|Vaira, Anna maria|
Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/29/2007
Publication Date: 6/13/2007
Citation: Vaira, A.M., Kleynhans, R., Hammond, J. 2007. First report of Freesia sneak virus infecting Lachenalia cultivars in South Africa. Plant Disease. 91:770. Interpretive Summary: Virus infections often adversely affect quality and productivity of crop plants, and especially vegetatively propagated ornamental plants. A virus was detected and identified in symptomatic plants of Lachenalia, a bulbous ornamental native to South Africa. A combination of electron microscopy and molecular biology techniques were utilized to identify the virus as a member of the Ophiovirus group. Nucleotide sequence comparisons of a portion of the viral genome showed that the virus from lachenalia was an isolate of Freesia sneak virus, previously reported to infect freesia plants in Europe. Identification of this virus in lachenalia will allow growers to select virus-free plants for propagation, resulting in higher yield and quality for the benefit of both producers and consumers.
Technical Abstract: Bulbs of several hybrid lines of Lachenalia were received from South Africa under APHIS permit, in order to identify the viruses causing foliar mosaic symptoms. Potyvirus-like particles were readily observed by electron microscopy of leaf extracts of most plants; a reverse transcription-polymerase chain reaction (RT-PCR) assay utilizing primers that amplify potyviruses, and enzyme-linked immunosorbent assay with potyvirus-specific monoclonal antibody confirmed the presence of potyviruses. Fine filamentous particles were also observed in some plants; these particles were similar to those reported for viruses of the genus Ophiovirus. An RT-PCR assay utilizing primers that amplify known ophioviruses yielded the 136 bp diagnostic PCR product. Analysis of the deduced amino acid sequence of the PCR product showed 100% identity with that of Freesia sneak virus (FreSV), previously identified in Italy from freesia plants. This is the first report of FreSV in lachenalia, and of FreSV from South Africa. Potyvirus infection was detected by RT-PCR and ELISA in several lachenalia lines obtained from U.S. commercial sources, including plants of one of the same lines (cv. ‘Fransie’) received from South Africa; however, no ophiovirus was detected in any lachenalia plants from U.S. sources. It is of interest that both known host genera of FreSV, Freesia and Lachenalia, are ornamental monocot genera originating in South Africa.