Darwin and Potato Blight
What is potato blight? It is caused by a fungal like organism.
Lynne Boddy, in The Fungi (Third Edition), 2016 says:
"The oomycetes, though not fungi operate in many similar ways, cause a range of diseases of plants and are studied by mycologists."
“Late blight, caused by Phytophthora infestans, is the most devastating disease of potatoes worldwide, especially in regions which often experience cool, damp weather. It kills stems and foliage at any time during the growing season, and can kill whole fields of plants in less than 2 weeks under optimal cool, wet conditions. Potato tubers and tomato fruits are also attacked, rotting in the field or during storage.”
The Irish Potato Famine
Watchers of the second series of “Victoria” will have seen how Ireland in particular was hit by famine conditions caused by potato blight.
A.B. Gould, in Encyclopedia of Microbiology (Third Edition), 2009 comments that:
“Late blight of potato, a disease caused by Phytophthora infestans (meaning ‘infectious plant destroyer’), has special historical significance. Controversy over the etiology of late blight (which caused the Irish potato famine in the mid-1840s) eventually led to the first accepted experimental proof that microorganisms, in this case fungi, are the cause of disease and not, as surmised at the time, the result of wet weather or the wrath of God.”
“The ensuing disease in the 1840s, the result of a combination of susceptible potatoes grown in monoculture, weather favorable for disease development, and a virulent pathogen, proved catastrophic to cultures, and especially Irish peasants, who depended heavily on the potato for sustenance.”
Now it struck me that Charles Darwin was living around that time, so what did he make of the potato blight, and did he have any suggestions regarding how to deal with it?
As Jean Beagle Ristaino and Donald H. Pfister remark:
“Potato late blight struck in Ireland and at Darwin's farm in England in the fall of 1845. It was Darwin who was among the first to suggest growing potatoes from true seed”
Darwin wrote to John Henslow, his Cambridge mentor in 1845 at the onset of the disease in Britain,
“My Dear Henslow, I have to thank you for several printed notices about the potatoes etc etc. What a painfully interesting subject it is; I have just returned home & have looked over my potatoes & find the crop small, a good many having rotted in the ground, but the rest well. I am drying sand today in the oven to store with the greatest care in baskets, my seed-potatoes”
Going back to wild stock
Ristaino and Pgister comment about this first attempt to find a cure in their article on " Charles Darwin's Studies of Potato Late Blight":
“In 1845, during the late blight outbreaks in the UK and Ireland, it was believed that “wild” or indigenous potatoes might possess resistance to the disease and were in high demand. There was a belief that by going back to the “motherland” of the host, one might be able to find resistance to the disease and rejuvenate the potato culture of Europe.”
There was some truth in this: potatoes in Europe, and especially in Ireland, had little diversity and formed what was called a “monoculture”. This meant that any disease such as late blight, could spread rapidly as there was not enough variability for resistance.
Going back to the wild origins of the potatoes, it was thought, might provide more diversity and hence more resistance to late blight.
William Fox, Darwin’s second cousin, writing in the Gardeners’ Chronicle in 1846 on “Potatoe disease” commented that:
“In the spring of 1835, Mr. Darwin collected some seeds from ripe tubers, in the Cordillera of central Chile, in a most unfrequented district, many miles from any inhabited spot, and where the plant was certainly in a state of nature. These vegetated under Professor Henslow's care in 1836 or 1837, and in that year or 1838, Mr. Darwin gave a tuber to me. It was either three or four years before the potatoes from it became eatable.”
Fox noted that this approach was not successful:
“I had them growing last year among many other kinds; and they are a late variety, they had not ceased growing when the disease appeared in Cheshire. They fared exactly the same as the other kinds, having blotched in the leaf and a few tubers decayed. This year the haulm [stem] was destroyed totally in the same manner as all my potatoes were and on taking up the tubers I find about the same number diseased as in other kinds. I fear this decides the point as to the usefulness of procuring seed from even the fountain head—the wild stock itself.”
