Late blight can attack many varieties of potatoes and most farmers use large quantities of fungicides to control this disease. Share Your Word File The disease can be managed with a timely application of fungicide, though epidemics can occur rapidly once crops are infected. Mancozeb and Chlorothalonil are the major fungicides which are presently used. At the planting time, the resting oospore germinates. It can infect and destroy the leaves, stems, fruits, and tubers of potato and tomato plants. Storage of potato tubers in cold storage rooms reduces or even checks the progress of the rot. 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. Consequently the tubers remain small and reduced in weight. 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. There are many different strains of P. infestans. The seed tubers should be free from the disease. The zoospores germinate rapidly at 12° to 15°C. The contents of the latter divide to form zoospores. The germ tube after emergence usually ends in a terminal sporangium. It is destructive to the crop grown in the rainy season. When the late blight occurs, the plants often die in the short term. Avoidance of injuries to tubers at harvest is also important. Under moist conditions they decay and emit a characteristic offensive odour. 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. Host Crops and Plants For a gardener, there is very little that is more heartbreaking than pouring time, energy and money into a … US-23). Late blight is the worst potato disease. A whitish growth of spore-producing structures may appear at the margin of the lesions on the underleaf surfaces. Destroy all cull and volunteer potatoes. The elongation of the branch proceeds and a new sporangium is formed. Severe damage to the foliage shortens the growing season (Fig. The infected potato tubers are the primary source of inoculums for causing initial infection of late blight. Share Your PPT File. Here are methods to help control the disease: 1. LATE BLIGHT OF POTATO 1. It is followed by hot summer months in the plains. Let us know if you have suggestions to improve this article (requires login). Late blight is a community disease, and effective management requires community management. The survival of the fungus in the soil in the Indian climatic conditions in any form appears remote. Which organelle is known as “power house” of the cell? Symptoms of Late Blight of Potato. 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. Late potato blight – sometimes just called potato blight – is a disease that can appear almost overnight and may decimate a potato crop. Late blight, also called potato blight, disease of potato and tomato plants that is caused by the water mold Phytophthora infestans. Disclaimer Copyright, Share Your Knowledge Use a seed piece fungicide treatment labeled for control of late blight (current list of fungicides can be found in the NDSU … >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. In other California potato-growing areas its occurrence is sporadic, depending on the presence of the pathogen and cool, damp weather conditions. These are applied before infection for effective control in two ways namely by spraying or dusting as follows:-. The infected tubers (A) are generally considered as the main source of primary infection in India. 3. Potato tubers are often infected in the field after the tops have been blighted. (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). De Bruyn (1926) opined that the fungus overwinters in the soil but this remains unconfirmed. According to De Bary (1876), the mycelium overwinters in the infected tubers. Plant late blight-free seed tubers. Some people claim that dusting the foliage with copper-lime dust is a more effective control measure. A fertile branch or sporangiophore is thus characterised by 9 or 10 such swellings occurring at intervals. This fungal disease is fostered by periods of cool, wet weather. De Bary. Resistance alone has not effectively checked the disease. The minimum relative humidity required is 91 percent with an optimum of 100 percent. Each retracts its flagella and secretes a wall around it. The thin-walled, ovoid or lemon-shaped sporangia, each with an apiculate tip, are borne singly at the tips of sporangiophores or their branches. The tubers get separate infections (G). Secondary fungi and bacteria (particularly Erwinia species) often invade potato tubers and produce rotting that results in great losses during storage, transit, and marketing. Therefore the complete control of blight is accomplished by the application of protectant fungicides. Management of early blight and late blight. Potato or tomato plants that are infected may rot within two weeks. 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. The sporangium functions as a conidium (Fa). Late blight is the most destructive of all potato disease and responsible for the Irish Famine in the middle of the 19 th century. This is accomplished by spraying with herbicides or flame throwers or by the use of mechanical vine beaters. 1. The hyphae are both intercellular and intracellular. 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) 22.7 E) of the pathogen pushing out through the stomata. Roy and Das (1968) found Brestan 60, Dithane M-45 and Zineb useful for the control of late blight in Assam. The temperature is high for the development of the disease. 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 Melhus (1915) confirmed De Bary’s observation. This article was most recently revised and updated by, https://www.britannica.com/science/late-blight. A number of such forecasting services are maintained at universities and governmental organizations across the world. On reaching a suitable host (potato), the sporangia germinate on the leaves (F). The disease first appears on the tops of the plants generally after the blossoming period but mostly in the month of January. There are two different types of blight that are commonly known to have a big impact on potatoes, early blight, caused by Alternaria solani, and late blight, which was the cause of the famine and what this article focuses on. Late blight is the most destructive potato disease in the world. 