Phytopathology(redirected from Plant pathogen)
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(also plant pathology), the science of plant diseases and of ways to prevent and do away with them. The field of study is subdivided into general and specialized phytopathology. General phytopathology deals with pathogens, the causes and conditions of outbreaks, and the patterns of development and spread of diseases, especially massive outbreaks; it also studies anatomical and physiological disturbances in diseased organisms, plant immunity, and quarantine. Specialists forecast outbreaks and devise means of protecting plants. General phytopathology also includes the study of monstrosities in plants.
Specialized phytopathology is applied to agriculture (crop diseases), forestry (tree and shrub diseases and the destruction of deadwood), and the cultivation of ornamental plants.
Phytopathologists make use of such varied sciences as plant anatomy, plant physiology, microbiology, mycology, genetics, breeding, horticulture, chemistry, and physics. Phytopathological findings constitute the theoretical basis for the protection of crops from serious diseases.
Brief historical sketch. The damage inflicted on plants by diseases has long been known to man. The works of the ancient Greek and Roman authors include descriptions of rust, smut, tree canker, and other diseases. In the early 18th century the French botanist J. de Tournefort attempted to classify plant diseases. Numerous experiments were conducted in the second half of the 18th century by A. T. Bolotov (Russia), M. Tillet (France), F. Fontana (Italy), and J. Fabricius (Denmark) to demonstrate that smut, rust, and other diseases are infectious; despite their research, the nature of the pathogens remained obscure.
In 1833, F. Unger of Austria proposed the exanthem theory, claiming that plant diseases result from the “spoiling of plant juices,” from which fungi or “exanthems” (eruptions, exudates) are self-generated. This antiscientific theory was refuted later in the century by the German scientist H. A. de Bary and the Russian mycologist M. S. Boronin and their students, all of whom demonstrated that many plant diseases are caused by fungi. Prior to the 1890’s, phytopathology developed mainly as a branch of mycology, and plants were regarded primarily as a passive habitat of pathogenic fungi. At the end of the century, phytopathology evolved as a comprehensive scientific discipline concerned with viral and parasitic diseases, as well as fungous diseases.
The classic research of D. I. Ivanovskii (1892) established the importance of virology in phytopathology, veterinary medicine, and other related sciences. Virological research advanced rapidly after the isolation of virus crystals of tobacco mosaic by W. Stanley of the USA in 1935. Research in nematode diseases was initiated by N. Cobb (USA), H. Goffart (Germany), M. Franklin (Great Britain), and I. N. Filip’ev, A. A. Paramonov, and N. M. Sveshnikova (USSR). In the late 19th century and especially in the first half of the 20th century, phytopathologists introduced methods of ecology, biocenology, physiology, biochemistry, and immunology. K. Müller in Germany demonstrated the relationship between the incubation period of downy mildew of grape and atmospheric temperature and humidity. Similar relationships were discovered for late blight of potato, rust of cereals, and apple and pear scab by E. van Everdingen (The Netherlands) and K. M. Stepanov, N. A. Naumova, and D. D. Verderevskii (USSR). As a result, it became possible to forecast many infectious diseases and to apply pesticides promptly and thus more effectively. Studies of farming practices, such as crop rotation, planting time, and methods of cultivation and fertilization, made it possible to plan appropriate control methods. Important research was conducted by P. Sorauer (Germany), A. A. Iachevskii, T. D. Strakhov, and V. N. Shchegolev (USSR), and G. Gate (USA).
In the same period, scientists paid increasing attention to plant immunity. The works of N. I. Vavilov, which are of particular importance in the theoretical development of the subject, analyze plant immunity from the ecological point of view, stressing the interaction of plants, pathogens, and environmental conditions. The resistance of plant varieties was found to be dependent on the parasitic specialization of pathogenic organisms; works on this subject were written by J. Eriksson (Sweden), E. Stakman and C. C. Christensen (USA), and N. I. Vavilov, A. A. Iachevskii, M. S. Dunin, and D. D. Verderevskii (USSR). Plants resistant not only to the most dangerous individual diseases but to their combinations are bred in many countries. Research is also conducted on active acquired immunity and on chemical immunization, for example, by D. Carbone (Italy) and I. M. Poliakov and M. N. Rodigin (USSR).
The chemical and toxicological approach to phytopathology was promoted by the discovery of bordeaux mixture by A. Millardet of France in the late 1890’s and the subsequent use of other fungicides, including Formalin, copper sulfate, and lime sulfur. Later, the production of synthetic fungicides developed rapidly. Thus, by the mid-20th century, phytopathology had evolved as a broad discipline integrating elements of mycology, virology, bacteriology, nematology, epiphytotology, immunology, and toxicology.
In the USSR. Soviet investigators have discovered some important patterns of pathogenesis and epiphytotology in many species of smut, rust, and mildew fungi, as well as pathogens of scab and blight. Based on work done from the 1930’s to 1950’s by S. I. Vanin at the Leningrad Academy of Forest Technology, forest pathology as a new discipline developed in the USSR. In the 1950’s, the extensive use of pesticides and awareness of the adverse effects of chemicals focused attention on the integrated protection of plants, that is, the combination of specific control methods to save as many useful organisms as possible, a matter of considerable importance for environmental protection. Integrated methods of controlling forest diseases and many crop diseases were developed by 1975, and plants are now effectively protected against the most harmful diseases. Research has been conducted since the late 1960’s on therapeutic agents, for example, those found in some antibiotics and systemic fungicides.
