Fungi associated with cankers and diebacks of fruit trees in Latvia and their pathogenicity on various fruit tree species

Abstract: Cankers, diebacks and wood rots are widespread on fruit trees and are caused by a variety of pathogenic fungi. Among these, diseases caused by pathogenic species belonging to Diaporthe, Valsa and Botryosphaeria are considered as the most damaging to their hosts. The research was initiated when severe canker and dieback symptoms and tree death were observed in fruit tree orchards in Latvia. To identify the causes of observed tree diseases, orchard surveys and samplings were performed from May to September. The samples from branches and trunks with symptoms of cankers and dieback were collected. Fungi were isolated from surface sterilised plant tissues on potato dextrose agar, sub-cultured in pure cultures and preserved for further studies. The isolated fungi were characterised and identified by morphological characters and sequencing of the ITS region. Several fungal isolates were selected and tested for their pathogenicity on seedlings of Malus domestica, Pyrus communis, Prunus mahaleb and Prunus cerasifera. During the surveys, overall decline, severe canker and dieback symptoms often causing a death of the plants was observed. Fungal isolates belonging to the known pathogenic genera causing of tree cankers and dieback, such as Diaporthe, Cytospora and Monilinia have been identified. The pathogenicity of the fungal isolates varied depending on the inoculated plant species.