First report of Iris yellow spot virus on onion and shallot in New Zealand
During a disease survey of Allium crops in New Zealand in 2007, characteristic diamond-shaped lesions resembling those of Iris yellow spot virus (Tospovirus, IYSV – EPPO Alert List) were observed on a few onion seed plants (Allium cepa cv. Early Long Keeper) in the Blenheim area of the South Island. Laboratory analysis (DAS-ELISA, RT-PCR, sequencing) confirmed the presence of IYSV. In New Zealand, more samples were collected from 28 Allium crops (samples of 100 plants per crop) and from 4 ornamental Allium species (1 plant for each species: Allium senescens, A. murrayanum, A. caesium and A. moly). Results showed that IYSV was widespread in onion and shallot crops (A. cepa) in both the North and South Islands, but it was not detected in garlic (A. sativa). The infected Allium crops showed a significant amount of thrips damage, but most plants had no IYSV symptoms. Two of the ornamental Allium species (A. senescens and A. murrayanum), tested positive for IYSV by ELISA but were symptomless. In addition, attempts to amplify the viral genome by RT-PCR for sequencing were unsuccessful. This is the first report of IYSV in onion and shallot but its economic impact on Allium crops still needs to be determined in New Zealand.
The situation of Iris yellow spot virus in New Zealand can be described as follows: Present, widespread in Allium cepa (onions and shallots) both in North and South Islands, but economic impact needs to be further studied.
Ward LI, Perez-Egusquiza Z, Fletcher JD, Ochoa Corona FM, Tang JZ, Liefting LW, Martin EJ, Quinn BD, Pappu HR, Clover GRG (2008) First report of Iris yellow spot virus on Allium cepa in New Zealand. New Disease Reports, Volume 17, February 2008 - July 2008. http://www.bspp.org.uk/ndr/july2008/2008-43.asp