Research Achievements in Plant Pathology and Crop Physiology

Lawrence E. Datnoff

The Department of Botany, Bacteriology and Plant Pathology was created in 1924 by combining faculty from the College of Arts and Sciences and the Louisiana Agricultural Experiment Station. Claude W. Edgerton was named the first head, and the department grew from three to 13 faculty members by 1930. In 1950, St. John P. Chilton became the head, and with increased research and teaching responsibilities, the department grew to a faculty of 28. The department was divided in 1962 to form a new Microbiology Department and the Department of Botany and Plant Pathology.

In 1970, the Department of Botany was formed and placed in the College of Arts and Sciences while the Department of Plant Pathology was placed in the newly formed Louisiana State University Agricultural Center (LSU AgCenter) with research administered by the director of the Experiment Station and teaching administered by the dean of the College of Agriculture. After Chilton retired, Weston J. Martin became head (1977-1982), and the name of the department was changed to its current name of Plant Pathology and Crop Physiology to more accurately reflect the disciplines of the faculty residing within the department.

In 2002, the weed science program was moved to the Department of Agronomy while the extension plant pathology faculty and programs were merged into the Department of Plant Pathology and Crop Physiology. Other department heads that have served are the following: David R. MacKenzie (1983-1989), John B. Baker (1989-1992), Johnnie P. Snow (1992-2002), Gerald Berggren (2002-2008) and Lawrence Datnoff (2008-present). From the 1980s to present, the number of faculty positions has ranged from 16 to 25.

Graduate Students

From 1924 to 2011, more than 640 M.S. and Ph.D. degrees were granted, and many former graduate students were placed in important academic and industry positions. These positions have included post-doctorates, assistant, associate and full professors with universities (Auburn University, Rice University, Southern Illinois University, University of California-Davis, University of Alabama, University of Florida, University of Georgia, University of Kentucky, Iowa State University, Harvard Medical School, Mississippi State University, North Carolina State University, Oregon State University and others), research scientists with government agencies (USDA-ARS, Florida Division of Plant Industries, Louisiana Department of Agriculture and Forestry, Virginia Department of Agriculture and others) as well as private industry (Bayer, Dupont, Horticultural Research International, Monsanto, PetoSeed Co., Syngenta and others). In Louisiana, graduates hold positions with agricultural chemical industries, crop consulting companies, and as faculty and staff members with the LSU AgCenter.


Since 1924, the overarching mission of the Department of Plant Pathology and Crop Physiology has been to advance and disseminate knowledge about the microorganisms and abiotic stress that cause plant diseases and their management in agronomic and horticultural crops, as well as coastal plants, grown in Louisiana. Plant diseases and environmental stress have seriously limited crop production in Louisiana. New diseases continue to appear because of changes in varieties and cultural practices and genetic shifts in existing populations of pathogens. In addition, new diseases are introduced into Louisiana from other states and countries. Faculty have led efforts to improve the management of diseases caused by plant pathogens (fungi, bacteria, viruses and nematodes) and environmental stress (temperature extremes, excess moisture, mineral toxicities) through programs of research, extension and teaching related to Louisiana commodities that include corn, cotton, fruit crops, grain crops, ornamentals, rice, soybean, sugarcane, sweet potato, turfgrass, vegetable crops and coastal plants.

Faculty Achievement

Following is a chronological history of some of the research achievements of the faculty:

Claude W. Edgerton (1908-1955) systematically catalogued diseases of crops in Louisiana including sugarcane, tomatoes, cotton, other vegetable crops and fruits. His research on Glomerella (+ and – strains) pioneered work on fungal genetics. His book, Sugarcane and Its Diseases, published by LSU Press in 1955, was the first comprehensive treatise on this subject. Antonios G. Plakidas (1927-1960) discovered that the widespread degeneration disease of strawberries was viral in nature. In 1943, he published a bulletin entitled Diseases of Some Vegetable and Fruit Crops and their Control. Thirty thousand copies were distributed in Louisiana, across the United States and in many foreign countries. Plakidas also authored the 1964 LSU Press book, Strawberry Diseases.

In the 1940s, Irwin L. Forbes conducted extensive research on sugarcane diseases, screening many varieties for disease resistance in coordination with the sugarcane breeding program. Many of his findings were published in LAES bulletins. Charles F. Moreland developed methods of photoperiod control to induce flowering of sugarcane under Louisiana conditions during the 1950’s, and this discovery was instrumental in the development of the sugarcane breeding program.

