Antagonism of Native Microorganisms on Phytophthora Infestans (Mont.) de Bary Isolated from Solanum Tuberosum L.

Abstract

The inadequate management of diseases in potato crops causes some pathogenic species to generate resistance to various pesticides, which increases the use of agrochemicals that cause pollution in soil and water, damaging human health. Phytophthora infestans (Mont.) de Bary (cause of late blight) limits the potatoes production (Solanum tuberosum L.) and causes significant economic losses. Potato is produced in the northeast region of Puebla, Mexico, and the presence of late blight is documented, which is controlled with the application of synthetic fungicides. In this study, the antagonist inhibition in vitro of two native microorganisms (Trichoderma sp. and Pseudomonas sp.) isolated from the rhizosphere of a wild Solanaceae (in the vicinity of a potato crop), was evaluated on P. infestans obtained from infected plants. Tests were performed using the antagonists independently and in combination. The effect of the antagonist on the pathogen was determined based on the percentage of radial growth inhibition, in the case of the fungus the type of hyphal interaction, the antagonistic capacity and form. The results show that the fungus can indirectly inhibit the growth of P. infestans (around 50%), while the direct inhibition, with both microorganisms evaluated separately, is more than 65%. The treatment using the combination of Pseudomona-Trichoderma decreased the growth in greater proportion (80%-92%) than any of the antagonists evaluated independently. Although the bacterium decreases the growth of the antagonist fungus, Trichoderma sp. produces compounds that indirectly affect the phytopathogen, causing a synergistic effect between the two native microorganisms to decrease the development of the pathogen in vitro cultures. We consider it is important to design a strategy to use native microorganisms present in the soils of the region as agents that reduce the incidence of late blight.