Virus

Today a significant number of threatened, endangered or extinct (in habitat) geophytes species are grown ex situ by hobbyists, institutions for conservation, as well as commercial growers large and small. In some cases only one clone of an endangered or rare species has been introduced into general cultivation. Sometimes tragically, the single clone becomes infected, and if it is self-sterile, there is little hope to obtain virus-free seedlings from it. Therefore, it is of utmost importance for all to exercise due diligence in ferreting out infected plants from our collections. This can be a tedious and an emotionally charged task, due to the rarity of and personal bonds formed with some of our cherished specimens.

Virused plants may show symptoms such as streaked or mosaic patterns on flowers and foliage. Leaves and stems can be twisted, distorted, and necrosed. Some apparently healthy plants do not show viral symptoms and only under stress that a latent virus may begin to show. In other cases, there are plants that do not show signs of disease at all. Example of such stress could be incorrect watering, inappropriate light exposure, temperatures outside ideal range, or fertilization. The best manner to determine the status of a plant in question is to have it tested by a lab.

Viruses may be spread by insects such as aphids, thrips, leaf hoppers, mealybugs, nematodes, snails, slugs, fungi, or mechanically. Possible mechanical transmission can occur via micro-abrasions as leaves rub against each other, handling with human hands that have virus particles on them (e.g. a tobacco smoker's unwashed hands), chewing by animals and birds that have chewed first on virused material, or by all manner of garden implements that have not been sterilised between the handling of each clone (secateurs, shears, scissors, trowels, shovels etc.). Not all of the viruses listed below spread in the same manner, but for those who desire to keep a virus free collection, a few generally accepted precautions can be taken:


Alstroemeria can have several types of virus. The photo below by Susan Hayek illustrates a virused plant with mosaic symptoms.

Virus in Alstroemeria pulchella, Susan Hayek

Brodiaea and other members of the Themidaceae are very susceptible to viruses, causing irregular streaking of the petals and uneven purple breaks at the lower portion of the leaves where they meet the soil. The photo below by Nhu Nguyen shows virused flowers of Brodiaea elegans.

Brodiaea elegans virused flowers, Nhu Nguyen

Clivia leaves can show virus symptoms. This photo by Germán Roitman shows that this plant may have more than one problem.

diseased Clivia leaf, Germán Roitman

Crocus are susceptible to virus disease. This is usually visible in the flowers. This distortion may take the form of twisted petals, streaking (as in tulip fire,) sometimes the flowers are depauperate and fail to open properly. The virus also reveals itself as light and dark blotching in the foliage which is most visible when the foliage first emerges. The pictures here have been manipulated to exaggerate the streaking in flower and foliage to make it more apparent. (Massive hike in contrast levels does this.) The vectors are aphids which find refuge especially on the backs of the leaves. The third picture shows one with distorted petals. The last two photos show a clean Crocus medius and one that has streaking in the petals that is virused. Pictures courtesy of Tony Goode.

Virus in Crocus, Tony GoodeVirus in Crocus, Tony GoodeVirus in Crocus, distorted petals, Tony GoodeCrocus medius, Tony GoodeVirus in Crocus, Tony Goode

The first photo below is of a plant with Cucumber Mosaic Virus (CMV) which has more than 1000 different hosts and more than 60 species of aphids can spread it. Often we can see multiple virus infections in one plant. These plants, if they flower, have serious distortions, like in the second photo of Crocus speciosus which is infected with CMV and Iris Severe Mosaic Virus. Photos below from Janos Agoston.

CMV infection in Crocus chrysanthus 'Fuscotinctus', Janos AgostonCMV & ISMV infected Crocus speciosus, Janos Agoston

Hippeastrum pictures below taken by Germán Roitman show the mottled and streaked leaves. See Hippeastrum mosaic virus below.

Virus in Hippeastrum, Germán RoitmanVirus in Hippeastrum, Germán RoitmanVirus in Hippeastrum, Germán RoitmanVirus in Hippeastrum, Germán RoitmanVirus in Hippeastrum, Germán Roitman

Lilium is also susceptible to many viruses. Some of the lily viruses do not cause symptoms, like Lily Symptomless Virus. As in tulips, most infected lilies have leaf mosaic and color break in their flowers, but one can see flower distortion, stunting and decreased bulb growth. The most common lily virus is the Lily Mottle Virus (LMoV). Formerly it was described as the Lily strain of Tulip Breaking Virus, but this "strain" is not able to infect tulips and molecular evidence shows it is a different species in the virus family Potyviridae. The folowing pictures are demonstrative examples of virus sympthoms in lilies.

Lily Mottle Virus symptoms on Lilium longiflorum 'White Heaven' leaves, Janos AgostonColour break on Lilium Orientale 'Aruba' caused by LMoV infection, Janos Agoston

Virused Phaedranassa photographed by Jennifer Hildebrand. Virus in Phaedranassa, Eucrosia, Eucharis, Stenomesson, Griffinia and Eustephia shows as longitudinal ridges (those leaves are perfectly flat if healthy), besides the mosaic stripes.