Others sought different varieties to find a resistant strain. John Lindley in 1848 in “Notes on the wild potato, Journal of the Royal Horticultural Society of London” said:
“Among the speculations that have been entertained respecting the Potato disease, one consisted in the belief that in order to secure against future ravages, it was necessary to bring the plant once more from its native country and begin over again the process of domesticating it.”
Lindley also concluded: ““neither renewal of seed, nor introduction from foreign countries could guarantee against the attacks.”
Applying Natural Selection to find Resistance Strains
Darwin published “The Variation of Animals and Plants under Domestication” in 1868 and “The Effects of Cross and Self Fertilisation in the Vegetable Kingdom” in 1876. Ristaino and Pgister note that: “Darwin focused attention on selection as a process by which specific characters could be introduced or enhanced. The potato was one example among many that he used.”
In 1876, James Torbitt, wine merchant, inventor, and potato breeder, began a correspondence with Darwin, which was to lead to an experiment programme endorsed by Darwin. Darwin wrote of this:
“Mr. Torbitt's plan of overcoming the potato-disease seems to me by far the best which has ever been suggested. It consists, as you know from his printed letter, of rearing a vast number of seedlings from cross-fertilised parents, exposing them to infection, ruthlessly destroying all that suffer, saving those which resist best, and repeating the process in successive seminal generations.”
“ My belief in the probability of good results from this process rests on the fact of all characters whatever occasionally varying. It is known, for instance, that certain species and varieties of the vine resist phylloxera better than others. Andrew Knight found one variety or species of the apple which was not in the least attacked by coccus, and another variety has been observed in South Australia. Certain varieties of the peach resist mildew, and several other such cases could be given. Therefore there is no great improbability in a new variety of potato arising which would resist the fungus completely, or at least much better than any existing variety.
“With respect to the cross-fertilisation of two distinct seedling plants, it has been ascertained that the offspring thus raised inherit much more vigorous constitutions and generally are more prolific than seedlings from self-fertilised parents. It is also probable that cross-fertilisation would be especially valuable in the case of the potato, as there is reason to believe that the flowers are seldom crossed by our native insects; and some varieties are absolutely sterile unless fertilised with pollen from a distinct variety.”
“There is some evidence that the good effects from a cross are transmitted for several generations; it would not, therefore be necessary to cross-fertilise the seedlings in each generation, though this would be desirable, as it is almost certain that a greater number of seeds would thus be obtained.”
“It would be advisable that some kind of potato eminently liable to the disease should be planted in considerable numbers near the seedlings so as to infect them.”
“Altogether the trial would be one requiring much care and extreme patience, as I know from experience with analogous work, and it may be feared that it would be difficult to find any one who would pursue the experiment with sufficient energy. It seems, therefore, to me highly desirable that Mr. Torbitt should be aided with some small grant so as to continue the work himself.”
Government funding was not available, but Darwin contributed financial support himself to the project and raised financing by subscription by some of his friends.
Darwin noted that: “Mr. Torbitt tells me that he still (1887) succeeds in raising varieties possessing well-marked powers of resisting disease; but this immunity is not permanent, and, after some years, the varieties become liable to the attacks of the fungus.”
As Ristaino and Pfister note:
“Torbitt's project was in no way a small undertaking. Millions of seeds were harvested, distributed free of charge to many farmers and even members of the House of Lords, who planted, raised, and observed these plants’ reaction to the potato late blight.”
M. Dearce in his study of Darwin's correspondence with Torbitt noted that:
“Torbitt (1876) reported the experiences of 22 farmers throughout the United Kingdom who had participated in a large field-experiment conducted with his seeds, planted in the spring of 1875. Five farmers reported totally disease-free crops. Of the 17 with diseased crops, eight reported better than 80% disease-free; five reported, respectively, better than 70%, two thirds, less than 50%, 40%, and 10% disease free; two reported disease in the leaves but not in the tubers, and two reported accidental loss of crop. In all cases, the healthy plants had grown within short distances of diseased plants”
Torbit was applying principles of natural selection to generate blight resistant varieties of potatoes, and he laid the foundation for some of the principles for cultivating modern blight resistant varieties, using evolutionary pressures selectively as a driving force.
