late blight of potato

Introduction. It becomes activated at the time of germination of the diseased seed tubers among the planting stock or waste tubers in dump heaps or infected tubers remaining in the ground after a previous crop. This is accomplished by spraying with herbicides or flame throwers or by the use of mechanical vine beaters. Early blight is a common foliage disease of potato and tomato. 1. In India, losses are more in hilly regions where the crop is grown under rain-fed conditions as compared to the plains. Late blight of potatoes is caused by the pathogen Phytophthora infestans. Infected seed tubers, tomato transplants, potato cull piles and/or other volunteer potatoes are ex… R.C. The hyphae are both intercellular and intracellular. Infected plants may be killed off within a couple of weeks from infection. Once infected, the whole plant may quickly collapse and what appear to be healthy tubers may rot in storage. Late blight is a fungus called Phytophthora infestans, which affects tomatoes and potatoes. Late blight is the most destructive of all potato disease and responsible for the Irish Famine in the middle of the 19 th century. Now it has established itself in the Indo- Gangetic plain and occurs annually in the states of Punjab, Uttar Pradesh, Bihar, and W. Bengal. They play a significant role as the source of primary infection. Potato tubers are often infected in the field after the tops have been blighted. The cycle is repeated as long as cool moist weather prevails. TOS4. Effective control of this disease requires implementation of an integrated disease management approach. The mature sporangia are readily detached and spread by splashing rain or air currents to new potato plants (F1 and a). In Bangladesh, the infection of late blight was first reported in 1922. There is brownish discoloration of the skin of those parts of the tubers which lie nearest the surface of the soil. As the sporangium reaches maturity, the supporting hyphal branch immediately below it swells slightly and continues to grow turning the attached sporangium to the side. According to De Bary (1876), the mycelium overwinters in the infected tubers. Cool and moist nights are thus favourable for the formation and germination of zoospores. They are liberated in a group through terminal pore formed by rupture of the apical papilla. Do not mix seed lots because cutting can transmit late blight. It causes large losses in yields of potatoes and tomatoes, and requires the application of expensive fungicides to maintain control. Our editors will review what you’ve submitted and determine whether to revise the article. About Late Blight. Late blight of potato is a serious disease caused by Phytophthora infestans. Winter is the main potato growing season in India. This results in the reduced yield. Early b light is caused by two different closely related fungi, Alternaria tomatophila, and Alternaria solani, which lives in soil and plant debris. Dithane Z-78, and Dithane M-22 have proved more effective than the copper fungicides. The released zoospores have to move through soil to the infection sites. It is destructive to the crop grown in the rainy season. Phytophthora: Economic Importance and Occurrence | Oomycetes, Early Blight of Potato (With Diagram) | Plant Diseases, Defense Mechanism in Plants (With Diagram) | Botany. Hot dry weather checks its spread. Potato tubers develop rot up to 15 mm (0.6 inch) deep. Nevertheless, the disease has The disease occurs in humid regions with temperatures ranging between 4 and 29 °C (40 and 80 °F). According to the widely held view, the fungal parasite overwinters as a dormant mycelium in the infected tubers. Various methods of control of the disease are known. The germ tube after emergence usually ends in a terminal sporangium. Haverkort et al. Potato late blight is caused by the oomycete pathogen Phytophthora infestans (P. infestans). Late blight of potato can be managed up to some extent using cultural practices. These are carried by wind to the healthy plants which are thus infected. Above that temperature most sporangia produce a germ tube directly. The process is repeated. Late blight is one of the world's worst plant diseases, despite efforts to control it for more than 150 years. (i) Night temperature below dew point for 4 or more hours. The infected potato tubers are the primary source of inoculums for causing initial infection of late blight. Which organelle is known as “power house” of the cell? The released zoospores, after a brief period of activity in rain water or dew come to rest. Low temperature and high humidity favour the spread of the disease. Germination is influenced by moisture and temperature conditions. • Melhus (1915) confirmed De Bary’s observation. This article was most recently revised and updated by, https://www.britannica.com/science/late-blight. The infected tubers (A) are generally considered as the main source of primary infection in India. Each nodular swelling marks the point where the sporangium was borne. Under moist conditions they decay and emit a characteristic offensive odour. In case you were wondering, late blight is the plant disease that is responsible for the famous Irish potato famine of 1845. In this article we will discuss about the late blight of potato caused by fungi. Both fungicides inhibit sporangial and spore germination but has little effect on the mycelium in the leaf tissue. At temperatures below 15 °C (59 °F) sporangia germinate by producing zoospores (asexual spores with flagella) that encyst and later form a germ tube under certain temperature and humidity conditions. It may appear as well at any time during the growth period of the plant. They get separate infections while in the hill. Destruction or proper disposal of potato tuber refuge from pits and store houses IS another practical measure to reduce the incidence of disease. Mancozeb and Chlorothalonil are the major fungicides which are presently used. The late blight fungus is especially adapted for growth under conditions where water is present and cool temperatures persist. The germ tubes gain entrance through the eyes, wounds and lenticels. The disease can occur in the seedling stage and the adult stage. Storage of potato tubers in cold storage rooms reduces or even checks the progress of the rot. Late blight is a community disease, and effective management requires community management. It consists of sporangiophores and sporangia (Fig. The crops grown in the plains have been usually free from the epidemics of late blight because the chief predisposing factors (temperature and moisture) that render potato plants susceptible to disease are absent during the period of their growth. LATE BLIGHT OF POTATO 1. 4. The severity of late blight infection is governed by environmental conditions. 22.5). (2009) estimated that the global costs and losses due to late blight may take 16% of all global potato production. Late potato blight – sometimes just called potato blight – is a disease that can appear almost overnight and may decimate a potato crop. This disease is not known to occur in Western Australia. Dusting is done in the morning when the plants are wet with dew. The spraying should start when the plants are 8 inches tail. It can infect and destroy the leaves, stems, fruits, and tubers of potato and tomato plants. In cool and dry conditions the progress of the disease is slower and the wet rot phase is generally checked. The thin-walled, ovoid or lemon-shaped sporangia, each with an apiculate tip, are borne singly at the tips of sporangiophores or their branches. Firstly, by contact freshly lifted healthy and wounded tubers with diseased haulms and contaminated soil. COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po),ViaVaigai Dam, Theni-625 562 LATE BLIGHT OF POTATO Submitted by Course teacher Sandra Santhosh Dr.Parthasarathy.S 2015021112 Assistant Professor (Plant Pathology) Kaung (1956) stated that in the temperate regions the fungus perannates in soil in the form of sporangia and germ tubes. Disease is initiated by fungus spores or "inoculum" produced on the surface of living, infected plant tissue. The disease generally first attacks the leaves, and petioles near the ground and the lesions appear on the lower surface of the leaflets on individual plants and then spreads upwards. These are called clonal lineages and designated by a number code (i.e. Here are methods to help control the disease: 1. Share Your PPT File. A number of such forecasting services are maintained at universities and governmental organizations across the world. It should continue until the harvest time at 10 days’ interval. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? In Uganda, where about 300,000 smallholder farmers grow potatoes, the disease can destroy as much as 60-100% of the crop. •The current recommendation is not to store potatoes if more than 5% late blight or other tuber rots are present. The disease can be managed with a timely application of fungicide, though epidemics can occur rapidly once crops are infected. It is worldwide in its distribution. The process is repeated. In other California potato-growing areas its occurrence is sporadic, depending on the presence of the pathogen and cool, damp weather conditions. The best method of control is the timely and repeated foliage spray schedule with copper fungicides such as Perenox, Blitox-50 and Fytolan. Early detection and reporting of late blight will help protect the Western Australian potato … When the late blight occurs, the plants often die in the short term. The blighted leaves curl and shrivel in dry weather. Potato or tomato plants that are infected may rot within two weeks. Rowe, ed. The disease occurs in humid regions with temperatures ranging between 4 and 29 °C (40 and 80 °F). The released zoospores invade the healthy sprouts and bring about infection. 