Identification and analysis of viruses isolated from Nerine

Nerine are perennial bulbous flowering plants originally from Southern Africa, with striking flowers. They are grown worldwide and are economically important for horticulture, floriculture and floristry industries. Nerine are grown commercially in several countries including the Netherlands, New Zealand and Japan and are becoming increasingly important in the UK. Nerine heritage and national collections are important to conservationists, growers, breeders and enthusiasts. Nerine can accumulate virus infections over time as they are perennial plants that are usually vegetatively propagated. The viral infections can be detrimental to the healthy growth and aesthetic value of the crop and viral infection is regulated by trade rules. Maintaining a virus-free crop is important for growth, sales and trade, therefore being able to effectively test for viruses is essential. Viral infection of UK Nerine was investigated and nerine latent virus (NeLV), nerine yellow stripe virus (NeYSV) and an nerine virus x (NVX)-like potexvirus have been identified and their complete genomes characterised. This represents the first instance of NeLV having been isolated and characterised from Nerine and the first full-length sequence of NeYSV. The NVX-like virus potentially represents a novel species of potexvirus. A UK wide survey to identify plants infected with NeLV, NeYSV and the NVX-like virus was undertaken and the results revealed a high level of natural infection, which occurred as single and mixed infection profiles. Symptomology and virus infection profiles were analysed, however, there was no consistent link between the virus(es) identified in the plant and the observed symptoms, suggesting that symptomology alone was not a reliable diagnostic method. PCR assays were the most sensitive and specific method of surveying plants for viral infection compared to hybridisation and lateral flow methods and the complete sequences of NeLV, NeYSV and potentially novel NVX-like potexvirus provided data from UK Nerine for specific primer development. This study supports the horticulture, floriculture and floristry industries by providing data that can improve testing methods for viruses infecting Nerine. Additionally, badnavirus-like sequences were identified that may represent a novel badnavirus, although its status as a potential endogenous viral element was unclear. Furthermore, potentially novel secoviridae-like sequences and potyvirus-like fragments that were not NeYSV were identified that require further investigation.