California Pest Rating for
Pea Seed-borne Mosaic Virus (PSbMV)
Pest Rating: B
PEST RATING PROFILE
There is no initiating event. The risk of infestation of Pea seed-borne mosaic virus in California is evaluated and a permanent rating is proposed.
History & Status:
Background: In 1966 a virus disease of pea was first reported in Europe. The same virus was also described in Japan as Pea seed-borne mosaic virus. During the early 1980s the virus was also discovered in New Zealand and England and is now known to be widespread throughout the globe due to the movement of infected pea seeds through high international trade. In California, the pathogen was first discovered in 2004 on pea cultivated in a field in Monterey County.
Pea seed-borne mosaic virus belongs to the genus Potyvirus in the family Potyviridae and RNA viruses group. The nucleic acid consists of a positive-sense single stranded RNA. The virus consists of several strains or pathovars that are serologically closely related. Three strains of PSbMV (P1, P2 and P4) have been identified and the most common strains include P-1 and P-4 from pea and the L-1 from lentil. Usually, differential hosts have been used to identify specific strains (Larsen, 2001).
Hosts: The host range for PSbMV includes at least 47 plant species belonging to 12 families. However, only three hosts are considered to be economically important, namely, Pisum sativum (pea), Lens culinaris subsp. culinaris (lentil), and Vicia faba (bean). Chickpea is also a susceptible host however, there is no evidence that it transmitted through contaminated seed. Other hosts include a wide range of experimental hosts.
Symptoms: Symptoms on peas are affected by age of plant at the time of infection, temperature, virus strain or pathotype and plant genotype. Symptoms may develop in as few as 3 days after infection. Certain pea cultivars never express symptoms (Khetarpal & Maury, 1987). Symptoms may be more severe on plants germinating from infected seed. Symptoms include general stunting, leaf mild chlorosis, shortening and downward rolling of leaflets, vein clearing and swelling, rosetting (due to reduction of internodal growth), mosaic, distorted flower or seed pods and failure to set pods. However, symptoms disappear soon after infection. Seed coats of PSbMV-infected seed may become cracked, split or banded and often serve as indicators of possible PSbMV infection although these symptoms may also be caused by physiological or environmental factors. Contrarily, healthy appearing seeds with normal seed coats may also bear the virus pathogen (CABI, 2014; Larson, 2001).
Damage Potential: The loss of market due to infected seed is a significant factor in the estimated economic loss caused by the virus. As much as 36% reduction in pea seed yields are estimated to be due to PSbMV infection (Khetarpal & Maury, 1987). Seed infections greater than 30% have been reported (CABI, 2014).
Transmission: The most common means of long-distance transmission of PSbMV is through infected seed. The virus infects seed internally and all parts of inflorescences from infected plants contain the virus. Infected seed is an important means of introducing the virus into new, non-infected areas. Spread from plant to plant is brought about mainly by aphid vectors and mechanical transmission. The virus can be transmitted in a non-persistent manner by 21 aphid species. The pea aphid (Acyrthosiphon pisum), green peach aphid (Myzus persicae), and cotton aphid (Aphis gossypii) are the most common vectors. Natural aphid vectors are the pea aphid, cowpea aphid (Aphis craccivora), black bean aphid (Aphis fabae), Dactynotus escalanti, mint aphid (Ovatus crataegarius), and bird cherry-oat aphid (Rhopalosiphum padi). If aphid populations are high and uncontrolled during a growing season, then only a few PSbMV-infected seeds can result in spreading the disease over a large percentage of a field. Typically, the aphid vector can acquire the virus in 5 min and transmit it after a single probe of one minute or less (Larsen, 2001). Hampton and Mink (1975) reported that aphids acquire PSbMV and inoculate it in 10-90 sec feeding periods without requiring a latent period. High aphid populations are favored by cool growing seasons thereby enabling effective spread of PSbMV.
Worldwide Distribution: PSbMV is distributed worldwide largely due to the distribution of pea germplasm infected with the seed-transmitted virus (Larsen, 2001; Hampton et al., 1993). It is distributed in Asia: India, Iran, Israel, Japan, Jordan, Lebanon, Nepal, Pakistan, Syria, Taiwan, Turkey, Yemen; Africa: Algeria, Egypt, Ethiopia, Libya, Morocco, South Africa, Sudan, Tanzania, Tunisia, Zambia, Zimbabwe; North America: Canada, USA; South America: Brazil; Europe: Belgium, Bulgaria, Czech Republic, former Czechoslovakia, Denmark, Finland, France, Germany, Netherland, Poland, Romania, Russian Federation, Serbia, Slovakia, Sweden, Switzerland, United Kingdom, Yugoslavia; Oceania: Australia, New Zealand.
