Bacteriophages as promising agents for the biological control of Moko disease (Ralstonia solanacearum) of banana

Abstract

“Moko disease”, caused by the bacterium Ralstonia solanacearum, is one of the most devastating diseases of banana and plantain. Its management is difficult, given its aggressiveness and easy dispersion, as well as the lack of products for its control. Effectiveness of antibiotics is quite low and their use in the field is restricticted, given environmental and human health concerns. Bacteriophages (phages) have emerged as an alternative for the control of bacterial plant diseases, but their potential for the control of Moko is yet to be tested. Thus, in this study, phages isolated from soils cultivated with banana and plantain were selected and evaluated for their capacity to control R. solanacearum, both in vitro and on banana plants under greenhouse conditions. For this, eight lytic phages were isolated from soil collected in plantations of banana and plantain in Colombia and tested against 65 native strains of R. solanacearum. The two most effective phages were further evaluated for their capacity to inhibit the growth in vitro and in a soil microcosm of a highly pathogenic strain, R. solanacearum UA1591. Here, both phages reduced the growth of the pathogen in liquid media and soil microcosm to levels that were below the threshold of detection in 24 h. Lastly, in a greenhouse experiment, plants treated with the two-phage cocktail were 100% protected from Moko, even though most plants treated with individual phages still displayed symptoms of the disease. These results support that two-phage cocktails are promising biological control agents against Moko disease.