As Darwin saw, this would be a continual struggle, because the pathogens would also mutate, and there were no easy shortcuts to success in scientific endeavour; it would take painstaking effort and time - "much care and extreme patience", and recording failures was as important as recording success so that - as in the case of the "wild stock" experiment, others could learn from that..
References
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/peronosporales
What is potato blight? It is caused by a fungal like organism.
Lynne Boddy, in The Fungi (Third Edition), 2016 says:
"The oomycetes, though not fungi operate in many similar ways, cause a range of diseases of plants and are studied by mycologists."
“Late blight, caused by Phytophthora infestans, is the most devastating disease of potatoes worldwide, especially in regions which often experience cool, damp weather. It kills stems and foliage at any time during the growing season, and can kill whole fields of plants in less than 2 weeks under optimal cool, wet conditions. Potato tubers and tomato fruits are also attacked, rotting in the field or during storage.”
The Irish Potato Famine
Watchers of the second series of “Victoria” will have seen how Ireland in particular was hit by famine conditions caused by potato blight.
A.B. Gould, in Encyclopedia of Microbiology (Third Edition), 2009 comments that:
“Late blight of potato, a disease caused by Phytophthora infestans (meaning ‘infectious plant destroyer’), has special historical significance. Controversy over the etiology of late blight (which caused the Irish potato famine in the mid-1840s) eventually led to the first accepted experimental proof that microorganisms, in this case fungi, are the cause of disease and not, as surmised at the time, the result of wet weather or the wrath of God.”
“The ensuing disease in the 1840s, the result of a combination of susceptible potatoes grown in monoculture, weather favorable for disease development, and a virulent pathogen, proved catastrophic to cultures, and especially Irish peasants, who depended heavily on the potato for sustenance.”
Now it struck me that Charles Darwin was living around that time, so what did he make of the potato blight, and did he have any suggestions regarding how to deal with it?
As Jean Beagle Ristaino and Donald H. Pfister remark:
“Potato late blight struck in Ireland and at Darwin's farm in England in the fall of 1845. It was Darwin who was among the first to suggest growing potatoes from true seed”
Darwin wrote to John Henslow, his Cambridge mentor in 1845 at the onset of the disease in Britain,
“My Dear Henslow, I have to thank you for several printed notices about the potatoes etc etc. What a painfully interesting subject it is; I have just returned home & have looked over my potatoes & find the crop small, a good many having rotted in the ground, but the rest well. I am drying sand today in the oven to store with the greatest care in baskets, my seed-potatoes”
Going back to wild stock
Ristaino and Pgister comment about this first attempt to find a cure in their article on " Charles Darwin's Studies of Potato Late Blight":
“In 1845, during the late blight outbreaks in the UK and Ireland, it was believed that “wild” or indigenous potatoes might possess resistance to the disease and were in high demand. There was a belief that by going back to the “motherland” of the host, one might be able to find resistance to the disease and rejuvenate the potato culture of Europe.”
There was some truth in this: potatoes in Europe, and especially in Ireland, had little diversity and formed what was called a “monoculture”. This meant that any disease such as late blight, could spread rapidly as there was not enough variability for resistance.
Going back to the wild origins of the potatoes, it was thought, might provide more diversity and hence more resistance to late blight.
William Fox, Darwin’s second cousin, writing in the Gardeners’ Chronicle in 1846 on “Potatoe disease” commented that:
“In the spring of 1835, Mr. Darwin collected some seeds from ripe tubers, in the Cordillera of central Chile, in a most unfrequented district, many miles from any inhabited spot, and where the plant was certainly in a state of nature. These vegetated under Professor Henslow's care in 1836 or 1837, and in that year or 1838, Mr. Darwin gave a tuber to me. It was either three or four years before the potatoes from it became eatable.”
