ISOLATION AND SELECTION OF RHIZOSPHERIC ACTINOMYCETES WITH ANTAGONISTIC ACTIVITY AGAINST POTATO PHYTOPATHOGENS (Solanum tuberosum spp. andigena)

Potato crops are affected by a great number of pathogens that decrease their quality and productivity. One way of controlling these phytopathogens is through the use of antagonistic microorganisms, especially those isolated from the microbial community located in the rhizosphere. In this study, 49 strains of actinomycetes were isolated and their antagonist capacity against phytopathogens that affect Solanum tuberosum was assessed. 26.5% showed antagonist activity against Pectobacterium carotovorum, 69.4% against Fusarium sp., 44.9% against Lasiodiplodia sp., 55.1% against Rhizoctonia solani and 46.9% against Phytophthora infestans. Cultures of two selected actinomycetes (AND 12 and AND 24) were treated with ethyl acetate, dichloromethane, hexane and butanol, whose crude extracts showed antimicrobial activity, being the most important the extract obtained with ethyl acetate due to its greater spectrum of inhibitory activity. The selected strains were identified by phylogenetic analysis of the 16S rRNA gene as members of the genus Streptomyces. Due to their antagonist capacity demonstrated in the present study, rhizospheric actinomycetes could be considered as potential candidates to be used in pathogen control programs that affect potatoes.