Plant beneficial effect of two strains of Proteus vulgaris isolated from tea plantations

Two strains of Proteus isolated from tea plantation soil were tested for their ability to colonise the roots of gram (Cicer arietinum), bean (Phaseolus radiatus) and mung (Phaseolus mungo) using a gnotobiotic system. Seeds bacterized with the two strains grew faster and showed significant increase in root and shoot enlargement of the plants tested. The bioactive fractions obtained from the culture filtrates and separated through HPLC showed that the plant growth promoting fractions were not always fungicidal and that the insecticidal fraction which was found only in RRLJ 16 was not plant growth promoting. These results suggest that the plant growth promotion effect of the plant beneficial bacteria may not always be due to disease suppression.