Effect of interaction between Phytophthora nicotianae and Meloidogyne spp. on the productivity and quality of tobacco plants (Nicotiana tabacum)

Summary Black shank disease caused by Phytophthora nicotianae is the most devastating pathology in tobacco ( Nicotiana tabacum ). In Colombia, an increase in the severity of P. nicotianae has been reported when parasitic nematodes are active in tobacco plants. The main objective of this study was to determine the pathogenicity, leaf quality and interaction between P. nicotianae (Races 0 and 1) with Meloidogyne spp. on tobacco plants in samples collected in 15 farms of Colombia. To quantify the interaction between both pathogens, variables such as plant survival, index of pathogenicity, and chemical and physical quality of the leaves were measured. Within a confidence level of 95% there is evidence of a positive synergistic effect between Meloidogyne incognita , M. javanica and P. nicotianae (Races 0 and 1) in a variety-dependent manner. For ‘ICA Servita’ the variables of index of pathogenicity, of root-knots and fresh weight of root, reduced the leaf price because of the interaction. For ‘K346’, Race 0 of P. nicotianae apparently reduced the pathogenicity of M. javanica in contrast to P. nicotianae Race 1. In addition, ‘ICA Servita’ and ‘K346’ showed susceptibility to nematodes. At the end of the harvest of ‘ICA Servita’, the interaction caused a considerable decrease in the physical and chemical quality of tobacco leaves, resulting in lower weight and number of leaves, affecting the price of tobacco in the market with reductions of more than 50%. Plant mortality of ‘ICA Servita’ and ‘K346’ was 50 and 60%, respectively, in interactions with both pathogens.