytophthora capsici.

AIM: To isolate and identify black pepper (Piper nigrum L) associated endophytic bacteria antagonistic to Phytophthora capsici causing foot rot disease.

METHODS AND RESULTS: Endophytic bacteria (74) were isolated, characterized and evaluated against P. capsici. Six genera belong to Pseudomonas spp (20 strains), Serratia (1 strain), Bacillus spp. (22 strains), Arthrobacter spp. (15 strains), Micrococcus spp. (7 strains), Curtobacterium sp. (1 strain) and eight unidentified strains were isolated from internal tissues of root and stem. Three isolates, IISRBP 35, IISRBP 25 and IISRBP 17 were found effective for Phytophthora suppression in multilevel screening assays which recorded over 70% disease suppression in greenhouse trials. A species closest match (99% similarity) of IISRBP 35 was established as Pseudomonas aeruginosa (Pseudomonas EF568931), IISRBP 25 as P. putida (Pseudomonas EF568932), and IISRBP 17 as Bacillus megaterium (B. megaterium EU071712) based on 16S rDNA sequencing.

CONCLUSION: Black pepper associated P. aeruginosa, P. putida and B. megaterium were identified as effective antagonistic endophytes for biological control of Phytophthora foot rot in black pepper.

SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides the first evidence for endophytic bacterial diversity in black pepper stem and roots, with biocontrol potential against P. capsici infection.