Influence of co-occurring weakly pathogenic bacterial species on bacterial spot disease dynamics on tomato

Abstract

AbstractMixed infections caused by multiple pathogenic and/ weakly pathogenic strains inhabiting the same host plants are common in nature and may modify pathogen dynamics. However, traditional plant pathogen studies have mostly focused on the binary interaction between a single host and a single pathogen. In this study, we have looked beyond this binary interaction and evaluated the impact of co-infection on disease dynamics on tomato using bacterial spot pathogen,Xanthomonas perforans(Xp) and two co-occurring weakly pathogenic strains ofX. arboricola(Xa) andPseudomonas capsici(Pc). Time-series greenhouse co-infection experiments monitoring disease severity and within-host population dynamics revealed higher disease severity in co-infection by three species compared to infection byXpalone. However, co-infection by dual species,XpandPcorXaresulted in lower disease severity compared toXpalone. Thus, co-infection outcomes depend on interacting species. Weak pathogens could exploitXpto colonize the host plant as indicated by their higher populations in co-infection. However,Xppopulation dynamics was dependent on co-infecting partner. While resource competition might be a possible explanation for lowerXppopulation in dual co-infection, interaction ofPcwith the host was found to influenceXppopulation. Interestingly,Xppopulation was higher in presence of three-species interaction compared toXpandXaco-infection, suggesting potential modulation of co-operative interactions amongXpandXain three-species co-infection rather than competitive interactions. Humidity played a significant role in population dynamics of the three species. Overall, this study highlighted importance of co-infection dynamics in studying plant disease outbreaks.