Crop physiology

Germination of wheat within the grain head before harvest is called pre-harvest sprouting (PHS). Periods of prolonged rainfall and high humidity after the grain has ripened and before it can be harvested can contribute to PHS, which can be thought of as a premature germination. Germination can begin as a wheat kernel absorbs moisture and swells. Visible indications of PHS include kernel swelling, germ discoloration, seed-coat splitting, and the root and shoot emerging.

Rain simulator used with
the screening of wheat
spikes for preharvest
sprouting tolerance

Sprouted wheat spike

Ears ready for evaluation

Alpha-amylase enzymes are produced to reduce the stored starch granules to simple sugars that can be used by the new plant. Wheat that has been subjected to amylase activity is not suitable for bread baking purposes. The amount of sprouting measured in a certain sample is directly correlated with the Falling Number (FN) test. A low FN (< 220s) is not suitable for bread baking.

The inherent dormancy of all commercially released wheat cultivars, as well as the breeding material from ARC-Small Grain Institute is evaluated in a rain simulator for their ability to resist germination under PHS conducible conditions.

This screening method is a laborious process. The scores determined are influenced by a number of environmental factors and should not be interpreted as predicting the likelihood of PHS in a particular year. However, relative differences among cultivars are representative of differences that exist when exposed to similar conditions. Some cultivars are less likely to develop PHS and may tolerate greater weathering prior to harvest.

The meganisms associated with sprouting tolerance are very complex and not easily manipulated. To ensure that only sprouting resistance cultivars are being released into the wheat market, all ARC-SGI breeding material are evaluated for their sprouting tolerance.

As the kernel matures, it starts to
germinate and sprouting occurs