The Southern corn leaf blight (SCLB) epidemic of 1970 devastated fields of T-cytoplasm corn planted in monoculture throughout the eastern United States. Leaf diseases of corn in Iowa in 1990 were probably the most severe since the 1970 epidemic of Southern corn leaf blight. Forty years ago, the Southern Corn Leaf Blight (SCLB) Epidemic, ravaged cornfields across the United States. No credit card required. The first lesson we learned as a result of this disease outbreak was the importance of diversifying agriculture and maintaining an adequate degree of genetic variation in major crops. A widespread epidemic caused by a new race (race T) of the southern corn leaf blight fungus occurred suddenly in 1970 on all corn hybrids containing the Texas cytoplasmic male sterility gene (used for efficient crossing and production of corn hybrids) and destroyed about 15% of all corn produced in the United States that year. No further disease outbreaks of a similar nature have occurred in corn production since that season of 1970. Foliar Fungal Diseases. It took a perfect storm of favorable conditions in 1970 for us to finally experience the worst case scenario. One was the Southern corn leaf blight epidemic of 1970 and the concern about its return in 1971. The finding of symptoms on ears was the first indication that something unusual was in the works (in the past C. heterostrophus had often been considered a foliar pathogen exclusively). 10:37-50 (Volume publication date ... Dothistroma Blight of Pinus Radiata I A S Gibson Annual Review of Phytopathology Some Properties and Taxonomic Sub-Divisions of … The short duration of the epidemic is one of the best examples of our discipline rising to the task of solving growers’ problems. By mid-July it was well established throughout the Corn Belt while also causing total crop failure in many fields in the South. Lim identified the toxin produced by the new strain of the fungus causing SCLB which allowed it to preferentially attack corn with the T source of cytoplasmic male sterility. Southern corn leaf blight (SCLB) was importance until 1970 when it caused an 15% of the U.S. corn crop with an estimated value of one billion dollars. This epidemic is considered by many to be the most economically devastating field crop disease of any developed area of … Southern corn leaf blight is caused by the fungus Bipolaris maydis, which primarily follows an asexual disease cycle. Jerald Pataky, U of I professor in the department of crop sciences, said this was a "shining moment" for Illinois. Ullstrup, A.J. The increased virulence was later demonstrated to be caused by a particular toxin (T-toxin) that only affected the T cytoplasm corn, while Race O did not produce the toxin and thus was not severe on either of the two types of corn. In 1970, almost 85% of US corn fields was planted with one type of corn, called Texas cytoplasmic male sterile (Tcms) corn. The southern corn leaf blight epidemic. This idea had been considered in the early 1900s but was abandoned due to projected seed costs. Southern corn leaf blight of corn. Our concern is with the effect of this disease, caused by the field fungus Hellllint!lOsjJoriulIl lIlaydis Nisik. Isolations of the pathogen made from stored corn in Iowa indicate its presence in that state to be at least as early as 1968. As a result of the findings explaining cause and effect for the SCLB epidemic of 1970, the demand for the normal cytoplasm greatly exceeded the supply for 1971. College of Agricultural, Consumer & Environmental Sciences. Fortunately the solution was obvious almost immediately to U of I researchers. Race T was unknown until the time of the epidemic, although race O, which does not produce T-toxin was discovered decades earlier. The 1970 SCLB epidemic stimulated rapid mobilization and teamwork among industry, federal, state and university research and extension personnel, spawning novel methods for disease monitoring and management. Tcms seedlings were severely affected while the normal cyctoplasm seedlings exhibited only mild symptoms of infection. During the spring months the pathogen continued a steady march into most of the major Corn Belt states in the eastern half of the United States. It is enlightening for us today to examine that one year (1970) and note that both the disease and pathogen caught lightning in a bottle. Lesions are tan, somewhat rectangular in shape, and have reddish-brown margins. What is Southern Corn Leaf Blight? Smith focused on the reproduction differences between the SCLB strains showing the new strain was much more aggressive than the old strain. The southern corn (Zea mays L.) leaf blight (SCLB) epidemic of 1970–1971 was one of the most costly disease outbreaks to affect North