Ac. Pappas et Ej. Paplomatas, PYRICULARIA LEAF-SPOT - A NEW DISEASE OF ORNAMENTAL PLANTS OF THE FAMILY MARANTACEAE, Plant disease, 82(5), 1998, pp. 465-469
A severe leaf spot disease incited by the fungus Pyricularia oryzae wa
s identified on Ctenanthe oppenheimiana and C. setosa ''Greystar.'' Pr
imary symptoms on young leaves consisted of individual circular to sli
ghtly irregular pinpoint spots with white necrotic centers zonated by
narrow brown-yellow halos. On mature leaves, extended necrotic areas r
esembling those caused by phytotoxicity were formed. Artificially inoc
ulated leaves with a spore suspension of the isolated fungus from the
above case showed symptoms after 3 to 4 days' incubation at 25 degrees
C and high humidity. Fungal isolates obtained from Ctenanthe plants o
f Brazilian origin were found to be highly pathogenic on various plant
s within the family Marantaceae when they were tested by an excised le
af assay method. By contrast, P. oryzae isolates obtained from rice pl
ants grown in Greece caused either hypersensitivity or immune response
symptoms in various Marantaceae. Analysis of esterase and lactate deh
ydrogenase isozymes showed different banding patterns for rice and Cte
nanthe isolates of P. oryzae. Conditions of prolonged leaf wetness com
bined with prevailing high temperature and humidity favored the epidem
ic appearance of the Pyricularia leaf spot disease on glasshouse-grown
plants during the summer months of 1995 in Greece.