Pepper mild mottle virus

Pepper mild mottle virus (PMMoV) is a plant pathogenic virus that occurs worldwide on species of field grown bell, hot and ornamental pepper species. It is caused by members of the plant virus genus Tobamovirus- otherwise known as the tobacco mosaic virus family. Tobamovirus are viruses that contain positive sense RNA genomes that infect plants. Symptoms of the disease vary depending on the cultivar. Typical symptoms include the chlorosis of leaves, stunting, and distorted and lumpy fruiting structures. The virus is spread by mechanical transmission and infected seeds. Avoidance is the best means of controlling the disease because once a plant is infected it cannot be treated. Only seeds that have been tested and treated for the pathogen should be planted. Pepper mild mottle virus (PMMoV) is a plant pathogenic virus that occurs worldwide on species of field grown bell, hot and ornamental pepper species. It is caused by members of the plant virus genus Tobamovirus- otherwise known as the tobacco mosaic virus family. Tobamovirus are viruses that contain positive sense RNA genomes that infect plants. Symptoms of the disease vary depending on the cultivar. Typical symptoms include the chlorosis of leaves, stunting, and distorted and lumpy fruiting structures. The virus is spread by mechanical transmission and infected seeds. Avoidance is the best means of controlling the disease because once a plant is infected it cannot be treated. Only seeds that have been tested and treated for the pathogen should be planted. The origin of PMMoV has been linked to Tomato mosaic virus, as they both reside in the Tobacco mosaic virus family. The Tunisian Journal of Plant Protection brought about the link between PMMoV to ToMV from a French study dating back to 1964. ToMV affects a wide range of Solanaceous crops and a strain of this virus likely mutated into PMMoV. Pepper mild mottle virus is the major viral pathogen of peppers (Capsicum spp.). The host range of PMMoV include most cultivars and species of pepper (Capsicum spp.). This virus strain does not infect tomato, eggplant, or tobacco; however, other members of the genus Tobamovirus can infect these other hosts PMMoV is one of at least 4 different species of Tobamovirus that infect peppers. The others include Tobacco mosaic virus (TMV), Tomato mosaic virus (ToMV) and Tobacco mild green mosaic virus (TMGMV). This pathogen is known to occur throughout the world and it frequently results in significant crop losses or reductions in both field and greenhouse plantings. The virus has been identified in places like Australia, Japan, China, Taiwan, Europe, and North Africa. Since 1997, PMMoV has been the cause of many major outbreaks in the southeastern states namely Georgia and Florida. Symptoms caused by this pathogen vary based on the specific host cultivar; however, a majority of the symptoms are very similar between the different hosts. Symptoms usually include various degrees of mottling, chlorosis, curling, dwarfing, and distortion of the fruit, leaves, and even whole plants. The symptoms on fruit include: a reduction in size, mottling and color changes, and an obvious distorted and lumpy appearance. Also, many times brown necrotic streaks or splotches can be seen on the leaves and fruit. The symptoms can easily be seen on new growth, and they are far more pronounced if the plant was infected when it was young rather than when it was older. This disease is harmful because of the mild foliar symptoms (chlorosis, necrosis, etc.) and due to this many times the pathogen goes unnoticed until the more evident symptoms on the fruit appear. This is why there are higher yield losses because symptoms only become evident during the fruiting stage right before the crops are supposed to harvested. PMMoV is a rigid rod shaped virus pathogen that can be easily transmitted to healthy plants via mechanical inoculation or contact between plants or another medium that can carry the pathogen such as hands, gloves, and clothing. The virus is commonly found on the outer seed coat and very rarely in the endosperm of seeds of the infected plants. Being seedborne, the virus primarily infects through mechanical contamination during seed transplanting and other agricultural procedures. It enters the plant/seed through microscopic abrasions or wounds. The virus is in vitro, which in this case means it can survive in an isolated environment, and being highly infectious it can easily be transmitted during normal crop maintenance. PMMoV is exceptionally stable and it is known to survive for extended periods of time in plant debris and on greenhouse structures, pots, and horticultural tools. There are no known insect vectors; however, humans can be considered the main vector for this pathogen. This virus is widespread and is found almost anywhere peppers are grown, this is because the virus is most often introduced with the pepper seed. The virus moves long distances on the seed and moves short distances via plant-to-plant contact, handling of plants by contaminated implements and workers aids in the spread of the virus. Soils with low organic matter content, specifically humus will much more readily promote the adsorption of PMMoV. Specifically, the allophanic clays and iron minerals in these soils will promote the adsorption of PMMoV. Disease incidence has occurred mainly in greenhouse environments and hot, humid environments like southwest and southeast Florida and in regions like North Africa, and Japan. This is an indication of the type of soil that is optimal for the virus; warm or hot and humid. Greenhouses, specifically, are an ideal production environment for rapid spread of the disease.