Extension Plant Pathologist UNL Panhandle Research and Extension Center. By the 1940s about 40 percent of the acreage was planted to hybrids with an average yield increasing to 35 bushels per acre. This factor combined with greatly reduced usage of the T-cytoplasm effectively halted the occurrence of a second severe epidemic in 1971. Leaf diseases of corn in Iowa in 1990 were probably the most severe since the 1970 epidemic of Southern corn leaf blight. 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. Our concern is with the effect of this disease, caused by the field fungus Hellllint!lOsjJoriulIl lIlaydis Nisik. Their team provided the definitive cause for the SCLB Epidemic in the October 1970 issue of Plant Disease Reporter. ", Photos available for three months at http://images.itcs.uiuc.edu/media/sclb40/, Researchers reflect on southern corn leaf blight epidemic. Use of Texas male‐sterile cytoplasm (T) in the production of hybrids was an important factor in the severity and spread of SCLB. Isolations of the pathogen made from stored corn in Iowa indicate its presence in that state to be at least as early as 1968. 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). Yields have been consistently and dramatically improved over the years with no apparent end in sight. Ullstrup, A.J. This idea had been considered in the early 1900s but was abandoned due to projected seed costs. Department of … 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. 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. WASHINGTON, Aug. 15—An epidemic of a new strain of plant disease is sweeping the American corn farms with potentially devastating results. Race O normally attacks only leaves. College of Agricultural, Consumer & Environmental Sciences. 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. acreage in the Corn Belt had slight or mild levels of infection. Forty years ago, the Southern Corn Leaf Blight (SCLB) Epidemic, ravaged cornfields across the United States. Congress appropriated millions of dollars for researchers to study this disease in 1971. Annual Review of Phytopathology, 10, 37-50. Get up-to-the-minute news sent straight to your device. Southern corn leaf blight is caused by the fungus Bipolaris maydis. 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. 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. The answer goes back to the summer of 1970. 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. CONCLUDING REMARKS ~n 1970 an epiphytotic of Southern Corn Leaf Blight caused an ap­ proximate 15 percent loss to the nation's corn crop. 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. Later, it was determined that a new strain (race T) of the fungus produced a toxin (T­toxin) which was highly aggressive on Unfortunately, it also obscured the potential pitfalls inherent in genetic uniformity in an agricultural crop. The other was the need to test and evaluate the technological breakthroughs that had recently been made in remote sensing. 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. A second fungus, Phyllosticta zeae-maydis, with the same biological specificity, appeared coincidentally. The disease became epidemic throughout Florida in late February and early March. Foliar Fungal Diseases. The extent of yield reductions and monetary losses to producers nationally was difficult to accurately assess. It was unusually wet in the United States that spring, thus further encouraging rapid progress of the disease northward. Enjoy more articles by logging in or creating a free account. No credit card required. 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 1970, almost 85% of US corn fields was planted with one type of corn, called Texas cytoplasmic male sterile (Tcms) corn. The discovery of the cause of the epidemic and the solution — detasseling — was spearheaded by corn pathologists at the University of Illinois. 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. Southern corn leaf blight of corn. Smith focused on the reproduction differences between the SCLB strains showing the new strain was much more aggressive than the old strain. 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 … Figure 1. "To me, that is the ideal way — to not allow things to reach catastrophic levels before research starts. Former U of I researchers Art Hooker, Dave Smith and Sung Lim led the race to find answers to this disease. 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. 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. Southern corn leaf blight is caused by the fungus Bipolaris maydis, which primarily follows an asexual disease cycle. 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. "It was one of the most exciting times anyone working in plant pathology could go through," Smith said. 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. Perhaps we are wiser now more than 40 years removed from this momentous event? According to Pataky, corn yields were reduced 20 to 25 percent nationwide, with higher loss occurring in the South. The take-home message was that genetic diversity in a crop is beneficial and a good general defense against diseases. 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. Do you ever wonder why you see so many fields of detasseled corn each summer? 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. 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. Typical disease life cycle of a corn foliar pathogen such as southern corn leaf blight. 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 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. In 1970, 80 to 85 percent of the corn grown in the U.S. was of the same variety. 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. What is Southern Corn Leaf Blight? "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.". Had the season's weather been warmer and more hUJDid, blight development would have been greater. The lag time to implement the solution was about a year. You have permission to edit this article. However, using the Tcms gene was too successful at producing hybrid seed easily and inexpensively. 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. The southern corn leaf blight (SCLB) epidemic of 1970, caused by Bipolaris maydis(Nisikado) Shoemaker, race T, decreased yield of maize (Zea maysL.) Its spores can be windblown to adjacent areas, surviving in dead plant tissues for several years. The widespread use of the Tcms corn is obviously recognized now as being equivalent to playing Russian roulette. The southern corn leaf blight epidemic of 1970, By Robert M. Harveson This crop serves as a particularly good example of the benefits and success of agricultural research in the U.S. As the 1970s began, yields had increased to 95 bushels, and today yields routinely exceed 200 bushels. Use of hybrid varieties drastically improved corn yields in the United States. 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 … 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. 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. 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. 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). 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 … An additional, but highly unusual factor contributing to the epidemic and its devastating effects was the arrival of a new race of the pathogen. During that summer, the southern leaf blight epidemic reduced corn yields by 20 to 25 percent nationwide, resulting in an estimated $1 billion loss. U of I continues to seek answers to the problems and plant diseases farmers are facing in the fields. 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. However, this success also came at a cost. This epidemic is considered by many to be the most economically devastating field crop disease of any developed area of … Hooker, now deceased, led the research team and coordinated their efforts. ). 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). 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 affects field corn, sweet corn and popcorn, and is most severe and spreads most rapidly in warm (70-90°F), wet conditions. The 1971 Corn Blight Watch (CBW) Experiment was the result of two major developments. The Impacts of the Southern Corn Leaf Blight Epidemics of 1970-1971. The Southern corn leaf blight (SCLB) epidemic of 1970 devastated fields of T-cytoplasm corn planted in monoculture throughout the eastern United States. 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