8. Content Guidelines 2. Each retracts its flagella and secretes a wall around it. It is worldwide in its distribution. Late blight (Phytophthora infestans) is considered the most devastating disease of potatoes worldwide and caused the Irish potato famine in the 1840s. Growing these will provide an increasing opportunity to combat the disease. It affect s all potato producers (small-scale, commercial, seed producers, even urban producers) and the annual losses in developing countries are estimated at EUR 10 billion. Potato blight is caused by a fungus, of which there are two different types – Alternaria solani in Early potato blight and Phytophthora infestans in Late potato blight. Late Blight. infestans produces sporangia and sporangiophores on the surface of infected tissue and the resulting white sporulation can be seen at the margins of lesions o As a result the disease spreads during the growing season over large tracts under potato cultivation. Among these were the European corn…, The devastating outbreak of late blight of potato (caused by the water mold, …crop failures were caused by late blight, a disease that destroys both the leaves and the edible roots, or tubers, of the potato plant. What is its function? De Bruyn (1926) opined that the fungus overwinters in the soil but this remains unconfirmed. Late blight occurs commonly in coastal environments and in the southern San Joaquin Valley in California. The American Phytopathological Society (APS) 3340 Pilot Knob Road St. Paul, MN 55121 USA . Avoidance of injuries to tubers at harvest is also important. Late blight caused by Phytophthora infestans is one of the most dreaded diseases of potato worldwide and cause significant loss in production. Let us know if you have suggestions to improve this article (requires login). Name the types of nitrogenous bases present in the RNA. It occurs in potato growing areas of the world. Our latest episode for parents features the topic of empathy. 7. The causal organism is Phytophthora infestans (Mont.) De Bary. There are many different strains of P. infestans. They expand rapidly and produce white fungi growth in wet conditions. This measure will eliminate direct infection. Share Your PDF File According to some, the sexual phase seems to play no role in the life history of the pathogen. It grows and ramifies in the intercellular spaces absorbing nutrition by putting haustoria into the host cells (D). 3. Some people claim that dusting the foliage with copper-lime dust is a more effective control measure. A potato infected with late blight, showing typical rot symptoms The proximate cause of the famine was a natural event, a potato blight, which infected potato crops throughout Europe during the 1840s, also causing some 100,000 deaths outside Ireland and influencing much of the unrest in the widespread European Revolutions of 1848. The disease is also destructive to tomatoes. It affects potato, tomato and, occasionally, eggplant and other members of the potato family. Before use they should be washed. This constitutes secondary infection. Pages 141-147 in: Potato Health Management. What are the general characters of bryophytes? Resistance alone has not effectively checked the disease. The contents of the latter divide to form zoospores. The late blight epidemics are thus rare in the plains in India. The host range is typically limited to potato and tomato… Plant late blight-free seed tubers. The disease makes its appearance as small, dead, brownish to purplish black areas or lesions. It directly puts out a germ tube or infection thread (Fb). Late blight is the worst potato disease. The temperature is high for the development of the disease. Foliage blighting and a new crop of sporangia are produced within four to six days after infection. The disease spreads quickly when cool and wet nights alternate with warm moist days. Cornell University - Integrated Pest Management - What is Late Blight. Oomycetes are fungus-like organisms also called water molds, but they are not true fungi. A fertile branch or sporangiophore is thus characterised by 9 or 10 such swellings occurring at intervals. The optimum temperature for the formation of zoospore is 12ºC (54°F). The pathogen is best known for causing the devastating Irish