Colonization of plant growth promoting rhizobacteria (PGPR) on two different root systems

Phytohormones producing bacteria enhance the plants growth by positively affecting growth of the root. plant growth promoting bacteria (pgpr) must colonize the plant roots to contribute to the plant’s endogenous pool of phytohormones. colonization of these plant growth promoting rhizobacteria isolated from rhizosplane and soil of different crops was evaluated on different root types to establish if the mechanism of host specificity exist. the bacteria were isolated from maize,wheat,rice,canola and cotton and phytohormone production was detected and quantified by hplc. bacteria were inoculated on surface sterilized seeds of different crops and seeds were germinated. after 7 days the bacteria were reisolated from the roots and the effect of these bacteria was observed by measuring increase in root length. bacteria isolated from one plant family (monocots) having fibrous root performed well on similar root system and failed to give significant results on other roots (tap root) of dicots. some aggressive strains were able to colonize both root systems. the plant growth promoting activities of the bacteria were optimum on the same plant from whom roots they were isolated. the results suggest that bacteria adapt to the root they naturally inhabit and colonize the same plant root systems preferably. although the observe trend indicate host specificity but some bacteria were aggressive colonizers which grew on all the plants used in experiment. © 2016,pakistan botanical society. all rights reserved.