Breeding Willow for Short Rotation Coppice Energy Cropping - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 67

Chapter 4
Breeding Willow for Short Rotation Coppice
Energy Cropping
Ian Shield, William Macalpine, Steve Hanley, and Angela Karp
Abstract Willow ( Salix ) is a diverse and adaptable genus that has served human
beings well for many thousands of years. The Roman scholar Pliny the Elder
(AD 23-AD 79) advised on willow planting in the Roman Empire. However, it
has only recently been subjected to controlled breeding (twentieth century). Willow
breeding has been able to benefit from the knowledge and technologies developed
by plant breeders across the globe. The breeding exploits the tremendous genetic
diversity and specifically the rapid growth rates observed in response to coppicing
on a 2-4 year cycle. Willow breeding cycles are short and commercial exploitation
rapid via vegetative propagation of the F 1 progeny. The latest molecular genetics
techniques are being deployed in Europe and North America to advance and
accelerate crop improvement. Willow is now being rapidly improved and deployed
for production of woody biomass, much of it for energy, but also for pulp,
potentially specific high value extracts, and applications associated with the
multifunctionality of the crop such as bioremediation. Most northern temperate
latitude areas have an interest in willow cropping.
Keywords Willow ￿ Salix ￿ Short rotation coppice ￿ Breeding ￿ Molecular
genetics ￿ Biomass ￿ Bioenergy
Introduction
The willow tree has been associated with and utilized by humans for many
thousands of years. Initially (and for several millennia), willow stems were used
for baskets on account of their flexibility and to some extent lightweight charac-
teristics. Perhaps implicit within this use was also a recognition that many species
are fast growing and could be easily cultivated. Long ago it was no doubt recog-
nized that after a willow had been cut back for useful wood, it quickly regrew from
the cut base again. However, it was not until the mid-twentieth century that this
ability for regrowth and the subsequent fast growth rate (compared to other trees)