Lack of influence of Meloidogyne incognita on resistance of bell pepper cultivars to Phytophthora capsici

Abstract

The root-knot nematode, Meloidogyne incognita, and the Phytophthora blight pathogen, Phytophthora capsici, cause root diseases in bell pepper under field conditions. However, limited information is available about the interactions between these two pathogens on different bell pepper cultivars. Greenhouse experiments were conducted on cultivars of bell pepper with different levels of resistance to P. capsici (‘Aristotle’, ‘Paladin’ and ‘Intruder’), by concomitant and sequential inoculation of both pathogens. The treatments included inoculating both pathogens simultaneously into the root zone, inoculating M. incognita 7 days before P. capsici, inoculating P. capsici 7 days before M. incognita, inoculating M. incognita or P. capsici alone, and an untreated control without any pathogens. In ‘Aristotle’ and ‘Intruder’, P. capsici inoculation with M. incognita simultaneously or 7 days before or after M. incognita reduced gall index significantly as compared with M. incognita alone. In ‘Paladin’, P. capsici inoculation 7 days before or after M. incognita lowered gall index compared with M. incognita – P. capsici simultaneous inoculation. Phytophthora blight severity was not influenced by M. incognita irrespective of inoculation methods used in the three genotypes. In ‘Aristotle’, M. incognita inoculation alone did not reduce fresh root weight, but P. capsici alone or combined with M. incognita reduced fresh root weight as compared with the untreated control. However, none of the treatments reduced fresh root weight in ‘Paladin’ or ‘Intruder’ as compared with the untreated control. The interaction between P. capsici and M. incognita seems to be one way in that P. capsici reduced galling of M. incognita, but the nematode had no effect on Phytophthora blight severity. The interaction was influenced by pepper cultivars, with a greater reduction in galling on ‘Aristotle’ and ‘Intruder’ than on ‘Paladin’.