Detection and characterization of quiescent infections of Neonectria ditissima in Brazilian commercial apple fruit

Abstract

Neonectria ditissima, the causal agent of European Canker and Neonectria fruit rot, is a quarantine apple pathogen in Brazil, restricted to some production areas of Rio Grande do Sul, Santa Catarina, and Paraná states. The quarantine rests on a product certification based on the absence of symptoms but it is not known whether the pathogen could be moving around in quiescent infections. In this work, we detected N. ditissima after incubation of asymptomatic commercial fruit. The identity of the pathogen was confirmed using morphological and molecular tools, and Koch’s postulates were fulfilled on “Gala” apples. We demonstrated that fruits are weak links in quarantine efforts. Fruit stored at low temperatures present quiescent N. ditissima infections, which may develop rapidly with abundant sporulation when exposed to more suitable conditions, as those of commercialization. Revised management strategies for flower and fruit treatment, as well as studies on efficient detection methods are strongly recommended.