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). The disease is also destructive to tomatoes. In Uganda, where about 300,000 smallholder farmers grow potatoes, the disease can destroy as much as 60-100% of the crop. Resistant tomato and potato varieties have been developed. The released zoospores have to move through soil to the infection sites. 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. It may appear as well at any time during the growth period of the plant. Growing these will provide an increasing opportunity to combat the disease. 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. Mistiming of sprays may have serious consequences for late blight control in N.E.U.S.A. 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. Updates? The germ tubes gain entrance through the eyes, wounds and lenticels. As a result the disease spreads during the growing season over large tracts under potato cultivation. 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. Tuber infection is dependent on the germination of sporangia, release and motility of zoospores. 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. Corrections? Secondly, during crop growth, the zoospores and sporangia washed down the stems into the soil by rain come in contact with the tubers. It is more common in moist, cool environments. In the indirect germination the protoplasmic contents of sporangium divided to form a number of (usually 8) biflagellate zoospores (F3). Introduction. This disease is not known to occur in Western Australia. 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. Cornell University - Integrated Pest Management - What is Late Blight. In India, losses are more in hilly regions where the crop is grown under rain-fed conditions as compared to the plains. They expand rapidly and produce white fungi growth in wet conditions. 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. Get exclusive access to content from our 1768 First Edition with your subscription. 8. The cycle is repeated as long as cool moist weather prevails. Under suitable conditions of temperature and humidity, the mycelium pushes out hyahne, branched, indeterminate sporangiophores through the stomata of the host leaves (E). These dry rot spots remain firm and extend to about half an inch below the surface. The disease spreads quickly when cool and wet nights alternate with warm moist days. April 1, 2019. It is worldwide in its distribution. During storage, the bacteria assist to set in the wet rot phase. It occurs in potato growing areas of the world. 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. Under dry and warmer conditions no zoospores are formed. 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. Considerable success has been achieved in the perfection of resistant varieties of potato at the potato breeding station, Simla. It affects potato, tomato and, occasionally, eggplant and other members of the potato family. Once infected, the whole plant may quickly collapse and what appear to be healthy tubers may rot in storage. Many clonal lineages affect both tomato and potato, but some lineages are specific to one host or the other. In cool humid areas killing of foliage a few days before harvest proves beneficial. The late blight epidemics are thus rare in the plains in India. After infection they grow best at a slightly higher temperature. The germ tubes show rapid growth at 21°C . 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. Potato late blight is caused by the oomycete pathogen Phytophthora infestans (P. infestans). Temperatures ranging from approximately 50 to mid 90s oF will enable disease progression in the field (Franc et al., 1996). Healthy Plants • Healthy World. What is the significance of transpiration? 4. The sexual phase seems to play no significant role in the life history of the pathogen. Both the surfaces of foliage should be properly protected by adequate spraying delivered with a considerable force in the form of fine mist. This chapter discusses the major potato diseases worldwide: late blight, early blight, wart, and powdery scab. Germination is influenced by moisture and temperature conditions. Hot dry weather checks its spread. The lower surface of the leaf is more susceptible than the upper. The scientific name of late blight is Phytophthora infestans, appropriately named for its terrible habits. R.C. In case you were wondering, late blight is the plant disease that is responsible for the famous Irish potato famine of 1845. Disease is initiated by fungus spores or "inoculum" produced on the surface of living, infected plant tissue. Name the types of nitrogenous bases present in the RNA. The disease occurs in humid regions with temperatures ranging between 4 and 29 °C (40 and 80 °F). It is caused by zoospores produced in foliage lesions (blighted tops) or present in the contaminated soil. The damage caused by the disease is frequently very high. In this article we will discuss about the late blight of potato caused by fungi. They get separate infections while in the hill. (iv) Rainfall during next 24 hours, at least 0.1 mm. It consists of sporangiophores and sporangia (Fig. 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. These appear on the tips and margins of the leaflets, rachis, petiole and stem. Under moist conditions hyaline mycelial hyphae and sporangiophores push out through the lenticels and appear on the surface of infected tubers. Late blight is one of the world's worst plant diseases, despite efforts to control it for more than 150 years. The drought and high temperature kill the fungus in the soil. It should continue until the harvest time at 10 days’ interval. Nevertheless, the disease has Late blight occurs commonly in coastal environments and in the southern San Joaquin Valley in California. Late blight is the major limiting factor to increase potato production. Now it has established itself in the Indo- Gangetic plain and occurs annually in the states of Punjab, Uttar Pradesh, Bihar, and W. Bengal. There is brownish discoloration of the skin of those parts of the tubers which lie nearest the surface of the soil. Firstly, by contact freshly lifted healthy and wounded tubers with diseased haulms and contaminated soil. 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. The American Phytopathological Society (APS) 3340 Pilot Knob Road St. Paul, MN 55121 USA . Late blight. It was first reported in the 1830s in Europe and in the US. 