Abstract
Mixed 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 of X. arboricola (Xa) and Pseudomonas 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 by Xp alone. However, co-infection by dual species, Xp and Pc or Xa resulted in lower disease severity compared to Xp alone. Thus, co-infection outcomes depend on interacting species. Weak pathogens could exploit Xp to colonize the host plant as indicated by their higher populations in co-infection. However, Xp population dynamics was dependent on co-infecting partner. While resource competition might be a possible explanation for lower Xp population in dual co-infection, interaction of Pc with the host was found to influence Xp population. Interestingly, Xp population was higher in presence of three-species interaction compared to Xp and Xa co-infection, suggesting potential modulation of co-operative interactions among Xp and Xa in 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.
Competing Interest Statement
The authors have declared no competing interest.
