GAMMA IRRADIATION EFFECT ON PHOSPHATE SOLUBILIZING BACTERIA ACINETOBACTER CALCOACETICUS

Abstract

Phosphorus deficiency is a growing global issue on approximately 40% of cultivated land, primarily in tropical, acidic, and alkaline regions. This deficit, as a result of soil fixation, erosion, and phosphorus lag behind absorption, severely limits plant growth, crop yield, and soil fertility. While chemical fertilizers are used regularly to correct this situation, excessive use leads to environmental pollution. Alternatively, phosphate-solubilizing bacteria (PSB), such as Acinetobacter calcoaceticus, offer a biodegradable solution through the conversion of insoluble phosphorus to plant-accessible forms. This study explores the application of gamma irradiation, a mutagenesis technique that induces genetic alterations to improve the phosphate-solubilizing capability in the bacteria. The results showed from 931 bacteria colonies chosen after the irradiation treatment, 9.88% of bacteria strains showed a hypermorphic effect on the phosphate solubilization compared to the control, and 36.84% of bacteria strains showed hypomorphic effects. The distribution of hypermorphic bacteria strains across the phosphate solubilization index (SI) range was the higher SI range (3.1-3.5) was 8, the middle SI range (2.1-2.5) was 50, and the lower SI range (1.1-1.5) was 0. Among the 8 higher hypermorphic mutants, B346, B394, C92, C371, D20, D49, D96, and D100, only 3 mutant strains (C371, D20, and D100) showed statistical significance compared to control. This study has successfully produced several improved Phosphate-Solubilizing Bacteria (PSB) strains with strong potential for development as biofertilizers.