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. (ii) Minimum temperature 10°C or slightly above. In cool and dry conditions the progress of the disease is slower and the wet rot phase is generally checked. The mature sporangia are readily detached and spread by splashing rain or air currents to new potato plants (F1 and a). This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Hot dry weather checks its spread. The causal organism is Phytophthora infestans (Mont.) 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. Oomycetes are fungus-like organisms also called water molds, but they are not true fungi. 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. Finally, a rapid and general blighting of foliage occurs. Late blight caused by Phytophthora infestans is one of the most dreaded diseases of potato worldwide and cause significant loss in production. Late blight of potato can be managed up to some extent using cultural practices. 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. This results in the reduced yield. American Phytopathological Society Press, St. Paul, MN. The disease occurs in humid regions with temperatures ranging between 4 and 29 °C (40 and 80 °F). The pathogen ( Phyhtophthora infestans ) have different mechanisms of survival and two infection phases in its life cycle. (2009) estimated that the global costs and losses due to late blight may take 16% of all global potato production. 22.5). The activated mycelium invades the healthy sprouts (B). According to some, the sexual phase seems to play no role in the life history of the pathogen. The Great Famine in Ireland in the mid-19th century was caused by late blight of the potato plant. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? 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. (i) Night temperature below dew point for 4 or more hours. Insects and fungi from Europe became serious pests in the United States, too. Rowe, ed. 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). Botany, Plant Pathology, Potato, Late Blight of Potato. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Foliage blighting and a new crop of sporangia are produced within four to six days after infection. Soft rot causes the stem to collapse quickly, turning into dark brown. What is its function? (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. These are carried by wind to the healthy plants which are thus infected. The clothed zoospores (cyst) then germinates by pushing out a germ tube or infection thread (F4). The process is repeated. Late blight (Phytophthora infestans) is considered the most devastating disease of potatoes worldwide and caused the Irish potato famine in the 1840s. Our editors will review what you’ve submitted and determine whether to revise the article. Do not mix seed lots because cutting can transmit late blight. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. The mycelium is aseptate conenocytic, hyaline and branched. The spraying should start when the plants are 8 inches tail. Before sharing your knowledge on this site, please read the following pages: 1. Kaung (1956) stated that in the temperate regions the fungus perannates in soil in the form of sporangia and germ tubes. Primarily a disease of potatoes and tomatoes, late blight may affect other members of the Solanaceae family as well. Under favourable conditions (low temperature and high humidity) the lesions rapidly increase in size involving the whole surface of the leaf. Moreover, the temperature during the day is never above 22°-23°C which is favourable for the appearance of disease. • About Late Blight. The tubers should be dipped in 1: 1,000 mercuric chloride solution for 90 minutes before storage. These are called clonal lineages and designated by a number code (i.e. 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. They play a significant role as the source of primary infection. 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. Various methods of control of the disease are known. They are liberated in a group through terminal pore formed by rupture of the apical papilla. Low temperature and high humidity favour the spread of the disease. The conditioning factor is the favourable environment. Each nodular swelling marks the point where the sporangium was borne. What are the general characters of bryophytes? Our latest episode for parents features the topic of empathy. The late blight fungus is especially adapted for growth under conditions where water is present and cool temperatures persist. Cool and moist nights are thus favourable for the formation and germination of zoospores. TOS4. Late blight of potatoes is caused by the pathogen Phytophthora infestans. Haverkort et al. Late blight of potato is a serious disease caused by Phytophthora infestans. Dusting is done in the morning when the plants are wet with dew. The causative agent of late blight is the water mold. Phytophthora survives in stored tubers, dump piles, field plants, and greenhouse tomatoes. 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. 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 []. It grows and ramifies in the intercellular spaces absorbing nutrition by putting haustoria into the host cells (D). The most prominent initial signs of late blight are brown spots or disease spots on plant stems. The host range is typically limited to potato and tomato… The process is repeated. The second view is that the thick-walled resting oospores which are found in abundance in the infected tubers are the important overwintering structures. 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. It is worldwide in its distribution. Phytophthora: Economic Importance and Occurrence | Oomycetes, Early Blight of Potato (With Diagram) | Plant Diseases, Defense Mechanism in Plants (With Diagram) | Botany. Introduction to the Late Blight of Potato: Late blight is a serious fungal disease of potatoes. 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. Where are the pollen grains formed in the flower? The infected leaves produce another crop of sporangia. Infected plants may be killed off within a couple of weeks from infection. LATE BLIGHT OF POTATO Late blight caused by Phytophthora infestans has historically been an important disease of potatoes and tomatoes worldwide. 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