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, *ranepomuceno@up.edu.ph
Abstract
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
Vol 45:(1) April 2020