Infected seed tubers, tomato transplants, potato cull piles and/or other volunteer potatoes are ex… They are liberated in a group through terminal pore formed by rupture of the apical papilla. Potato or tomato plants that are infected may rot within two weeks. •The current recommendation is not to store potatoes if more than 5% late blight or other tuber rots are present. It occurs in potato growing areas of the world. 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. These are applied before infection for effective control in two ways namely by spraying or dusting as follows:-. The pathogen ( Phyhtophthora infestans ) have different mechanisms of survival and two infection phases in its life cycle. The clothed zoospores (cyst) then germinates by pushing out a germ tube or infection thread (F4). The zoospores germinate rapidly at 12° to 15°C. They are produced in smaller numbers. 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. Disease is initiated by fungus spores or "inoculum" produced on the surface of living, infected plant tissue. Late blight of potato can be managed up to some extent using cultural practices. Consequently the tubers remain small and reduced in weight. The conditioning factor is the favourable environment. It may appear as well at any time during the growth period of the plant. This chapter discusses the major potato diseases worldwide: late blight, early blight, wart, and powdery scab. Late blight is one of the world's worst plant diseases, despite efforts to control it for more than 150 years. This is accomplished by spraying with herbicides or flame throwers or by the use of mechanical vine beaters. Healthy Plants • Healthy World. The disease makes its appearance as small, dead, brownish to purplish black areas or lesions. Share Your PDF File 8. Storage of potato tubers in cold storage rooms reduces or even checks the progress of the rot. Introduction to the Late Blight of Potato: Late blight is a serious fungal disease of potatoes. Under dry and warmer conditions no zoospores are formed. Moreover, the temperature during the day is never above 22°-23°C which is favourable for the appearance of disease. (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. Destruction or proper disposal of potato tuber refuge from pits and store houses IS another practical measure to reduce the incidence of disease. Late blight is caused by the oomycete Phytophthora infestans. A fertile branch or sporangiophore is thus characterised by 9 or 10 such swellings occurring at intervals. The Great Famine in Ireland in the mid-19th century was caused by late blight of the potato plant. Share Your Word File It directly puts out a germ tube or infection thread (Fb). As a result the disease spreads during the growing season over large tracts under potato cultivation. Early b light is caused by two different closely related fungi, Alternaria tomatophila, and Alternaria solani, which lives in soil and plant debris. 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 American Phytopathological Society (APS) 3340 Pilot Knob Road St. Paul, MN 55121 USA . Early blight is a common foliage disease of potato and tomato. 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 infected leaves produce another crop of sporangia. The causal organism is Phytophthora infestans (Mont.) Secondly, during crop growth, the zoospores and sporangia washed down the stems into the soil by rain come in contact with the tubers. This fungal disease is fostered by periods of cool, wet weather. 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. 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. It can infect and destroy the leaves, stems, fruits, and tubers of potato and tomato plants. The minimum relative humidity required is 91 percent with an optimum of 100 percent. Share Your PPT File. The drought and high temperature kill the fungus in the soil. The disease occurs in humid regions with temperatures ranging between 4 and 29 °C (40 and 80 °F). Late blight, also called potato blight, disease of potato and tomato plants that is caused by the water mold Phytophthora infestans. 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. Under favourable conditions (low temperature and high humidity) the lesions rapidly increase in size involving the whole surface of the leaf. Late potato blight – sometimes just called potato blight – is a disease that can appear almost overnight and may decimate a potato crop. 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. The process is repeated. Under moist conditions hyaline mycelial hyphae and sporangiophores push out through the lenticels and appear on the surface of infected tubers. This constitutes secondary infection. 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. Late blight, also called potato blight, disease of potato and tomato plants that is caused by the water mold Phytophthora infestans. 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 survival of the fungus in the soil in the Indian climatic conditions in any form appears remote. Updates? Both sexual oospores and asexual sporangia are dispersed by the wind to nearby plants, in which infection may occur within a few hours. The disease is also destructive to tomatoes. The disease first appears on the tops of the plants generally after the blossoming period but mostly in the month of January. 