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Temperate Pulse Viruses: Pea Seedborne Mosaic Virus (PSBMV) | AG1267 |
Mohammad Aftab and Angela Freeman, Horsham
November 2006
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Pea seedborne mosaic virus (PSBMV) is distributed worldwide. It was first introduced into Australia in 1978 from seed imported from Sweden. It infects pulse crops and pasture legumes and the natural host range is limited to Fabaceae. The virus may be symptomless or show mild mosaic symptoms on peas and other legumes. It may cause considerable yield loses in early infections. PSBMV also affects the seed quality of pea, faba bean, lentil, chickpea, lathyrus and other legumes by causing brown rings patterns and spots on the seeds. Seed transmission of this virus may be as high as 100% in peas and reach significant levels in other legumes. The virus is also transmitted mechanically and by aphids.
Host Range
The natural host range of PSBMV is limited to the Fabaceae. It infects temperate pulses (chickpea, faba bean, field pea, lentil) other legumes (garden pea, narbon bean) and pastures (lathyrus and vetch). A number of PSBMV pathotypes have been recognised by their ability to infect a number of pea differential genotypes.
Symptoms
PSBMV symptoms are often difficult to identify under field conditions as the virus may be symptomless or show mild mosaic symptoms. PSBMV may severely damage the quality of pulse seed by causing brown rings or line patterns on the seed surface, which may lead to downgrading of seed from human consumption to stockfeed standard.
Field symptoms of PSBMV on pulses are as follows:
- Field peas develop various degrees of stunting, downward rolling of leaflets and a transient clearing and swelling of leaf veins of most cultivars. Infected plants may produce distorted flowers, which often give rise to small distorted pods. Ovule development in affected pods may be uneven, with only one or two seeds produced. Seed coats may split as the seeds mature. The symptoms on seeds result in brown rings and tan spots (Figure 2).
- Faba beans develop systemic dark and light-green zonal leaf mottle, leaf margins become upright and leaf blade is reduced (Figure 3). The seeds from infected plants show brown ring patterns and reduced size (Figure 4).
- Chickpeas develop yellowing on new shoots, mottling of leaves, down curling of leaves and plant stunting.
- Lentils may show no symptoms or there may be chlorosis in new shoots, mottling on leaves, shoot tip necrosis and stunting of plants.
Economic Importance
PSBMV is of economic importance in pea, faba bean and lathyrus, mainly due to its effect on seed quality. It has been mistakenly considered to be a minor disease because it often causes only minor yield loss and mild symptoms, However, at the International Centre for Agriculture in the Dry Areas (ICARDA), Syria, glasshouse studies on yield losses due to PSBMV in chickpea, faba bean, lentil and pea showed losses of 66%, 40.5%, 44.6% and 49.2% respectively.In SA, glasshouse experiments showed that pathotypes P1 and P4 could reduce seed yield by 35% and 82% respectively.Surveys of pulse crops over a number of years in Vic and SA showed that up to 15% of crops were infected with PSBMV, with a within crop incidence of up to 5% of plants. In surveys in WA in 1999, PSBMV was found in 42% of field pea crops and the level of virus detected in pea seed stocks was up to 63%. The surveys in WA indicated that PSBMV has a severe effect on seed quality of pulse crops with seed coat symptoms evident on >80% of faba bean, >50% of lathyrus species and field peas and 5% of chickpea seed. At NSW-DPI Tamworth, screening of pea germplasm in the field for resistance to PSBMV has shown that highly susceptible lines may be 100% infected late in the season (Van Leur, unpublished). (See references).
Transmission
The virus is believed to have spread worldwide through the exchange of infected seed. Seed transmission rates of up to 100% in peas and up to 44% in lentils have been reported. In Victoria, we have detected PSBMV at low levels in some commercial chickpea seedlots (0.4% of seed) and at higher levels in field pea and lentil seedlots (greater than 2% of seed). In the USA, 3% PSBMV infection in pea seedlots and 32-40% in lentil seedlots have been reported. At ICARDA, PSBMV was found to be transmitted through lentil seeds at rates of up to 44%. PSBMV is also transmitted in a non-persistent manner by more than 20 aphid species and by mechanical means. The most efficient vector is the pea aphid (Acyrthosiphon pisum). The other species are as follows: A. pelargoni, A. sesbaniae, Aphis craccivora, A. fabae, A. gossypii, A. nasturtii, Aulacorthum circumflexum, A. solani, Brevicoryne brassicae, Cryptomyzus ribis, Dactynotus escalantii, Macrosiphum avenae, M. euphorbiae, M. pisi, M. rosae, Metopolophium dirhodum, Myzus persicae, Ovatus crataegarius, Phorodon cannabis, Rhopalosiphum padi and Semiaphis dauci. In Victorian pulse crop surveys, we have found cowpea aphid (Aphis craccivora), foxglove aphid (Aulacorthum solani), and green peach aphid (Myzus persicae), which are all vectors of PSBMV.
Management | Figure 1. Field pea show stunting and downward curling of leaf margins (Photograph courtesy of Rohan Prince Ag.WA
Figure 2. Field pea seeds develop brown rings and tan spots on the surface (Photograph courtesy of Jenny) Davidson SARDI)
Figure 3. Faba beans develop yellow and green mosaic patterns
Figure 4. Faba bean seeds develop brown ring patterns and shrivelling |
Seed is considered to be the main source of PSBMV, therefore sowing virus tested seed is the most effective way of controlling this virus. Commercial seed tests are available (see AG1250: Seed Health Testing in Pulse Crops).Currently, NSW DPI, Tamworth are screening pea germplasm for PSBMV resistance. Initial field experiments showed considerable differences among current pea cultivars in PSBMV resistance as well differences in the rate of seed to seedling virus transfer. Kaspa, Excell and Dundale were found to be highly susceptible with high seed transmission rates, wheras Cressy Blue, which becomes infected, shows only a very limited transfer of the virus through its seed (Van Leur, unpublished). The newly released NSW variety Yarrum is resistant to PSBMV. Chemical control of aphids is not an effective method for controlling non-persistently transmitted viruses, such as PSBMV. Pulse crops should be sown away from other legumes to minimise the spread of PSBMV.
More information
Makkouk KM et al. (1993). Netherland Journal of Pathology 115-124.
Ali A and Randles JW (1998). Australasian Plant Pathology 27, 226-233.
Latham LJ, Jones RAC (2001). Australian Journal of Agricultural Research 52, 771-790.
Acknowledgement
Thanks to Wendy Bedggood for preparation of this Note.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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