American agriculture, destroying 15% of the crop at a cost of US$1.0 billion (≥$6.0 billion by 2015 standards. The sudden and widespread appearance of the disease and the tremendous damage incurred was due to a number of confluent factors. The discovery of the cause of the epidemic and the solution — detasseling — was spearheaded by corn pathologists at the University of Illinois. That season the combination of the new physiologically specialized pathogenic race, favorable weather, and millions of acres of a uniform, susceptible host, created one of the most widely dispersed epidemics in history. This epidemic is considered by many to be the most economically devastating field crop disease of any developed area of the world during the 20th century. "Exploring the evolutionary history of the Cochliobolus heterostrophus Tox1 locus responsible for T-toxin production and the Southern Corn Leaf Blight Epidemic of 1970" - Jon Gonzalez Wednesday, May 1, 2019 at 12:20pm Plant Science Building, 404 Enjoy more articles by logging in or creating a free account. Its spores can be windblown to adjacent areas, surviving in dead plant tissues for several years. It was further noted that diversity of the genetic materials for breeding purposes must be maintained at both the genetic and cytoplasmic level for all important crop species to avoid being universally vulnerable to attack by pathogens, insects, or environmental stress. During that summer, the southern leaf blight epidemic reduced corn yields by 20 to 25 percent nationwide, resulting in an estimated $1 billion loss. However, using the Tcms gene was too successful at producing hybrid seed easily and inexpensively. "Ironically, our researchers already had solved the problem just as it was reaching the forefront of public interest," Pataky said. The Impacts of the Southern Corn Leaf Blight Epidemics of 1970-1971. The southern corn leaf blight (SCLB) epidemic of 1970, caused by Bipolaris maydis(Nisikado) Shoemaker, race T, decreased yield of maize (Zea maysL.) By the 1940s about 40 percent of the acreage was planted to hybrids with an average yield increasing to 35 bushels per acre. The potential for a disaster of this nature had been predicted by a number of scientists decades prior to the 1970 outbreak but no one paid attention to the warning signs. You have permission to edit this article. "Everyone here knew the solution was at hand, but they needed a growing season to be able to make the changes necessary to implement that solution.". (Recall from Part I that the Tcms gene had been incorporated into almost 90 percent of the hybrids used in the United States due to its ability to produce seed more cost effectively without the laborious method of de-tasseling female seed plants). Diseases that involve host-selective toxins have caused some of the world's worst plant disease epidemics, including the Southern Corn Leaf Blight epidemic of 1970 in the U.S. Southern corn leaf blight (SCLB) is an important foliar disease of maize crop and caused by fungi Cochliobolus heterostrophus, and also known as Bipolaris maydis (ascomycetes). Leaf blight, stalks rot, seedling blight and smuts are the most important diseases of corn crop (Hafiz, 1986). The lag time to implement the solution was about a year. Nevertheless it is still clear that the effects of this disease were substantially damaging to the economies of the south and the Corn Belt, with the southern states being hit the hardest. Unfortunately, it also obscured the potential pitfalls inherent in genetic uniformity in an agricultural crop. Department of … The early start of the hurricane season reflects some similarities between the soybean rust situation and the southern corn leaf blight epidemic in 1970. When all this Tcms corn was introduced into hybrid seed production, it was obviously not foreseen that the T cytoplasm germplasm source was also extremely susceptible to a new unknown race of the pathogen causing SCLB, but it should have been. Get up-to-the-minute news sent straight to your device. "It was a unique situation because the solution to control the disease was apparent from the same series of experiments which defined the problem," Smith said. The SCLB observations Hooker made in the fall of 1969 were defined in the research conducted in April 1970. Use of Texas male‐sterile cytoplasm (T) in the production of hybrids was an important factor in the severity and spread of SCLB. Southern corn leaf blight (SCLB) is a fungal disease of maize caused by the plant pathogen Bipolaris maydis (also known as Cochliobolus heterostrophus in its teleomorph state). WASHINGTON, Aug. 15—An epidemic of a new strain of plant disease is sweeping the American corn farms with potentially devastating results. Annual