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Research Fellow, Crop Genetics Research and Development, Dupont Agriculture and Nutrition, P.O. Box 552, Johnston, IA 50131
dwight.tomes{at}pioneer.com
Edited by H. John Newbury. Blackwell Publishing LTD, CRC Press LLC, 2000 Corporate Blvd., N.W., Boca Raton, FL 33431, USA. 2003. Hardcover, 265 pp., $143.96. ISBN 1-84127-321-X.
Plant breeding has been in rapid transition as more molecular tools are applied to commonly accepted field techniques. Predictably, the scientific development of this field is headed toward sequence-based knowledge which should improve both reliability and adoption in agriculture. The eight chapters in this volume are an excellent venue for students, professors, and other professionals to update their knowledge of the technical advances that can now be applied to plant breeding. This book describes the application of molecular technologies to plant breeding with a heavy emphasis on marker-assisted breeding and less emphasis on genetic engineering approaches to plant breeding. The authors are well known and represent a good sample from major research centers around the world. The examples used in this book to illustrate the most effective use of molecular markers are those in which effective phenotypic assays exist and for which relatively smaller errors are associated with the phenotypic assays. Tomato (Lycopersicon esculentum Mill.) fruit size and flowering date in a variety of species were specifically described. One weakness in the application of molecular breeding is the general lack of better phenotypic measurement tools for components of yield in agronomic crops. This weakness occurs, in large part, because detailed, precise phenotypic measurements are not available in agronomic crop species for many traits (e.g., drought tolerance, standability), and it represents a severe limitation to the application of molecular breeding at this time. The organization of the subject matter is intermediate between a subject matter focus and a commodity (species) focus. The commodity focus loses some of the clarity that might have come from detailed subject matter discussion with appropriate examples in a range of species. This was particularly noticeable in the chapter devoted to Plant Genetic Engineering (Chapter 4) that is primarily technique oriented and much less trait–gene oriented (see below).
The first chapter is devoted to a review of the principals of quantitative genetics as well as newer subject matter on developing populations for identification of QTLs for specific phenotypic assays. The discussion of cloning QTLs combines excellent theoretical background with relevant examples of traits whose heritability is sufficient to permit fine structure mapping. The emphasis on cloning QTLs also serves to unite the concept of genetic markers distributed on a physical genetic map with genes that are located at a specific chromosomal location. The widespread use of backcross breeding to recover elite genetics following genetic transformation has given new life to this often overlooked breeding technique. The theoretical principals of using backcross breeding with flanking markers to recover desired traits in traditional breeding was discussed in detail (Chapter 2) although the most common use in commercial breeding is recovery of a transgene in different genotypic backgrounds. In this latter case, selectable makers as well as the molecular markers associated with the transgene are considerations. The discussion concerning linkage drag (carrier chromosome) was particularly insightful. This linkage drag often points out how little recombination may be occurring in breeding (chromosomal breeding compared to larger scale recombination within and between linkage groups). The concept of selection and its complexities was discussed with an appropriate mixture of potential gains and pitfalls. The concept and usefulness of genetic colinearity (Chapter 3) was clearly explained from both the advantages and disadvantages points of view. The increased use of molecular breeding and focus on sequence based research has directly impacted the amount of effort devoted to both theoretical and applied use of synteny. Since rice (Oryza sativa L.) has been sequenced, comparison of syntenic regions can be used as one tool to find similar genetic regions in maize (Zea mays L.) and ultimately to obtain sequence details in maize. The traits mentioned also illustrate how specific traits may differ in the ease of application of synteny between species to aid plant improvement. Among the examples cited, disease resistance is on one extreme (little synteny) and plant height (good synteny between species) on the other for relative ease of use.
Chapter 4, Plant Genetic Engineering, is very well written although the clear emphasis on the technical grounding of the subject rather than the potential application of the technology for molecular breeding is a major shortcoming. The technical background is more generally available in the literature than potential applications. The introduction had a short but interesting section describing trait areas and "target" genes that have been used to modify specific traits. The missing part of this chapter was a description of how transformation technology could be used in conjunction with identification of sequence-based markers to manipulate native gene variation. In addition, transformation technology and genomic information have both matured to the point where entire biochemical or signal transduction pathways can be dissected. Advanced use of this technology clearly has power to validate the importance of specific proteins or genes for plant breeding. This treatment of the subject is of limited use for developed plant breeding programs but might have more utility for less well-developed programs seeking to begin transformation in species uncharacterized for transformation capacity.
The utility of plant germplasm collections is clearly described in Chapter 5, especially in the context of how gene pools can be used at the molecular level to serve as a wider source of variation. The clear message from this chapter is that the newer tools will lead to potentially very important utility for genes that were not accessible when the limits were based either on direct use or sexual hybridization. Chapters 6, 7, and 8 are devoted to a discussion of molecular breeding of maize, wheat (Triticum spp.), and tuber crops, respectively. The examples with these species connect the more theoretical considerations with how the application of different technology components might be realized. Maize represents the most developed from a technology perspective while the tuber crops have a smaller reservoir of background knowledge.
This book could be used as a reference source for undergraduates or established professionals who are seeking further depth or updated information in specific areas associated with plant breeding and applied genetics. Since the chapters have somewhat different writing styles, the editor should be commended for the readability and quality of the individual chapters and the effort as a whole. Perhaps one of the most important perspectives is that molecular technology offers the promise of more efficient application of the science of plant breeding to new species and applied problems in both developing and advanced agricultural settings.
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