Worldwide, most of the cultivated wheat varieties are hexaploids (Triticum aestivum) There are some cultivated TETRAPLOIDS, most notably T. durum Annual or winter annual grass

ADAPTATION

TEMPERATURE

Wheat is a cool season crop

Not widely grown in warm, humid regions because of diseases

Has a slightly higher heat requirement and a slightly longer growing season than other small grains

Minimum growth - some winter wheat will grow at temp's as low as 38 F

Ideal temps: Daytime highs of 70‑80oF

Winterhardiness (cold tolerance) Rye > wheat > barley > oats

Length of growing season

Winter grains: Wheat > Rye

Spring grains: Wheat > Oats > Barley

MOISTURE

Most wheat grown in areas that have 15‑35" annual precip
Some grown in areas with < 10" annual precip by alternating with SUMMER FALLOW USA - N.DAK. Australia
Timing of precip
Important for both winter and spring wheat
Early season moisture is critical for both W and S types

SOIL

Best suited to fertile, medium‑to‑heavy textured soils that are well‑drained
Does poorly on sandy, acid soils that are poorly drained
Wheat can have problems with aluminum toxicity in low pH soils
Aluminum tolerant cultivars have been developed

Vegetative characteristics

Similar to other small grains

alternate leaf arrangement, etc
small auricles

Roots

Fibrous root system
seminal, crown, and brace roots
Winter wheat - more extensive root system than sp wheat
Wheat - deeper rooting than barley and oats, not as deep as rye

Pubesence

Reproductive characteristics

Infloresence = Spike

One spikelet per rachis node with 3 or more florets/spikelet 2 primary florets
outer 1 secondary florets
inner
Spikelets are subtended by two glumes
Glumes - thick - important in classification

Many varieties are awned (awn- extends from lemma)

Photosynthesis (PS) occurs in awns
Awns contribute to grain yield in semiarid conditions, but usually not in more humid conditions
Semiarid conditions
- lower leaves dry up early, so awns compensate for this loss in leaf area and ps.
- Awns may increase yields by 5-10%
More humid conditions - contribution of awns is insignificant when compared to ps from leaves

Pollination

Begins in the central part of the spike
Proceeds upward and downward over a period of 2‑3 days
Wheat is normally self‑pollinating, but cross‑pollinating lines have been developed
Several companies have worked extensively with hybrid wheat, but hybrids are not yet widely grown
Although hybrids in some areas of the US have performed very well, they have not consistently outyielded the best pure line
Hybrids have to outyield the best pure lines by 15-20% to be economically feasible
Wheat is free threshing

Kernel parts:

Kernels of wheat species and varieties differ according to

Size
Shape
Color
Texture
Hardness vs softness
- Hard = vitreous
- Soft = nonvitreous
Crease width and depth