Fox noted that this approach was not successful:
“I had them growing last year among many other kinds; and they are a late variety, they had not ceased growing when the disease appeared in Cheshire. They fared exactly the same as the other kinds, having blotched in the leaf and a few tubers decayed. This year the haulm [stem] was destroyed totally in the same manner as all my potatoes were and on taking up the tubers I find about the same number diseased as in other kinds. I fear this decides the point as to the usefulness of procuring seed from even the fountain head—the wild stock itself.”
Others sought different varieties to find a resistant strain. John Lindley in 1848 in “Notes on the wild potato, Journal of the Royal Horticultural Society of London” said:
“Among the speculations that have been entertained respecting the Potato disease, one consisted in the belief that in order to secure against future ravages, it was necessary to bring the plant once more from its native country and begin over again the process of domesticating it.”
Lindley also concluded: ““neither renewal of seed, nor introduction from foreign countries could guarantee against the attacks.”
Applying Natural Selection to find Resistance Strains
Darwin published “The Variation of Animals and Plants under Domestication” in 1868 and “The Effects of Cross and Self Fertilisation in the Vegetable Kingdom” in 1876. Ristaino and Pgister note that: “Darwin focused attention on selection as a process by which specific characters could be introduced or enhanced. The potato was one example among many that he used.”
In 1876, James Torbitt, wine merchant, inventor, and potato breeder, began a correspondence with Darwin, which was to lead to an experiment programme endorsed by Darwin. Darwin wrote of this:
“Mr. Torbitt's plan of overcoming the potato-disease seems to me by far the best which has ever been suggested. It consists, as you know from his printed letter, of rearing a vast number of seedlings from cross-fertilised parents, exposing them to infection, ruthlessly destroying all that suffer, saving those which resist best, and repeating the process in successive seminal generations.”
“ My belief in the probability of good results from this process rests on the fact of all characters whatever occasionally varying. It is known, for instance, that certain species and varieties of the vine resist phylloxera better than others. Andrew Knight found one variety or species of the apple which was not in the least attacked by coccus, and another variety has been observed in South Australia. Certain varieties of the peach resist mildew, and several other such cases could be given. Therefore there is no great improbability in a new variety of potato arising which would resist the fungus completely, or at least much better than any existing variety.
“With respect to the cross-fertilisation of two distinct seedling plants, it has been ascertained that the offspring thus raised inherit much more vigorous constitutions and generally are more prolific than seedlings from self-fertilised parents. It is also probable that cross-fertilisation would be especially valuable in the case of the potato, as there is reason to believe that the flowers are seldom crossed by our native insects; and some varieties are absolutely sterile unless fertilised with pollen from a distinct variety.”
“There is some evidence that the good effects from a cross are transmitted for several generations; it would not, therefore be necessary to cross-fertilise the seedlings in each generation, though this would be desirable, as it is almost certain that a greater number of seeds would thus be obtained.”
“It would be advisable that some kind of potato eminently liable to the disease should be planted in considerable numbers near the seedlings so as to infect them.”
“Altogether the trial would be one requiring much care and extreme patience, as I know from experience with analogous work, and it may be feared that it would be difficult to find any one who would pursue the experiment with sufficient energy. It seems, therefore, to me highly desirable that Mr. Torbitt should be aided with some small grant so as to continue the work himself.”
Government funding was not available, but Darwin contributed financial support himself to the project and raised financing by subscription by some of his friends.
Darwin noted that: “Mr. Torbitt tells me that he still (1887) succeeds in raising varieties possessing well-marked powers of resisting disease; but this immunity is not permanent, and, after some years, the varieties become liable to the attacks of the fungus.”
As Ristaino and Pfister note:
“Torbitt's project was in no way a small undertaking. Millions of seeds were harvested, distributed free of charge to many farmers and even members of the House of Lords, who planted, raised, and observed these plants’ reaction to the potato late blight.”
