engleski

Characterization of Colletorichum species causing bitter rot of apple in Croatia

Fungi from the genus Colletotrichum are important pathogens of numerous crops worldwide. In recent years, plant diseases caused by Colletotrichum species were observed on apple, pear, plum, pepper, olive and strawberry. Among these, it was noticed that the observations of Colletotrichum are becoming more and more common on apple, where these fungi cause field and storage disease known as bitter rot. In an orchard where yield losses due to postharvest diseases were measured during four seasons, bitter rot caused by Colletotrichum was found on 0.1 - 2.8 % of fruits. Totally 42 Colletotrichum isolates were collected from apple fruits affected with bitter, from three locations, in the field and in the storage. The morphology of single-spore isolates was analysed on potato-dextrose agar (PDA), oatmeal agar (OA) and on artificially inoculated fruits. In a number of isolates, the variability in morphology of conidia formed on PDA, OA and on inoculated fruits was observed. It was concluded that the morphology of isolates are to variable to allow accurate identification of species, and sequencing of ITS1 region, 5.8S rRNA gene, and the ITS2 region was performed, amplified with primers ITS1 and ITS4. Taking into account morphological features and sequence data, isolates from apple were identified as Colletotrichum acutatum and Colletotrichum gloeosporioides. Colletotrichum acutatum was the dominant species on two locations, while Colletotrichum gloeosporioides was the only species found in one location. All isolates caused typical symptoms of bitter rot when condial suspensions were injected into apple fruits, while more than 80 % of isolates caused bitter rot when inoculated on unwounded fruits. The development of different isolates on inoculated fruit in controlled conditions was more or less the similar.

Apple; bitter rot; Colletotrichum

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