History of Ecological Sciences, Part 44: Phytopathology during the 1800s

Abstract

Click here for all previous articles in the History of the Ecological Sciences series by F. N. Egerton Every ecologist knows the basic history of evolutionary theory—Lamarck's inability to sway many naturalists with his flawed arguments, and Darwin's only gradual success with his masterful presentation. Much less well known is the struggle to establish the germ theory of disease, with many defenders and skeptics for well over a century before it gained acceptance. Although the germ theory of disease is narrower in scope than evolutionary theory, its practical importance is at least as great, and therefore its history merits greater familiarity. We saw in part 29 (Egerton 2008) that both mycology and phytopathology made notable advances during the 1700s—with small steps toward a germ theory—though these advances were not widely known or appreciated. Researchers during the 1800s built upon the work of their predecessors. The science of phytopathology began with investigations of fungi, the earliest known culprits, and fungi were already being accused during the 1700s, though there was a hung jury rather than a clear verdict of guilt (Egerton 2008). If guilt was to be established, it was important for botanists to have a standard system to classify what they knew and make clear what was a new discovery when one occurred. Mycology and phytopathology had to advance together. Although John Needham (1713–1781), whom we met in part 24 (Egerton 2007:147), discovered a "worm" (a nematode now named Anguina tritici) in wheat galls (Needham 1743:640–641), D. J. Raski (1959:386) dates the beginning of nematology to the Histoire naturelle des helminthes ou vers intestinaux 1845 by Felix Dujardin (1801–1860). In 1854–1856, Dujardin's fellow countryman, Casimir-Joseph Davaine (1812–1882) studied the nematode that causes seed-gall disease in wheat, and in 1868 Davaine also discovered a bacterium that caused a plant disease. Not until the late 1800s were there evidences of a virus as a cause of plant disease. Nature is one, but scientists partition it into sciences they can master. Although phytopathology and animal parasitology developed as separate sciences, their concerns overlap in cases of fungal diseases of animals, including humans, and nematode diseases of plants; and both phytopathology and parasitology overlap with bacteriology and virology concerning bacterial and viral diseases. The history of nematode parasitism of plants was outside the scope of both Large's (1940) and Ainsworth's (1981) histories of phytopathology, but nematodes are discussed in textbooks on phytopathology (Heald 1926:831–851, Walker 1969:533–548, Agrios 2005:826–874). With many simultaneous developments occurring, it seems best to discuss studies of fungi first, nematodes and bacteria second and third, and viruses last, in Europe, then in North America. The botanist who began to put the fungal house in order was Christiaan Hendrik Persoon (ca.1761–1836), of Dutch heritage, from Cape Town, South Africa (Donk 1974, Ainsworth 1976:255–258, Magnin-Gonze 2004:170–171). In 1775 he went to Germany, where he received his botanical education, and in 1802 he moved to Paris, where he lived alone, in poverty. He corresponded with many botanists and exchanged specimens with them, exemplified by his correspondence with James E. Smith (Ramsbottom 1934). In 1828 he gave his botanical collections to the Dutch government in exchange for a pension, and when he died he left his remaining collections and his library to the Dutch government. (a) Christiaan Hendrik Persoon in 1796. (b) Elias Magnus Fries. Ainsworth 1976:256, 260. Persoon published his first article on fungi in 1793 (Schmid 1933), introduced his classification system in 1794, and produced his Synopsis methodica fungorum in 1801, which became the foundation of modern mycological systematics. Geoffrey Ainsworth (1976:258) found that "almost all the hundred genera and subgenera he recognized are universally accepted genera of today." Persoon brought together the rusts and smuts in the Dermatocarpi, and he named Fontana's small parasitic plants, brown and black rust on wheat, Uredo linearis and Puccinia graminis (Fig. 2). However, Persoon accepted the prevailing belief that these species could arise from abnormal sap or tissue in the host plant, and his description of P. graminis was vague (Ainsworth 1981:34, 43). Black rust Puccinia graminis, figures 57–59 (upper left corner). Drawn by John Edward Sowerby (1825–1870). Cooke 1865: Plate 4, facing 56. (a). Joseph Banks. (b) Thomas Andrew Knight. Simmonds 1954:following 468. Germination and growth of bunt spores. Prévost 1807, 1939: Plate 1, Figs. 1–32. (a) Agostino Maria Bassi. Bassi 1958: facing title page. (b) David Gruby, age 75. Ainsworth 1976:169. John Ramsbottom (1913:81–84) evaluated Persoon's classification of the Uredinales, which classification is probably a fair sample of Persoon's Synopsis. Persoon