Root colonization and association of phosphate- solubilizing bacteria at various levels of triple supper phosphate in aerobic rice seedlings

Abstract

Phosphate-soubilizing bacteria (PSB) have the ability to solubilize substantial amount of insoluble phosphorus from native soil. An experiment was conducted in vitro condition at Universiti Putra Malaysia, Malaysia, to study the effect of different doses of triple supper phosphate (0, 30 and 60 kg P2O5 ha-1) on colonization and association of two Bacillusspp. (PSB9 and PSB16 strains) in aerobic rice system. Root colonization was examined under scanning and transmission electron microscope (SEM and TEM). Bacterial association as well as, its effects on plant growth with different rates of P fertilizer was determined during 30 days of growth. There was a significant interaction effect found in PSB × TSP doses × days for plant P uptake. Significantly, the highest available P (31.75 mg kg-1) and P uptake (0.78 mg P Pot-1) was found with PSB16 inoculated treatments at 60 kg P2O5 ha-1, where as, highest biomass (82.25 mg plant-1) and root growth obtained at 30 kg of P2O5 ha-1. The SEM and TEM micrograph proved inoculated PSB successfully colonized on the surface as well as root interior. The bacterial population survived during the planting period and there was no significant population difference found between the two strains. While, the highest PSB16 rhizosphere population (8.16 log10 cfu g-1) was recorded after 30 days of planting at 30 kg of P2O5 ha-1. Hence, present study proved thePSB inoculation along with the TSP fertilizer improved association, P uptake, available soil P and growth of aerobic rice. Key words: Biomass, P uptake, rhizosphere, scanning electron microscope, transmission electron microscope.