Diversidade e potencial biotecnológico da comunidade bacteriana associada ao pinhão-manso (Jatropha curcas L.)

Abstract

The present work was developed from four objectives: (1) biochemical characterization of 63 rhizobacteria, associated with Jatropha curcas, as for potential for promoting plant growth and enzyme production; Of these isolates, 27% tested positive for biological nitrogen fixation, 73% produced IAA and 69% solubilized inorganic phosphate. Regarding the antagonism test the rhizospheric isolates showed antagonistic activity with potential for biocontrol of the following phytopathogenic fungi: Alternaria alternata (39%), Colletotrichum sp. (42%), Fusarium oxysporum (30%) and F. profileratum (36%). In vitro enzymatic activity tests revealed that 30% of rhizobacteria showed amylolytic, 19% cellulolytic, 40% sterolytic, 26% lipolytic, 30% pectinolytic and 70% proteolytic activity. Among the 27 bacterial isolates identified by partial sequencing of the 16S gene, the presence of Bacillus genera was observed; Chryseobacterium; Enterobacter; Klebsiella; Pseudomonas; Serratia and Staphylococcus. (2) Characterization and comparison of diversity by metagenomic analysis of the bacterial community of jatropha rhizospheric soil from three treatments: non-irrigated / dryland; drip irrigation and pivot irrigation. Where it was possible to identify in the samples, sequences of Acidobacteria and Chloroflexi phyla, 4 orders (Acidimicrobiales, Chthoniobacterales, Gaiellales and Rhodospirillales), 7 families (Solibacteraceae, Chitinophagaceae, Acidobacteriaceae, Tepidisphaeraceae, Nitrosomonadaceae, Gemmatimonadaceae and Xanthobacteraceae and 8 genera, Acidothermus, Bacillus, Bradyrhizobium, Bryobacter, Reyranella, Sphingomonas, Steroidobacter and Variibacter. There was no significant increase in diversity in any evaluated treatment. However, species richness was increased in the drip and pivot areas when compared to the non-irrigated area. The bacterial groups that differed significantly between pivot irrigated treatment and rainfed treatment are the Bryobacter genus and Filo Chloroflexi. (3) Evaluation of plant growth promotion of maize (Zea mays) in greenhouse when inoculated with bacteria endophytically isolated of Jatropha curcas. These bacteria were considered potentially positive in the previously performed in vitro biochemical characterization in relation to the potential of plant growth promotion of these isolates. It was not possible to prove the ability to promote growth under greenhouse conditions by the transmission of only endophytic bacteria by seeds evaluated in the proposed methodologies. (4) Evaluation of the antagonistic potential of Jatropha-associated bacteria with potential to control the development of three species of Lasiodiplodia subglobosa, L. euphorbicola and L. pseudotheobromae, phytopathogenic to Jatropha. We evaluated 135 bacterial isolates associated with Jatropha curcas as their ability to inhibit the growth of phytopathogens. 36 isolates (26,67%) had good rates of antifungal activity. Eight isolates (5,9 %) were shown to inhibit in vitro growth above 75%. phytopathogen, especially the rhizospheric isolates of the genera Pseudomonas sp. and Bacillus subtillis.