Identification of Plant-endophytic Bacteria from Bell Pepper (Capsicum annuum L.) Grown under Different Production Systems and Water Regimes

Endophytic bacteria can be defined as several species of bacteria primarily derived from rhizospheric soil that can ubiquitously reside in the internal tissues of host plants for all (or part of) their life span, promote plant growth, and impose non-pathogenic symptoms. It has been shown that the species populations recovered from plant tissues varied by different production and management practices. We investigated the diversity of the isolated endophytic bacteria from seed-surface sterilized bell pepper plants grown under organic and conventional production systems and subjected to different tillage (strip tillage and plasticulture) applications with two irrigation (well-watered and drought) regimes in 2011 and 2012 in order to determine the effects of each production system on the presence of endophytic bacteria. Endophytic bacteria were isolated from plants grown under each management system. Plants were uprooted and then separated into root, shoot, leaf, and fruit prior to isolation. Endophytes were isolated from those tissues and cultured onTryptic Soy Agar (TSA) Medium. After cultivation, colonies were separated based on morphological characteristics and their DNA were extracted and stored for future use. Two pairs of primers,8F (5’-AGAGTTTGATCCTGGCTCAG- 3’) and 1520R (5’- AAGGAGGTGATCCAGCCGCA- 3’), and 22F (5’-CTCAGATTGAACGCTGGCG- 3’) and 1085R (5’- ACATTTCACAACACGAGCTG- 3’), were used for PCR reaction to amplify the 16S rRNA gene. Sequence results were tested through BLAST for their homological identity. Results indicated that there were unique 57 species and 3 phyla present. Approximately 52% of the total isolates from both years were identified into Firmicutes, 33% into Proteobacteria, and 12% into Actinobacteria. Within the Firmicutes, Bacillus is the most abundant genus, which proportioned over 60% of total isolates. Bacillus sp., B. amyloliquefaciens, B. Pumilus, B. Subtilis, Pseudomonas sp., and Enterobacter sp. were the most abundant species. The isolates from 2011 were more diverse than isolates from 2012. There were 9 species presented in the isolates of both 2011 and 2012. Generally, a total of 21 species were only originated from organically grown plants, while 15 species were only from conventionally grown plants. However, 11 species were only from plants under water stress. The results suggested that production system and environment may influence the presence of endophytic bacteria in pepper plants.