CeBiTec – Colloquium
Monday, December 09, 2019, 17 c.t.
G2-104, CeBiTec Building
Prof. Dr. Luciane M. P. Passaglia
Universidade Federal do Rio Grande do Sul, Departamento de Genética, Núcleo de Microbiologia Agrícola (Brazil)
Plant growth-promoting capabilities and genomic analysis of the beneficial Azospirillum sp. Vi22 isolated from sunflower rhizosphere
Azospirillum is one of the most important genera of plant growth-promoting bacteria (PGPB), and some strains are successfully used as commercial inoculants in South America agriculture. Production of indolic compounds and nitrogen-fixing are among the characteristics broadly studied for this genus. The proliferation of root hairs and the increase of tolerance for abiotic and biotic stresses are frequently associated with the benefits provided to the plants inoculated with Azospirillum strains. Although known by the interaction with cereals, grasses, and legumes, different isolates have been found in association with other plant types. Here we presented an isolate from the rhizosphere of sunflower grown in fields of Rio Grande do Sul State (Brazil). In previous studies, the isolate designated Vi22 was identified as belonging to the genus Azospirillum according to the 16S rRNA gene and presented positive results for nitrogen fixation, siderophores and indolic compounds production. This isolate was also able to degrade oxalic acid in vitro, precursor molecule and the main virulence factor of Sclerotinia sclerotiorum – the pathogenic fungus with the most significant impact on Brazilian sunflower crops. In a field experiment (completely randomized block design with four replicates and plots of 4.2 m × 6.0 m), a high grain yield (about 4,000 kg ha−1) was observed in the treatment with a half dose of nitrogen fertilizer and bacterial inoculation (P ≤ 0.05). The genome of Vi22 was sequenced, and a common set of genes related to the plant-associated bacteria were found. As examples, genes related to the metabolism of vitamins, production of antibiotics and phytohormones (including indole-3-glycerol phosphate synthase), nitrogen fixation (including an alternative nitrogenase), siderophore transporters, flagella and exopolysaccharide biosynthesis, and chemotaxis regulators were identified. According to the genomic metrics analyses based on the orthologous average nucleotide identity (Ortho–ANI), Vi22 is closely related to the strains Sp245, Az39, and REC3 of A. brasilense species, presenting ANI values ranging from 95.49 to 98.57%. Further studies should be carried out to evaluate the potential of this isolate for the biocontrol of S. sclerotiorum and its performance in different field conditions.
Host: Prof. Dr. Volker F. Wendisch