Isolation and Characterization of Plant Growth promoting Rhizobacteria from Bamboo Rhizosphere and Their Role in Plant Growth Promotion

Abstract

Plant growth-promoting rhizobacteria (PGPR) are a group of root-associated bacteria that intimately interact with the plant roots and consequently enhance growth by extemporising nutrient retrieval or phytohormone production. We isolated and screened indigenous phosphate solubilising and auxinproducing PGPR from bamboo rhizosphere. 66 soil samples from bamboo (Bambusa nutans subsp. cupulata, B. balcooa and B. tulda) rhizospheres were collected from Dhanusha, Mahottari and Sarlahi districts, Nepal. 120 isolates of PGPR were obtained by serial dilution method in (PVK) agar and Luria Bertani agar. 92 out of 120 isolates of PGPR with the ability to solubilise phosphate were selected based on the halo colony ratio in PVK agar medium and auxin production in Luria Bertani agar. Among them, six isolates having high phosphate solubilising index and high production capacity of indole-3-acetic acid were further screened. Biochemical analysis revealed that these isolates belonged to the genus Pseudomonas. Phosphate solubilising index and indole-3- acetic acid production by six isolates ranged from 4.19±0.8 to 7.65±1.3, and IAA production ranged from 72.93±0.2 to 82.48±0.9µg/ml respectively. These isolates significantly increased shoot length (13.26±0.56cm), shoot fresh weight (16.26±1.02mg), shoot dry weight (10.56±0.09mg), root length (4.9±0.5cm), root fresh weight (7.56±1.05mg), root dry weight (3.21±0.01mg), and chlorophyll ‘a’ and chlrophyll‘b’ and carotenoid (2.16±0.01mg/g, 1.19±0.06mg/g and 0.92±0.01mg/g respectively) of B. nutans subsp. cupulata seedlings. This study suggests that PGPR isolated from bamboo rhizosphere demonstrated outstanding contribution to the growth promotion of seedlings of B. nutans subsp. cupulata as compared to negative control.