| Lily contains lots of varieties, and it's an important economical crop, widely cultivated in China. New varieties have been intruduced into China in recent years, even through China has a long time for partial production of this crop. Viral diseases occur in all the area where lily is planted and the influence of viral diseases is become more and more obvious. However, research work on viruses infecting lily remains scarcity in China. In this report, viral pathogens naturally occurred on lily crops were identified systemically by biological and molecular techniques. Cucuber mosaic virus (CMV), Lily symptomless virus (LSV) and Lily mottle virus (LMoV) were found being commonly distributed on lily crops. We also found that Prunus necrotic ringspot virus (PNRSV) infected the lily crops at natural condition. It is the first report of PNRSV as the pathogenic virus on lily. In an attempt to understand the occurrence of LSV and PNRSV, samples collected from Zhejiang Province and Beijing, were detected for their infection by using KNA spot hybridization, with total RNA extracted from leaf tissue.Lily was co-infected by many plant viruses with a survey by electron microscopic examination and serological tests with field samples. Natural-infected lily crops exhibited diversiform symptoms such as mottling, mosaic, necrotic spotting, malformation, breaking and witches' broom. The symptom become usually more severe when infected with more than one virus. Host range tests suggested these viruses had narrowly host ranges, so it is very difficult to identify them by host reaction test. CMV was detected in 25 out of 64 samples by enzyme-linked immumnosorbent assay ( ELISA ), so the infection rate of CMV was 39.1%. Virus particles of filamentous and flexuous, resembling potyvirus, were detected in 58 out of 75 samples by electron microscopy ( EM), so the infection rate of filament virus was 77.3%. Pinwheel inclusions were observed in the cytoplasm of the mesophyll cells in 27 out of 40 samples, which indicated the rate of potyvirus infection was 67.5%.CMV was found to be one of the most principal viruses infecting lily crops at natural condition in China. These isolates formed a new subgroup of CMV although they were collected from different terrain. The coat protein genes of two lily-infecting CMV isolates (CMV-LS, CMV-ZH) were cloned to T-easy vector, after RT-PCR amplification. The homologies at the nucleotide level were 88.2% to 99.7% between the two isolates and other subgroup I isolates of CMV, but only 68.6% to 78.3% homology was found between them and subgroup II isolates of this virus. At the amino acid level,CMV-LS, CMV-ZH shared 94.1% to 99.1% homology with other subgroup I isolates and 65.7% to 78.5% homology with subgroup II isolates respectively. Therefore, we had a conclusion that CMV isolates of CMV-LS, CMV-ZH should be classified as belonging to subgroup I of CMV. The evolutionary relationships of the isolates of CMV were characterized by comparing their phylogenetic trees for the CP gene. The lily CMVs always formed a distinct cluster within subgroup I in CP. Both the phylogenetic tree topology and the sequence identity for the lily CMV isolates suggested that they had formed a new subgroup within CMV subgroup I. The above result indicated that lily-infecting CMV has developed host adoption in nature.LoMV was confirmed as one of the principal viruses infecting the lily crops at natural condition by molecular identification, then potyvirus infecting lily and tulip could be classified by their homology. The 3' end partial sequences of cDNA of two LMoV isolates (LMoV -G, LMoV-X) were cloned and nucleotide sequence of 3' end partial sequence, Nib, CP, 3'-UTR and deduced amino acid sequence of Nib, CP between LMoV-G, LMoV-X isolates were obtained and compared with those of document references. Multiple alignments of these sequences showed that 3' end partial sequence, Nib nucleotide sequence , Nib amino acid sequence, CP nucleotide sequence, CP amino acid sequence and 3'-UTR nucleotide sequence varied fro... |
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