Review of Phytopathology Vol. The southern corn leaf blight epidemic of 1970, By Robert M. Harveson The southern corn (Zea mays L.) leaf blight (SCLB) epidemic of 1970–1971 was one of the most costly disease outbreaks to affect North American agriculture, destroying 15% of the crop at a cost of US$1.0 billion (≥$6.0 billion by 2015 standards.). Typical disease life cycle of a corn foliar pathogen such as southern corn leaf blight. Without any biodiversity, it is easy for a fungus to move in and wipe out a crop, and that is exactly what happened. The disease became epidemic throughout Florida in late February and early March. This year's hurricane season started early and the arrival of Tropical Storm Arlene has raised some concerns regarding the risk of soybean rust (SBR) this season. Do you ever wonder why you see so many fields of detasseled corn each summer? Following the severe Southern Corn Leaf Blight epidemic in 1970, his attention turned to the mechanism of action of the T-toxin in development of this disease. southern leaf blight that caused serious losses to the 1970 corn crop in the United States. The other was the need to test and evaluate the technological breakthroughs that had recently been made in remote sensing. Part I summarized the development of hybrid corn, which played a major role in promoting the disease. Under the right conditions, conidia (asexual spores) are released from wounds of a diseased corn plant and dispersed to surrounding plants through splashing rain or wind. Annual Review of Phytopathology, 10, 37-50. The disease has been estimated to have reduced yields that year by at least 700 million bushels, causing prices of corn futures to skyrocket and creating a degree of universal publicity for agriculture not often seen by the general public. U of I continues to seek answers to the problems and plant diseases farmers are facing in the fields. This factor combined with greatly reduced usage of the T-cytoplasm effectively halted the occurrence of a second severe epidemic in 1971. It resulted from … The extent of yield reductions and monetary losses to producers nationally was difficult to accurately assess. Southern corn leaf blight earned its place in history during an epidemic in 1970. Extension Plant Pathologist UNL Panhandle Research and Extension Center. Happily, yield results that year also returned to pre-1970 numbers, and in fact produced a new record crop nationally. The pathogen can also remain alive and viable on corn kernels or residue within fields. In January 1970, the first reports of a similar disease causing serious damage on corn containing the Tcms germplasm source were made from southeastern Florida in the area of Belle Glade, east of Lake Okeechobee. It affects field corn, sweet corn and popcorn, and is most severe and spreads most rapidly in warm (70-90°F), wet conditions. The answer goes back to the summer of 1970. However, this success also came at a cost. "Our team met weekly to pool our results from the previous week and develop strategies for what research we'd move forward with next.". Pathogenicity tests confirmed the identity of the causal agent as the southern corn leaf blight pathogen (C. heterostrophus). There are two races of the pathogen. Forty years ago, the Southern Corn Leaf Blight (SCLB) Epidemic, ravaged cornfields across the United States. Yields have been consistently and dramatically improved over the years with no apparent end in sight. For example, in the 1930s, average yields were 22 bushels per acre. and Miyake) swept the U.S. corn belt. It was unusually wet in the United States that spring, thus further encouraging rapid progress of the disease northward. The 1971 Corn Blight Watch (CBW) Experiment was the result of two major developments. Later, it was determined that a new strain (race T) of the fungus produced a toxin (Ttoxin) which was highly aggressive on Figure 1. Until 1970, the disease was considered to be of only minor importance and primarily restricted to the warmer corn growing areas of the southern United States. In addition to increased virulence, the new race also caused lesions on all above ground plant parts while lesions from the old race were normally restricted to leaf tissues. Surprisingly, it was additionally observed causing severe damage on Texas male sterile cytoplasm (Tcms) varieties with only mild symptoms consisting of small inconspicuous leaf lesions forming on the normal cytoplasm plants. The combination of the monoculture and genetic uniformity on a susceptible host, ideal weather conditions for disease development stretching from Florida to the Canadian border, and the debut of a new virulent pathogen, resulted in an extremely rare but highly damaging epidemic. The 