Authors
S.
Tanaka
,
H.
Nishii
,
S.
Ito
,
M.
Kameya-Iwaki
,
Faculty of Agriculture, Yamaguchi University, Yoshida, Yamaguchi 753, Japan
; and
P.
Sommartya
,
National Biological Control Research Center, Kasetsart University, P.O. Box 9-52, Bangkok 10900, Thailand
ABSTRACT
During 1992 to 1994, 442 orchid plants from 24 genera in 43 nurseries and locations in eight provinces of northern, central, and southern regions of Thailand were examined for Cymbidium mosaic potexvirus (CyMV) and Odontoglossum ringspot tobamovirus (ORSV) with rapid immunofilter paper assay (RIPA). Both viruses were confirmed in all three regions. However, CyMV was detected in 17 genera in 93% nurseries, while ORSV was detected in only four genera (Arachnis, Cattleya, Oncidium, and Vanda) in 40% of nurseries tested. These results indicate that CyMV is more prevalent than ORSV in Thailand. Mixed infections of ORSV and CyMV were often found, and double infections were observed in 95% of ORSV-infected plants. The virus infections were divided into two categories: infection by CyMV alone and double infection by both viruses in Cattleya and Oncidium. CyMV was often detected alone from symptomatic or asymptomatic plants of certain orchid genera. In Oncidium, however, CyMV was detected alone from 79% of plants without symptoms, while both viruses were detected from 90% of plants with mosaic and necrotic spot symptoms on leaves. Expression of symptoms may be promoted by the double infection of CyMV and ORSV in Oncidium.
