Assessment of bacterial inoculant formulated with Paraburkholderia tropica to enhance wheat productivity.

Paraburkholderia tropica is an endophytic nitrogen-fixing bacterium isolated from the rhizosphere, rhizoplane, and internal tissues of sugarcane and corn plants in different geographical regions. Other plant-growth-promoting abilities, such as phosphate solubilization and antifungal activity, have also been reported for this bacterium. With an aim at investigating the potential use of P. tropica as an inoculant for improving the performance of wheat crop, in this work we evaluated an experimental inoculant formulated with P. tropica MTo-293 with respect to root colonization, the practical aspects of its application, and the effects under field conditions when applied to wheat seeds. Bacterial colonization was monitored by culture dependent techniques and the wheat yield determined by quantifying the total grain production in two different seasons. Rhizoplane and endophytic colonization in wheat roots was achieved efficiently (on average, 8 and 4 log colony-forming units/g fresh weight, respectively) even at relatively low concentrations of viable bacteria in the inoculum under controlled conditions. P. tropica was compatible with a widely used fungicide, maintained viability for 48 h once applied to seeds, and was also able to colonize wheat roots efficiently. Furthermore, we were able to formulate an inoculant that maintained bacterial viability for relatively long time periods. Preliminary field assays were realized, and even though the average yields values for the inoculated treatments remained above the uninoculated ones, no significant effects of inoculation were detected with or without fertilization. The correct physiologic behavior of P. tropica suggests the necessity to continue with field experiments under different conditions.

Trichoderma spp. from Misiones, Argentina: effective fungi to promote plant growth of the regional crop Ilex paraguariensis St. Hil.

Ilex paraguariensis St. Hil (yerba mate) is an important crop in the north of Argentina, mainly in Misiones province. The application of Trichoderma as a biocontroller and biofertilizer can replace or reduce the use of agrochemicals, decreasing the negative ecological impact. In this research, we evaluated in vitro and in vivo antagonistic and plant growth promoting (PGP) properties of Trichoderma species isolated from different regions of Misiones province. Dual culture assays of Trichoderma against phytopathogenic fungi associated with yerba mate showed that T. stilbohypoxyli LBM 120 was the most effective antagonist, inhibiting in more than 75% all phytopathogen growth. Trichoderma atroviride LBM 112 and T. stilbohypoxyli LBM 120 were positive on endoglucanase, protease, chitinase, siderophore production, and phosphate solubilisation showed the best biological control agents and PGP properties. The PGP properties of Trichoderma spp. evaluated in vivo on yerba mate seedlings showed that T. atroviride LBM 112, T. stilbohypoxyli LBM 120, and T. koningiopsis LBM 219 enhanced plant dry weight over 47% in total and 24% in the aerial part. Moreover, T. koningiopsis LBM 219 increased root dry weight 25% in contrast with in vitro controls. In conclusion, native Trichoderma strains could be a sustainable solution to improve yerba mate yield.