Bread wheat is an allohexaploid species that was formed by sequential hybridizations between three wild grass species: T. monococcum (AA genome), T. turgidum (AABB genome), and T. tauschii (DD genome), resulting in bread wheat's AABBDD genome. This hexaploid nature enables translocations between genomes that can introduce disease resistance and the resynthesis of new wheat varieties from T. turgidum and T. tauschii. Major diversity types of cultivated wheat include winter/spring types defined by vernalization genes, winter hardiness, and photoperiod response important for northern regions. Basic wheat breeding procedures involve hybridization, inbreeding,

1. Breeding Wheat

2. Allohexaploid nature of bread
wheat
T. monococcum
AA
T unknown
BBx
T. turgidum
AABB
T. tauschii
DDx
T. aestivum
AABBDD
Enables:
•Translocations (1BL/1RS)
Disease resistance
•Resynthesis
New resistance from T. turgidum
and T. tauschii
•Triticale
Hexaploid AABBRR
Octaploid AABBDDRR

3. Major diversity types
of cultivated wheat
• Winther/spring types (genes for vernalisation)
– almost only winther types in DK, spring types further
north in Scandinavia
– Winther types higher yielding than spring types
– Winther types lower baking quality than spring types
• Winther hardiness
– frost tolerance, disease resistance, spring regrowth
• Photoperiod response
– important for northern areas including DK

4. Basic breeding procedures
• Hybridisation, inbreeding and selection of pure
lines
– recombination of adapted material
– backcrossing from less adapted material
• Hybrid cultivars are not competitive
– cms, restorations: A, B and R lines (T. timophevi)
– gametocides

5. Breeding goals
(North western Europe)
• Yield and yield stability (many site testing)
• Earliness (escape drought or heat, ready
before autumn)
• Lodging resistance (dwarfing genes)
• Winther hardiness (in situ and ex situ testing)
• Disease resistance
– yellow rust, leaf rust, powdery mildew, Septoria

6. Breeding goals
dry warm areas
• Sufficient early to exploit accessible moisture
• Drought tolerance
• Insect resistance
– Hessian fly (larvae feeding on straw etc)
– Greenbug and other types of aphids
– leaf beetles

7. Quality of hexaploid wheat
• Baking types (hard types)
– loaf volume by baking test (see picture p 275)
– protein content
– falling number
– sedimentation value
• Feed types (soft types), biscuits (picture 277)
– protein content
– lysine, methinine and cystein content (Lysimax)
– Phytin content (Transgenic approaches)