GROWING WHEAT FOR HIGH ALCOHOL YIELD –HOMOGENEOUS AND HETEROGENEOUS APPROACHES - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 167

and the absence of appropriate testing procedures [66]. The distilling industry has devised a
laboratory test, based on a scaled-down version of the industrial process [1], but this is not
applicable to the very large numbers of lines generated in a breeding programme.
From an annual UK crop of around 16 million tonnes [4] the proportion required for
distilling constitutes around 4% and, within a European context, is inconsequential, hence the
minimal interest of wheat breeders in this market. However, ethanol derived from plant-based
materials, frequently referred to as bioethanol, is now used as a partial petrol replacement in a
number of countries, creating increased demand [65]. Unmodified engines can accommodate
up to 10% petrol replacement [52]. With engine modifications, vehicles can run on fuels with
blends of 85% ethanol:15% petrol and such fuels are readily available in Brazil [43] and,
increasingly, in the USA. In the USA, bioethanol has been produced since the 1970s [52],
through a distillation process that uses maize as a feedstock. Interest in Europe has centred on
the use of wheat, which can give both the grain and the alcohol yields required for a positive
energy balance, when the energy released by the fuel produced is compared with that
expended in growing and processing the crop [48].
The production of Scotch whisky is covered by legislation which constrains or eliminates
the use of certain additives [46]. In particular the enzymes required for starch degradation
must come only from malted barley. However, as the wheat used in grain distilling primarily
acts only as a substrate for such enzymes, Swanston and Newton [65] suggested that the
suitability of wheat for alcohol production was likely to be independent of the source of the
enzymes. Initial commercial use of wheat appeared to confirm this view [58] as the preferred
varieties for fuel ethanol production were the same as those used for grain distilling. As the
market for soft wheat with high alcohol yield potential seemed to be growing, there was
increasing interest in varietal production and agronomic practise that would permit such
potential to be fully realised. In this chapter we consider the development of selection tools
that can facilitate the breeding process, but also the most effective means of deploying and
cultivating the products of these breeding programmes.
S ELECTION FOR D ISTILLING Q UALITY
As noted in the previous section, the distilling industry has devised a testing procedure
that can be applied to samples of 30g [1], but includes a fermentation stage that requires 68 h,
so is unsuited to rapid screening of large populations. It is, however, a useful procedure for
testing new varieties and is applied to all soft wheat candidates for recommendation in the
UK. This permits the distilling industry to identify the varieties that they are willing to accept
and suitability for distilling is included as a characteristic on UK recommended lists produced
by HGCA (www.hgca.com), for England and Wales and SAC (www.sac.co.uk), for Scotland.
Results are obtained from samples grown at a range of sites across the UK [70] and these can
cover a fairly wide range of grain protein contents and alcohol yields. This enables the mean
performance of individual varieties to be assessed, although genotype x environment
interaction can cause changes in the relative performance of varieties between both sites and
seasons and this is illustrated in the comparison of two distilling varieties in Figure 2. Some
varieties may perform less well in certain areas and this is usually reflected in regional, rather
than national, recommendations.