Potato Viral Diseases

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

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Serious threat

Currently, about 40 viral, viroid and phytoplasmic diseases are known. They are among the most common and harmful, and are manifested in the form of a variety of mosaics, deformations, chlorosis, growth inhibition, the death of plants or their individual parts. All known viruses and viroids are obligate parasites. Those. they can reproduce only in living cells of susceptible organisms.

The following viral, viroid and phytoplasmic diseases are most common: mottling, leaf twisting, leaf twisting, banded and folded mosaics, aucuba mosaic. Fusiform tubers, pillar wilt, witch's brooms, round-leaved, purple twisting of the top, variegated stems, paniculate virus of the top of the potato are of limited distribution.

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Wrinkled mosaic

Refers to a mixed type of infection. The main causative agent of the disease is Potato virus Y. Y-virus of potato (YBK). Wrinkled mosaic causes swelling of the leaf blade between the veins. The leaves become wrinkled, the midrib is shortened, the edges are bent down. The disease leads to profound physiological disorders in plants. The activity of the stomatal apparatus is disrupted, plant tissues have a reduced water-holding capacity. This explains the frequent death of plants affected by wrinkled mosaics during the onset of drought. The infection is transmitted with tubers, viruses are spread by aphids during the growing season, as well as mechanically. Some of these can be seed borne. The yield shortfall from wrinkled mosaics reaches 40-60% or more.

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Striped mosaic

The main causative agent of the disease is the usual strain of Potato virus Y. The infection manifests itself on the lower and middle leaves in the form of a mosaic. Later, necrotic dark stripes, dots and spots are formed on the veins and in the corner between them (angular spotting), which are especially clearly visible from the underside of the leaves. Usually, necrosis first appears on small veins along the edge of the leaf, and then on large veins, on leaf petioles and stems. In diseased plants, the leaves become brittle, darken, die off, fall off or remain hanging on thin, dried petioles at an acute angle to the main stem. A combination of striped mosaic with wrinkles is often observed. Winters in potato tubers. The disease is very harmful, it causes a sharp decrease in the potato yield - from 10 to 30%.

Speckled, or ordinary mosaic

The causative agent of the disease is Potato virus X. It usually manifests itself on young leaves in the form of a thin light green speck of irregular shape, on a number of potato varieties the signs of the disease disappear during aging, and on some varieties the disease is characterized by the formation of black necrotic spots. There are varieties in which the external signs of the disease are masked. It can only be detected by a serological reaction. The disease is tuber-transmitted. When plants were infected with infection, the yield of tubers decreased by 34-63%, the average weight of one tuber and the number of tubers in one bush, as well as their marketability, significantly decreased.

Rolling the leaves

The causative agent of the disease is the L-virus (LSLV) - Potato leaf roll virus. In the first year of the diseased plant, the edges of the lobules of the upper young leaves are twisted. Sometimes the upper side of them is colored yellow, and the lower - pink. In the second and third years, curling of the leaves of the lower, and then more upper tiers is observed. The leaves become leathery, brittle, yellowish, often with a reddish, purple or bronze tint. Slices of affected leaves roll up along the midrib into a tube. The petioles of the leaves are at a sharper angle to the stem, resulting in the plants acquiring an elongated Gothic shape. The virus also infects tubers, on the cut of which net necrosis is found. The virus causes thickening of the cell walls of the primary phloem in the stems and petioles as a result of callose deposition on them. In diseased plants, the outflow of carbohydrates from the leaves to other organs is disturbed. Tuberization in affected plants is suppressed. The pathogen is transmitted by tubers, and during the growing season - by aphids. The harmfulness is significant. The lack of harvest of tubers, depending on the degree of manifestation of the disease, is 30-80% or more.

Mosaic curling of leaves

The causative agent of the disease is M-virus - Potato virus M (PVM). The most typical signs are observed on young plants in the form of more or less pronounced mosaicism and upward curling of the edges of the upper leaf lobes. The curled young leaves look like the leaves of plants affected by Rhizoctonia. Sometimes there is a waviness of the edge of the lobes, a weak reddish coloration of the leaves or their yellowing. On some varieties of potatoes, the disease manifests itself in the form of curliness, streakiness of petioles, stems, necrosis of veins, or is asymptomatic. In the second half of the growing season of potato plants, the external symptoms of the disease are generally masked. The virus is transmitted mechanically, by aphids, bedbugs and potato bugs. Mosaic leaf curling is one of the most harmful viral diseases, causing a decrease in tuber yield by 15 to 70%.

Folded mosaic (curly leaves)

The causative agent of the disease is A-virus (AVK) - Potato virus A (PVA). It manifests itself on young developing potato leaves in the form of a large-spotted mosaic, which is accompanied by a bulge (swelling) of tissue sections of the leaf lobes between the veins. Sometimes there is a pronounced waviness of the edge of the leaf lobes and the bending of the apex of the final leaf lobe to the side. The disease also manifests itself in the form of chlorotic mottling, apical necrosis, or is asymptomatic. The virus is transmitted through tubers, and in the field - by contact and various types of aphids. The yield shortage from the disease is insignificant, however, with severe forms of the disease, which are observed with a mixed infection in combination with the X virus, they can reach 60-80%.

Aucuba mosaic

The causative agent of the disease is the aucuba mosaic virus (PAMV) - Potato aucuba mosaik virus (PAMV). The virus manifests itself mainly on the lower leaves of potatoes in the form of a more or less pronounced bright yellow spot. In some varieties, yellow spots can appear on the entire plant, in others there are no symptoms of the disease. In affected plants, wrinkling of the leaf blades, their mosaic coloring, as well as the appearance of necrotic spots on the leaves, petioles and stems can be observed. The infection is transmitted by tubers, and during the growing season of plants - and by contact with various species of aphids. The lack of harvest of tubers from the disease can be 5-30% or more (V. G. Ivanyuk, S. A. Banadysev, G. K. Zhuromsky, 2005).

Fusiform potato tubers, or Gothic

The causative agent of the disease is the Potato spindle tuber virus (PSTV), a potato spindle tuber virus (PSTV), an infectious low molecular weight RNA that penetrates into plant cells, replicates in them due to the biosynthetic mechanisms of the host plant and disrupts the vital activity of the entire plant. Plants infected with a viroid are noticeably elongated, their leaves are small with weakly twisted lobules along the midrib, have a dark green or purple color, wrinkled. They move away from the stem at a sharper angle than in healthy plants. Tubers are fusiform, multi-eyed, with irregular outlines. The disease is transmitted by mechanical means, by contact, various types of aphids, field bugs, dodders. The harmfulness of the disease consists in a decrease in plant productivity, a decrease in starch content in tubers. The crop shortfall is 85%.

The high harmfulness of phytopathogenic viruses on potatoes is due to the fact that under the influence of a viral infection, the growth and development of plants deteriorates, the yield, quality and marketability of tubers decrease. Usually, the accumulation of viral infection in potato seed and the manifestation of signs of disease progresses with an increase in the number of field generations.

It is sometimes difficult to recognize viruses by the symptoms of infected plants. In some cases, even experts find it difficult to identify viruses, and the external symptoms of their manifestation may sometimes be absent. Therefore, along with the acquisition of practical skills in recognizing the symptoms of viral diseases on plants and tubers, it is important to use modern laboratory methods of virological control based on enzyme immunoassay (ELISA) and molecular hybridization analysis (MGA).

Viral diseases can be prevented by using only high quality certified seed for planting.