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). Host Crops and Plants Soft rot causes the stem to collapse quickly, turning into dark brown. These dry rot spots remain firm and extend to about half an inch below the surface. A whitish growth of spore-producing structures may appear at the margin of the lesions on the underleaf surfaces. The causative agent of late blight is the water mold. LATE BLIGHT OF POTATO 1. It affects both potato foliage in the field and tuber in the storage which can absolutely destroy a crop, producing a 100% crop loss. Winter is the main potato growing season in India. It should continue until the harvest time at 10 days’ interval. In the indirect germination the protoplasmic contents of sporangium divided to form a number of (usually 8) biflagellate zoospores (F3). They play a significant role as the source of primary infection. Privacy Policy3. 22.7 E) of the pathogen pushing out through the stomata. The infected tubers (A) are generally considered as the main source of primary infection in India. >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. 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). Symptoms of Late Blight of Potato. Hot dry weather checks its spread. In other California potato-growing areas its occurrence is sporadic, depending on the presence of the pathogen and cool, damp weather conditions. 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 []. 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. The tubers get separate infections (G). It is followed by hot summer months in the plains. The activated mycelium invades the healthy sprouts (B). In cool moist weather the sporangia function as zoosporangia (F1-3). Winter is the main potato growing season in India. The mycelium is aseptate conenocytic, hyaline and branched. The disease can occur in the seedling stage and the adult stage. The germ tube after emergence usually ends in a terminal sporangium. 2. Do not mix seed lots because cutting can transmit late blight. Sporangia and zoospores come in contact with the tubers in two ways. Hot dry weather checks its spread. Where are the pollen grains formed in the flower? Considerable success has been achieved in the perfection of resistant varieties of potato at the potato breeding station, Simla. Use a seed piece fungicide treatment labeled for control of late blight (current list of fungicides can be found in the NDSU … (iv) Rainfall during next 24 hours, at least 0.1 mm. In cool and dry conditions the progress of the disease is slower and the wet rot phase is generally checked. 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. Name the types of nitrogenous bases present in the RNA. Secondary fungi and bacteria (particularly Erwinia species) often invade potato tubers and produce rotting that results in great losses during storage, transit, and marketing. Each nodular swelling marks the point where the sporangium was borne. Disclaimer Copyright, Share Your Knowledge The most prominent initial signs of late blight are brown spots or disease spots on plant stems. There is brownish discoloration of the skin of those parts of the tubers which lie nearest the surface of the soil. It is more common in moist, cool environments. Content Guidelines 2. It is of common occurrence both in cold as well as in warm regions in India and abroad where, potatoes and tomatoes are grown. • The germ tubes show rapid growth at 21°C . 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. The blighted leaves curl and shrivel in dry weather. (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). Resistance alone has not effectively checked the disease. 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. 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 Tuber infection is dependent on the germination of sporangia, release and motility of zoospores. Late blight is the most destructive of all potato disease and responsible for the Irish Famine in the middle of the 19 th century. Under suitable conditions of temperature and humidity, the mycelium pushes out hyahne, branched, indeterminate sporangiophores through the stomata of the host leaves (E). American Phytopathological Society Press, St. Paul, MN. Low temperature and high humidity favour the spread of the disease. Late blight is a serious fungal disease of potatoes. 7. This measure will eliminate direct infection. 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. After infection they grow best at a slightly higher temperature. It causes large losses in yields of potatoes and tomatoes, and requires the application of expensive fungicides to maintain control. The elongation of the branch proceeds and a new sporangium is formed. Above that temperature most sporangia produce a germ tube directly. Pages 141-147 in: Potato Health Management. The released zoospores, after a brief period of activity in rain water or dew come to rest. The second view is that the thick-walled resting oospores which are found in abundance in the infected tubers are the important overwintering structures. The sexual phase seems to play no significant role in the life history of the pathogen. Effective control of this disease requires implementation of an integrated disease management approach. April 1, 2019. Primarily a disease of potatoes and tomatoes, late blight may affect other members of the Solanaceae family as well. 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) Therefore the complete control of blight is accomplished by the application of protectant fungicides. Late blight of potato is a serious disease caused by Phytophthora infestans. In India, losses are more in hilly regions where the crop is grown under rain-fed conditions as compared to the plains. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. This requires strict seed tuber inspection at the cutting time. It is caused by zoospores produced in foliage lesions (blighted tops) or present in the contaminated soil. In Uganda, where about 300,000 smallholder farmers grow potatoes, the disease can destroy as much as 60-100% of the crop. In this article we will discuss about the late blight of potato caused by fungi. R.C. Botany, Plant Pathology, Potato, Late Blight of Potato. Germination is influenced by moisture and temperature conditions. 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. (2009) estimated that the global costs and losses due to late blight may take 16% of all global potato production. What are the general characters of bryophytes? Late Blight. 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 is the major limiting factor to increase potato production. Plant late blight-free seed tubers. Late blight can attack many varieties of potatoes and most farmers use large quantities of fungicides to control this disease. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Late blight is a fungus called Phytophthora infestans, which affects tomatoes and potatoes. What is a mushroom shaped gland? The process is repeated. Insects and fungi from Europe became serious pests in the United States, too. Let us know if you have suggestions to improve this article (requires login). This results in the reduced yield. Late blight occurs commonly in coastal environments and in the southern San Joaquin Valley in California. The spraying should start when the plants are 8 inches tail. In cool humid areas killing of foliage a few days before harvest proves beneficial. The released zoospores invade the healthy sprouts and bring about infection. It consists of sporangiophores and sporangia (Fig. The severity of late blight infection is governed by environmental conditions. Severe damage to the foliage shortens the growing season (Fig. There are many different strains of P. infestans. In Bangladesh, the infection of late blight was first reported in 1922. 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. Rowe, ed. What is its function? 4. It grows and ramifies in the intercellular spaces absorbing nutrition by putting haustoria into the host cells (D). The germ tubes gain entrance through the eyes, wounds and lenticels. Our editors will review what you’ve submitted and determine whether to revise the article. Both the surfaces of foliage should be properly protected by adequate spraying delivered with a considerable force in the form of fine mist. Cool and moist nights are thus favourable for the formation and germination of zoospores. These are carried by wind to the healthy plants which are thus infected. The temperature is high for the development of the disease. 1. These are called clonal lineages and designated by a number code (i.e. Oomycetes are fungus-like organisms also called water molds, but they are not true fungi. The mature sporangia are readily detached and spread by splashing rain or air currents to new potato plants (F1 and a). It is a serious disease for potatoes and outdoor tomatoes, but … Now it has established itself in the Indo- Gangetic plain and occurs annually in the states of Punjab, Uttar Pradesh, Bihar, and W. Bengal. It was first reported in the 1830s in Europe and in the US. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Late blight of potatoes is caused by the pathogen Phytophthora infestans. A number of such forecasting services are maintained at universities and governmental organizations across the world. Our mission is to provide an online platform to help students to share notes in Biology. Once infected, the whole plant may quickly collapse and what appear to be healthy tubers may rot in storage. Get exclusive access to content from our 1768 First Edition with your subscription. What is the significance of transpiration? Welcome to BiologyDiscussion! 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. The best method of control is the timely and repeated foliage spray schedule with copper fungicides such as Perenox, Blitox-50 and Fytolan. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? 3. Destroy all cull and volunteer potatoes. According to the widely held view, the fungal parasite overwinters as a dormant mycelium in the infected tubers. Finally, a rapid and general blighting of foliage occurs. Haverkort et al. In case you were wondering, late blight is the plant disease that is responsible for the famous Irish potato famine of 1845. Melhus (1915) confirmed De Bary’s observation. Mistiming of sprays may have serious consequences for late blight control in N.E.U.S.A. Potato late blight is caused by the oomycete pathogen Phytophthora infestans (P. infestans). 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. LATE BLIGHT OF POTATO Late blight caused by Phytophthora infestans has historically been an important disease of potatoes and tomatoes worldwide. 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. 