Articles
OCCURRENCE, MOLECULAR CHARACTERISATION, AND PATHOGENICITY OF NEOSCYTALIDIUM DIMIDIATUM ON CITRUS IN ITALY
Article number
892_27
Pages
237 – 243
Language
English
Abstract
During 2008 and 2009, a new disease was noticed in eastern Sicily (Italy) in two re-grafted citrus orchards (Citrus sinensis (L.) Osbeck) on sour orange rootstock.
Symptoms consisted of blight of vigorously growing shoots and a sooty canker on shoots and rootstock trunks.
A Scytalidium-like fungus was isolated consistently from symptomatic tissues on 2% potato-dextrose agar (PDA). The mycelium was composed of branched, septate, brown hyphae which disarticulated into 0-1-septate phragmospores.
In culture it also produced a pycnidial synanamorph, with hyaline conidiogenous cells that were intermingled with paraphyses.
Conidia were ellipsoid to ovoid, hyaline, with an acutely rounded apex, truncate base, initially aseptate, becoming brown and 2-septate at maturity, with the central cell darker than the end cells.
Genomic DNA was extracted from mycelia of single-conidial isolates cultivated on 2% malt extract agar and the nuclear rRNA operon spanning the 3 end of 18S rRNA gene, the internal transcribed spacers, the 5.8S rRNA gene, and a part of the 5 end of the 28S rRNA gene was amplified and sequenced.
On the basis of morphological characters and molecular data, the fungal isolates were identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers.
Kochs postulates were satisfied and confirmed the pathogenicity of the fungus. N. dimidiatum appears to pose a serious threat to re-grafted citrus orchards.
Symptoms consisted of blight of vigorously growing shoots and a sooty canker on shoots and rootstock trunks.
A Scytalidium-like fungus was isolated consistently from symptomatic tissues on 2% potato-dextrose agar (PDA). The mycelium was composed of branched, septate, brown hyphae which disarticulated into 0-1-septate phragmospores.
In culture it also produced a pycnidial synanamorph, with hyaline conidiogenous cells that were intermingled with paraphyses.
Conidia were ellipsoid to ovoid, hyaline, with an acutely rounded apex, truncate base, initially aseptate, becoming brown and 2-septate at maturity, with the central cell darker than the end cells.
Genomic DNA was extracted from mycelia of single-conidial isolates cultivated on 2% malt extract agar and the nuclear rRNA operon spanning the 3 end of 18S rRNA gene, the internal transcribed spacers, the 5.8S rRNA gene, and a part of the 5 end of the 28S rRNA gene was amplified and sequenced.
On the basis of morphological characters and molecular data, the fungal isolates were identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers.
Kochs postulates were satisfied and confirmed the pathogenicity of the fungus. N. dimidiatum appears to pose a serious threat to re-grafted citrus orchards.
Authors
G. Polizzi, D. Aiello, I. Castello, A. Vitale, J.Z. Groenewald, P.W. Crous
Keywords
Citrus sinensis, sour orange rootstock, shoot blight, gummosis, sooty canker
Online Articles (48)