Characterisation of fungal pathogens associated with stem-end rot of avocado fruit in Italy
2015
Guarnaccia, V. | Aiello, D. | Cirvilleri, G. | Polizzi, G. | Susca, A. | Epifani, F. | Perrone, G.
The Sicilian coasts provide suitable environmental conditions for production of high-quality tropical and subtropical fruits. In particular, avocado (Persea americana) and mango (Mangifera indica) orchards increased in last years on this area. Postharvest infections of tropical and subtropical fruits commonly occur wherever the crops are cultivated. Several fungal species are reported as causal agents of anthracnose and stem-end rot. Among these, Botryosphaeria spp. and Colletotrichum spp. are the mostly spread worldwide. In Mediterranean environment, decays caused by several fungal pathogens are reported on plants and fruit of mango, but extensive surveys on avocado orchards were never done. The aim of this study was to determine the occurrence of stem-end rot disease in one of the major avocado growing areas in southern Italy and to identify the fungal species associated with decay symptoms based on morphological and molecular analysis. Approximately 100 'Hass' avocado fruit were collected in four orchards in Catania province and incubated in the laboratory. Stem-end rot developed from 5 to 10 days. Small pieces of symptomatic flesh from the margin of infected area were placed onto potato dextrose agar. A total of 47 isolates were recovered. Conidia characteristics and colony morphology were determined. Multilocus sequence analysis was performed using beta-tubulin gene, internal transcribed spacers of the ribosomal DNA and translation elongation factor gene (for Botryosphaeria spp.) or histone 3 gene (for Colletotrichum spp.). The molecular analysis allowed the identification of 68% of isolates as Neofusicoccum parvum, 17% as Colletotrichum gloeosporioides and 15% as C. fructicola. To our knowledge, these are the first data on the occurrence of N. parvum, C. gloeosporioides and C. fructicola associated with stem-end rot of avocado in Europe. Further studies on pathogenicity ability of these species, in pre- and postharvest conditions, should be carried out.
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