began a revision of his Synopsis entitled Mycologia Europea (three volumes, 1822–1826), but left it incomplete, no doubt because a younger rival, Elias Magnus Fries (1794–1878) had begun his authoritative Systema Mycologicum (three volumes, 1821–1829 + 2 supplements, 1830–1832). Fries quite literally followed in the footsteps of Linnaeus: his father was a church vicar from the southern Swedish province of Småland, he studied at the Växjö secondary school, then at the University of Lund, and eventually became Professor of Botany at Uppsala University (Eriksson 1952, 1972, Fries 1952, Ainsworth 1976:259–263). At Lund he studied fungi, but before going there he had independently learned between 300 and 400 species (compared to Linnaeus' listing of 92 species). He found Persoon's classification unsatisfactory, and Fries's Systema Mycologicum "did for mycology what Linné did for phanerogamic taxonomy," with his descriptions being "models of accuracy and conciseness" (Fries 1952:180). His Systema is the starting point for fungal names, just as Linnaeus's names are for higher plants; however, Fries worked without a microscope. He did not confine his studies to fungi, but his other studies are beyond the scope of this discussion. Elias Fries was the first of four generations of Fries botanists. We met Sir Joseph Banks (1743–1820) in part 43 (Egerton 2012:200) as the botanist with whom Thomas Andrew Knight (1759–1838) corresponded, and who published Knight's letters in the Philosophical Transactions of the Royal Society of London. Banks was president of the Royal Society for 42 years, so he was a well-respected member of the scientific community (Foote 1970, Carter 1987, O'Brian 1997, Knight 2004). In 1805, in response to an extensive outbreak of black rust (Puccinia graminis) in 1804 (Ordish 1976:115), Banks published A Short Account of the Cause of the Disease in Corn, called by Farmers the Blight, the Mildew, and the Rust, in which he asked, "Is it not more than possible that the parasitic fungus of the barberry and that of wheat are one and the same species, and that the seed transferred from the barberry to the corn [wheat], is one cause of the disease?" (quoted from Ramsbottom 1913:85). He had read Felice Fontana's Observazioni sopora la ruggine del grano (1767), which was little known in Britain. One would think that Banks also would have read A Botanical Arrangement of All the Vegetables Naturally Growing in Great Britain (edition 1, 1776) by William Withering (1841–1899), that claimed the Berberis shrub "should never be permitted to grow in corn [grain] lands, for the ears of wheat that grow near it never fill, and its influence in this respect has been known to extend as far as 300 or 400 yards across a field" (quoted from Ramsbottom 1913:81). However, Banks' claim that "It has long been admitted by farmers, though scarcely credited by botanists, that wheat in the neighbourhood of a barberry bush seldom escapes the Blight" (quoted from Ramsbottom 1913:85) seems to indicate he had not read Withering's work. Banks' pamphlet had two interesting enlarged color illustrations by Francis Bauer (1758–1840) of the rust imbedded in the wheat tissue (one reproduced in Ordish 1976: plate 3; see also Ainsworth 1969:15). Examining the barberry bush attentively, I found upon its fruit a species of fungus similar in colour to that on the straws of the wheat, but its seed vessels were larger, and more spherical. I was, however, much disposed to believe the parasitical plants of the same species, and that the difference in the form and size of the seed vessels arose only from the difference of the nutriment they derived from the wheat and from the acrid juice of the barberry. The distant (control) wheat was healthy until Knight took a diseased barberry branch to that wheat, where he sprinkled the branch with water and brushed it over the healthy wheat, which 10 days later became diseased. Simultaneously, he took some diseased wheat to healthy wheat, moistened the diseased wheat and brushed it over the healthy wheat, but the healthy wheat remained healthy. Ramsbottom (1913:86) suggested that Knight was "the first to try inoculation experiments on heteroecism." Knight did not write a letter to Banks about this experiment until after he had read Bank's pamphlet, on 20 March 1806. In 1806, Banks published a second edition of his pamphlet and appended Knight's letter (Banks 1806:26–36, Ramsbottom 1913:85, Dawson 1958:501). In Philadelphia, a retired physician and immigrant from Bath, England, Anthony Fothergill (1732?