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). The contents of the latter divide to form zoospores. De Bary. The scientific name of late blight is Phytophthora infestans, appropriately named for its terrible habits. Introduction. This article was most recently revised and updated by, https://www.britannica.com/science/late-blight. The tubers should be dipped in 1: 1,000 mercuric chloride solution for 90 minutes before storage. Late blight (Phytophthora infestans) is considered the most devastating disease of potatoes worldwide and caused the Irish potato famine in the 1840s. Some people claim that dusting the foliage with copper-lime dust is a more effective control measure. Late blight is the most destructive potato disease in the world. The optimum temperature for the formation of zoospore is 12ºC (54°F). Answer Now and help others. Mancozeb and Chlorothalonil are the major fungicides which are presently used. For a gardener, there is very little that is more heartbreaking than pouring time, energy and money into a … 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. Corrections? The lower surface of the leaf is more susceptible than the upper. At the planting time, the resting oospore germinates. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. 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 disease spreads quickly when cool and wet nights alternate with warm moist days. 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. It is destructive to the crop grown in the rainy season. 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. Kaung (1956) stated that in the temperate regions the fungus perannates in soil in the form of sporangia and germ tubes. The infected sprouts emerge above ground and produce shoots which contain the mycelium (C). Before use they should be washed. Cornell University - Integrated Pest Management - What is Late Blight. It affects potato, tomato and, occasionally, eggplant and other members of the potato family. Late blight is a community disease, and effective management requires community management. Resistant tomato and potato varieties have been developed. The longer the zoospores continue to swim and greater their number, the greater are the chances of infection. It is worldwide in its distribution. On reaching a suitable host (potato), the sporangia germinate on the leaves (F). TOS4. The late blight epidemics are thus rare in the plains in India. The late blight fungus is especially adapted for growth under conditions where water is present and cool temperatures persist. About Late Blight. US-23). Phytophthora: Economic Importance and Occurrence | Oomycetes, Early Blight of Potato (With Diagram) | Plant Diseases, Defense Mechanism in Plants (With Diagram) | Botany. Here are methods to help control the disease: 1. De Bruyn (1926) opined that the fungus overwinters in the soil but this remains unconfirmed. It affects leaves and stems as well as tubers. Management of early blight and late blight. It occurs in potato growing areas of the world. 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. The released zoospores have to move through soil to the infection sites. Which organelle is known as “power house” of the cell? Potato or tomato plants that are infected may rot within two weeks. Early detection and reporting of late blight will help protect the Western Australian potato … 22.5). Potato tubers develop rot up to 15 mm (0.6 inch) deep. The damage caused by the disease is frequently very high. Many clonal lineages affect both tomato and potato, but some lineages are specific to one host or the other. Nevertheless, the disease has 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. Omissions? Various methods of control of the disease are known. According to some, the sexual phase seems to play no role in the life history of the pathogen. They expand rapidly and produce white fungi growth in wet conditions. Our latest episode for parents features the topic of empathy. Potato tubers are often infected in the field after the tops have been blighted. The optimum temperature for this direct germination of sporangia is about 24° or ’25°C. It is worldwide in its distribution. Avoidance of injuries to tubers at harvest is also important. They get separate infections while in the hill. During storage, the bacteria assist to set in the wet rot phase. Each retracts its flagella and secretes a wall around it. Foliage blighting and a new crop of sporangia are produced within four to six days after infection. Roy and Das (1968) found Brestan 60, Dithane M-45 and Zineb useful for the control of late blight in Assam. Firstly, by contact freshly lifted healthy and wounded tubers with diseased haulms and contaminated soil. The hyphae are both intercellular and intracellular. This disease is not known to occur in Western Australia. These appear on the tips and margins of the leaflets, rachis, petiole and stem. The disease can be managed with a timely application of fungicide, though epidemics can occur rapidly once crops are infected. €¦ late blight is a community disease, and effective management requires community management sporangia serve to spread disease! Overnight and may decimate a potato crop in yields of potatoes and tomatoes, and greenhouse tomatoes thread! In Biology essays, articles and other allied information submitted by visitors like.... A timely application of protectant fungicides injuries to tubers at harvest is also important infection in India ``! Its flagella and secretes a wall around it the germ tubes gain entrance through the stomata which tomatoes... Mycelium invades the healthy sprouts and bring about infection rot phase tubers remain small and reduced in weight of. 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