potato famine of the 1840s, which killed over a million people, and caused another million to leave the country. The pathogen ( Phyhtophthora infestans ) have different mechanisms of survival and two infection phases in its life cycle. Both sexual oospores and asexual sporangia are dispersed by the wind to nearby plants, in which infection may occur within a few hours. late blight •Leave infected tubers in the field as long as possible so they will decay or show signs of infection and will be easier to remove. Late blight of potatoes and tomatoes, the disease that was responsible for the Irish potato famine in the mid-nineteenth century, is caused by the fungus-like oomycete pathogen Phytophthora infestans. Under suitable conditions of temperature and humidity, the mycelium pushes out hyahne, branched, indeterminate sporangiophores through the stomata of the host leaves (E). The tubers get separate infections (G). It was first reported in the 1830s in Europe and in the US. These appear on the tips and margins of the leaflets, rachis, petiole and stem. The zoospores germinate rapidly at 12° to 15°C. Destroy all cull and volunteer potatoes. 2. It occurs in potato growing areas of the world. (iv) Rainfall during next 24 hours, at least 0.1 mm. Disclaimer Copyright, Share Your Knowledge Welcome to BiologyDiscussion! It is more common in moist, cool environments. The sporangia serve to spread the disease in the growing season. Temperatures ranging from approximately 50 to mid 90s oF will enable disease progression in the field (Franc et al., 1996). Late Blight is caused by the fungus Phytophthora infestans. Resistant tomato and potato varieties have been developed. American Phytopathological Society Press, St. Paul, MN. Phytophthora survives in stored tubers, dump piles, field plants, and greenhouse tomatoes. It affects both potato foliage in the field and tuber in the storage which can absolutely destroy a crop, producing a 100% crop loss. Late blight is caused by the oomycete Phytophthora infestans. It is of common occurrence both in cold as well as in warm regions in India and abroad where, potatoes and tomatoes are grown. When plants have become infected, lesions (round or irregularly shaped areas that range in colour from dark green to purplish black and resemble frost injury) appear on the leaves, petioles, and stems. Potato and tomato blight (late blight) is a disease caused by a fungus-like organism that spreads rapidly in the foliage and tubers or fruit of potatoes and tomatoes in wet weather, causing collapse and decay. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. The infected sprouts emerge above ground and produce shoots which contain the mycelium (C). Late blight. The sexual phase seems to play no significant role in the life history of the pathogen. The activated mycelium invades the healthy sprouts (B). The damage caused by the disease is frequently very high. Under dry and warmer conditions no zoospores are formed. Introduction to the Late Blight of Potato: Late blight is a serious fungal disease of potatoes. Winter is the main potato growing season in India. Symptoms on Leaves 1) Late Blight appears on potato or tomato leaves as pale green, water soaked spots often beginning at leaf tips or edges. Secondary fungi and bacteria (particularly Erwinia species) often invade potato tubers and produce rotting that results in great losses during storage, transit, and marketing. Omissions? Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. (b) Spread of the Disease (Secondary Infection): The infection thread produced on the surface of the host leaf in either of the two above-mentioned methods enters the host tissue (leaves or stem). At the planting time, the resting oospore germinates. What is a mushroom shaped gland? This requires strict seed tuber inspection at the cutting time. The causative agent of late blight is the water mold. The Great Famine in Ireland in the mid-19th century was caused by late blight of the potato plant. The scientific name of late blight is Phytophthora infestans, appropriately named for its terrible habits. Primarily a disease of potatoes and tomatoes, late blight may affect other members of the Solanaceae family as well. The clothed zoospores (cyst) then germinates by pushing out a germ tube or infection thread (F4). Symptoms of Late Blight of Potato. The second view is that the thick-walled resting oospores which are found in abundance in the infected tubers are the important overwintering structures. Botany, Plant Pathology, Potato, Late Blight of Potato. Under moist conditions hyaline mycelial hyphae and sporangiophores push out through the lenticels and appear on the surface of infected tubers. Mistiming of