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Poster: Diseases of Plants: Disease Detection & Diagnosis


Mycosphaerellaceae associated with greasy spot of citrus in different climatic regions
A. VICENT (1), V. Aguilera-Cogley (2), J. Armengol (3), M. Berbegal (3) (1) Instituto Valenciano de Investigaciones Agrarias (IVIA). Moncada 46113, Valencia, Spain., Spain; (2) Laboratorio de Protección Vegetal, Instituto de Investigaciones Agropecuarias

Citrus greasy spot is distributed in humid areas in the Caribbean and Central America. The disease is characterized by yellow-brown spots on leaves and premature defoliation. Symptoms similar to greasy spot were observed in semi-arid areas in the Mediterranean Basin, although with low severity. The fungus Zasmidium citri-griseum (= Mycosphaerella citri) has been identified as the causal agent of greasy spot in the Caribbean and Central America, but disease etiology in the Mediterranean is unknown. A selection of 42 isolates of Mycosphaerellaceae obtained from greasy spot symptoms in humid areas in Ghana and Panama and arid regions in Spain and Morocco was studied. Isolates were characterized based on morphology, growth rate at different temperatures, multi-locus analysis (ITS, EF-1α and RPB2), and pathogenicity tests. Isolates from Panama and Ghana (n=24) were identified as Z. citri-griseum whereas isolates from Spain and Morocco (n=20) were identified as Amycosphaerella africana. The optimum growth temperature of Z. citri-griseum was 27.9ºC while A. africana grew better at 22.8ºC. Isolates of Z. citri-griseum from Panamá were pathogenic to ‘Valencia’ sweet orange plants. None of the A. africana isolates from Spain induced symptoms in ‘Ortanique’ plants. These results confirmed Z. citri-griseum as the causal agent of greasy spot in Panama, being associated also with the disease in Ghana. Greasy spot symptoms in Spain and Morocco were associated with A. africana.