Email: Jeremy.curry@dpird.wa.gov.au

Pre-harvest sprouting is a seed quality issue that occurs when grains germinate on the mother plant, usually in response to rainfall. In wheat, this precocious germination leads to the production of hydrolytic enzymes that reduce the grain’s suitability for a range of food products, decreasing its value. Australia predominantly produces white wheat genotypes that exhibit low levels of grain dormancy, meaning that wet conditions near harvest can lead to significant levels of pre-harvest sprouting in some seasons.

The germination capability of grains changes significantly throughout the progression of seed development, maturation, and after-ripening. Along with these temporal changes, the environmental conditions that the mother plant is exposed to causes significant phenotypic plasticity. As a result, the incidence of pre-harvest sprouting in the field is the consequence of complex interactions between genotype, environment, and development stage that influence germination capability.

Field research conducted over multiple seasons in Western Australia has observed detrimental levels of pre-harvest sprouting occurring during the maturation drying phase (prior to harvest maturity). Increased levels of pre-harvest sprouting have been linked to cool and wet conditions that prolong the duration of grain drying, with elevated grain moisture promoting more rapid grain germination upon exposure to rainfall.

This transient period of increased risk during maturation drying challenges the idea that pre-harvest sprouting risk is simply determined by the decline in grain dormancy after physiological maturity and highlights the importance of the maturation drying phase in determination of the immediate and ongoing risk of germination.

The germination traits of seed populations from genotypes of contrasting dormancy levels produced under variable grain development and maturation conditions has been assessed to understand how grain moisture content, grain dormancy, and environmental conditions interact to determine the pre-harvest sprouting risk of wheat crops in the field. These results will be discussed in the context of trait improvement for pre-harvest sprouting under field conditions.