potato farmers conquer devastating with paper

In moderate climates, such as in South Africa, aphids are thought to reproduce asexually on weeds, other crops, indigenous plants and garden plants. Hosts such as weeds and other crops serve as breeding grounds for these aphids and form a temporary area of colonization before the aphids migrate to the potato fields. In cold climates aphids spend the winter either as wingless aphids giving birth to live young (viviparae) or as eggs. The most common manner of PVY infection of plant material in the field is through the aphid, and although aphids on their own can directly damage potato plants, it is their role as viral vectors which has the greatest economic impact. PVY may be transmitted to potato plants through grafting, plant sap inoculation and through aphid transmission. Tubers damaged by PTNRD become unmarketable and infection by PVY NTN thus results in a larger economic impact than infection by the other strains. The PVY NTN has been accredited with the ability to induce potato tuber necrotic ringspot disease (PTNRD).

In Europe these two strains have been shown to have recombined to form PVY NTN.

Both PVY N and PVY O are aphid transmissible and occur in South Africa. Infection of a potato plant with the PVY O strain results in mild tuber damage and does not cause leaf necrosis. The ordinary strain of PVY is denoted as PVY O. PVY N results in leaf necrosis and mild or even no damage to the tubers. This strain was described in tobacco plants growing close to potato plants. did not identify any of the local isolates as being PVY C but it has been reported to occur to in South Africa. Unlike the other strains of PVY, some PVY C strains are non-aphid transmissible. These reactions include the formation of mild mosaic patterns or stipple streak. PVY C induces hypersensitive responses in a wide range of potato cultivars. PVY C, originally known as Potato Virus C, was the first to be recognized and was identified in the 1930s. Traditionally three chief strains of PVY are recognized: PVY C, PVY N and PVY O. Occurrence of a variety of symptoms and the emergence of the necrotic PVY NTN has led to a search for more reliable classification tools than simple serological identification. Extensive biological, serological and molecular variability of PVY isolates makes the classification of isolates as particular strains particularly difficult. It has been shown that the PVY has different isolates according to the symptoms they induce in various potato plant species. Infection of a potato field with PVY may ultimately result in 10-100% loss in yield. Resistance to PVY infection by hosts is low in many cases. The level of damage to crop is determined by the strain of PVY infecting the plants, the viral load, the time at which infection occurs as well as the tolerance the host possesses toward the virus. These include potato ( Solanum tuberosum), tobacco ( Nicotiana tabacum), tomato ( Solanum lycopersicum) and pepper ( Capsicum spp.). PVY infects many economically important plant species. The genus includes more than 200 species that bring about significant losses in the agricultural arena. PVY belongs to the genus Potyvirus, the largest genus of plant viruses and possibly the most destructive one in potato crops. Potato illustrating necrotic ringspot disease Potato virus Y hosts, strains and symptoms An increase in the average temperature of winters as a consequence of global warming has also led to an increase in aphid numbers, which in turn has led to an increase in viral distribution. These include a marked decrease in the effectiveness and administration of chemicals used in vector control, the use of infected seed potatoes in cultivation, incorrect irrigation and farming methods as well as a lack of a sensitive, rapid and reliable method of detection. The increased rate of infection may be attributed to several factors. This means that using the same line of potato for production of seed potatoes for several consecutive generations will lead to a progressive increase in viral load and subsequent loss of crop.Īn increase in potato plant infection with viruses over the past few years has led to considerable losses to the South African potato industry. PVY is transmissible by aphid vectors but may also remain dormant in seed potatoes. Necrotic ringspots render potatoes unmarketable and can therefore result in a significant loss of income. The mildest of these symptoms is production loss, but the most detrimental is 'potato tuber necrotic ringspot disease' (PTNRD). PVY infection of potato plants results in a variety of symptoms depending on the viral strain. Potato virus Y (PVY) is a plant pathogenic virus of the family Potyviridae, and one of the most important plant viruses affecting potato production.

Potato farmers conquer devastating with paper