Ornithogalum: a new host of Cucumber mosaic virus (CMV) from India

Ornithogalum thyrsoides (family Hyacinthaceae) is an ornamental cut flower crop which has a long vase life and is resistant to extreme temperatures. Plants have been reported to be infected with Ornithogalum mosaic virus (OMV) and Tobacco necrosis virus (TNV) (Burger & Wechmar, 1995).

Ornithogalum plants growing in a floriculture field at IHBT, Palampur, were found exhibiting severe mosaic on the leaves (Fig. 1). The causal virus was found to be transmitted mechanically causing local lesions on Chenopodium album and C. amaranticolor, and systemic mosaic on Nicotiana clevelandii, N. glutinosa, N. megalosiphon and N. tabacum cv. White Burley. In ELISA, the virus reacted with Cucumber mosaic virus (CMV)-specific antibodies procured from Agdia (USA). Leaf dip preparations from virus infected plants in electron microscopy revealed the presence of c. 29 nm isometric particles. In immuno-electron microscopy (IEM), the virus was readily trapped and decorated with CMV-specific antibodies.

Total RNA was isolated from healthy and naturally-infected ornithogalum, as well as from inoculated plants, using RNAqueous (Ambion, USA) as per the manufacturer's instruction. Reverse transcription-polymerase chain reaction (RT-PCR) was performed using the CPTALL primer pair (Choi et al., 1999). Amplicons of expected size (~950 bp) were obtained in virus-infected and inoculated plants. No amplification was observed in healthy ornithogalum plants. PCR amplified products were cloned and sequenced (AJ745092). BLAST searches revealed the nucleotide and deduced amino acid sequence showed 97% and 93-95% similarity with the available sequences of CMV subgroup II respectively, confirming the association of CMV with the severe mosaic on ornithogalum. This is the first definitive report of CMV infecting ornithogalum.