Abstract
During the winter of 2018, 3-years-old trees of avocado (Persea americana) cv “Hass” from Trapani province (Sicily, Italy) showed symptoms of stem and crown rot. Two different fungi were consistently isolated from infected tissues. Morphological characterization and multi-locus phylogenies using five genomic loci (ITS, tef1, tub2, his3, and rpb2) identified these fungi as Cylindrocladiella peruviana and Pleiocarpon algeriense. Pathogenicity tests on healthy 5-months-old seedlings and 3-year-old trees of avocado reproduced similar symptoms as those observed in nature, and Koch’s postulates were fulfilled for both pathogens. Moreover, the tested fungal isolates revealed a different pathogenic behaviour among two species. Two isolates of Pleiocarpon algeriense resulted more aggressive than Cylindrocladiella peruviana isolates causing major lesions on young seedlings. This study is the first to report of stem and crown rot on avocado caused by Cylindrocladiella peruviana and Pleiocarpon algeriense.
Highlights
Avocado (Persea americana Mill.) is native to Mexico but is spread around the world in tropical and subtropical regions
A recent research conducted in Australia demonstrated that several Dactylonectria spp. and C. ilicicola are pathogenic to avocado, compared to other isolates of Ilyonectria sp., Cylindrocladiella pseudoinfestans and Gliocladiopsis peggii that did not result pathogenic (Parkinson et al 2017b)
This study reveals for the first time the presence and pathogenicity of C. peruviana and P. algeriense on avocado
Summary
Avocado (Persea americana Mill.) is native to Mexico but is spread around the world in tropical and subtropical regions. A wide study on branch cankers and stem-end rot conducted in the main avocado growing area in eastern Sicily revealed the presence of different species such as Neofusicoccum parvum (the highest virulent), Diaporthe foeniculina (=D. foeniculaceae), D. sterilis, Colletotrichum gloeosporioides, C. fructicola, and a novel species Neocosmospora perseae (Guarnaccia et al 2016, 2018). These reports show how woody cankers and stem-end rot could be considered the most important threats for avocado production in Italy so far. Root rot caused by the oomycete Phytophthora cinnamomi, and collar rot caused by P. citricola have been considered for decades the most important root diseases in avocado orchards (Erwin and Ribeiro 1996)
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