Maize Starch for Industrial Applications - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 180

The waxy:sugary-2 and waxy:amylose-extender gene combinations have inter-
esting food applications and potential to reduce reliance on chemical modification
for functionality. Neither gene combinations seem to have an immediately apparent
large-scale industrial application. Petrochemicals in the United States and many
other countries continue to provide the least expensive source of hydrocarbons for
industry; however the sustainable production of naturally sourced starch can be a
very attractive resource for some markets.
High-amylose starch can be heated and electrostatically aligned to form strong
films. These films differ from oil-derived films in that they have greater permeabil-
ity and are biodegradable [ 63 ] . These attributes have the potential to make them
preferable in use for food packaging and other applications that require short-term,
rather than indefinite or long-term, persistence.
Amylose starches have been extruded to form packing peanuts and into sheets
and shapes for packaging. For forms and films, greater amylose content confers
greater strength, and amylose modifier discovery, such as SBE1, will facilitate
amylose hybrid development and work to reduce the high-amylose yield drag.
Because the majority of high-amylose starches are used in food applications,
most if not all, high-amylose hybrids used for industrial starches are also used for
food applications. The development of a high-amylose hybrid specifically for an
industrial production target relies on the establishment of a market of sufficient
scale and size.
The ethanol industry provides a large market, and while profit calculations
revolve around grain yield, total starch content, and ethanol/acre, some very
interesting approaches have been taken. The Enogen trait is transgenic bacterial

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α -amylase that becomes active during the fermentation process [ 64 ]. A similar

approach that affects amylose or amylopectin structure for industrial use would be
very interesting.

Breeding Strategies for the Development of Specialty
Hybrids and Integration of New Approaches

The genetics of the waxy and amylose specialties accommodate different breeding
approaches. For the development of waxy inbred lines, backcross conversion and
line verification are commonly used. With amylose, the quantitative nature of the
trait is more amenable to population development and pedigree line selection.
Both waxy and amylose must, at some point, use self-pollination to identify and
fix the homozygous recessive specialty gene. Testcrosses or markers to verify the
presence of the heterozygote are effective and save generational time but require
extra cost.
A transgenic waxy or amylose specialty trait would have several advantages,
dominant expression of specialty starch genetics would allow visualization of the
trait in each generation, combination with a herbicide selection marker would allow