This book originated from a presidential meeting of the British Society of Plant Pathology in 1995, following the theme "Gene-for-gene specificity in host-parasite interactions at the molecular, cell, plant and population levels of organization." The book is a collection of 22 chapters, divided into three major sections: Genetic Analyses and Utilization of Resistance (5 chapters); Population Genetics (9 chapters); and Cell biology and Molecular Genetics (8 chapters). This great diversity renders a succinct summary of this book difficult, however one common theme is the quality of the different chapters. The chapters are informative, well written and accessible for non-specialists in a particular discipline. Ecologists, evolutionary biologists, molecular and cell biologists, and plant pathologists and physiologists alike should find chapters of interest in this book, and can read about current developments in the other disciplines studying the gene-for-gene relationships in plant-parasite interactions.
The gene-for-gene concept impacts various biological disciplines and this book provides a good overall perspective of the topic. The gene-for-gene concept has important practical applications, as race-specific resistance genes are commonly used in agriculture (Cultivar Mixtures in Intensive Agriculture, Chapter 4; and Crop resistance to parasitic plants, Chapter 5). The resistance genes used in a crop can act as strong selective agents on the pathogen population (The UK Cereal Pathogen Virulence Survey, Chapter 6; and Modeling virulence dynamics of airborne plant pathogens in relation to selection by host resistance in agricultural crops, Chapter 10). Moreover, understanding the factors which influence the diversity of virulence genes in the pathogen population should help us design better strategies to deploy resistance genes in the crop and consequently improve crop yield (Adaptation to Powdery Mildew Populations to Cereal varieties in relation to durable and non-durable resistance, Chapter 7; Virulence dynamics and Genetics of cereal rust populations in North America, Chapter 8; and Interpreting population genetic data with the help of genetic linkage maps, Chapter 9).
Polymorphisms for resistance genes are commonly found in natural populations (The Genetic Structure of Natural Pathosystems, Chapter 13), and if the resistance genes carry such a strong selective advantage one must wonder why such genes are not driven to fixation in the population. In natural populations, genetic, epidemiological and ecological factors can affect the distribution and maintenance of genetic polymorphisms for resistance and virulence genes (Epidemiological approach to modeling dynamics, Chapter 11). Within population (frequency-dependent selection) and metapopulation approaches have been proposed to explain the distribution and maintenance of genetic polymorphisms for resistance and virulence genes in natural populations (Modeling gene frequency dynamics, Chapter 12; and The Evolution of gene-for-gene interactions in natural pathosystems, Chapter 14).
Recent advances in the molecular biology of resistance genes have led to a flurry of studies in the area of host/pathogen interactions. Over 40 avirulence genes have now been cloned and characterized (The Molecular genetics of specificity determinants in plant pathogenic bacteria, Chapter 16; Molecular Characterization of Fungal avirulence, Chapter 17; and The Molecular genetics of plant-virus interactions, Chapter 18). Various plant resistance genes have been cloned (Organization of resistance genes in Arabidopsis, Chapter 1; Genetic fine structure of resistance loci, Chapter 2; and Mutation analysis for the dissection of resistance, Chapter 3). Studies of physiological variation in phenotypic response of different resistance genes are also under way (Phenotypic expression involving fungal and bacterial pathogens, Chapter15). It is becoming clear that resistance genes often occur in clusters and that some resistance genes can respond to more than one elicitor. Some genes are implicated in recognition; many genes are often involved in the signal transduction, while some are implicated in the disease resistance response. Thus, disease resistance is a process that results from several gene products working in concert.
Do these molecular finding jeopardize the gene-for-gene concept? (Molecular genetics of disease resistance: an end to the gene-for-gene concept?, Chapter 19). The gene-for-gene concept refers to the differential responses of plants to different races of pathogens. This differential response of plants implies that the recognition stage is involved as mutations in the later stages of signal transduction and plant defense response would affect all pathogen races similarly. Thus, so far, the findings of molecular biology can easily be reconciled with the gene-for-gene concept.
This book presents a nice overview of various developments related to the gene-for-gene concept in plant-pathogen interactions. Efforts to combine molecular, natural populations and agricultural problems are welcome as only then can one understand the impact of the gene-for-gene concept in plant biology. I strongly recommend this book to anyone interested in plant-pathogen interactions. - Johanne Brunet, Department of Botany and Plant Pathology, Oregon State University, Corvallis