Virus in Phaedranassa, Jennifer Hildebrand

The pictures below show Sparaxis with color breaks in the flowers. These plants were very vigorous and increased rapidly in the garden and I had no idea they were virused. Photo by Mary Sue Ittner. These pictures were referenced during a PBS list discussion about virus, see here and here.

Virus in Sparaxis, Mary Sue IttnerVirus in Sparaxis, Mary Sue Ittner

The pictures below show Tulip hybrids infected with viruses. Notice the color break and leaf symptoms. Photos by Janos Agoston

Tulip Breaking Virus (TBV) was first described in 1928. The 10,000 times diluted sap of an infected tulip can still infect a healthy one. Member of the virus family Potyviridae.

Tulip Breaking Virus infection on Tulipa Darwin-hybrid 'Oxford', Janos AgostonTBV in Tulipa Double Late 'Blue Diamond' (on the right), Janos AgostonHealthy (on the right) and TBV infected Tulipa Fringed 'Lambada' (left), Janos AgostonTBV in Tulipa viridiflora 'Artist', Janos AgostonTulip Breaking Virus infection, Janos Agoston

Photos 1-2 below show early leaf symptoms of TBV. Years after infection the original colour and shape of the tulip can be masked by TBV, like on this unidentifiable red tulip. Photo 3 illustrates this. Viruses not only break colours, but also reduce fertility, vigor, bulb growth, and also reduce stem length. This is shown in photo 4 of a Tulipa Single Late 'Kingsblood'

Healthy (bottom) & infected (top) tulip leaves in spring, Janos AgostonTypical reddish-brown lines on the backside of TBV infected tulip leaf, Janos AgostonA formerly red tulip lost almost all of its original colour thanks to TBV infection, Janos AgostonStem length reduction caused by TBV in Tulipa Single Late 'Kingsblood', Janos Agoston

There are several other Potyviruses which can infect tulips, like the Tulip Band Breaking Virus and the Tulip Top Breaking Virus. Tulip Band Breaking Virus causes basal, wide mosaic on tulips, while Tulip Breaking virus causes thin, line mosaic.

Tulip Band Breaking Virus (tulip with bud), Tulip Breaking virus (single leaf), Janos AgostonTulip Top Breaking Virus, as its name says, causes only break on the edge of the petals, Janos Agoston

Unfortunately other polyphagous viruses can infect tulips too, like Cucumber Mosaic Virus. It does not cause leaf mosaic, or very mild mosaic, but on the flowers it makes thin color breaks like on this Tulipa Darwin-hybrid 'Big Chief'

CMV infection on Tulipa Darwin-hybrid 'Big Chief', Janos Agoston

The list below was created by Nhu Nguyen and Jacob Uluwehi Knecht as a resource for bulb growers who are concerned about bulb viruses. The focus is on geophytes and is by no means inclusive. Most of the data came from the NCBI (National Center for Biotechnology Information) Universal Virus Database which gathered these data from many sources over decades of research. A few important caveats about the list below: Species and families listed are limited to those subjected to testing. This does not mean that these are the only ones that can be infected. Some geographic information date back to the 1950's. As a result of bulb movement throughout the world, some of these viruses have likely spread further than reported here. From this database, it seems that some viruses are host specific, but others spread prolifically and rapidly. Because of unknown species range, it is assumed that all members of a family are susceptible if one species is susceptible. You will find below that sometimes this is not the case, revealed only through testing of multiple species within a family. All families known to be susceptible are listed as a precaution for those who grow both dicots and momocots. And finally, non-persistent means that the virus is lost when the host insect molts; it does not mean that the virus has or will disappear from the plant.


Alstroemeria mosaic virus


Alstroemeria streak virus


Alstroemeria virus


Amazon lily mosaic virus


Dahlia mosaic virus


Crinum mosaic virus


Eucharis mottle virus


Freesia leaf necrosis virus


Freesia mosaic virus


Hippeastrum mosaic virus


Hyacinth mosaic virus


Iris fulva mosaic virus


Iris mild mosaic virus


Iris severe mosaic virus


Leek yellow stripe virus


Lily mottle virus


Narcissus degeneration virus


Narcissus late season yellows virus


Narcissus latent virus


Narcissus mosaic virus


Narcissus tip necrosis virus


Narcissus yellow stripe virus


Nasturtium mosaic virus


Nerine latent virus


Nerine virus X


Nerine Y virus


Nerine yellow stripe virus


Nothoscordum mosaic virus


Ornithogalum mosaic virus


Tuberose mild mosaic virus


Tulip breaking virus


Tulip chlorotic blotch virus


Tulip virus X


Tropaeolum virus 1 & 2


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Page last modified on April 10, 2014, at 05:51 PM