Virus invasions of the New Zealand flora

Abstract

More than 200 plant viruses and many of their invertebrate vectors have invaded New Zealand (NZ) in the last two centuries. All of these invaders are associated with introduced agricultural, horticultural and/or weed species. At least 16 of the viruses have invaded the native flora, including some rare and critically endangered species. Patterns are emerging: aphid transmitted viruses which are able to infect species from a number of families are prominent. For example, cucumber mosaic virus infects native species from seven families. There are also examples of viruses with more restricted host ranges invading individual families, particularly the native grasses. The yellow dwarf viruses have escaped from cereals and pasture into native grasses. Some of the species are also native to Australia and the Pacific Islands and the review and its literature should be of interest to those working further afield. Prospects for controlling or mitigating the effects of the viruses in agricultural systems have limited application in the native flora but they are relevant to propagation and rescue strategies. Biosecurity measures are not only the first line of defence against threats to agriculture but also to the conservation estate. The protection of native floras from virus invasion is another justification for the control measures and legislative procedures already in place to protect agriculture. High throughput sequencing to detect all viruses at the border, and genetic engineering and RNAi technologies to mitigate the effects of invasions are promising developments for the protection of the native flora.

New Virus Diagnostic Approaches to Ensuring the Ongoing Plant Biosecurity of Aotearoa New Zealand

“…Over the past two centuries exotic plants have established in NZ, bringing with them some of their viruses and many of their invertebrate vectors [ 13 , 14 ]. Records of plant viruses increased from around 100 species in the 1990s [ 14 , 15 , 16 , 17 ] to 258 species in 2021 [ 18 ] ( Figure 2 ).…”

“…Over the past two centuries exotic plants have established in NZ, bringing with them some of their viruses and many of their invertebrate vectors [ 13 , 14 ]. Records of plant viruses increased from around 100 species in the 1990s [ 14 , 15 , 16 , 17 ] to 258 species in 2021 [ 18 ] ( Figure 2 ). Most plant virus records in NZ are from economically important plants including horticultural, ornamental, and unwanted invasive plant species (the latter acting as virus reservoirs) [ 14 , 16 , 18 ]; however, it is probable that some of these new viruses are endemic to NZ [ 14 , 18 , 19 ].…”

“…Records of plant viruses increased from around 100 species in the 1990s [ 14 , 15 , 16 , 17 ] to 258 species in 2021 [ 18 ] ( Figure 2 ). Most plant virus records in NZ are from economically important plants including horticultural, ornamental, and unwanted invasive plant species (the latter acting as virus reservoirs) [ 14 , 16 , 18 ]; however, it is probable that some of these new viruses are endemic to NZ [ 14 , 18 , 19 ]. The increase in the cumulative total number of viruses reflects not only new incursions but also changing technologies and our ability to detect and identify viruses.…”

“…Except for the thrips-transmitted tomato spotted wilt virus (48 species), the viruses recorded from the majority of hosts are also aphid-transmitted: cucumber mosaic virus (93 species), alfalfa mosaic virus (58 species), turnip yellows virus (39 species), and watermelon mosaic virus (32 species). A recent review by Guy et al [ 14 ] identified that at least 16 viruses had infected native plant species (including native grasses, cresses, solanums, and cucurbits) likely jumping from crops, weeds, and garden ornamentals.…”

“…The use of high-throughput sequencing (HTS) in plant diagnostics has accelerated the discovery of new viruses in native plants in recent years [ 18 , 19 , 20 ], including potential endemic viruses from the Emaravirus genus [ 18 ], such as the recently identified and characterized Karaka Ōkahu purepure virus [ 19 ]. There are still limited data available on the true extent of virus diseases in native ecosystems in NZ with information available from only five of the ten largest plant families [ 14 ]. From the current data it is possible to see that of the introduced viruses, those that are aphid-transmitted have the highest percentage (40%) with luteoviruses, carlaviruses, and potyviruses as the main groups [ 14 , 16 ].…”