Plant Growth-Promoting (PGP) Traits of Endophytic Bacteria from In Vitro Cultivated Tectona grandis L.f

Abstract

Tectona grandis L.f. (teak) is a tropical tree cultivated mainly due to its resistance, valuable wood and tolerance to biotic and abiotic factors. An abundant bacteria community exists in teak tissues and knowledge of the functional roles of teak endophytic bacteria, from in vitro tissue culture, is essential for improving micropropagation techniques. In this study, we isolated endophytic bacteria with plant growth-promoting (PGP) traits from two teak clones (Proteca® A3 and E4) in calli, leaves, and stems segments in a culture medium. We analyzed colony pigmentation, gram reaction, and evaluated PGP traits (phosphorous solubilization, nitrogen fixation and indol-acetic acid production) of 54 colonies from clone A3 and 50 colonies from clone E4. A total of 35 colonies of clone A3 and 42 colonies of clone E4 were capable of fixing nitrogen. Four isolated bacteria from clone A3 were capable of solubilizing phosphorous (P-Ca3(PO4)2), while no strain of E4 clone showed that capacity. Furthermore, 49 endophytic bacteria from clone A3 showed capacity to synthesize indol-acetic acid, while only 4 bacteria from the E4 clone presented that characteristic. We also identified six teak endophytic bacteria, by analysis of the 16S-23S rDNA intergenic spacer region, showing high identity with the genera Curtobacterium sp., Ochrobactrum sp., and Bacillus spp. Therefore, we demonstrate here that the abundant bacterial community existing in teak tissues, including those of in vitro cultivated plants, have PGP traits that can be further harnessed for preparation of bioformulations, for example. Our findings open the possibility for studying these isolated endophytic bacteria more closely in order to understand their association with teak growth.

Some Direct and Indirect Mechanisms of Endophytic Bacteria That Associated with The Medicinal Plant Areva javanica from Shada Al-Asfal Mountain

“…The isolates have been classified as diazotrophic bacteria due to their capacity to convert gaseous nitrogen into a useful form of ammonia [41]. The results align with the discoveries made by Hassan [36] and Pinto et al [38]. All of the bacterial strains that were examined showed positive results for the HCN production test.…”

“…The genera that exhibited the highest level of productivity were Bacillus and Pseudomonas. Pinto et al [38] have documented comparable findings. Endophytic bacteria have the ability to produce indole acetic acid (IAA), which is an important hormone that regulates plant growth.…”

“…Mcap_H18, Enterobacter cloacae, Pseudomonas aeruginosa, Delftia sp., Bacillus licheniformis, and Brevibacillus parabrevis. Bacillus, Enterobacter, and Pseudomonas are the predominant genera of bacterial endophytes, as described by Hassan [36], Ben Slama et al [37], and Pinto et al [38].…”