Wheat

T. aestivum

Agronomy

Crop development

Crop management decisions require the knowledge of stage of development of the crop. In particular, spring fertilizers applications, herbicides, fungicides, growth regulators are typically applied at specific stages of plant development.

Related Topics:
Fertilizer - Herbicide - Fungicide - Growth regulator

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

For example, current recommendations often indicate the second application of nitrogen be done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadoks scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely suceptible to low temperatures (under 4 °C) or high temperatures (over 25 °C). Farmers also benefit from knowing when the flag leaf (last leaf) appears as this leaf represents about 75% of photosynthesis reactions during the grain filling period and as such should be preserved from disease or insect attacks to ensure a good yield.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.

Related Topics:
Feekes - Zadoks scale

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Wheat stages

• Wheat at the anthesis stage (face and side view)

Diseases

Wheat is subject to more diseases than other grains, and, in some seasons, especially in wet ones, heavier losses are sustained from those diseases than are felt in the culture of other cereal crops. Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or straw, and ultimately deprives the grain of sufficient nourishment; from mildew on the ear; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Examples of wheat diseases:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Bacterial diseases

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Bacterial leaf blight Pseudomonas syringae subsp. syringae
• Bacterial sheath rot Pseudomonas fuscovaginae
• Basal glume rot Pseudomonas syringae pv. atrofaciens
• Black chaff = bacterial streak Xanthomonas campestris pv. translucens
• Pink seed Erwinia rhapontici

Fungal diseases

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Alternaria leaf blight Alternaria triticina
• Anthracnose Colletotrichum graminicola
• Ascochyta leaf spot Ascochyta tritici
• Black head molds = sooty molds Alternaria spp., Cladosporium spp.
• Common bunt = stinking smut T. tritici, T. laevis
• Downy mildew = crazy top Sclerophthora macrospora
• Dwarf bunt Tilletia controversa
• Ergot Claviceps purpurea
• Foot rot = dryland foot rot Fusarium spp.
• Leaf rust = brown rust Puccinia triticina
• Pink snow mold = Fusarium patch Microdochium nivale
• Powdery mildew = Blumeria graminis
• Scab = head blight Fusarium spp., Gibberella zeae, Microdochium nivale
• Septoria blotch Septoria tritici = Mycospharella graminicola
• Smut (fungus)Smut = Ustilaginomycotina clade of the class Teliomycetae, subphylum Basidiomycota
• Storage moulds Aspergillus spp., Penicillium spp.

Nematodes, parasitic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Grass cyst nematode Punctodera punctata
• Root gall nematode Subanguina spp.

Viral diseases and viruslike agents

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Agropyron mosaic genus Rymovirus, Agropyron mosaic virus (AgMV)
• Barley stripe mosaic genus Hordeivirus, Barley stripe mosaic virus (BSMV)
• Oat sterile dwarf genus Fijivirus, Oat sterile dwarf virus (OSDV)
• Tobacco mosaic genus Tobamovirus, Tobacco mosaic virus (TMV)
• Wheat dwarf genus Monogeminivirus, Wheat dwarf virus (WDV)
• Wheat yellow mosaic Wheat yellow mosaic bymovirus

Phytoplasmal diseases

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Aster yellows phytoplasma

Link between air pollution and septoria blotch

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A team of researchers examined a library of British wheat samples dating back to 1843. For each year, they determined the levels of Phaeosphaeria nodorum and Mycospharella graminicola DNA in the samples. After accounting for influences such as growing and harvesting methods and weather conditions, they compared the DNA data with estimates of emissions of air pollutants. The effect of sulfur dioxide correlated with the abundance of the two fungi. P. nodrum grew more successful with the dawn of the Industrial Revolution. M. graminicola was more abundant before 1870 and since the 1970's. The success since the 1970's is a reflection of reductions in sulfur dioxide emissions due to environmental regulations. (Bearchell, et al., 2005)

Related Topics:
DNA - Sulfur dioxide - Industrial Revolution

~ ~ ~ ~ ~ ~ ~ ~ ~ ~