Assessment of Potential Plant Growth Promoting Compounds Produced In Vitro By Endophytic Bacteria Associated with Nipa Palm (Nypa fruticans)

The study determined the plant growth promoting compounds produced in vitro by endophytic microorganisms isolated from nipa palm (Nypa fruticans). These compounds include indoleacetic acid (IAA) production, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, phosphate solubilization, siderophore production, nitrogen fixation, and starch hydrolysis. Nitrogen-free medium was used to isolate endophytic bacteria. Fifty-one isolates from nipa palm (roots, bark, leaves, etc.) taken in Bulacan, Quezon, and Agusan provinces were screened for the production of growth-promoting compounds. Forty-two isolates produced IAA, six were able to produce siderophore as shown by orange halo around the colonies, and 21 showed ACC deaminase activity. Of the 51 isolates, 37 dissolved precipitated tricalcium phosphate as shown by clearing zone around isolates grown in Pikovskaya's medium. Thirty-six isolates are nitrogen-fixing bacteria while 18 isolates were able to hydrolyzed starch. Five isolates were selected from among 51 isolates for further study. Selection was based on their growth rates, IAA production and phosphate solubilization. Endophytic bacteria associated with nipa palm produced growth-promoting compounds that may promote plant growth. However, assessment was done in vitro only. Evaluation of the selected isolates under growth room and screenhouse conditions is recommended to determine its effectiveness as plant growth promoter.