Bacterial wilt biocontrol by the endophytic bacteria Gluconacetobacter diazotrophicus in Rio Grande tomato cultivar

RODRIGUEZ M. VICTORIA; CARRAU, ANALÍA; CORTADI AA; TANO, JOSEFINA; FERRETTI MD; SREBOT M. SOL; MARTINEZ ML; ORELLANO, ELENA G.

San Pablo

Congreso; 2nd São Paulo XanthoMeeting (2018): Plant pathogens, antimicrobial agents, disease management and control.; 2019

SBBq Society for Biochemistry and Molecular Biology

Environmental problems produced by several synthetic agricultural agents generate demands in the search of alternative ways to control pests and pathogen. Novel natural products and organisms offer opportunities for innovation in agroindustry. Gluconoacetobacter diazotrophicus Pal5 (Gb) belongs to PGPBEs (Plant-Growth-Promoting Bacterial Endophytes). PGPBEs facilitate plant growth via three interrelated mechanisms: phytostimulation, biofertilization and biocontrol. Ralstonia solanacearum (Rso) is a phytopathogenic bacterium that causes important economic losses. Rso attacks a wide variety of crops, including tomato and potato. In this study were used an argentine cultivar of tomato plant ?Rio Grande?. Tomato seedlings were inoculated with Gb to test its ability to colonize them and to evaluate its protective potential against Rso.Seeds were grown in a controlled growth chamber under a light/dark cycle of 16 and 8 h, respectively, at 28 °C for 7 days. Four treatments were performed: non-inoculated plantlets controls, inoculated with G. diazotrophicus, inoculated with R. solanacearum, inoculated with Gb and Rso.To determine endophytic colonization, plant tissues were disinfected and the colony forming units (CFU) were counted after incubation at 28 °C for 3 days. Different growth parameters were determined at 7 and 14 days post-inoculation (dpi). To evaluate Gb biocontrol, samples were taken at 9 dpi with Rso. Wilt symptoms were analysed and Rso and Gb bacterial concentration were determined. Anatomical features of control and infected seedlings were investigated by microscopic analysis. Root and stem colonization of tomato plantlets by Gb was achieved. While the establishment of Gb in tomato plants has already been reported, this is the first time in Rio Grande cultivar, a highly demanded tomato type at industrial level. Stem height and the leaf size were markedly affected by the inoculation with Gb.Plants without Gb showed wilting at 9 dpi with Rso. Pathogen could be detected through histological thin sections along stem. Section showed xylem vessels filled with bacteria and exopolysaccharide deposition. Stem bacterial concentration was 1.5.108 CFU/mL at 9 dpi. In contrast, plants with Gb remained asymptomatic and Rso growth was observed to a lesser extent in the stem and root (3.6.103 CFU/mL).This study shows that G. diazotrophicus confers beneficial effects as growth promotion and pest protection to Rio Grande tomato, after endophytic colonization. Further studies are required to determine the possible mechanisms that produce these effects.