Plant diseases are all about us, in the city and in the countryside. They often go unnoticed, except by the initiated, yet they are essential components of most natural plant communities. They are of immense social and economic importance, cause massive losses in agriculture, horticulture and forestry, and have sometimes changed not only the landscape but also the course of history.
The mechanisms by which plant pathogens – fungi, bacteria, viruses and their relatives and even some higher plants – interact with their hosts are endlessly fascinating and have led generations of scientists to try to unravel their mysteries. These efforts have contributed to many major scientific discoveries, including the structure of DNA, and have resulted in many novel products and technological innovations such as antibiotics, plant growth regulators (‘hormones’), disease-resistant crops and techniques for producing genetically modified foods.
This book has been written in the hope that it will introduce to a wider audience our enthusiasm for, and enjoyment of, plant diseases. In the first three chapters we are concerned to understand the relationship between pathogen and host, a relationship that seems simple on the surface yet is often more complex than that between mammals and their pathogens (the animal system, based in large part on the circulatory system with circulating antibodies and leucocytes, is not available to the plant). The remaining chapters deal with the interaction between selected groups of pathogens and their hosts and the role, sometimes spectacular, of the resulting diseases in human affairs. Our greatest difficulty, as for most scientific authors, has been to find a suitable balance between technical accuracy, often involving unfamiliar terminology, and our desire to make the writing comprehensible to all. We hope that the finished product does indeed combine these two aims to the satisfaction of most readers.
Writing the book has been a true collaboration, and neither one of us can be regarded as the ‘senior author’. It has revitalised a friendship and shared enthusiasm that began almost forty years ago, in October 1960, when we met in a lecture theatre, NFR as Professor and DSI as a first year student of plant pathology. Between us we span almost sixty years of work on plant disease, from simple cultural studies of parasitic fungi to the modern age of biochemistry and molecular genetics. In this period we have been closely acquainted with many great plant pathologists of the past and present; their views have so much influenced us that what we have written has inevitably derived, at least in part, from our contact with them.
The early studies of plant disease are easily accommodated in a natural history. More recent but equally important insights from biochemistry, genetics and molecular biology are perhaps less obviously part of such an approach. But if natural history is to go forward it must be ready to absorb, step by step, new scientific knowledge as it is developed, a way of thinking that the New Naturalist series seeks to promote. Moreover naturalists, who have played a significant role in the development of the science of plant pathology in the past, can continue to do so long into the future. Their contribution may embrace both detailed observation and the testing of hypotheses by experiment. It will be especially important, for example, in adding to knowledge of the role and distribution of plant diseases in natural plant communities, still poorly understood, and in unravelling details of the life cycles and host ranges of the innumerable pathogens that have not yet attracted the full attention of professional plant pathologists.
Finally, a word about plant diseases and conservation. Although the counterintuitive notion that plant pathogens should be conserved together with their hosts has hardly been mentioned in our book, it is a subject now dominating the scientific thinking of one of us, and may turn out to be just as important as the conservation of more obviously useful components of biodiversity. For those who wish to know more about this developing aspect of plant pathological thinking an appropriate reference (DSI, 1999) is included in the Bibliography.
We sincerely hope that all who read this book will gain the same immense pleasure and intellectual stimulus from the study of plant diseases as we have.
David Ingram & Noel Robertson
Aberlady and Walkerburn, Scotland
July 1999
Noel Robertson died peacefully on 2nd July 1999, just a few days after this foreword was written.
ACKNOWLEDGEMENTS
We have received help from many colleagues and former students during the writing of this book but acknowledge particularly help with difficult technical problems from: Clive Brasier, Don Clarke, James Duncan, John Friend, Chris Gilligan, Brian Harrison, Stefan Helfer, Paul Holliday, Anne Osbourn, Doug Parbery and Roy Watling. We also thank Monica Goldspink for checking the Latin and Greek derivations used in the Glossary. However, we take full responsibility for any interpretation or misinterpretation of the information and advice given so freely by all those we consulted. In a book of such scope the task of establishing a credible taxonomic framework has been greatly helped by reference to A Dictionary of Plant Pathology by Paul Holliday, Microfungi on Land Plants by Martin and Pamela Ellis and the many monographs and references mentioned in the Bibliography. The photographs are acknowledged individually in the captions and we are grateful to all who supplied them. However, we owe a particular debt of gratitude to Debbie White of the Royal Botanic Garden Edinburgh for all her hard work on our behalf. We also thank Mary Bates for the line drawings which are such an important element of the book. Finally we thank Alison Ingram, who typed and managed the manuscript for us, and without whom the book would not have been completed.
This book was written while DSI was Regius Keeper and then Honorary Fellow of the Royal Botanic Garden Edinburgh, and NFR was Honorary Fellow of the Royal Botanic Garden Edinburgh.