Breeding Willow for Short Rotation Coppice Energy Cropping - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 71

taxes based upon the polluting potential of fossil fuels to make the crop financially
attractive. Joining the European Union in 1996 temporarily slowed the rate of
expansion, but policy was able to maintain incentives and 16,000 ha were planted
by 2000. More recently there has been turnover of crop area but no great expansion
[ 8 , 9 ].
Other European countries are known to have up to several thousand hectares of
willow in production: France, Belgium, Denmark, Germany, and Poland. Further
east, Czech Republic, Romania, Ukraine, and the Baltic States all have an emerging
interest in willow cropping for biomass. The majority of those countries already
have an established basketry industry.
In the Northeastern United States, there were more than 400 ha of willow planted
by 2008. Plantings in Canada are thought to be of similar area. As in Europe recent
increases in returns from arable farming have slowed the rate of increase, but an
additional major factor in North America has been the decrease in gas prices as
greater quantities of shale gas are exploited. This has impacted upon the price for
biomass for energy.
Genetic Resources
The UK National Willow Collection is one of the largest genetic resources of Salix
spp. known. At the present time there are approximately 1,500 accessions grown as
coppiced stool beds at Rothamsted Research. Collecting began at the former Long
Ashton Research Station in 1922, and the germplasm collection increased to
approximately 1,000 accessions before the closure of the site and transfer of the
collection to Rothamsted in 2002. The composition of the collection reflects the
history. Collecting began in response to the rapid decline in the willow basketry and
hurdle industry. Many of the early additions were of naturally occurring willows
that had been taken into cultivation by people engaged in these craft industries (the
equivalent of landraces). Many willows had been moved around the world and were
often given different names, so origins were not always clear. Therefore, not all
willows collected could be described as native. Recently, AFLP and microsatellite
analyses of the germplasm collection have identified several duplicates.
The collection has always been associated with basketry, hurdles, and biomass
(whether for pulp or bioenergy), and the application has primarily been to exploit
the rapid growth characteristic that follows coppicing. Therefore, the collection
shows a domination of species from the shrub willows, subgenus Vetrix . Work in
the 1960s on using willow and poplar for frost protection of fruit orchard trees
brought the tree willows, subgenus Salix , greater prominence. Finally, recent
scientific investigation of the phenomenal morphological diversity observed in
the genus has encouraged collection of many new genotypes from across the
world, regardless of their immediate application. Apart from Europe, the collection
now contains representative accessions from North America, North Africa, the
former Soviet Union, China, Japan, and other parts of the Far East.