In the late 1940s and early 1950s, Weston J. Martin advanced the understanding of sweet potato diseases. He was the first to demonstrate that soil rot of sweet potato was caused by Streptomyces ipomoeae. He further found that circular spot was caused by Sclerotium rolfsii and helped determine the etiology of bacterial root and stem rot, caused by Erwinia chrysanthemi. Norman L. Horn initiated fungicide testing on soybeans in the early 1970s. This research led to the general use of fungicides on soybeans in Louisiana, which was responsible for large increases in soybean yields.

Harry E. Wheeler (1950s and 1960s) authored numerous papers in the areas of fungal genetics and physiology of parasitism. He was known for his research on sexuality in Glomerella and on the causal role of the pathotoxin victorin. G.Don Lindberg in the 1960s provided the first evidence of a transmissible agent (virus) in the fungi. Lindberg also discovered a bacterium that produced the antifungal antibiotic tropalone. Wray Birchfield in the 1960s developed management strategies, such as nematicides and host resistance, against the reniform nematode on cotton. John P. Hollis in the 1960s/1970s showed the importance of hidden problems in rice being caused by nematodes (Hirschmanniella and Criconemella).

In 1961, James B. Sinclair developed sanitation methods to avoid the transmission of tobacco mosaic virus in tomato and compared methods of delivering fungicides for controlling “sore-shin,” caused by Rhizoctonia solani, in cotton. Louis Anzalone and Ellis D. Paliatsias (1960s/1970s) conducted the sugarcane breeding program for many years in which seed and seedlings were produced and then seedlings screened for resistance to sugarcane mosaic virus.

Gordon E. Holcomb (1965-2006) discovered, identified and described many new ornamental plant diseases, which included centipedegrass mosaic (virus), coleus mosaic (virus), web blight of rosemary, Guignardia leaf spot of camellia, Amphobotrys blight of poinsettia and many others. He also described the new fungus Alternaria (Nimbya) alternantherae from alligatorweed and showed that it also infected ornamental Amaranthaceae members. Holcomb identified Sclerotinia blight as a serious disease in wild populations of a native Trillium species and developed a host list of 145 species for the pathogenic green alga, Cephaleuros virescens, many of which were new to the continental United States.

Kenneth S. Derrick (1970-1987) developed the Serologically Specific Electron Microscopy (SSEM) method, which was a major breakthrough for identifying and screening for viruses. Lowell L. Black (1968-1996) demonstrated the use of reflective plastic mulch for reducing insect and virus problems in vegetable production. In the late 1970s, Kenneth E. Damann and his student showed the newly discovered bacterial cause of ratoon stunting disease produced pectinaceous xylem plugging gels in sugarcane that supported microcolony development of the bacterium.

Milton “Chuck” Rush (1970s-2009) initiated a comprehensive fungicide testing program for rice that led to the registration of Benlate 50WP, demonstrating the potential of fungicides for economically controlling fungal rice diseases. He identified and reported new rice diseases in Louisiana and the United States including the causal agents of rice panicle blight, Burkholderia glumae and B. gladioli.

In 1974, Kenneth Whitam started the first Plant Disease Diagnostic Clinic in Louisiana and served as its first diagnostician. Clayton A. Hollier (1982-present) identified new diseases in ornamentals; determined yield losses of important diseases in rice, sugarcane and wheat; and found hybrids with good levels of tolerance to southern corn rust. In addition, he educated county agents and farmers in how to recognize plant diseases and the importance of integrated pest management in reducing environmental harm. In 2005, he initiated the first soybean sentinel plots to determine the presence and spread of soybean rust in Louisiana and surrounding states.

Christopher Clark (1977-2011) helped to develop 11 disease-resistant sweet potato varieties. He elucidated the etiology of sweetpotato chlorotic leaf distortion, caused by Fusarium denticulatum, an unusual epiphytic pathogen. He also demonstrated that viruses reduce sweet potato yields by 25 percent to 40 percent and developed a program for providing virus-tested tissue culture plants to the LSU AgCenter foundation seed program, providing farmers with an option for healthy “seed.”

Since 1978, the Nematode Advisory Service, under the supervision of Charles Overstreet, has processed more than 40,000 nematode samples saving producers millions of dollars in production costs because of better nematode management strategies.

In 1984, Marc A. Cohn’s group reported the first evidence for gaseous nitrogen oxides as seed dormancy-breaking agents; in studies from 1983-1992, the Cohn lab established the first quantitative structure-activity relationships (QSAR) for seed dormancy-breaking chemicals and showed that cell acidification was a common response, indicating that dormancy was regulated by cell pH.

