First Report of Leaf Blotch Caused by Marssonina coronaria on Apple in Italy

Plant Disease
G Tamietti, A Matta

Abstract

During the early summers of 2001 and 2002, in Forno Canavese in northwest Italy, a leaf disease was observed on the old apple cv. Furnas in a domestic orchard. Lesions on the upper side of the leaf were brownish, irregular in size and shape with somewhat dendritic margins, became black, and often coalesced with time. On the underside, lesions were smaller with more definite margins. Beginning in July, scattered acervuli (95 to 170 μm) were observed erupting through the epidermis on the upper side of leaves. Conidia were ampule shaped, 1-septate, constricted at the septum, hyaline, guttulate, and 6.1 to 8.4 × 14.6 to 22.0 μm. Severely diseased leaves abscised prematurely. The fungus was identified as Marssonina coronaria (Ellis & J.J. Davis) J.J. Davis, teleomorph Diplocarpon mali (1) although the conidia were slightly shorter than those originally described for this fungus. Monoconidial isolates were obtained by spreading mini-suspensions of conidia taken from acervuli on malt agar (MA) and transferring single-germinated conidia to MA, potato dextrose agar, V8 agar, or apple leaf agar (ALA). The fungus grew slowly, producing small colonies on V8 and ALA only. On ALA medium, after 3 months incubation at 20 to 22°C, the colonies ...Continue Reading

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