Coinoculation of soybean plants with Bradyrhizobium japonicum and Trichoderma harzianum: coexistence of both microbes and relief of nitrate inhibition of nodulation

ANDRES FAURA; JULIETA PEREZ GIMENEZ; ESTEBAN TOMÁS ITURRALDE; CECILIA MONACO; ANIBAL LODEIRO; MARINA STOCCO; CORDO, CRISTINA

Biotechnology Reports

Elsevier

Año: 2020 vol. 26 p. 1 - 6

2215-017X

Coinoculation of plants with two or more beneficial microbe species sometimes produces synergistic effects. In this study, the effect of soybean coinoculation with Bradyrhizobium japonicum E109a N2-fixing symbiontand Trichoderma harzianum Th5cca plant-growth-promoting and biocontrol funguswas analyzed. Nodulation by E109 was not hampered by Th5cc, which antagonized five out of seven soybean pathogens tested. Furthermore, the presence of Th5cc relieved nitrate inhibition of nodulation, thus enabling the formation of nodules containing infected cells that were occupied by bacteroids in spite of the presence of the otherwise inhibitory 10 mM KNO3. T. harzianum Th5cc released micromolar amounts of auxin, and addition of 11 µM indoleacetic acid to soybean plants inoculated with B. japonicum E109 in the absence of Th5cc also induced nodulation in the presence of 10 mM KNO3. Thus, T. harzianum Th5cc may release auxins into the soybean rhizosphere, which hormones might participate in overcoming the nitrate inhibition of nodulation. Our results suggest that soybean plants coinoculated with these microorganisms might benefit from biocontrol while contributing to soil-nitrogen preservation.