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Jean Beagle Ristaino is an American scientist and William Neal Reynolds Distinguished Professor of Plant Pathology. She is best known for her work on the epidemiology and population genetics of Oomycete plant pathogens in the genus Phytophthora and her work on the population genomics of historic outbreaks of the Irish famine pathogen, Phytophthora infestans
Ristaino received her B.S. degree in biological sciences in 1978 and her M.S. degree in plant pathology in 1982 from the University of Maryland. She received her Ph.D. from the University of California, Davis in 1987. Since 1987, Ristaino has been on the faculty of North Carolina State University, and she currently holds the rank of William Neal Reynolds Distinguished Professor.
In 2012, Ristaino served as a Jefferson Science Fellow in the Bureau for Food Security of the United States Agency for International Development]. In 2016, she received the Excellence in International Service Award from the American Phytopathological Society In 2019 she was awarded the Global Engagement Award from NC State University.
Ristaino serves as the director of the “Emerging Plant Disease and Global Food Security” cluster at NC State, has served as a Jefferson Science Fellow for the US Department of State and received a Fulbright European Research Scholar Award to work with the University of Catania on late blight in Italy in 2018. In August 2020, she was elected a Fellow of the American Phytopathological Society and named a AAAS Fellow in November, 2020.
Ristaino's lab at NC State works on emerging plant diseases that threaten global food security. A major focus of research is to understand the factors that contribute to disease emergence including the epidemiology and population genetics of Oomycete plant pathogens in the genus Phytophthora. Phytophthora infestans caused the Great Famine of Ireland in the 1840s, and is a reemerging threat to global food security. She studies the population genetics and migrations of both historic and present day strains of the pathogen. Her lab was part of a multi-investigator group that sequenced the genome of the pathogen. She is now using the genome sequence to develop novel strategies for managing disease in the field. Her team has developed a web portal called USAblight.org that can be used to track recent outbreaks of disease using geospatial analytics. She also works on other pathogens of tropical crop plants including black Sigatoka on banana, downy mildew of tobacco, soilborne fungi and coffee rust that are threats to global food security.
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Plant pathology or phytopathology is the scientific study of plant diseases caused by pathogens and environmental conditions. Plant pathology involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases.
Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight. Early blight, caused by Alternaria solani, is also often called "potato blight". Late blight was a major culprit in the 1840s European, the 1845–1852 Irish, and the 1846 Highland potato famines. The organism can also infect some other members of the Solanaceae. The pathogen is favored by moist, cool environments: sporulation is optimal at 12–18 °C (54–64 °F) in water-saturated or nearly saturated environments, and zoospore production is favored at temperatures below 15 °C (59 °F). Lesion growth rates are typically optimal at a slightly warmer temperature range of 20 to 24 °C.
Blight is a specific symptom affecting plants in response to infection by a pathogenic organism.
The Oomycetes, or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.
Phytophthora is a genus of plant-damaging oomycetes, whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. The cell wall of Phytophthora is made up of cellulose. The genus was first described by Heinrich Anton de Bary in 1875. Approximately 210 species have been described, although 100–500 undiscovered Phytophthora species are estimated to exist.
Rebecca J. Nelson is an American biologist and a professor at Cornell University and a MacArthur Foundation Fellow.
Phytophthora palmivora is an oomycete that causes bud-rot of palms, fruit-rot or kole-roga of coconut and areca nut. These are among the most serious diseases caused by fungi and moulds in South India. It occurs almost every year in Malnad, Mysore, North & South Kanara, Malabar and other areas. Similar diseases of palms are also known to occur in Sri Lanka, Mauritius, and Sumatra. The causative organism was first identified as P. palmivora by Edwin John Butler in 1917.
Phytophthora capsici is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops. It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in Las Cruces in 1922 on a crop of chili peppers. In 1967, a study by M. M. Satour and E. E. Butler found 45 species of cultivated plants and weeds susceptible to P. capsici In Greek, Phytophthora capsici means "plant destroyer of capsicums". P. capsici has a wide range of hosts including members of the families Solanaceae and Cucurbitaceae as well as Fabaceae.
Plant disease epidemiology is the study of disease in plant populations. Much like diseases of humans and other animals, plant diseases occur due to pathogens such as bacteria, viruses, fungi, oomycetes, nematodes, phytoplasmas, protozoa, and parasitic plants. Plant disease epidemiologists strive for an understanding of the cause and effects of disease and develop strategies to intervene in situations where crop losses may occur. Destructive and non-destructive methods are used to detect diseases in plants. Additionally, understanding the responses of the immune system in plants will further benefit and limit the loss of crops. Typically successful intervention will lead to a low enough level of disease to be acceptable, depending upon the value of the crop.
