Growth Enhancement of Rice (Oryza sativa L.) by Zinc-Solubilizing Bacteria Isolated from Vesicular-Arbuscular Mycorrhizal Root Inoculant (VAMRI)
Robert A. Nepomuceno*, Cristine B. Brown, Allysa Mae P. Gargarino, Mannix S. Pedro and Marilyn B. Brown

National Institute of Molecular Biology and Biotechnology (BIOTECH), University of the Philippines Los Baños, 4030 College Los Baños, Laguna, Philippines. *Corresponding author, *


Zinc deficiency is the most common soil micronutrient deficiency all over the world. An effort to isolate, zinc solubilizing microorganisms (ZSMs) in VAMRI, a commercial mycorrhizal inoculant, was undertaken to realize the possibility of solving soil zinc deficiency through microbial inoculation. Five bacterial isolates (Sphingobacterium multivorum, Burkholderia cenocepacia, Bacillus xiamenensis, Burkholderia ambifaria, and Bacillus aerius) grown in LGI medium supplemented with insoluble zinc compound (0.1%) tested positive for zinc solubilization with solubilization index ranging 3.09±0.07 to 5.21±0.07. Subsequent quantification of zinc solubilization of select bacterial isolates through atomic absorption spectroscopy revealed a significant increase in available zinc ranging 679.64-1017.23 ppm over the uninoculated control. Sand culture experiment also showed the isolates significantly increased rice height, with isolate B. cenocepacia (V3) having similar performance as the positive control with available zinc. Hence, the inoculation of ZSMs shows great prospect in alleviating soil zinc deficiency in rice.

Keywords: zinc solubilizing bacteria, soil zinc deficiency, biofertilizer