Viral diseases of potato are a group of diseases caused by different types of Viruses that affect potato crops worldwide and, although they do not affect human or animal health since they are viruses that only infect vegetables, they are a source of great economic losses annually. About 28 viruses have been reported infecting potato crops. However, potato virus X (PVX), potato virus Y (PVY), and potato leafroll virus (PLRV) are the most important viruses worldwide. Some others are of economic importance only in some regions. Such is the case of potato virus M (PVM) in some Asian and European countries. An additional problem is the co-infection of two or more viruses on the same plants. In fact, the joint occurrence of PVX and PVY, or either or both of them with PLRV or Potato virus A (PVA), produces much more severe symptoms than separate infection of each. The magnitude of economic losses associated with this synergistic effect depends on the types of viruses that are interacting, their respective races, their interaction with the host potato cultivar, the viral vectors involved, and the environment. Diseases caused by viruses are one of the main limiting factors of potato cultivation worldwide, not only because of the immediate damage they can cause, but also because their effect is cumulative over time. Since potato is an asexually propagated species, the viruses present in a given plant are passed on to the next clonal generation through the tuber pieces used for multiplication. In the new generation, new viruses of the same or other species may be added to the existing ones, increasing the virus load of these plants. This accumulation of viruses is mainly responsible for the so-called gradual degeneration of potato varieties, the consequences of which are a gradual decrease in the vigor and yield of the crop as well as an increase in quality losses due to a reduction in the possible shelf life of the tubers after harvest. Most potato viruses can be diagnosed by the presence of characteristic symptoms, such as mosaic patterns on leaves, stunting of plants, and deformations of leaves and tubers. However, these symptoms do not always manifest themselves due to interactions between the virus(es) involved, the potato variety and the environment (soil fertility, climate or the age at which the plant is infected, among many other variables). For this reason, in recent years, serological and molecular detection techniques have been used to diagnose and characterize the viruses affecting the crop to take the most appropriate control measures. The following is a description of several of the viral diseases of potato crops, their symptoms and management possibilities.
Main viruses
Potato leafroll virus (PLRV)
Potato leafroll virus (PLRV), also known as "leafroll" or "yellow dwarfism", is a phloem-limited Luteovirus, which is transmitted by aphids, the green peach aphid (Myzus persicae) being one of the most important vectors. This virus needs 20 to 30 minutes to be acquired and 24 to 48 hours to be transmitted by aphids, since it needs to move inside the insect's digestive tract and come out again through the salivary glands. Symptoms of PLRV in potato include a characteristic erect growth habit and the classic "inward" rolling of the leaf blades that gives the virus its name. In addition, chlorosis (i.e., yellowing) or reddening of leaves and necrotic spots along the leaf veins due to phloem cell death may be visualized. The consistency or texture of the leaves also changes, as they become more leathery. Reduced plant height (a symptom called "dwarfism") and net necrosis in tubers complete the repertoire of symptoms shown by potato plants affected by PLRV. Because the acquisition, transmission and dissemination of PLRV requires a few days, insecticide applications to eliminate insect vectors can be effective as a control measure. The use of virus-free seed tubers is of fundamental importance to achieve healthy crops. During cultivation, removal of plants showing symptoms helps prevent the spread of PLRV. Also, early harvesting of tubers can help prevent infection later in the season. The virus is not spread or transmitted mechanically.
Mosaics
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