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Preface

This second edition of Biotechnology of Fruit and Nut Crops has been preceded by two earlier CABI publications: Biotechnology of Perennial Fruit Crops published in 1992 and edited by F.A. Hammerschlag and R.E. Litz and Biotechnology of Fruit and Nut Crops first edition published in 2005 and edited by R.E. Litz. In many ways, these books are milestones, and they captured the advances and state of the art of biotechnology that had been applied to important fruit and nut species. This heterogeneous group of perennial species had been largely neglected by breeders and geneticists due to roadblocks that they share: long juvenile periods that can be as long as 15–20 years, reliance on vegetative propagation to maintain superior phenotypes often for several centuries, e.g. mango, pear and Musa (banana and plantain), and the absence of will and resources to assemble, maintain and study genetic resources. In fact, some of the crops included here can even now be considered as orphan crops.

In 1992, the second green revolution (biotechnology) had already been recognized as the future and was already changing the direction of breeding and improvement of some of the most important agronomic crops, e.g. maize, soybean, etc. None the less, it was acknowledged at that time that probably no other group of economic plant species would benefit as much from the new biotechnologies as the trees, i.e. fruit, nut and forest species, and other perennial species, i.e. banana and plantain, papaya and strawberry. In 1992, with most of the authors working primarily in laboratories in developed countries, there had been significant advances with a few species, particularly with respect to ‘older’ biotechnologies: micropropagation, protoplast isolation and culture, and mutation breeding. Genetic transformation was limited to a few crop species, e.g. walnut, papaya, mango, citrus, and few molecular markers were available for use in breeding programmes. A major constraint was the clonal nature of many of the trees. In order to improve a fruit or nut tree cultivar for a specific trait, an efficient de novo regeneration pathway from the mature phase is a prerequisite. This information had not been reported for many tree species at that time. Indeed, this problem continues to be a significant hurdle for many of the fruit and nut tree species. Molecular markers were starting to be used routinely in annual crops and the first advances were also made in some fruit and nut crops.

When the first edition appeared in 2005, the excitement in this field was palpable. The authors represented 16 countries and major advances were presented for cell culture, genetic transformation and molecular biology. Except for papaya, plum and walnut, genetic transformation was largely focused on technique, and genes for very few horticulturally important traits had been identified and transferred to fruit and nut crop species. Molecular markers were routinely used for fingerprinting, diversity evaluation and gene tagging studies. The first reports of functional genomics of a few species appeared and signalled important changes to come. The first edition is still surprisingly relevant and fresh for many tree crop species, perhaps due to difficulties of researching these plants.

The current edition arrives after a period of consolidation and introspection. Biotechnology and GMOs (genetically modified organisms) in particular were heralded a few years ago as the future of sustainable crop production in the face of global warming and the unstoppable spread of pests and diseases into new production areas. In those regions where this debate has been most tendentious, new technologies emerged, i.e. cisgenics and intragenesis, grafting of non-GM scions onto GM rootstocks, reverse breeding, etc. More recently, the prospect of gene editing using CRISPR/Cas9 has taken the centre stage. All new technologies depend on greater understanding of the genome, and the second edition has highlighted significant progress made in mapping of draft genomes. New increasingly cheaper sequencing technologies, and the enormous capacity of data storage and analysis, are resulting in a qualitative change in breeding programmes for most of these species, and this trend will exponentially increase in the next future. A putative third edition of Biotechnology of Fruit and Nut Crops most certainly will be very different from the preceding editions.

Richard E. Litz

Professor Emeritus

Tropical Research and Education Center

University of Florida

USA

Fernando Pliego-Alfaro

Departamento de Biología Vegetal

Instituto de Hortofruticultura Subtropical y

Mediterránea ‘La Mayora’ (IHSM-UMA-CSIC)

Universidad de Málaga

Spain

Jose Ignacio Hormaza

Instituto de Hortofruticultura Subtropical y

Mediterránea ‘La Mayora’ (IHSM-UMA-CSIC)

Spain