Neopestalotiopsis siciliana sp. nov. and N. rosae Causing Stem Lesion and Dieback on Avocado Plants in Italy.

Abstract

Avocado (Persea americana) represents an important emerging tropical crop in Italy, especially in the southern regions. In this study, young plants of avocado showing symptoms of stem and wood lesion, and dieback, were investigated. Isolations from symptomatic tissues consistently yielded colonies of Neopestalotiopsis-like species. The characterization of representative isolates was based on the observation of morphological characters, the effect of temperature on mycelial growth rate, and on the sequencing of three different gene regions, specifically ITS, TEF1, and TUB2. Phylogenetic analyses were conducted based on maximum parsimony and maximum likelihood approaches. The results showed the presence of two species, viz. Neopestalotiopsis rosae and N. siciliana, the latter of which is here described as a new species. Pathogenicity tests were conducted using the mycelial plug technique on young potted avocado trees for both Neopestalotiopsis species. The results showed that both species were pathogenic to avocado. This study represents the first report of these two species affecting avocado and results in the description of a new species within the genus Neopestalotiopsis. Based on phylogeny, Pestalotiopsis coffeae-arabicae is combined in Neopestalotiopsis.