Fungal pathogens and antagonists in root-soil zone in organic and integrated systems of potato production

Occurrence of culturable Fungi and Oomycota in root-soil habitat of potato cv. Owacja in organic and integrated production systems at Osiny (northern Poland) was compared in 2008–2010. The densities of both pathogens were significantly greater in the organic system. The eudominant fungal taxa (with frequency > 10% in at least one habitat) included species of Fusarium + Gibberella + Haematonectria, Penicillium, Phoma and Trichoderma. The dominant taxa (with frequency 5–10%) included species from 13 genera. In the rhizoplane, rhizosphere and non-rhizosphere soil, the total density of potential pathogens was greater in the integrated system, and of potential antagonists in the organic system. Among eudominant and dominant pathogens, Fusarium oxysporum and Gibellulopsis nigrescens occurred at greater density in the integrated system and Haematonectria haematococca and Phoma spp. in the organic system. Among eudominant antagonists, Trichoderma species occurred at greater density in the organic system. The organic system provided more disease suppressive habitat than the integrated system. The occurrence of brown leaf spot and potato blight was however similar in both systems. The mean yield of organic potatoes (24.9 t · ha–1) was higher than the mean organic potato yield in Poland (21.0 t · ha–1) and similar to the mean in other European countries (Germany 25.1 t · ha–1, Great Britain 25.0 t · ha–1). The organic system, based on a 5-year rotation, with narrow-leafed lupin, white mustard and buckwheat as a cover crop, inorganic fertilization based on ground rock phosphate + potassium sulphate, and biological and chemical control of insects and diseases (Bacillus thuringiensis ssp. tenebrionis + copper hydroxide + copper oxychloride), may be recommended for use in central Europe.