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Species Page

alfalfa yellow spot

Alfalfa mosaic virus
This information is part of a full datasheet available in the Crop Protection Compendium (CPC). Find out more information on how to access the CPC.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Extent
Invasive
Origin
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Host plants / species affected

Main hosts

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Apium graveolens (celery)
Apium graveolens var. rapaceum (celeriac)
Arabidopsis thaliana
Capsicum annuum (bell pepper)
Cicer arietinum (chickpea)
Cucurbitaceae (cucurbits)
Glycine max (soyabean)
Lablab purpureus (hyacinth bean)
Lactuca sativa (lettuce)
Medicago sativa (lucerne)
Nicotiana tabacum (tobacco)
Phaseolus (beans)
Solanum lycopersicum (tomato)
Solanum tuberosum (potato)
Trifolium incarnatum (Crimson clover)
Trifolium pratense (red clover)
Trifolium repens (white clover)
Viburnum opulus (Guelder rose)
Vigna radiata (mung bean)
Vigna unguiculata (cowpea)

List of symptoms / signs

Leaves - abnormal colours
Leaves - abnormal patterns
Roots - reduced root system
Stems - discoloration of bark
Vegetative organs - internal rotting or discoloration
Whole plant - dwarfing

Symptoms

Symptoms of AMV may differ according to the strain of virus, genotype of host and/or time of year. In general AMV causes various mosaic, mottles and flecking. In some hosts, such as peas or tomatoes, it can cause necrosis; many strains in mechanically-inoculated Phaseolus vulgaris seedlings induce necrotic local lesions which can be used to assay the virus. Details of symptoms in some important hosts are given in Jaspars and Bos (1980) and Edwardson and Christie (1997). Lists of strains of AMV are given in Hull (1969) and Jaspars and Bos (1980).

Prevention and control

Introduction

As AMV is both seed and aphid transmitted, a range of control measures are required. Use of virus-free seed is an obvious initial requirement. Seed potatoes have been freed of virus by thermotherapy (Kaiser, 1984). Control of spread from overwintering hosts by spatial separation or by controlling the vector is the next major step. Insecticides are of limited use as the virus is transmitted non-persistently by aphids. However, combining insecticides with mineral oil (Reagan et al., 1979) or application of mulches between the rows (Kemp, 1978) gives sufficient insect control to limit infection. Various sources of resistance to AMV have been reported (see Hull, 1969) but these do not appear to be very effective. Transgenic protection has been reported (Fincham and Beachy, 1993; Brederode et al., 1995) and may be an effective future approach.

Host-Plant Resistance

Two sorts of transgenic protection have been demonstrated. Expression of AMV coat protein (CP) gene in tobacco, tomato, pea, medicago and lucerne leads to a significant delay in symptoms and a reduction in virus accumulation (Fitchen and Beachy, 1993; Jayasena et al., 1997; Xu et al., 1998, 1999; Jayasena et al., 2001; Timmerman-Vaughan et al., 2001). Transformation of tobacco with mutated AMV replicase genes gave high levels of protection (Brederode et al., 1995). By analogy with other systems it is expected that CP-mediated protection would be effective against a wider range of strains than that afforded by the replicase.

Impact

AMV is of local economic importance in celery, peppers, tomatoes, lucerne, peas, potatoes and Trifolium spp. It has a different economic impact on different crop types and the situation in which they are grown. On forage crops it will decrease herbage and root production (see Bailiss and Ollennu, 1986; Jones, 1992). In temperate climates it can reduce the ability of perennial legumes to overwinter (Gibbs, 1962). Infection reduces the flowering and seed yield of Trifolium subterraneum (Jones, 1992) and the crop yield of Vigna angularis can be reduced by up to 70% (Iizuka, 1990).