Wheat Rusts AN ATLAS OF RESISTANCE GENES RA McIntosh, CR Wellings and RF Park Plant Breeding Institute, The University of Sydney CSIRO AUSTRALIA B A D Adult plant symptoms of A. leaf rust, B. stripe rust and C. stem rust. D. Symptoms on paired seedling leaves. Upper and lower leaf surface of (L-R): leaf rust, stem rust and stripe rust. C ii F O R E W O R D World food security will depend on increased production of two major cereal crops — wheat and rice. Of these, wheat is of greater importance, in terms of tonnage if not in financial value. One significant constraint to increased wheat production is the variety of rust diseases attacking this crop — leaf rust, stem rust and stripe rust. Sources of resistance to these diseases are known, and have been utilised by wheat breeders for a long time. However, achieving durable resistance can be difficult, and the rust diseases continue to evolve and circumvent the breeders' achievements. This book provides an important and powerful tool for breeders in their continuing fight to outwit the rusts. In a valuable introductory section, Wheat Rusts: An Atlas of Resistance Genes gives a concise summary of the rusts, their interactions with the host plant and the nature and genetic bases of host resistance; then the main body of the work provides a comprehensive and descriptive catalogue of most known sources of rust resistance in wheat. Catalogues of the resistance genes in wheat have been published and updated regularly by RA McIntosh, but in this book they are presented together for the first time with full descriptions and colour photographs of their phenotypes. Wheat Rusts: An Atlas of Resistance Genes will, therefore, be a unique and invaluable aid to all involved in developing wheats for resistance to the rust pathogens. Such a compilation has only been possible because of the breadth and depth of experience of the authors. RA McIntosh is an international leader and authority on the genes for resistance to rust fungi in wheat. He is Director of Rust Research in the Plant Breeding Institute of The University of Sydney. He has recently been awarded a personal chair in the University as Professor in Cereal Genetics and Cytogenetics, and has been elected a Fellow of the Australian Academy of Sciences. Dr Wellings and Dr Park are experts on resistance genes to the stripe (yellow) and leaf rust fungi in wheat. The rust program at the Plant Breeding Institute plays a major role in monitoring the evolution of virulence in the rust fungi and in assessing resistance to them in Australia and New Zealand. The Plant Breeding Institute is world renowned and provides valuable advice and leadership for similar endeavours in other countries. The Australian Centre for International Agricultural Research (ACIAR) has been pleased to be associated with this team in a wheat rust project between Australia, India and Pakistan. In the course of this project Professor McIntosh and his colleagues were untiring and generous in sharing their experience with their overseas colleagues, and ACIAR is now very happy to be able to make the authors' knowledge and expertise more widely available through support for the present publication. We trust that Wheat Rusts: An Atlas of Resistance Genes will be of value in the continuing battle to feed a growing world. Paul Ferrar Research Program Coordinator (Crop Sciences) Australian Centre for International Agricultural Research (ACIAR) Canberra, Australia iii CSIRO Cataloguing-in-Publication Entry McIntosh, Robert Alexander Wheat Rusts: An Atlas of Resistance Genes. R.A. McIntosh, C.R. Wellings and R.F. Park. Includes bibliographies and index. ISBN 0 643 05428 6. 1.Wheat Rusts. 2. Wheat - Disease and pest resistance. 3. Wheat - Breeding. I. Wellings, Colin Ross. II.Park, Robert Fraser. III. CSIRO. IV. University of Sydney. Plant Breeding Institute. 633.119425 ©CSIRO Australia 1995 This book is available from: CSIRO Publications, PO Box 89 (314 Albert Street), East Melbourne, Victoria 3002, Australia Telephone: (03) 418 7217 Fax: (03) 419 0459 For international inquiries Telephone: + (61 3) 418 7217 Fax: + (61 3) 419 0459 __________________________________________________ Managing Editor: Kevin Jeans Editor: Alexa Cloud-Guest Cover Design: Anita Adams Text design and layout: Julie Fitzpatrick Production Manager: Jim Quinlan __________________________________________________ SPONSORS AUSTRALIAN CENTRE FOR INTERNATIONAL AGRICULTURAL RESEARCH The University of Sydney iv P R E F A C E The production of this book that describes the individual genes for resistance to wheat rusts and illustrates them with various aspects of host:pathogen interactions has required many years of research and development. Therefore, in bringing this book to fruition, we wish to recognise