Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 5/5/2017
Publication Date: 2/2/2018
Citation: Bampi, D., Reinsel, M.D., Hammond, J. 2018. Identification of Narcissus yellow stripe virus and a closely-related potyvirus isolate in plants of Allium carinatum. Acta Horticulturae. 1193:39-46. 10.17660/ActaHortic.2018.1193.6.
Interpretive Summary: Infection by plant viruses adversely affects the yield and quality of many crops, and is an especially significant problem in vegetatively produced crops. Many species of the genus Allium are grown as ornamentals, whereas a few species (onion, garlic, leeks, and shallots) are important edible field crops grown in many countries. The viruses infecting edible Allium species have been well-studied, but little work has been reported on the viruses affecting ornamental Allium species. A survey was carried out of the viruses present in 14 species of ornamental Allium. Several viruses previously reported from edible Allium were also detected in some of the ornamental Allium species, but two potyviruses not previously reported from edible Allium were also detected. One of these was Narcissus yellow stripe virus, previously reported only from Narcissus (daffodils), whereas the other was closely related to Narcissus yellow stripe virus, but may represent a new species of the genus Potyvirus. These newly detected viruses in ornamental Allium may also pose a threat to edible Allium crops, so their identification could be important for production of both ornamental and edible Allium crops.
Technical Abstract: A survey of varieties and species of ornamental Allium revealed the presence of multiple viruses, including potyviruses, carlaviruses, and allexiviruses. Most of these viruses have been previously identified in A. sativum (garlic), A. cepa (onion), A. porrum (synonym A. ampeloprasum var. porrum; leek), or other edible Allium species. However, two samples of Allium carinatum were found by generic potyvirus PCR and transmission electron microscopy to be infected with potyvirus isolates which were not amplified with primers specific for Leek yellow stripe virus (LYSV) or Onion yellow dwarf virus (OYDV), the potyviruses most commonly found in cultivated Allium spp. These samples also yielded negative results in ELISA tests with LYSV- or OYDV-specific antibodies. Broad spectrum PCR primers for the Nuclear inclusion b to 3’ end (NIb-3') were then used to amplify and clone this portion of the genome of the potyvirus isolates from A. carinatum, which were then sequenced. The sequences generated were used to identify one isolate as a strain of Narcissus yellow stripe virus (NYSV), and the other as a potyvirus most closely related to NYSV, but differing sufficiently to be regarded as either a potential novel species based on current criteria for species boundaries, or possibly a recombinant isolate between NYSV and an unknown parent. However, divergent isolates of NYSV and Narcissus late season yellows virus have been reported from narcissus in Australia, suggesting that an intermediate between these species occurs, which might be either regarded as a third species, or the two species collapsed into one by broadening the species demarcation criteria. Independent of the eventual status of the second isolate, Allium carinatum is a new host of NYSV, which has previously been reported only from Narcissus spp. and Nerine bowdenii.