Zinc Solubilizing Fungi from Zinc-Deficient Philippine Rhizospheric Soil: Isolation and Characterization
Cristine Marie Brown, Robert Nepomuceno, Mannix Pedro and Marilyn Brown
National Institute of Molecular Biology and Biotechnology (BIOTECH), University of the Philippines, Los Baños
Zinc deficiency in the soil presents a significant long-term challenge to achieving optimal crop yields. This issue is particularly pressing in the Philippines and worldwide, with the deficiency expected to rise from 42% to 63% by 2025 due to ongoing soil fertility depletion and unsustainable agricultural practices. In response, we initiated a project to isolate microorganisms capable of solubilizing zinc for use as potential inoculants. Rhizospheric soil samples were collected from rice, corn, and cassava fields in zinc-deficient regions, specifically Nueva Ecija, Nueva Vizcaya, Laguna, Mindoro, Aurora, and Aklan. Solubilization studies were conducted using LGI medium with glucose (2%) as the carbon source and insoluble zinc compounds (0.1%). All 22 tested isolates exhibited positive results for zinc solubilization, with solubilization indices ranging from 1.23 to 4.44. Halozone measurements ranged from 0.07 to 8.09 mm, with some isolates forming halozones covering the entire Petri plate. The most promising zinc-solubilizing isolates were obtained from the rhizosphere of cassava in Tarlac and corn in Los Banos.