Effect of Combined Inoculation of Xanthomonas and Meloidogyne Pathogens on the Development of Tomato Root Knot Disease

Bacteria (Xanthomonas campestris pv. vesicatoria) and root-knot nematode (Meloidogyne incognita) independently can damage and cause considerable damage to tomato (Solanum lycopersicum L.). In a disease complex, interrelationship of 2 or more pathogenic species can produce different symptoms on the same host plant. Generally simultaneous occurrence of these pathogens in a field can infect hosts plant at the same time. During development of a disease complex pathogens could influence and/or suppress each other, through synergism and or antagonism respectively. In this study the pathogens (Meloidogyne incognita and Xanthomonas campestris pv. vesicatoria), were used to determine how co-occurrence affects development of pathogens and disease severity, and define prerequisites for interrelation between pathogens. Root knot infection did not occur when tomato plants were inoculated with Xanthomonas campestris 1 week prior to inoculation with Meloidogyne incognita. When M. incognita was inoculated 1 week prior to X. campestris, infection by root knot nematode was highest compared to bacterial spot incidence in susceptible plants. Simultaneous inoculation of M. incognita + X. campestris caused severe gall production with moderate severity of bacterial spot disease. The reproduction of 1 pathogen can be affected by a subsequent inoculation of other pathogen. It is suggested that bacterial spot disease enhances the development of root knot disease.