–1813), read a paper on 11 November 1806 to the Philadelphia Society for Promoting Agriculture, arguing that grain rust was caused by "clusters of a fungus or parasitical plant…[that] insinuate themselves into the pores of the absorbent vessels of the stem, and deprive the grain of the sap destined for its nourishment" (1808, quoted from Campbell et al.1999:33). In 1818, a Danish schoolteacher, Schoeler, carried out the Knight experiment with the same results (Parris 1968:24). Knight recommended in 1818 the use of flowers of sulfur against pear scab (Lycoperdon cancellatum), and in 1834 he recommended the sprinkling in early spring of peaches with sulfur and lime to control leaf curl. John Roberts recommended in 1821 using soap to cause wetting of sulfur in water to control peach mildew, and in 1824 he reported his successful experimental transmission of peach mildew (Knight 1818, 1842, Roberts 1824, Parris 1968:25–26, Ainsworth 1976:160, 1981:32–33, 110). Phytopathologist George L. McNew divided the history of his profession into five periods, with periods three and four occurring during the 1800s (McNew 1963:166–172). Period three he labeled "The Predisposition Period," during which the prevailing view was that fungi originated in diseased plant tissue. Three authors published treatises on plant pathology and remedies in 1807. Freiherr von Werneck and Filippo Ré represented the consensus in not accepting fungi as the cause of the diseases (Whetzel 1918:32, Parris 1968:23, Walker 1969:20–22). Isaac-Bénédict Prévost (1755–1819) did think fungi caused diseases (Keitt 1939a, Large 1940:76–79, Robinson 1975, Ainsworth 1981:30–32). He was the son of a teacher-pastor in Geneva, but at age 22 he became a tutor in Montauban, France, where he remained for the rest of his life. His interests included mathematics, physics, chemistry, biology, and philosophy. In 1797 a member of the Society of Montauban read a memoir on the carie or charbon (bunt or smut) disease of wheat, and the society asked other members to study the problem. Prévost read previous studies on the problem, including those by Duhamel du Monceau (1728) and Mathieu du Tillet (1755), discussed in part 29 (Egerton 2008), and especially Henri Alexandre Tessier's Traité des maladies des grains (Paris, 1783), which attributed rust to stoppage of transpiration, caused by mists. Tessier repeated some of Tillet's experiments and agreed that bunt was contagious (Parris 1968:19). Tessier also stressed the importance of soaking wheat seeds in lime water before planting, which greatly diminished the loss of wheat from bunt in France (Large 1940:76). The owner of a nearby estate made available to Prévost land for large-scale experiments. George Keitt (1939b) provided an excellent guide to and evaluation of Prévost's achievement along with his English translation of the Mémoire. Prévost could not discover everything he wished, but he was remarkably thorough and clear in the presentation of his findings. Tillet had demonstrated in 1755 that bunt (carie, charbon) of wheat was spread by an infectious agent (Egerton 2008:237), but had not demonstrated that the agent was a fungus. Prévost was able to induce the bunt dust to germinate in water and illustrated its growth, thus demonstrating the dust was fungal spores. He illustrated its progressive development on the first of his three plates. To those believing a fungus arose within the wheat plant, he replied that he only observed branches from the spore growing from the surface into the seedling (1939:34–35, paragraphs 44–46). Fruiting bodies grew within ears of wheat and spores were disseminated by the wind. Prévost scattered spores on soil where wheat seed was planted and concluded that it was only at germination, or soon after, that infection occurred (Prévost 1939:38, paragraph 57). He discovered that copper dust suspended in water, or liquid copper compounds, inhibited spores from germinating (Prévost 1939:72–82, paragraphs 138–177, Ainsworth 1976:160–161, 1981:124–126), and arsenic was reported in England to have the same effect (Prévost 1939:83, paragraph 178). The Society of Montauban sent a published copy of Prévost's Mémoire to the Institute [de France?] in Paris for evaluation. Tessier reported for a review committee favorably, but no actions were taken. Mendel was by no means the only author of a clear publication that failed to gain the recognition deserved upon publication. Lavoisier, Lyell, and Darwin achieved their scientific revolutions in part because of prominence in their scientific communities. Prévost and Mendel were amateurs on the periphery of their scientific communities, who were neglected, rather than being either challenged or widely recognized. Nevertheless, Prévost gave the first experimental proof of the pathogenicity of a microorganism, and he first described motile spores (zoospores) in fungi (Ainsworth 1976:62, 147). In Italy, Agostino Maria Bassi (1773–1856), like Prévost, was on the periphery of science, but his important parasitical work did attract the attention it deserved, because he promoted it (Belloni 1961:20–26, Robinson 1970, Ainsworth 1976:163–168). He grew up near Pavia and attended its university. He studied law there to please his parents, but his interests were in science, and he studied under Antonio Scarpa, anatomist, Alessandro Volta, physicist, and Giovanni Rasori (1766–1836), pathologist. Rasori (portrait in Belloni 1961:22) wrote a book