Fontanilla, Antonio Jr., B.2026-07-092026-07-092020-06Fontanilla, A. B. (2020). solation, screening, and identification of rhizospheric bacteria from lowland Rice and its effect on rice seedling vigor. [Unpublished thesis, Don Mariano Marcos Memorial State University-North La Union Campus, Sapilang, Bacnotan, La Union]. Lakasa ti Sirib, DMMMSU Institutional Repository.https://lakasa.dmmmsu.edu.ph/handle/123456789/2095Continuous use of inorganic fertilizers affects soil conditions and climate. Thus, agricultural production is based on a more sustainable and environmentally friendly approach, like biofertilizers, which is an effective alternative for increasing soil’s nutrient supply. The study evaluated the performance of plant growth-promoting bacteria in rice. It aimed to: (a) isolate and screen rice rhizosphere bacteria for their growth-promoting activities; (b) select and identify rice rhizosphere bacterial isolate using morphological and biochemical analysis; and (c) evaluate the effectiveness of potential bacterial isolates on rice seedling vigor under laboratory conditions. Twenty-seven bacterial isolates from the rice rhizosphere collected from the experimental field of Philippine Rice Research Institute (PhilRice), Central Experiment Station (CES), Science City of Muñoz, Nueva Ecija were screened and tested for the following plant growth promoting activities: 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity assay, indole-3-acetic acid (IAA) production assay, starch hydrolysis assay, and phosphate solubilization assay. From the 27 isolates, 17 showed ACC deaminase activity; 15 were positive for IAA production; 21 were able to solubilize phosphate; and 14 were able to hydrolyze starch. Four bacterial isolates were selected based on their growth promoting activities such as IAA production and/or phosphorus solubilization properties. The identified bacterial isolates using BIOLOG GEN III Microbial Identification System were: Bacillus amyloliquefaciens (N222-5); Pectobacterium carotovorum ss carotovorum (N222-7); Bacillus cibi (B158-18); and Bacillus amyloliquefaciens (B158-26). After eight day of evaluation, seeds inoculated with bacteria were significantly shorter in roots and shoots as well as on seedling vigor. Germination percentage was not affected. Further screen house trials where seeds inoculated with single bacterial isolates or in combination are planted directly into the soil are needed to verify the effect of the identified isolates on the growth and development of rice.en-USThesis