1970 southern corn leaf blight epidemic focused public awareness on the risks of genetic vulnerability in crops. Sentinel plots were established across the Corn Belt for observation purposes with additional efforts focused on the creation of a disease forecasting system and initiating aerial remote sensing experiments using color infrared photography. Their team provided the definitive cause for the SCLB Epidemic in the October 1970 issue of Plant Disease Reporter. Southern corn leaf blight is caused by the fungus Bipolaris maydis. An additional, but highly unusual factor contributing to the epidemic and its devastating effects was the arrival of a new race of the pathogen. But that takes a certain level of commitment from a university or company so you don't have to start at ground zero when a problem hits.". Race O normally attacks only leaves. But in 1970, the Southern corn leaf blight epidemic (Helminthosporium maydis Nisik. Monetary losses were officially estimated to total $1 billion (worth more than $6 billion dollars today) for the nation as a whole, with 20-30 percent yield loss averages being common. (1972) The Impacts of the Southern Corn Leaf Blight Epidemics of 1970-1971. The rapid re sponse to the corn blight of 1970 greatly enhanced the scientific credibility of plant pathologists in the eyes of the agricultural community. "It didn't require 10 years of additional research. ", Photos available for three months at http://images.itcs.uiuc.edu/media/sclb40/, Researchers reflect on southern corn leaf blight epidemic. Collectively, they all worked on identifying additional sources of resistance, their inheritance, SCLB economics and its ultimate control. The almost irrational drive for greater and higher yields dominated the attitude and mentality of farmers, breeders and seed companies alike. It has been the subject of voluminous research in the efforts to mold it into different forms, including corn of all colors and sizes, field, sweet and popcorn; and for types adapted to differing environmental conditions. This original concept of promoting some degree of variability was initially published in 1939, but we had to learn this lesson all over again in 1970. 15% nationwide. and Miyake, on the in dustrial utilization of corn and its use in foods … The take-home message was that genetic diversity in a crop is beneficial and a good general defense against diseases. The discovery of male sterility made the production of commercial hybrid seed more practical. This epidemic underscored the need for genetic diversity, led to the development of certified seed and is the reason why detasseling of hybrid seed corn fields still … "It was one of the most exciting times anyone working in plant pathology could go through," Smith said. Former U of I researchers Art Hooker, Dave Smith and Sung Lim led the race to find answers to this disease. A second fungus, Phyllosticta zeae-maydis, with the same biological specificity, appeared coincidentally. It has additionally been postulated that Race T was either introduced into the Corn Belt or was created by mutation and transported from the Corn Belt into the southern United States on seed. The epidemic was driven by race T, a previously unseen race of Cochliobolus heterostrophus. The widespread use of the Tcms corn is obviously recognized now as being equivalent to playing Russian roulette. Southern corn leaf blight (SCLB) is a fungal disease caused by Cochliobolus heterostrophus, often found in the literature under various names formerly used for the asexual stage, including Bipolaris maydis and Helminthosporium maydis. Pataky believes these researchers are great examples of how universities can help producers make progress. This crop serves as a particularly good example of the benefits and success of agricultural research in the U.S. Author’s note: this article is the second of a two part series that tells the story of the 1970 southern corn leaf blight disease epidemic. Pataky said, "Their unpretentious, straightforward work should be a reminder to all researchers that the technological sophistication of our research is not nearly as essential as our ability to observe and recognize significant phenomena and to design experiments that provide definitive answers to questions of importance. The disease is The leaf diseases resulted in an "early maturing" of the corn in many fields which was attributed erroneously to a late season heat stress in many popular reports. CONCLUDING REMARKS ~n 1970 an epiphytotic of Southern Corn Leaf Blight caused an ap proximate 15 percent loss to the nation's corn crop. Perhaps we are wiser now more than 40 years removed from this momentous event? Part II is presented here and relates the details of that serious