Soviet breeders and phytopathologists have developed valuable wheat varieties resistant to rust; sunflower varieties immune to rust, broomrape, powdery mildew, white rot, and gray mold; and tobacco varieties immune to tobacco mosaic virus, black root rot, and powdery mildew. Major work is being conducted to develop wilt-resistant cotton varieties and improve methods of controlling the disease. The All-Union Institute of Horticulture has been especially important in mobilizing world plant resources and particularly in developing forms and varieties that are highly resistant to a variety of diseases and are capable of being used in the breeding of resistant varieties as donors of resistance.
Advances in phytopathology have contributed to progress in plant protection and the solution of new problems. These advances include the study of factors and patterns of plant immunity and the investigation of plant resistance, which has led to the development of new phytopathological techniques and facilitated the early diagnosis of diseases. Research on the pathogenesis of fungous, bacterial, viral, and other diseases is also important. Research has been conducted on chemical immunization by various agents that permit disease resistance to be transmitted to the next two to four generations. Methods of long-range forecasting are developed for planning the scope of protective measures and discovering new techniques of plant protection.
Research in phytopathology is conducted in scientific research institutions and in institutions of higher learning, for example, the All-Union Institute of Plant Protection and similar republic-level institutes. Phytopathological laboratories are maintained by specialized agricultural institutes of the V. I. Lenin All-Union Academy of Agricultural Sciences and the Ministry of Agriculture of the USSR. Related research is conducted in institutes of microbiology, genetics, plant physiology, and biochemistry of the Academy of Sciences of the USSR and in subdepartments of phytopathology and lower plants at universities and agricultural schools. Research is coordinated by the division of plant protection of the Academy of Agricultural Sciences. Universities, agricultural institutes, and technicums offer special courses in phytopathology. Some higher agricultural schools have organized departments or divisions of plant pathology.
Works by phytopathologists are published in the journals Mikologiia i fitopatologiia (since 1967), Doklady Vsesoiuznoi ordena Lenina akademii s.-kh. nauk im. V. I. Lenina (Reports of the V. I. Lenin Order of Lenin All-Union Academy of Agricultural Sciences, since 1936), Vestnik sel’skokhoziaistvennoi nauki (Review of Agricultural Science, since 1956), Zashchita rastenii (Plant Protection, since 1956), Sel’skokhoziaistvennaia biologiia (Agricultural Biology, since 1966), and Khimiia v sel’skom khoziaistve (Chemistry in Agriculture, since 1963). Works on the subject are also published in journals of abstracts, transactions of agricultural institutes, collections dealing with specific aspects of phytopathology, and monographs.
Abroad. Phytopathology is developing rapidly in the socialist countries. Studies are conducted in scientific research institutes, networks of plant-protection stations, phytopathological laboratories, and in the system of specialized scientific research institutes and experiment stations. The socialist countries cooperate extensively through the Council for Mutual Economic Assistance (COMECON). In the capitalist countries, research is most advanced in the USA, the Federal Republic of Germany (FRG), Great Britain, Japan, The Netherlands, Belgium, India, Mexico, France, and Italy. National phytopathology societies play an important role, especially in the USA, Japan, Great Britain, and the FRG. The largest research centers in the USA are located in Beltsville, Md. (run by the US Department of Agriculture), and in state universities. Great Britain has laboratories in Harpenden (the Rothamsted Experimental Station) and Belfast. In Japan, research in phytopathology is conducted at the National Institute of Agricultural Sciences in Tokyo, which has a network of prefectural stations, and at state universities in Tokyo and Kyoto. Other foreign research centers include the division of mycology and plant pathology of the Central Agricultural Research Institute in New Delhi and the Center for Agrobiological Research in Wageningen, The Netherlands.
The subject areas most thoroughly studied in other countries include the integrated protection of plants, chemistry of pesticides, biological methods of disease control, and phytopathological methodology. Crops are being successfully bred for immunity to diseases. The numerous phytopathological journals include Phytopathology (since 1911, USA), Annual Review of Phytopathology (since 1963, USA), Nachrichtenblatt der Deutschen Pflanzenschutzdienst (since 1921, German Democratic Republic), Phytoma (since 1948, France), and Ochrana rostlin (since 1921, Czechoslovakia). International congresses and conferences are held regularly to discuss aspects of phytopathology, including pesticides and plant protection. The Eighth International Plant Protection Convention was held in 1975.
REFERENCESGorlenko, I. V. Sel’skokhoziaistvennaia fitopatologiia. Moscow, 1968.
Zhuravlev, N. I., and D. V. Sokolov. Lesnaia fitopatologiia. Moscow, 1969.
Poliakov, I. M. Khimicheskii metod zashchity rastenii ot boleznei, 2nd ed. Leningrad, 1971.
Stepanov, K. M., and A. E. Chumakov. Prognoz boleznei sel’skokhoziaistvennykh rastenii, 2nd ed. Leningrad, 1972.
Melody fitopatologii. Edited by M. V. Gorlenko. Moscow, 1974. (Translated from English.)
Peresypkin, V. F. Selsko’khoziaistvennaia fitopatologiia, 2nd ed. Moscow. 1974.
Tarr, S. A. Osnovy patologii rastenii. Edited by M. S. Dunin. Moscow, 1975. (Translated from English.)
M. S. DUNIN and IU. N. FADEEV