Native putatively endophytic bacteria from Handroanthus impetiginosus improve its in vitro rooting

Abstract

Plant growth promoting bacteria inoculation is a new explored biotechnological tool for in vitro systems with positive impacts in micropropagation. The aim of this work was to study plant growth promotion ability of putatively endophytic bacteria previously isolated from Handroanthus impetiginosus on in vitro rhizogenesis of this tree. Rooting experiments were performed with shoots induced or not with 30 μΜ IBA for 3 days. Then they were transferred to half-strength MS (Murashige and Skoog in Physiol Plant 15:473–497, 1962) salts with B5 vitamins (Gamborg in Exp Cell Res 50(1):151-158, 1968), and inoculated with one of the putative endophytic strains (Pseudomonas sp. (L2), Paenibacillus sp. (L6), Bacillus sp. (L9 and L15), Methylobacterium sp. (L10) or Rhizobium sp. (L12)). Non-inoculated treatments were controls. Rooting percentages were recorded periodically. Biometric and biochemical parameters were measured at the end of the experiment. Also a biometric parameter index was constructed. Experiments showed that inoculation with Rhizobium sp. L12 and Paenibacillus sp. L6 significantly increased rooting percentage, whereas Rhizobium sp. L12 and Bacillus sp. L15 improved aerial and root parameters. Protein and lignin contents were also modified in inoculated plants. In conclusion, putatively endophytic bacteria isolated from ex vitro H. impetiginosus promoted in vitro rooting, increased biometric parameters and modified some biochemical components, and these strains could be used as biofertilizers for sustainable agriculture.