In the USA is it has been found in California, Idaho, Maryland, Minnesota, New York, Oregon, Vermont, Washington, and Wisconsin (CABI, 2014; EPPO, 2014).
Official Control: Since 1995, PSbMV has been listed by Argentina and Brazil as an A1 quarantine pathogen (EPPO, 2014). The pathogen is on the ‘Harmful Organism List’ for nine countries: Australia, Costa Rica, Georgia, Japan, Nambia, Nauru, South Africa, Taiwan and Uruguay (PCIT, 2014).
California Distribution: Monterey County, California.
California Interceptions: There are no official records of PSbMV detected in incoming plant shipments to California.
The risk Pea seed-borne mosaic virus would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:
– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.
Risk is Medium (2) – The establishment of PSbMV within CA is closely related to the establishment of its major hosts and associated aphid vector. Cultivation of pea and bean plants requires cool and humid climate – such as is found mainly along the California’s coastal regions. Already PSbMV is established in Monterey County, California.
2) Known Pest Host Range: Evaluate the host range of the pest. Score:
– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.
Risk is Medium (2) – PSbMV has a moderate host range of 47 plant species belonging to 12 families. However, the main hosts of economic importance are pea, bean and lentil. The former two crops are in limited commercial production in California.
3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:
– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.
Risk is High (3) – The spread of PSbMV is through infected seed and several (21) Aphid species. The combination of both agents, plus the high rate of multiplication of the virus within an infected host render the pathogen a high risk potential for spread to non-infected sites.
4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:
A. The pest could lower crop yield.
B.The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.
– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.
Risk is High (3) –Incidence and spread of PSbMV could adversely affect pea and bean production in California by lowering crop yield, value, increasing production costs, affecting local and international markets, negatively change normal cultivation practices to prevent incidence of further occurrence and spread of the virus and its whitefly vector.
5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.
A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.
Score the pest for Environmental Impact. Score:
– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.
Risk is Medium (2) – Several weeds may be hosts of PSbMV and serve as sources of inoculum acquired by aphids against economically important hosts. However, several weed hosts may be asymptomatic and it is not known how well the whitefly vector will acquire the virus from such infected hosts that may comprise natural environments. The effect on these hosts in nature is not known. Nevertheless, PSbMV infections may impact home/urban gardening and cultivation of ornamentals.
Consequences of Introduction to California for Peas seed-borne mosaic virus
Add up the total score and include it here. (Score)
-Low = 5-8 points
-Medium = 9-12 points
-High = 13-15 points
Total points obtained on evaluation of consequences of introduction of PSbMV to California = (12).
6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)
-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.
Evaluation is (-1).
7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)
Final Score: Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11
Current field data is always needed on the probable establishment and spread of PSbMV beyond the known infested regions of Monterey County. Such information would be obtained through periodic surveys. Also not known is the distribution of the virus in natural environments and the potential that infected natural hosts may play in its possible spread to legume fields.
Conclusion and Rating Justification:
Based on the evidence provided above the proposed rating for Pea seed-borne mosaic virus is B.
CABI 2014. Pea seed-borne mosaic virus full datasheet. Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/1695
EPPO, 2014. Pea seed-borne mosaic virus (PSBMV0). New PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://newpqr.eppo.int
Hampton, R. O and G. I. Mink. 1975. Pea seed-borne mosaic virus. CMI/AAB Descriptions of Plant Viruses. No. 146, 4pp. Wellesbourne, UK: Association of Applied Biologists. http://www.dpvweb.net/dpv/showdpv.php?dpvno=146.
Hampton, R. O, J. M. Kraft, F. J. Muehlbauer. 1993. Minimizing the threat of seedborne pathogens in crop germ plasm: elimination of pea seedborne mosaic virus from the USDA-ARS germ plasm collection of Pisum sativum. Plant Disease, 77(3):220-224
Larsen, R. C. 2001. Pea Seedborne mosaic virus. In: Compendium of Pea Diseases and Pests Second Edition. St.Paul, USA: APS Press, 37-38.
PCIT. 2014. USDA Phytosanitary Certificate Issuance & Tracking System. https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.
Dr. John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.
Pest Rating: B
Posted by ls