epidemic to corn growers throughout the United States, and what we have since learned from that mistake. Use of hybrid varieties drastically improved corn yields in the United States. In 1970, 80 to 85 percent of the corn grown in the U.S. was of the same variety. As the 1970s began, yields had increased to 95 bushels, and today yields routinely exceed 200 bushels. Hooker, now deceased, led the research team and coordinated their efforts. And by 1972, SCLB caused by race T was already a thing of the past. Had the season's weather been warmer and more hUJDid, blight development would have been greater. The answer goes back to the summer of 1970. Congress appropriated millions of dollars for researchers to study this disease in 1971. The B. maydis fungus that ravaged corn fields resulted in withered plants, broken stalks, and malformed or completely rotten cobs that were covered in a grayish powder. The second lesson was the comprehension of the benefits resulting from the tremendous spirit of cooperation demonstrated among scientists both within and between various disciplines. Furthermore, in 1971, breeders brought back the use of the old normal cytoplasm, again employing hundreds of students for the summer as labor for de-tasseling the female parents in seed fields. "To me, that is the ideal way — to not allow things to reach catastrophic levels before research starts. Southern corn leaf blight incited by Helminthosporium maydis Nisikado & Miyake evolved from a minor disease that causes an average annual loss of less than 1 percent, to one that caused more than the … We are now well aware of the expensive lesson this disease epidemic has taught us; a lesson we should not have been forced to learn in 1970. Cochliobolus heterostrophus race T strain C4 In 1970, race T, a previously unseen strain of the filamentous ascomycete, Cochliobolus heterostrophus caused the worst epidemic [Southern Corn Leaf Blight (SCLB)] in US agricultural history, destroying more than 15% of the maize crop. The origin of this new virulent pathogenic race is uncertain. A dramatic shift in the genetics of host-parasite interaction and balance occurred in the U.S. corn crop in the 1970 growing season. In January 1970, the first reports of a similar disease causing serious damage on corn containing the Tcms germplasm source were made from southeastern Florida in the area of Belle Glade… Corn has proven to be an extremely plastic crop. The two races were then re-designated as “Race T” for the new race virulent on Tcms corn and “Race O” for the old pathogenic race known worldwide as a minor pathogen for many years. Fortunately the environmental conditions for most of the south were unfavorable for disease development in 1971, resulting in much less severe disease problems than the previous season. Race T attacks leaves, husks, stalks, leaf sheaths, shanks, ears, and cobs. In 1969, a new and unfamiliar disease affecting corn leaves and ears was noted sporadically in a few localized areas of several corn-producing states (Iowa, Indiana, and Illinois). acreage in the Corn Belt had slight or mild levels of infection. The Great Epidemic of Southern Corn Leaf Blight of 1970 startled this nation that thought that its technology was able to protect its supermarkets from the vagaries of Nature. These tremendous yield improvements allowed the United States to become the leader in this field, accounting for nearly one half of the world’s production. However, this hasn’t been a major disease of concern since the 1970’s, and we don’t anticipate it to be a chief concern here in NY compared as compared to our regional issues with northern corn leaf blight and gray leaf spot. The history of SCLB in the United States clearly illustrates the dangers of genetic uniformity in modern agriculture. This remained a major theme in his research through the rest of his career, and several of his MS and PhD students worked in this area. However, through the use of comparative inoculations of isolates collected in 1970 within the greenhouse, on Tcms and normal cytoplasm-type seedlings, confirmed the presence of a new distinct race of the pathogen. PM-toxin has exactly the same biological specificity as the polyketide secondary metabolite, T-toxin, produced by Cochliobolus heterostrophus race T causal agent of the 1970 Southern Corn Leaf Blight epidemic. ). Tatum LA. Symptoms and disease severity are dependent upon the type of hybrid, occurrence of other diseases, crop stage at infection, environmental variables such as rainfall, dew, or temperatures and race of the pathogen. According to Pataky, corn yields were reduced 20 to 25 percent nationwide, with higher loss occurring in the South.
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