RESUMO
Plant-growth-promoting bacteria are often used to enhance crop yield and for biological control of phytopathogens. Bacillus sp. CHEP5 is a biocontrol agent that induces systemic resistance (ISR) in Arachis hypogaea L. (peanut) against Sclerotium rolfsii, the causal agent of root and stem wilt. In this work, the effect of the co-inoculation of Bacillus sp. CHEP5 and the peanut nodulating strain Bradyrhizobium sp. SEMIA 6144 was studied on induction of both systemic resistance and nodulation processes. Bradyrhizobium sp. SEMIA 6144 did not affect the ability of Bacillus sp. CHEP5 to protect peanut plants from S. rolfsii by ISR and the priming in challenged-plants, as evidenced by an increment in phenylalanine ammonia-lyase enzyme activity. Additionally, the capacity of Bradyrhizobium sp. SEMIA 6144 to induce nodule formation in pathogen-challenged plants was improved by the presence of Bacillus sp. CHEP5.
Assuntos
Arachis/microbiologia , Ascomicetos/fisiologia , Bacillus/fisiologia , Bradyrhizobium/fisiologia , Arachis/metabolismo , Agentes de Controle Biológico , Clorofila/metabolismo , Resistência à Doença , Doenças das Plantas/microbiologia , Raízes de Plantas/microbiologia , SimbioseRESUMO
Peanut is an economically important legume nodulated by slow-growing bacteria of the genus Bradyrhizobium. In this study, a collection of native slow-growing peanut rhizobial isolates from Argentina was obtained and characterized. The phenotypical characterization included the determination of the symbiotic properties, whereas the genetic and phylogenetic diversity was assessed through ERIC-PCR and sequencing of the internal transcribed spacer (ITS) region, as well as the dnaK and nodA genes. The results obtained indicated that peanut nodulating bradyrhizobia were phenotypically and genotypically diverse, and included locally adapted variants of B. yuanmingense and B. iriomotense carrying novel nodA alleles.
Assuntos
Arachis/microbiologia , Bradyrhizobium/classificação , Nódulos Radiculares de Plantas/microbiologia , Argentina , Bradyrhizobium/genética , Bradyrhizobium/isolamento & purificação , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Variação Genética , Genótipo , Fenótipo , Filogenia , Reação em Cadeia da Polimerase/métodos , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Microbiologia do Solo , SimbioseRESUMO
In this study, bacteria hosted in root nodules of single plants of legume Arachis hypogaea L. (peanut) cv Tegua Runner growing at field were isolated. The collection of nodule isolates included both fast and slow growing strains. Their genetic diversity was assessed in order to identify the more frequently rhizobial strain associated to nodules from single plants. Molecular fingerprinting of 213 nodular isolates indicated heterogeneity, absence of a dominant genotype and, therefore, of a unique strains highly competitive. Efficient nitrogen-fixing isolates were identified as Bradyrhizobium sp. by phylogenetic analysis of the sequences of their 16S rRNA genes. The genetic diversity of 68 peanut nodulating isolates from all the collected plants was also analyzed. Considering their ERIC-PCR profiles, they were grouped in eighteen different OTUs for 60% similarity cut-off. Results obtained in this study indicate that the genetic diversity of rhizobia occupying nodules from single plant is very high, without the presence of a dominant strain. Therefore, the identification of useful peanut rhizobia for agricultural purposes requires strongly the selection, among the diverse population, of a very competitive genotype in combination with a high-symbiotic performance.