Abstract:
FOREWORD
The majority of present-day fruit and nut crops under intensive cultivation were consumed in The Neolithic Age.
Some of them have been so transformed by continuous selection and genetic recombination that they are far removed from their wild progenitors, yet a few, fig, date, and almond for example, seem little changed from antiquity.
Throughout the millennia genetic improvement of these species has been achieved by grower selection: first from natural seedling populations and then from grower fields with unique genotypes fixed by vegetative propagation, particularly grafting.
In fact, much of the world fruit industry is still based on grower-selection from chance seedlings and as a result is characterized by a narrow germplasm base.
These elite seedlings have unique attributes such as outstanding flavor and texture, high fruitfulness and productivity, but also special problems associated with limited adaptations, and pest and disease susceptibilities.
Deficiencies, in many cases, have been ameliorated through cultural practices to prop them up including the use of rootstocks, insect and disease control practices via chemical pesticides, growth regulators, and special handling and storage technology.
Systematic fruit breeding is a relatively new technology dating back to Thomas Andrew Knight (1759–1838) who first made controlled crosses of apple, cherry, nectarine, plum, red currant, and strawberry and released new seedlings.
Jean Baptiste Van Mons (1765–1842) collected clones of pears and sequentially planted open-pollinated seed of the best selections, the first long-term selection program in tree fruits.
Gregor Mendel (1822–1884), the father of genetics, was involved in apple and pear breeding programs.
Finally, an American nurseryman, Luther Burbank (1849–1926) was the first to consider fruit breeding as a commercial endeavor.
Conventional breeding is now based on selection from genetically variable populations derived from sexual recombination, including wide crosses.
The system is powerful because it is evolutionary; progress can be cumulative with improved individuals continually serving as parents for subsequent cycles of breeding.
The occurrence of sports due to mutation has also been an important factor in fruit improvement.
Conventional breeding has had enormous consequences for some fruits, particularly those crops with short life cycles such as peach, where the industry is based on cultivars developed by both public and private breeding programs.
In a number of fruit and nut crops and nuts improvement through breeding has been slow and incremental.
Progress with conventional breeding strategies in tree fruits has been constrained by a long juvenile period, problems with sterility and incompatibility, large plant size, the randomness of induced mutations, limitations of the sexual system to incorporate small changes, the dependence upon naturally occurring variation, and the high costs required to select, identify, and evaluate desirable recombinants.
The biotechnological revolution in the last half of the 20th century is based upon novel genetic strategies derived from microbial and molecular techniques including embryo rescue, protoplast fusion, marker-assisted selection, and recombinant DNA (transgene) technology.
These techniques are now being intensively implemented in fruit breeding programs despite the fact the immediate future of transgene technology is jeopardized by legal issues and consumer resistance.
It is clear that these new technologies have re-invigorated the art and science of fruit breeding, but it is also fair to say that only a few improved cultivars can be directly attributed to biotechnology.
This volume of Acta Horticulturae consists of papers presented at a four-day symposium on Tree Fruit and Nut Breeding held as a part of the 26th International Horticultural Congress held in Toronto, Canada, August 11–17, 2002. The beginning of a new century, in fact a new millennium, is an opportune time to review past progress, examine the state of our profession, and to plan for the future.
The symposium consisted of both oral presentations and posters based on five themes: Progress and Prospects, Breeding Methods, Key Traits, Rootstocks, and Programs.
The symposium was well attended from beginning to end and the discussions were spirited.
It was truly international in scope with all fruit-growing continents represented by participants and authors.
A wide range of tree fruit and nut crops were included.
Many of the papers emphasized new technologies including protoplast fusion, transgene technology, and marker-assisted selection.
It is clear that the future of fruit breeding lies in the use of these techniques as a tool to enhance, but not replace, traditional methods.
The success of the symposium was due to many fruit breeders and organizations including EUCARPIA, EUFRIN, and the American Society for Horticultural Science that cosponsored the symposium.
I wish to make special mention of the financial contribution of the Fruit Breeding Working Group of the American Society for Horticultural Science, The American Pomological Society, The 26th International Horticultural Congress, and UNAPROA (National Union of fruit, citrus and vegetable producers of Italy). Finally I wish to give special thanks to my colleague Anna Whipkey for her help with the projection at the symposium and with her extraordinary editorial and computer skills in the production of this volume.
Jules Janick
Convener and Editor
Purdue University
USA
PREFACE
The papers contained in this volume of Acta Horticulturae report the proceedings of a symposium on Genetics and Breeding of Tree Fruits and Nuts.
Keynote speakers and authors of selected contributed oral and poster presentations were given the opportunity to submit a manuscript for publication.
These manuscripts were reviewed by the symposium editor and other referees.
Only those papers judged suitable for publication following the authors consideration of reviewer suggestions appear in this volume of Acta Horticulturae.
The ISHS acknowledges and appreciates the contribution of all editors and reviewers.
They have made a significant contribution to assuring the quality of this publication.
The ISHS Board of Directors
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