Niklaus J. Grünwald is a biologist and plant pathologist born and raised in Caracas, Venezuela of German and Swiss ancestry. He is currently a research scientist with the USDA Agricultural Research Service, a Professor (Courtesy) in the Department of Botany and Plant Pathology at Oregon State University, and a Professor (Adjunct) in the Department of Plant Pathology and Plant-Microbe Biology at Cornell University.
Collar rot is a symptomatically described disease that is usually caused by any one of various fungal and oomycete plant pathogens. It is present where the pathogen causes a lesion localized at or about the collet between the stem and the root. The lesions develop around the stem eventually forming a "collar". Observationally, collar rot grades into "basal stem rot", and with some pathogens is the first phase of "basal stem rot" often followed by "root rot". Collar rot is most often observed in seedings grown in infected soil. The pathogens that cause collar rot may be species or genera specific. But generalist pathogens such as Agroathelia rolfsii are known to attack over 200 different species. While bacteria caused collar rot is not common, trees infected with Fire blight may develop collar rot. Non-parasitic collar rot may be caused by winter damage.
Buckeye rot of tomato is caused by three species of pathogens in the genus Phytophthora: P. nicotianae var. parasitica, P. capsici, and P. drechsleri. It is an oomycete that thrives in warm, wet conditions and lives in the soil. It is characterized by a bull’s eye pattern of dark brown rotting on the tomato fruit, and affects fruit that is close to, or lying on the soil. The easiest management is to keep the plant out of contact with the soil, although other chemical methods can be very effective. This disease commonly occurs in the southeast and south central areas of the United States. The disease has affected a large portion of crop yield in the United States as well as India. The relatively small genome size of Phytophthora parasitica compared to Phytophthora infestans gives researchers the unique ability to further examine its ability to cause disease.
Charlotte Elliott (1883-1974) was a pioneering American plant physiologist specializing in bacterial organisms that cause disease in crops who was the author of a much-used reference work, the Manual of Bacterial Plant Pathogens. She was the first woman to receive a Ph.D. in botany from the University of Wisconsin, Madison.
Phytophthora hydropathica is an oomycete plant pathogen that is found in aquatic environments such as irrigation and river water. The pathogen was previously classified as P. drechsleri Dre II before being categorized as its own distinct species. P. hydropathica has been primarily found in association with ornamental plant nurseries. The pathogen has been isolated throughout the Southern United States, as well as internationally in Mexico, Italy, and Spain.
The Vertifolia effect is a well documented phenomenon in the fields of plant breeding and plant pathology. It is characterized by the erosion of a crop’s horizontal resistance to disease during a breeding cycle due to the presence of strong vertical resistance, characterized by the presence of R genes. This effect was observed in late blight of potato. This phenomenon was first described by J.E. Van der Plank in his 1963 book Plant Disease: Epidemics and Control. Van der Plank observed that under artificial selection the potato variety Vertifolia had stronger vertical resistance to the potato late blight pathogen, Phytophthora infestans, as measured by the presence of specific R genes. However, when the pathogen overcame these R genes Vertifolia exhibited a greater loss of horizontal resistance than varieties with fewer R genes and lower vertical resistance. This effect suggests that when a pathogen evolves an avirulence gene to counteract a variety’s R gene, that variety will be more susceptible to the pathogen than other varieties.
Maria Petronella Löhnis was a Dutch phytopathologist, microbiologist and botanist noted for studying potato diseases.
Jan Elnor Leach is an American plant pathologist. She is known for her research of the molecular biology of plant pathogens, particularly those affecting rice plants. She was the co-editor of the Annual Review of Phytopathology from 2015-2022 and is a fellow of the American Association for the Advancement of Science and a member of the National Academy of Sciences.
John Colhoun was a British mycologist, phytopathologist, and professor of cryptogamic botany. For a one-year term from 1963 to 1964 he was the president of the British Mycological Society.
John M. McDowell is the J.B. Stroobants Professor of Biotechnology at Virginia Polytechnic Institute and State University. His major area of research is phytopathology and plant-pathogen interactions. He has used gene-sequencing technology to examine the genome of Phytophthora capsici and to develop strains of soybean plants that are better able to defend against pathogens.