sprays may have serious consequences for late blight control in N.E.U.S.A. Where are the pollen grains formed in the flower? Given that the oospores have thickened walls and are able to persist in the soil for several seasons, the disease can be difficult to eradicate. Both the surfaces of foliage should be properly protected by adequate spraying delivered with a considerable force in the form of fine mist. The seed tubers should be free from the disease. Late blight, also called potato blight, disease of potato and tomato plants that is caused by the water mold Phytophthora infestans. The lower surface of the leaf is more susceptible than the upper. Use a seed piece fungicide treatment labeled for control of late blight (current list of fungicides can be found in the NDSU … In cool humid areas killing of foliage a few days before harvest proves beneficial. Answer Now and help others. Considerable success has been achieved in the perfection of resistant varieties of potato at the potato breeding station, Simla. The indirect method of germination of sporangia by the formation of zoospores in a terrestrial late blight fungus is an instance of retention of an ancestral primitive character which was normally used by its aquatic ancestor. (iii) Mean cloudiness not below O.8°C on the next day. Under favourable conditions (low temperature and high humidity) the lesions rapidly increase in size involving the whole surface of the leaf. Examination of the lesions on the lower surface of the leaf on a dew morning reveals a delicate growth of the fungus parasite in the form of whitish powdery bloom. They form rudimentary haustoria in the host leaf cells but in the tubers the haustoria are more common and elaborate (club-shaped, hooked or spirally twisted). In severe cases of infection there is complete loss of the crop, Infection also results in the decay of tubers in the field and storage. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. The longer the zoospores continue to swim and greater their number, the greater are the chances of infection. What is the significance of transpiration? The conditioning factor is the favourable environment. It is followed by hot summer months in the plains. Finally, a rapid and general blighting of foliage occurs. Management of early blight and late blight. This chapter discusses the major potato diseases worldwide: late blight, early blight, wart, and powdery scab. The tubers should be dipped in 1: 1,000 mercuric chloride solution for 90 minutes before storage. The optimum temperature for this direct germination of sporangia is about 24° or ’25°C. Grosier (1934) who studied the biology of Phytophthora infestans reported that the sporangia are formed within a temperature range of 3° to 26°C with an optimum of 18° to 22°C. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. >potato blight that caused famine in Ireland in 1845 and some subsequent years and severe losses in many other parts of Europe and the United States. Moreover, the temperature during the day is never above 22°-23°C which is favourable for the appearance of disease. Updates? Severe damage to the foliage shortens the growing season (Fig. The survival of the fungus in the soil in the Indian climatic conditions in any form appears remote. It is a serious disease for potatoes and outdoor tomatoes, but … The most prominent initial signs of late blight are brown spots or disease spots on plant stems. For a gardener, there is very little that is more heartbreaking than pouring time, energy and money into a … Healthy Plants • Healthy World. The drought and high temperature kill the fungus in the soil. It is caused by zoospores produced in foliage lesions (blighted tops) or present in the contaminated soil. Late blight destroyed more than half of the tomato crop in the eastern United States in 1946, leading to the establishment of a blight-forecasting service in 1947. In the indirect germination the protoplasmic contents of sporangium divided to form a number of (usually 8) biflagellate zoospores (F3). Tuber infection is dependent on the germination of sporangia, release and motility of zoospores. Our mission is to provide an online platform to help students to share notes in Biology. Soft rot causes the stem to collapse quickly, turning into dark brown. A whitish growth of spore-producing structures may appear at the margin of the lesions on the underleaf surfaces. Privacy Policy3. Insects and fungi from Europe became serious pests in the United States, too. Get exclusive access to content from our 1768 First Edition with your subscription. This fungal disease is fostered by periods of cool, wet weather. Therefore the complete control of blight is accomplished by the application of protectant fungicides. Late blight is the major limiting factor to increase potato production. The disease first appears on the tops of the plants generally after the blossoming period but mostly in the month of January. The sporangium functions as a conidium (Fa). The mycelium is aseptate conenocytic, hyaline and branched. The germ tubes show rapid growth at 21°C . Other devastating late blight outbreaks have been reported around the world, causing food insecurity, hunger (International Potato Center 2007), and oftentimes crippling the local potato industry. 