Phosphate solubilizing endophytic actinomycetes from mangrove plants Rhizophora mucronata and Sonneratia caseolaris and its effect on Seedling vigour

The aim of the present study was to isolate phosphate solubilizing endophytic actinomycetes from two mangrove plants Rhizophora mucronata and Sonneratia caseolaris, to estimate phosphate solubilization quantitatively and to check its efficiency on Seedling vigour. The plant parts were surface sterilized and were plated on Oat meal agar supplemented with 10% sea water and a total of 11 endophytic actinomycetes were isolated. The isolates were screened for Phosphate solubilization using Pikovskaya's agar medium. The potent isolates were subjected for fermentation and the broth culture was subjected for quantitative estimation of phosphate solubilization by Johnson and Koening method. The effect of extracts of endophytic actinomycetes was also evaluated by seed germination and seedling vigour test. Of the total 11 isolates, Isolate RO 4, RO 7, RO 9, RO 10 and RO 11 demonstrated Phosphate solubilizing activity in the form of halo zone around the colonies and were selected for further studies. The broth cultures showed high amount of phosphate release compared to the standard. Highest amount of phosphate was recorded for Isolate RO 11 about 1410pg/ml. Isolate RO 7 and RO 11 showed the highest effect on Seedling vigour index. The results of the present study reveal that phosphate solubilizing endophytic actinomycetes can be used as a source of biofertilizer.