Inoculation of Tomato with Ralstonia solanacearum, Xanthomonas campestris, and Meloidogyne javanica

Abstract

The pathogenic bacteria Ralstonia solanacearum (Smith) Yabuuchi et al., Xanthomonas campestris (Pammel) Dowson, and Meloidogyne javanica (Treub) Chitwood are associated with tomato (Solanum lycopersicum L.) under field conditions. The effects of R. solanacearum, X. campestris, and M. javanica applied alone or in combination were examined to determine how individual and combined inoculations and order of inoculation affected tomato. Individual inoculation of R. solanacearum, M. javanica, and X. campestris caused significant reductions in plant growth. Inoculation of M. javanica alone caused a greater reduction in plant growth, followed by R. solanacearum and X. campestris. Inoculation of M. javanica plus R. solanacearum or M. javanica plus X. campestris caused a greater reduction in plant growth than the use of R. solanacearum plus X. campestris. Inoculation of M. javanica before inoculation with a bacterial pathogen caused a greater reduction in plant growth compared to inoculation of a bacterial pathogen prior to inoculation with the nematodes or inoculation of one bacterial pathogen prior to inoculation with another bacterial pathogen. Inoculation of M. javanica prior to R. solanacearum plus X. campestris caused the highest reduction in plant growth than other treatments except when all the three pathogens were inoculated together. R. solanacearum and X. campestris adversely affected nematode multiplication and galling, but the effect of R. solanacearum alone was greater than that of X. campestris alone. The greatest reduction in nematode multiplication and galling was when R. solanacearum plus X. campestris was inoculated prior to inoculation with M. javanica. The wilting index was 3 when R. solanacearum was inoculated alone. The bacterial spot index was 3 when X. campestris was inoculated alone. When R. solanacearum and X. campestris were inoculated together or these were inoculated with M. javanica, the indices were 5. Generally, in combined inoculations the adverse effects of pathogens on plant growth and disease development were additive. The combination that caused the least damage to tomato was when both bacteria were inoculated either simultaneously or one prior to another.