Tomato Mottle Mosaic Virus | Pest Rating Proposals and Final Ratings

California Pest Rating for

Tomato Mottle Mosaic Virus (ToMMV)

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

On September 17, 2015, the CDFA was notified by a seed company of the detection of Tomato mottle mosaic virus (ToMMV) in tomatoes grown at the company’s farm in San Joaquin County. Subsequently, the CDFA will collect official samples of ToMMV-infected tomato plants for pathogen diagnosis and the seed company disposed of infected plants and fruit and administered sanitization measures to prevent the possible spread of this pathogen to the environment. The risk of infestation of Tomato mottle mosaic virus (ToMMV) in California is evaluated and a permanent rating is proposed.

History & Status:

Background: Tomato mottle mosaic virus is a relatively new plant virus that was first reported in 2013 from Tamazula, Jalisco in Mexico, after being isolated from symptomatic tomatoes which were discovered in a greenhouse in 2009 (Li et al., 2013). In the USA, ToMMV was first reported from Florida in 2014, following a 2010 and 2012 discovery of symptomatic tomato plants grown in a commercial tomato field and greenhouse respectively (Webster et al., 2014).

Tomato mottle mosaic virus belongs to the genus Tobamovirus in the family Virgaviridae. Other tobamoviruses that naturally infect tomato include tomato mosaic virus and tobacco mosaic virus – both which are known to be widely distributed within California. Complete genomic sequences were determined for the Mexico and USA isolates and reported to be 99% identical (Fillmer et al., 2015; Li et al., 2013; Webster et al., 2014). Tomato mottle mosaic virus is closely related to, but distinct from tomato mosaic virus. In fact, Webster et al., (2014) compared gene sequences of tomato mosaic virus, deposited in GenBank, from pepper and tomato and determined that those were closely identical (98-100% nucleotide and deduced amino acid identity) to ToMMV, suggesting that in prior reports, ToMMV may have been misidentified as tomato mosaic virus and therefore, may be more wide spread than currently reported.

Hosts: Presently, natural hosts include tomato (Lycopersicon esculentum) and pepper (Capsicum annuum)

Symptoms: Foliar mosaic of light and dark green symptoms, chlorosis, and leaf deformation in mature tomato (Webster et al., 2014), whereas a rapid tissue necrosis occurred on the upper leaves inoculated tomato seedlings (Li et al., 2013). Foliar mottle, shrinking, and necrosis occur in pepper plants (Li, et al., 2014).

Damage Potential: Presently, there are no reports of quantitative crop yield losses specifically caused by ToMMV, nevertheless, losses similar to those caused by the closely-related tomato mosaic virus can be expected. Tomato mosaic virus can cause yield losses up to 25% in infected non-resistant greenhouse or field-grown susceptible tomato crops (CABI, 2015). ToMMV has the potential of damaging tomato and pepper production mainly through the destruction of foliar growth.

Transmission: As a member of the genus Tobamovirus – tomato mottle mosaic virus is most likely transmitted in similar manner as tomato mosaic virus, and therefore, is contagious and transmitted through plant to plant contact as well as mechanically via contaminated hands, clothing, and tools; insects, contaminated irrigation water, contaminated soils, infected plants, plant debris, and seed. No particular insect vector species has been reported for ToMMV. Healthy seedlings can be infected in contaminated soils through minor wounds caused by natural damage to roots without involvement of vectors (CABI, 2015).

Worldwide Distribution: Asia: China, Iran; North America: USA (Florida), Mexico; South America: Brazil (Li et al., 2013; Li et al., 2014; Webster et al., 2014).

Official Control: None reported.

California Distribution: Tomato mottle mosaic virus is not known to be established within California. However, ToMMV was detected by a seed company in their farm site in Acampo, San Joaquin County. Consequently, infected plants were removed and sanitization measures were administered (see “Initiating Event”).

California Interceptions: There are no records of ToMMV detected in incoming plant shipments to California.

The risk Tomato mottle 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 High (3) – It is likely that Tomato mottle mosaic virus can establish a widespread distribution in California wherever tomato and pepper plants are cultivated, similar to its closely related species, Tomato mosaic virus.

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 Low (1) – Presently, the host range for Tomato mottle mosaic virus is limited to tomato and pepper plants.

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) – As a tobamovirus,Tomato mottle mosaic virus is easily transmitted through plant to plant contact as well as mechanically via contaminated hands, clothing, tools, and insects;contaminated irrigation water, contaminated soils, infected plants, plant debris, and seed. No particular insect vector species has been reported for ToMMV. Healthy seedlings can be infected in contaminated soils through minor wounds caused by natural damage to roots without involvement of vectors.

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) – Tomato mottle mosaic virus is expected to cause economic impact similar to its closely related species, tomato mosaic virus. Therefore, this pathogen could lower crop yield and market value, alter normal cultural production and irrigation practices to prevent spread to non-infected regions, and be vectored by contaminated insects to non-infected plants.

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) – The host range is limited to tomato and pepper – cultivated crops, therefore no significant detrimental impact to the environment is expected. However, home/urban gardening of host plants may be impacted if infected by ToMMV.

Consequences of Introduction to California for Tomato mottle 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 ToMMV 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 not established. Tomato mottle mosaic virus is not known to be established within California. Detection in San Joaquin led to removal of diseased plants and sanitization treatments.

Final Score:

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 = 12.

Uncertainty:

Presently, only tomato and pepper have been reported as hosts of this relatively new plant virus. It is probable that in due time, other members of the Solanaceae plant family may be included as hosts. Therefore, reports of host range studies may provide additional information on other possible hosts. Furthermore, based on gene sequence analysis of tomato mosaic virus, researchers have suggested that ToMMV may have been misidentified as tomato mosaic virus. The latter species is widely distributed in California, but whether or not it also includes ToMMV is not known.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Tomato mottle mosaic virus is B.

References:

CABI 2015. Tomato mosaic virus full datasheet. Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/1695.

Fillmer, K., S. Adkins, P. Pongam and T. D’Ella. 2015. Complete genome sequence of a Tomato mottle mosaic virus isolated from the United States. Genome Announcements, 3 (2): e00167-15. doi:10.1128/genomeA.00167-15.

Li, R., S. Gao, Z. Fel and K. Ling. 2013. Complete genome sequence of a new Tobamovirus naturally infecting tomatoes in Mexico. Genome Announcements, 1(5):e00794-13. doi:10.1128/genomeA.00794-13.

Li, Y. Y., C. L., Wang, D. Xiang, R. H. Li, Y. Liu and F. Li. 2014. First report of Tomato mottle mosaic virus infection of pepper in China. Plant Disease, 98 (10):1447. http://dx.doi.org/10.1094/PDIS-03-14-0317-PDN.

Webster, C.G., E. N. Rosskopf, L. Lucas, H. C. Mellinger and S. Adkins. 2014. First report of Tomato mottle mosaic virus infecting tomato in the United States. Plant Health Progress, doi:10.1094/PHP-BR-14-0023.

Responsible Party:

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.