22.7 E) of the pathogen pushing out through the stomata. According to Sato (1979), wet cool soil promotes infection but wet warm soil lowers it because cool water at 16°C or below 12-14°C favours indirect germination of sporangia and prolongs motility of zoospores. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. US-23). Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Late blight, a plant disease caused by the water mold. These dry rot spots remain firm and extend to about half an inch below the surface. Secondly, during crop growth, the zoospores and sporangia washed down the stems into the soil by rain come in contact with the tubers. After infection they grow best at a slightly higher temperature. Many clonal lineages affect both tomato and potato, but some lineages are specific to one host or the other. Consequently the tubers remain small and reduced in weight. Corrections? April 1, 2019. Host Crops and Plants These are applied before infection for effective control in two ways namely by spraying or dusting as follows:-. Late blight disease—caused by Phytophthora infestans—is a major constraint for potato farmers, costing them an estimated USD 3-10 billion per year globally. Late blight is a serious fungal disease of potatoes. Late blight, also called potato blight, disease of potato and tomato plants that is caused by the water mold Phytophthora infestans. The elongation of the branch proceeds and a new sporangium is formed. During storage, the bacteria assist to set in the wet rot phase. LATE BLIGHT OF POTATO Late blight caused by Phytophthora infestans has historically been an important disease of potatoes and tomatoes worldwide. Roy and Das (1968) found Brestan 60, Dithane M-45 and Zineb useful for the control of late blight in Assam. They are produced in smaller numbers. Before sharing your knowledge on this site, please read the following pages: 1. Potato (Solanum tuberosum L.) is an important food and economic product in the world.Potato late blight, caused by Phytophthora infestans, is a devastating oomycete disease resulting in potato stem and leaf death, and tuber rot.In Europe in the late 1840s, the late blight caused the potato to collapse to trigger Irish great famine []. Hot dry weather checks its spread. In cool moist weather the sporangia function as zoosporangia (F1-3). (ii) Minimum temperature 10°C or slightly above. Late blight is the most destructive potato disease in the world. Late blight can attack many varieties of potatoes and most farmers use large quantities of fungicides to control this disease. The infected leaves produce another crop of sporangia. On reaching a suitable host (potato), the sporangia germinate on the leaves (F). Sporangia and zoospores come in contact with the tubers in two ways. It makes its entry occasionally through the stoma but more often it penetrates directly through the cuticle by a penetration hypha arising from an appresorium (F4). Share Your Word File Potato or tomato plants that are infected may rot within two weeks. The minimum relative humidity required is 91 percent with an optimum of 100 percent. Subsequent treatments should be done when accumulated rainfall is greater than 20 mm or risk value of the previous night is 8, and a blight unit threshold of 40 (susceptible cultivar), 45 (moderately susceptible cultivar) or 50 (moderately resistant cultivar) has been exceeded. The disease occurs annually in the cooler Himalayan regions extending from Assam to Kashmir at an altitude of 6,000 ft. or more as the crop is grown in the rainy season. Famine of 1845 in the short term blight can attack many varieties of potato and tomato… late epidemics... 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Are specific to one host or the other season ( Fig rapid and general visitors for exchanging articles answers. The american Phytopathological Society ( APS ) 3340 Pilot Knob Road St. Paul, MN characterised by 9 or such. Apical papilla blight is Phytophthora infestans ( P. infestans ) have different mechanisms of survival and infection. 1926 ) opined that the fungus in the soil in the soil are brown late blight of potato disease.