Viabilidade de fungos necrotróficos sob diferentes métodos de preservação

Abstract

The ex situ fungal cultures collections represent important biological heritage and is useful for mycologists and plant pathologists, supporting several scientific works. They provide viable pathogens anytime and assisting at identification, morpho-physiological aspects, life cycle, epidemiology, resistance to fungicides and breeding programs in resistance of diseases. However, there is not a universal preservation method that is efficient and suitable for the different groups of fungi. The most appropriate is the one that maintain, even after long periods, the original characteristics of culture: viability, sporulation and pathogenicity, excluding mutations and undesirable contamination. The choice will depend of the laboratory infrastructure, micro-organism, objectives, preferences and knowledge of the researcher. For necrotrophic fungi, after passing their life cycle stage as saprophytes they can be isolated in growing medium, using different preservation methods, especially: periodic transfer, dried host tissues, sterile water (Castellani), mineral oil, sterile soil, freezing, silica gel, lyophilization and cryopreservation. The study aimed to describe the efficiency of sterile soil (68 isolates), resistant structures (Sclerotinia sclerotiorum) in 4°C (10 strains), gelatin (17 strains), mineral oil (31 strains) and silica gel (14 strains) on the maintenance of viability, sporulation and colonization-pathogenicity of phytopathogenic necrotrophic fungi preserved in different dates, in Laboratório de Micologia e Proteção de Plantas (LAMIP), Uberlândia (MG), and in Laboratório de Microbiologia e Fitopatologia (LAMIF), Monte Carmelo (MG). The gelatine method has never been tested for fungi. The viability remained in 38 strains of sterile soil; three of mineral oil, 10 of gelatin. Sclerotia's maximum time of preservation was four years, and all fungal strains were viable on silica gel.