defending the contagium vivum theory that appeared posthumously in 1837. Both Rasori and Bassi were influenced by the writings of Lazzaro Spallanzani (1729–1799), who discredited the theory of spontaneous generation and accepted the conclusions of Fontana and Targioni-Tozzetti that small parasitic plants can cause diseases in vascular plants (Egerton 2008:235, 239). The silk industry could flourish in northern Italy and in France, if it could eliminate an epidemic disease, muscardine (calcinaccio). In 1807 Bassi decided to investigate; he grew silkworms, assuming the disease (Bassi 1958:4) …arose spontaneously in the silk worm and was due to some difference in the atmosphere, the food, or the method of breeding, or rather to the various fumes emanating from the fermenting litter… He varied environmental conditions for different groups but failed to induce the disease in his caterpillars. When he obtained diseased caterpillars, he found the disease spread at temperatures of 7°–30°R, but not above 38°R (Bassi 1958:8). The disease could be transmitted to caterpillars of other species. It was contagious, because it always began with one or a few caterpillars, whereas an environmental or physiological disease could affect all individuals about the same time. Bodies of dead caterpillars became covered with "a patina or efflorescence like flakes of pure snow" (Bassi 1958:7). In 1835, Bassi announced that muscardine was caused by a fungus, and he added a footnote (Bassi 1958:10, note on 15) The and of the and were the first to put the that the disease is produced in the silk worm by the development of a species of fungus, it on the that from which have died of that and in that they to to experiments to this these last, it as the of a had they the to they have by that these able were not and had on the Although Bassi the for their to the one many read this or knew to an Bassi his English gave a more to the than is in this Bassi indicate his was in response to their but if he had made his discovery without read their he would have In he (Bassi If this parasitic plant is observed with the of the which the more than it be possible to see all its in and its as He that the was spread by water, and and for (Bassi The English translation of is to part 1, on theory In Bassi published part on to the disease. included or and in (Ainsworth and Bassi that his would be and he to his experiments for members at the University of and provided a by including and in the footnote quoted Bassi then published their in his to part (Bassi named the fungus Bassi discovered and an translation of part was published in Paris in Both botanist and for the des Sciences in Paris and published with a plate of illustrations of the fungus Belloni is reproduced by Ainsworth was the first known fungal of an Prévost had already demonstrated a fungal of In the early two published of fungal disease in David was a who obtained his in in and to Paris, where he and published Ainsworth Although the claim that he was one of the of the 1800s and seems an his were important for both and His important scientific all rather are from into English and In he published his that was caused by a in he that of the was caused by an He named of these fungi, but in he the cause of and named the fungus to though his were repeated by the Paris community remained of his conclusions and He also discovered during the early before the rest of his to a successful was and to at age In he discovered the fungal of but did not this until He was then a physician in a by Professor J. L. and named the fungus Ainsworth in footsteps as an English Joseph had a in that eventually to his the of the 1800s Ramsbottom Ainsworth 1970, and He attended but left two before John became its of an he and earliest published were on and he only began to on fungi in when William to write the fungal of The English to plant pathology occurred in when the that had been discovered in in 1842, and occurred in the in Campbell et and in in then spread to Britain and When its in became Sir a scientific to study the (Large under Botany Professor John and Professor who had received his under (Large The went to but did not a clear cause of the disease. (a) Joseph Ainsworth (b) found a fungus with which he named on 1845 (portrait in Ainsworth He was about the fungus caused the but sent his and to his at first However, F. of a of in the fungus caused the and he inoculation experiments to the claim agreed with before his study on the disease also published (one of which is in the for the disease an environmental cause and the who this theory and then he the for "The is the of the of the and not the of the He his article with a and English description of and species of like are no in that Large that article many but not all did not spore germination, did he the infection of the (a) Joseph Ainsworth (b) became both and plant and he the in over the cause of a new disease, discovered by a in 1845 near re

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