For investigators engaged in the study of toxins generally, and host-specific toxins in particular, it is a rare treat to attend a meeting in which toxins involved in plant pathogenesis are emphasized. A gathering of this type provides opportunity to consider the discovery of new toxins, their chemical structures, genes encoding enzymes that control their biosyntheses, their sites of action and physiological effects on plants, and their roles (if any) in pathological processes. Having acknowledged the inspiration fostered by a 'toxin meeting', however, it is important to point out that the program of this symposium was generously sprinkled with 'nontoxin' talks. These contributions generated cross-disciplinary discussion and promoted new ways of thinking about relationships among factors required for plant disease development. The point can be illustrated by considering just one example. We have in the past often regarded diseases mediated by host-specific toxins and diseases involving 'gene-for-gene' relationships as representing two different classes of fungal/plant interaction. This is largely because the key molecular recognition event in so-called 'toxin' diseases leads to compatibility, whereas the corresponding event in 'gene-for-gene' diseases leads to incompatibility. Yet the race specific elicitors produced by the 'gene-for-gene' fungi Cladosporium fulvum (De Wit, Adv. Bot. Res. 21:147- 185, 1995) and Rhynchosporium secalis (Rohe et a1. , EMBO J.

The field of the molecular basis of plant disease is rapidly developing. The nineteen chapters of current information in Molecular Strategies of Pathogens and Host Plants are written by well known experts in the United States and Japan, and cover recent progress in the genetics and molecular biology of bacteria and fungi which are pathogens of plants. This research emphasizes the genes which are responsible for production of toxins, enzymes, and hormones that lead to pathogenicity and specificity in plant-pathogen interactions. Several chapters also examine the biochemistry of the plant's response to microbial attack.

Studies of the interactions between plants and their viral, bacterial and fungal pathogens are of major importance in plant and crop production. More than 10% of potential agricultural yield is lost to these organisms annually worldwide, and major epidemics can cause significant local economic and environmental damage. Molecular Plant Pathology addresses the underlying molecular principles of plant/pathogen interactions, in a readily-accessible textbook format.

Toxins in Plant Disease presents a comprehensive coverage of plant disease toxins, both those for which there are reasonable evidence and those with fewer credentials. This book is primarily concerned with the mechanism wherein substances that interfere with metabolism or that alter the normal structure of protoplasm are produced and released (category 1); this includes the traditional toxins, which are usually of low molecular weight. It also describes category 2 mechanism, wherein substances that interfere with normal control of growth and development are produced and released; these microorganisms are classified as growth-affecting compounds. Moreover, this text addresses some high-molecular-weight compounds that contribute to vascular dysfunction. It further talks about the production, isolation, assay, genetics of production, mechanism of action, structure-activity relationship, metabolism, and applications of these toxins. This publication will provide a rational basis for future investigations and contribute to the eventual understanding of the role that toxins play in disease causation.

Studies on the phenomenon of plant pathogenesis (disease development) have been useful to have a deep insight into the interactions between host plant and the pathogen. Depending on the levels of susceptibility (compatibility) or resistance (incompatibility) of the host plant and virulence of the pathogen, disease development may progress, either leading to symptom expression or result in the suppression of pathogen proliferation. Molecular techniques have been applied to elucidate the nature of interactions between the gene products of the plant and pathogen at cellular and molecular levels. Successful evasion of host’s surveillance system and subsequent activities of metabolites of the pathogen (enzymes and toxins) encoded by pathogen genes counteracting the effects of various defense-related antimicrobial compounds present already or produced by the host plants, after initiation of infection have been critically studied by applying various molecular techniques. In addition to studying various phases of disease development in individual plants, molecular methods have been demonstrated to be effective, in gathering data on various aspects of epidemiology under natural conditions where the interaction of pathogen with populations of plants is influenced significantly by the environmental conditions existing in different ecosystems. This volume focuses on the possibility of applying the knowledge on pathogenesis and molecular epidemiology to determine the vulnerable stages in the life cycles of the pathogens that can be disrupted to achieve more effective disease control.

Studies on the phenomenon of plant pathogenesis (disease development) have been useful to have a deep insight into the interactions between host plant and the pathogen. Depending on the levels of susceptibility (compatibility) or resistance (incompatibility) of the host plant and virulence of the pathogen, disease development may progress, either leading to symptom expression or result in the suppression of pathogen proliferation. Molecular techniques have been applied to elucidate the nature of interactions between the gene products of the plant and pathogen at cellular and molecular levels. Successful evasion of host’s surveillance system and subsequent activities of metabolites of the pathogen (enzymes and toxins) encoded by pathogen genes counteracting the effects of various defense-related antimicrobial compounds present already or produced by the host plants, after initiation of infection have been critically studied by applying various molecular techniques. In addition to studying various phases of disease development in individual plants, molecular methods have been demonstrated to be effective, in gathering data on various aspects of epidemiology under natural conditions where the interaction of pathogen with populations of plants is influenced significantly by the environmental conditions existing in different ecosystems. This volume focuses on the possibility of applying the knowledge on pathogenesis and molecular epidemiology to determine the vulnerable stages in the life cycles of the pathogens that can be disrupted to achieve more effective disease control.