Doubled haploid technology is an important tool for plant breeding. It allows for significant time reduction in the achievement of homozygous breeding lines of value in crop improvement. This volume provides an excellent overview of haploid induction and the application of doubled haploids. The authors emphasize advances made in the understanding of microspore embryogenesis, but treat also advances in gynogenesis and the manipulation of parthenogenetic haploid development. The text contains a thorough discussion of the application of haploidy to the improvement of a number of species from various families, including Brassicaceae, Poaceae, and Solanaceae. The various methods applicable to these species are described in detail. Each chapter contains critical evaluation of the scientific literature and an extensive list of references. This volume is ideally suited for plant breeders, geneticists, and plant cell biologists.

This richly illustrated volume describes how somatic hybrids can contribute to the improvement of crops. It comprises 24 chapters dealing with interspecific and intergeneric somatic hybridization and cybridization, providing valuable tools for plant breeders.

The importance of haploids is well known to geneticists and plant breeders. The discovery of anther-derived haploid Datura plants in 1964 initiated great excitement in the plant breeding and genetics communities as it offered shortcuts in producing highly desirable homozygous plants. Unfortunately, the expected revolution was slow to materialise due to problems in extending methods to other species, including genotypic dependence, recalcitrance, slow development of tissue culture technologies and a lack of knowledge of the underlying processes. Recent years have witnessed great strides in the research and application of haploids in higher plants. After a lull in activities, drivers for the resurgence have been: (1) development of effective tissue culture protocols, (2) identification of genes c- trolling embryogenesis, and (3) large scale and wide spread commercial up-take in plant breeding and plant biotechnology arenas. The first major international symposium on “Haploids in Higher Plants” took place in Guelph, Canada in 1974. At that time there was much excitement about the potential benefits, but in his opening address Sir Ralph Riley offered the following words of caution: “I believe that it is quite likely that haploid research will contr- ute cultivars to agriculture in several crops in the future. However, the more extreme claims of the enthusiasts for haploid breeding must be treated with proper caution. Plant breeding is subject from time to time to sweeping claims from ent- siastic proponents of new procedures.

There are clearly many directions in which the further development of the GUS gene fusion system can progress. Some of these have been outlined above, but others can be imagined. There are no reasons to limit our conceptions of the use of GUS gene fusions to analysis and manipulation of single genes. We can envision numerous marked genes - perhaps with several new fusion systems - giving valuable information about gene interaction, or population structure. The study of plan- pathogen and plant symbiont interactions can progress rapidly with simple quantitative markers for genes and individuals. We can imagine ways of using gene fusions to report on crop physiology or other complex phenotypes, thereby enhancing the accuracy and speed of screening. Introduction of the biosynthetic pathway for glucuronide detoxification by expressing genes for the UDP-glucuronyl transferases in plants may result in novel mechanisms for plants to deal with xenobiotics such as insecticides or herbicides. Synthesis of substrates, which until now has been performed chemicall- resulting in expensive compounds - can be done biosynthetically. This should make the system not only the most powerful gene fusion system for agriculture, but also the most accessible.

In continuation of Somaclonal Variation and Crop Improvement I (1990), this volume is comprised of twenty-four chapters dealing with somaclonal variants showing resistance to salt/drought, herbicides, viruses, Alternaria, Fusarium, Glomerella, Verticillium, Phytophthora, fall armyworm, etc. in a number of plants of economic importance. It is divided into two sections: Section I. Somaclonal Variation in Agricultural Crops: wheat, rice, maize, sorghum, potato, tomato, Lotus, Stylosanthes, banana, strawberry, citrus, colt cherry. Section II. Somaclonal Variation in Medicinal and Aromatic Plants: Atropa, Carthamus, Hypericum, Lavatera, Nicotiana, Primula, Rauwolfia, Scilla, and Zinnia. This book will be of great assistance to research workers, teachers, and advanced students of plant pathology, tissue culture, pharmacy, horticulture, and especially plant breeding.

The results obtained to date involving the use of in ~ methods to facilitate wide hybridization in plants are voluminous and impressive. The techniques of embryo culture, ovule culture, and in~ pollination and fertilization represent an extension of the normal sexual hybridization process. Successes recorded in obtaining hybrids stem largely from circumventing prezygotic or postzygotic hybridization barriers. Numerous recent successful hybridizations were possible because of the development of improved tissue and cell culture systems for crop plants and attention given to genotypes used in hybridization attempts. Interspecific and intergeneric hybridization utilizing the process of protoplast fusion will bypass the limits set by all sexual me'thods. In addition to combining complete genomes from two different species through protoplast fusion, this system affords unique opportunities for creating novel cytoplasmic combinations, transfer of individual chromosomes, transfer of cytoplasmic organelles, manipulation of male sterility, and for single gene transfer. Some caution must be noted with regard to the extent of hybridization possible between distantly related species. Although practically no limit exists to the physical fusion of protoplasts from widely divergent species, the restrictions imposed by somatic incompatibility have not been adequately addressed. Regeneration of plants from the protoplast or single heterokaryon level is still a major hurdle for many important crop species before somatic cell fusion can be exploited to produce interspecific and intergeneric hybrids. Identification and selection of hybrids is also a limitation to the efficient application of cell fusion methods.

Proceedings of a symposium jointly organized by the IAEA and FAO, Vienna, 19-23 June 1995. The aim of the symposium was to review current aspects of mutation and molecular biology techniques for use in crop improvement and to bridge the gap between practical plant breeding and molecular techniques. Problems of crop improvement worldwide, and their possible solution, were discussed. It was concluded that use of all available approaches, including mutation and molecular biology techniques, will be crucial to future plant breeding programmes in order to meet the world's food production challenges.