our colleagues, both past and present especially the late EP Baker, NH Luig, TT The and the late IA Watson, who made significant contributions to the direction and development of cereal rust research at the Plant Breeding Institute (PBI), The University of Sydney. The catalogue and illustrations in Wheat Rusts: An Atlas of Resistance Genes provide a basis for the identification of the genes for resistance to the wheat rusts. The actual low seedling and adult plant responses to the wheat rust pathogens conferred by resistance genes provide a preliminary indication of the identity of a particular resistance gene. The pattern of response to an array of pathogen cultures, the effects of environment on response, and pedigree of the host line or cultivar provide further insight to support or contradict those early indications. These considerations usually reduce the number of genes for postulation to three or four, or even less — being able to exclude candidate genes is an important aspect of resistance gene identification. The reduction of choices to three or four represents a substantial saving in time and resources and can be achieved before a single cross is made for genetic analysis. Whereas the major aim of the book was to illustrate infection types, we have also attempted to provide detailed genetic and physiological information, and indicate past and potential use of each gene. Potential resistance sources are often those that are effective now, but not yet genetically analysed, and the breeder can ill-afford to wait until genetic analyses are completed before attempting to utilise them as breeding donors. Indeed, the breeder may not have the luxury of genetic advice and must work in the absence of such information or depend on information from other places. In Chapter 1 we provide some basic information on principles, methods and problems, and outline some of the questions that must be addressed by breeders in order to achieve effective and hopefully lasting resistance. Our aim was to complement rather than duplicate some of the excellent and detailed publications available on the cereal rusts and breeding for rust resistance. In this regard, we direct readers to the following: 1988 The Cereal Rusts, Volume 1 (Bushnell and Roelfs, 1984) 1989 The Cereal Rusts, Volume 2 (Roelfs and Bushnell, 1985) 1990 Breeding Strategies for Resistance to the Rusts of Wheat (Simmonds and Rajaram, 1988) 1991 The Wheat Rusts: Breeding for Resistance (Knott, 1989) 1992 Rust Diseases of Wheat: Concepts and Methods of Disease Management (Roelfs et al., 1992) In choosing particular photographs we have attempted to emphasise different aspects of resistance gene:avirulence gene behaviour, while attempting to maintain an interesting variation in approach. The production of the more than 500 photographs from which we selected examples was interrupted by the move of the Institute from Castle Hill to Cobbitty, New South Wales, in 1991 and the retirement and resignation of assistants. Nevertheless, the pictures are a credit to the three persons involved, namely DJS Gow, DL Milne and P Abell, and we sincerely acknowledge their contributions. The collection of photographs was expanded by the generous donation of illustrations from R Johnson, AP Roelfs and our Plant Breeding Institute colleagues. In addition, CR Wellings was able to obtain further stripe rust photographs while on study leave at the Research Institute for Plant Protection, Wageningen, The Netherlands. The technical work of planning, planting and inoculation conducted by L Ferrari, NM Maseyk, DB McDonald, DL Milne and RM Pfeiffer are especially acknowledged. We thank PL Dyck, R Johnson, GHJ Kema, DR Knott, RG Rees, AP Roelfs and the late RW Stubbs for reviewing various sections of the text, and for offering many suggestions as well as published and unpublished genotype information. Assistance in preparing the v many drafts of the manuscript was provided by Mrs Betty Gibson and Ms Hun Sun Hwang and we thank them for their durable patience. The support of our PBI colleagues during the course of this project, particularly JD Oates, is greatly appreciated. Finally, the project would not have been possible without financial support. The Australian Centre for International Agricultural Research (ACIAR) is acknowledged for underwriting the project and permitting provision of a limited number of copies free of charge to scientists in developing countries. The Australian Grains Research and Development Corporation (GRDC) support the positions of RA McIntosh and RF Park and finance much of our research. CR Wellings is an employee of New South Wales Agriculture on secondment to the Plant Breeding Institute, Cobbitty. RA McIntosh CR Wellings RF Park Plant Breeding Institute, The University