Effect of Phosphate Solubilizing Bacteria (PSB) on Growth and P Uptake of Wallapatta (Gyrinops walla Gaertn.) Seedlings

Abstract

Gyrinops walla Gaertn (wallapatta) is a highly valuable agarwood producing plant species endemic to Sri Lanka. Due to over-exploitation of the species, the natural habitats are tremendously under pressure, thus commercial-scale cultivation is needed to meet the increasing demand. Propagation through seeds is found to be hampered by inadequate availability of seeds, poor viability and germination and delayed rooting of seedlings. As the use of Phosphate Solubilizing Bacteria (PSB) is recognized to be a sound technology that could enhance the growth of different crops, the present research was carried out to investigate the effect of isolated five PSB strains on growth and P uptake of wallapatta seedlings. Significant (P ≤ 0.05) increase in plant height, stem diameter, shoot and root dry weight of wallapatta plants were recorded from the seedlings raised with the PSB inoculated seeds compared to non-inoculated seeds. The best growth performances (52.67 cm, 7.52 mm, 7.62 g/plant, and 3.89 g/plant for plant height, stem diameter, shoot and root dry weight, respectively) were recorded from the seedlings inoculated with the strain PSB5 followed by PSB3. Significant (P ≤ 0.05) decrease in soil pH and increased available P contents were recorded in rhizosphere soil samples taken from PSB inoculated seedlings than that of the non-inoculated seedlings. The lowest soil pH and the highest available soil P contents (6.05 and 18.24 mg/Kg soil respectively) were recorded from the rhizosphere soils inoculated with the strain PSB5 followed by PSB3. The strain PSB5 which enhanced the highest growth performances and P uptake of wallapatta seedlings was identified as Enterobacter cancerogenous. Therefore, present results provide much needed baseline information for future studies on the use of PSB as bioinoculants to enhance the early growth of wallapatta seedlings.