Effect of Pseudomonas protegens EMM-1 Against Rhizopus oryzae in Interactions with Mexican Autochthonous Red Maize

In the present study, the strain Rhizopus oryzae EMM was isolated from germinated autochthonous red maize seeds, which were harvested in a region of San Diego-Buenavista, Papalotla, Tlaxcala, Mexico, where cobs with fungal infections have been observed. This fungal strain caused wilting in the maize seedlings. Pseudomonas protegens EMM-1 was tested for its ability to inhibit R. oryzae EMM, both in culture media and in association with maize plantlets. P. protegens EMM-1 inhibited the growth of R. oryzae EMM under all culture media conditions explored. The ability of P. protegens EMM-1 to inhibit the growth of R. oryzae EMM associated with plants was evaluated in both a hydroponic system and in vermiculite. In both systems, P. protegens EMM-1 strongly inhibited the growth of R. oryzae EMM. The dry weight of root plants infected with R. oryzae EMM and inoculated with P. protegens EMM-1 increased to 0.43 g, while that of plants infected only with R. oryzae EMM reached just 0.19 g under hydroponic conditions. However, no differences were observed under vermiculite conditions. The dry weight of the aerial region of plants infected with R. oryzae EMM and inoculated with P. protegens EMM-1 was greater than that of plants infected only with R. oryzae EMM, both under hydroponic and vermiculite conditions. These results indicate that P. protegens EMM-1 inhibits the infection caused by R. oryzae EMM, thereby improving plant growth. Moreover, the genome analysis of P. protegens EMM-1 revealed the presence of several genes that potentially encode for antimicrobial compounds, which could strengthen the potential use of P. protegens EMM-1 as a biocontrol agent in maize plants.