Sugar Beet, Energy Beet, and Industrial Beet - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 92

industrial precursors. It has been suggested that phenolic cross-linking interferes
with efficient saccharification and fermentation by reducing access of hydrolytic
enzymes and inhibiting microbes [ 105 ].

Seed Production

Beets are long-day plants and normally flower in the spring and early summer, after
vernalization for biennial types. Vernalization can be completed on plants at
practically any stage of growth. Typically, temperatures of 4-6 C for 10-16
weeks are sufficient for vernalization, after which the plants should be moved to
12-15 C with higher-intensity lighting for a period of a few weeks to ensure the
flowering response is committed. Beets will de-vernalize if temperatures are too
high for too long (

20-25 C for

1 week). The de-vernalization process is not
very well understood but is often more a problem in greenhouse seed production
than field environments. The requirement of a period of cold to induce bolting and
flowering is governed largely by the bolting locus, B [ 76 , 106 ]. Annual beet
generally has the dominant allele B , and commercial beets are homozygous reces-
sive ( bb ) at the flowering locus. Understanding genetic pathways controlling
vernalization and bolting is fundamental for controlling weed beet contamination,
synchronizing flowering for seed production, and enabling earlier spring or fall
sowing without yield reductions caused by premature flowering [ 107 ].
Cytoplasmic male sterility (CMS) makes hybrid sugar beet production practical.
Beets are normally allogamous, governed by a complex gametophytic self-
incompatibility system, which prevents self-pollination but allows almost any two
plants to cross-pollinate. Commercial seed production [ 108 ] relies heavily on
stecklings, which are young field-grown roots of 8-12 weeks of age, or otherwise
kept small by dense planting, which are sown in one environment, harvested and
vernalized en masse, and transplanted into a hybrid seed production field. A few
specialized areas support the full life cycle for seed production, such as those found
in the Willamette Valley of Oregon, USA, or areas closer to the northern shore of
the Mediterranean Sea (e.g., southern France, northern Italy). In Mediterranean
areas, care must be exercised that wild and ruderal beets are not flowering in the
same area, or the hybrid seed crop will be contaminated with annual beets.
Typically, seed production fields are isolated from other pollinators by a distance
of 2-4 km. Commercial sugar beet hybrid seed is typically harvested from 8 to
12 rows of a CMS parent, which is alternated with 4-6 rows of a suitable pollinator
parent. Often the CMS parent is directly sown in late August and early September
and vernalized in situ, while pollinator stecklings are vernalized elsewhere and
transplanted into the seed production field the following spring as temperature and
day length increase. Seed yield and quality are often quite variable, and a great deal
of processing is devoted to removing immature seed, removing the corky fruit
tissue surrounding the seed (decortication), sizing fruits, and, in many instances,

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