M. Dearce in his study of Darwin's correspondence with Torbitt noted that:
“Torbitt (1876) reported the experiences of 22 farmers throughout the United Kingdom who had participated in a large field-experiment conducted with his seeds, planted in the spring of 1875. Five farmers reported totally disease-free crops. Of the 17 with diseased crops, eight reported better than 80% disease-free; five reported, respectively, better than 70%, two thirds, less than 50%, 40%, and 10% disease free; two reported disease in the leaves but not in the tubers, and two reported accidental loss of crop. In all cases, the healthy plants had grown within short distances of diseased plants”
Torbit was applying principles of natural selection to generate blight resistant varieties of potatoes, and he laid the foundation for some of the principles for cultivating modern blight resistant varieties, using evolutionary pressures selectively as a driving force.
As Darwin saw, this would be a continual struggle, because the pathogens would also mutate, and there were no easy shortcuts to success in scientific endeavour; it would take painstaking effort and time - "much care and extreme patience", and recording failures was as important as recording success so that - as in the case of the "wild stock" experiment, others could learn from that..
References
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/peronosporales
“What a Painfully Interesting Subject”: Charles Darwin's Studies of Potato Late Blight
Jean Beagle Ristaino Donald H. Pfister
https://academic.oup.com/bioscience/article/66/12/1035/2646818
https://potatoes.ahdb.org.uk/sites/default/files/publication_upload/Paul_Birch_Phytophthora_Infestans_genome.pdf
Correspondence of Charles Darwin on James Torbitt’s project to breed blight-resistant potatoes
M. DEARCE
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.870.4782&rep=rep1&type=pdf
Jean Beagle Ristaino Donald H. Pfister
https://academic.oup.com/bioscience/article/66/12/1035/2646818
https://potatoes.ahdb.org.uk/sites/default/files/publication_upload/Paul_Birch_Phytophthora_Infestans_genome.pdf
Correspondence of Charles Darwin on James Torbitt’s project to breed blight-resistant potatoes
M. DEARCE
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.870.4782&rep=rep1&type=pdf
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1 comment:
As blight, other pathogens and insect resistance in plants is, generalising, because the plants evolve substances that are poisonous and/or repellent to the pests, one has to remember that the vast majority of these natural substances have never been tested for toxicity, carcinogenicity etc. It's been known since the 90s that 99.9% of pesticide substances ingested (by Americans) are substances naturally existing in even the organic fruit and vegetables we eat.
Using the same lab tests that are employed to assess the carcinogenicity etc of pesticides, glyphosate etc., Ames et al found that many common foodstuffs contain natural pesticides which can be hundreds of times more 'toxic' than even the artificial pesticides of the 90s. Ames invented the test for carcinogenicity so he should know!
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC54831/pdf/pnas01044-0440.pdf
Mitchell asserts that plants with high BRIX values are both almost invulnerable to disease and are more nutritious and healthy for us; thus plants with higher concentrations of natural chemicals are, in Mitchell's view, better.
Following the logic, this means that Mitchell's 'natural - beyond organic' produce will be, if tested using the very same methods that establish the relative toxicity of artificial substances, more toxic/carcinogenic than the evil 'watery supermarket produce' laden with pesticide residues.
So. An organic kale smoothy or a Big Ag spud or carrot? If one is concerned about ingesting carcinogenic substances, no matter in what irrelevantly small quantities, it's a no-brainer! Never let a 'healthy' five a day organic fruit or vegetable darken your door.
Of course, in reality, the amount of natural pesticides/toxic substances in modern produce is far less than the minimum that would cause any actual toxicity. The dose makes the poison.
Mitchell and Nigel Jones spread a narrative that the chemical companies somehow addicted farmers to their products because they were evil black hat exploiters. More accurately vegetables were bred to taste better - the (mostly) bitter tasting substances that the plant had evolved to fight infection and pests were reduced because humans didn't like them, so crops became more susceptible to disease at the same time as monoculture was developed to feed the growing population, which also made them more susceptible...
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