Ray Schneider’s group (1984-present) was instrumental in developing the use of nitrate utilization mutants for testing vegetative compatibility between strains of fungi and for assessing genetic diversity within and among populations of plant pathogenic fungi. This test has been used worldwide to establish the clonal nature of Fusarium spp., and it provided conclusive evidence that the Cercospora leaf blight pathogen of soybean is undergoing genetic recombination.

In 1989-1993, Lowell L. Black and Rodrigo Valverde conducted field research on the epidemiology of tomato spotted wilt virus on tomato and pepper and found new overwintering hosts and vectors for this virus. In 1990s-2000s, Valverde discovered techniques for studying dsRNA plant viruses, and these methods are being used worldwide for the diagnosis and characterization of these viruses.

In the 1990s, Mary Musgrave’s space biology program had plants complete their life cycle (seed to seed) in microgravity on several space shuttle missions and on the Russian Mir Space Station. N. Murai and his group (1990-1993) conducted the first genetically modified rice field trial in the world at the Rice Research Station with USDA approval. They demonstrated that agronomic traits of GM rice were identical to non-GM rice. From 1995 to 1997, Norimoto Murai and his group produced transgenic rice plants with bean/pea storage proteins thus improving the rice seed nutritional quality.

Jeffrey W. Hoy and his group (1983-2011) were instrumental in reducing the incidence of ratoon stunting disease, the long-time most important disease of sugarcane, from 51 percent in 1997 to less than 1 percent through a public and private sector partnership to produce healthy planting material for farmers and the establishment of the Sugarcane Disease Detection Lab to provide disease monitoring. Hoy’s group also assessed the threat posed by incursions into Louisiana during the past 30 years by major sugarcane diseases, including smut, leaf scald and yellow leaf. They developed appropriate management practices to prevent severe yield losses.

Since 2004, Charles Overstreet has demonstrated the effectiveness of site-specific application of nematicides to manage nematodes in cotton. In 2004, the first discovery of soybean rust in Louisiana and the United States was made by Ray Schneider. He along with Boyd Padgett were instrumental in developing commercial fungicide protocols for managing this disease in Louisiana and many other states.

Kenneth Damann and a student showed that a 2007 population of Aspergillus flavus revealed specificity in the soil population with some VCG’s appearing only in soil and others capable of infecting corn kernels. Also, the kernel infecting isolates were predominantly two VCG’s, one that produced very low aflatoxin and the other produced high aflatoxin, suggesting that the low toxin producing strains were acting as a natural biocontrol agent to limit aflatoxin contamination of corn.

In 2010-2011, Edward C. McGawley and Charles Overstreet were the first to document reproductive and pathogenic variation in geographic isolates of reniform nematode on cotton and soybean in the United States. Zhi-yuan Chen (2005-present) has identified several soybean lines to be fairly field resistant to Cercospora leaf blight of soybeans as well as two African corn lines to have excellent aflatoxin resistance. Don Ferrin (2005-present) has developed and presented educational materials statewide on plant pathogens, diseases they cause and their management to stakeholders in the horticultural industries. He has trained extension field faculty in plant disease identification and management, and he has developed educational materials for commercial producers.

M. Catherine Aime (2007-present) has discovered, described and published one new class (Tritirachiomycetes), one new genus (Guyanagaster) and 46 new species of fungi. Raghuwinder “Nick” Singh (2007-present) diagnoses thousands of plant samples yearly submitted by residents of Louisiana including homeowners and commercial clients since 2010, when the Plant Diagnostic Center was established.

Jong Ham’s (2007-present) laboratory group has discovered several new genetic elements of Burkholderia glumae, the causal agent of panicle blight of rice important for bacterial virulence. This achievement has provided new insights on disease etiology and new approaches for disease control.

The Future

The disease-conducive environment in Louisiana and the latest incursions of new pathogens and pathogen-vectors into the state make it clear that plant diseases are and will continue to be one of the primary limiting factors in crop production, in the home and urban landscapes, and in the environment. Each time a new pathogen arrives and a new disease outbreak occurs in Louisiana, it is the Department of Plant Pathology and Crop Physiology that has provided the leadership for generating basic knowledge and applied solutions for managing these diseases as well as environmental stresses.

Lawrence E. Datnoff, Head, Department of Plant Pathology & Crop Physiology, LSU AgCenter, Baton Rouge, La.

(This article was part of the spring 2012 issue of Louisiana Agriculture, which featured the 125th anniversary of the Louisiana Agricultural Experiment Station. This article is available online only; it did not appear in the print version of this issue.)

3/12/2020 4:36:05 PM
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