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Studies Examine Relationship Between Modern Plant Science and Darwin
A section of the new issue of Pest Management Science is devoted to the relationship between modern pest science and the work of Charles Darwin. 2009 marks the 200th anniversary of Darwin’s birth, and this November, his seminal work, On the Origin of Species, celebrates its 150th anniversary.
The topics include research by Derek W. Hollomon, of the School of Medical Sciences at the University of Bristol, and Keith J. Brent, a consultant and a leading authority on fungicide resistance, which focuses on the issue of combating modern plant diseases, and their connection to Darwin’s work. The paper explores the relevance of Darwin’s ideas to three problem areas with respect to plant diseases caused by fungi: the emergence of new diseases; the loss of disease resistance bred into plants; and the development of fungicide resistance.
Darwin was well aware of the importance of plant diseases. He was interested in the possibility of raising blight-proof potatoes from crosses with South American species and is said to have encouraged the breeding of plants that would be disease-resistant.
The paper explores the ways in which evolutionary change through variation, selection and inheritance, as expounded by Darwin, can still occur in plant pathogens, and how it can affect efforts to control plant diseases.
A paper by Jonathan Gressel, of the Weizmann Institute of Science, focuses on the evolving understanding of the evolution of herbicide resistance. His research details the fact that more and varied modes of resistance have evolved in weeds than in other plants. Weeds, pathogens and insects are a subset of organisms that are fast runners in the evolutionary race, using a panoply of mutator mechanisms that enable adaptation, invasiveness and evolution of resistance.
Herbicides are typically selective between plants, meaning that before deployment there are already some crops that possess natural resistance. Weeds have evolved resistance mechanisms unknown even in antibiotics. It is even possible that cases of epigenetic, “remembered” resistances may have appeared.
The evolution of herbicide resistance has extreme agricultural significance, and has also been an important contributor to the understanding of many basic phenomena. Agriculture is the largest evolution laboratory present on earth today, with herbicides as the most ubiquitous man-made artificial selector for evolution on the planet. The future of herbicides resistance may foreshadow developments in antibiotics, anti-cancer drugs as well as with other pesticides.
A paper by Aaron J. Gassmann, of Iowa State University, and David W. Onstad and Barry R. Pittendrigh, of the University of Illinois, focuses on the evolutionary analysis of herbivorous insects in natural and agricultural environments.
Herbivorous insects offer a remarkable example of the biological diversity that formed the foundation for Darwin’s theory of evolution by natural selection. The ability of insects to rapidly evolve resistance to insecticides and host-plant resistance present a continual challenge for pest management.
The paper considers how genetic constraints, host-plant availability and evolutionary trade-offs affect the evolution of herbivorous insects in natural and agricultural environments. It also examines the extent to which lessons learned from studying natural systems may be applied to improve insect resistance management in agricultural systems.
Evolutionary trade-offs often accompany adaptations by herbivores. They arise when the benefit of a trait, such as ability to feed on a novel host plant, or to survive in the presence of an insecticide, is counter-balanced by a cost that decreases survival ability in the absence of the selective agent. For resistance to insecticides, these costs may act as an evolutionary constraint, and delay or prevent the evolution of resistance.
The paper also discusses how pest management capabilities can be advanced by learning from natural systems, which are often heterogeneous and dynamic. Scientists must fit concepts, models and experimental designs to nature, not constrain nature to match these intellectual constructs. This concept was espoused by Charles Darwin, who challenged the dogma of his time and helped people appreciate the heterogeneity and dynamics of nature.