BIODIVERSITY OF ENDOPHYTIC BACTERIA WHICH COLONIZE RED-CLOVER NODULES, ROOTS, STEMS AND FOLIAGE AND THEIR INFLUENCE ON HOST GROWTH

The aim of this study was to identifiy the endophytic bacteria recover ed from the foliage, tap roots and nodules of red clover plants (Trifo lium pratense L.); and to assess the effects of the nodule bacteria, a lone and in combination with Rhizobium spp., on the growth and develop ment of red clover seedlings. Thirty-one bacteria species from 14 diff erent genera were recovered from within the foliage, roots and nodules of red clover plants cv. AC Charlie. Genera diversity and species num ber were greatest in foliage tissues. Pantoea agglomerans (59.6%) was the most frequent species recovered in foliage tissues, Agrobacterium rhizogenes A in the tap root (49.2%) and Rhizobium leguminosarum BV ph aseoli and R. loti B in the nodules (27.2% each). Recovery of Rhizobiu m species was not restricted to the nodules, and species of this genus were systemic throughout the plant. Clover root nodules were host to 12 bacteria species other than rhizobia, of which 8 were specific to t his tissue. Using non-selective media, R. leguminosarum BV trifolii co nstituted only 8.8% of all the root nodule bacteria recovered. In root bacterization experiments, species of nodule bacteria promoted growth of red clover more often when applied in combination with R. legumino sarum BV trifolii than when applied singly. However, Bacillus megateri um, Bordetella avium and Curtobacterium luteum consistently promoted g rowth either individually or in combination with R. leguminosarum BV t rifolii. Nodulation was promoted when R. leguminosarum BV trifolii was coinoculated with Bacillus insolitus, B. brevis or A. rhizogenes A. S ingle isolate applications of Rhizobium species to roots always led to the depression of clover growth, but mixtures of R. leguminosarum BV trifolii and R. leguminosarum BV phaseoli resulted in growth promotion . The latter is considered further evidence of the beneficial allelopa thic side effect of strain competition for the same ecological niche.