Genetic Characterization and Growth Promotion Mechanisms of Burkholderia vietnamiensis Isolated from Rice Cultivars in Peru

Burkholderia is a versatile bacterial genus, and from a biotechnological point of view, it is a source of diverse secondary metabolites with enormous application potential, especially in agriculture.

This study aimed to isolate diazotrophic Burkholderia bacteria-associated rice roots and study the genetic and PGPR diversity among strains and the effect of their inoculation in two rice cultivars.

Strains were isolated using nitrogen-free semisolid media and tested by specific amplification of the recA gene. The production of auxins, siderophores, phosphate solubilization, and antagonism against phytopathogenic fungi was evaluated, and finally, their inoculation into two rice varieties was also examined.

Only 5.13% of the isolated strains were positive for the amplification of the recA gene with Burkholderia-specific primers. Sequence analysis showed high similarity with Burkholderia vietnamiensis. These strains produced auxins in tryptophan-supplemented broth (up to 13.98 µg mL^-1), siderophores (up to 139.52%), phosphate solubilization (up to 15.99 mg PO₄ mL^-1), as well as antibiotic and antagonistic capacities against five pathogenic fungi of rice. These strains increased the vigor index in two rice cultivars compared to the non-inoculated or non-fertilized treatment. The antibiotic and antifungal activities of B. vietnamiensis strains against two pathogenic fungi, Nakataea sigmoidea and Nigrospora oryzae, are described for the first time.

Due to the taxonomic affinity of our strains within the Burkholderia cepacia complex, their direct use in agriculture is not recommended; however, further research is required to exploit their biotechnological potential for the synthesis of useful metabolites.