Evaluating Post-Harvest Dormancy in Soft White Winter Wheat.

Dormancy is the inability of viable seed to germinate under optimal environmental conditions. Unfortunately, dormancy is low in soft white winter wheat cultivars, making it highly susceptible to pre-harvest sprouting (PHS) if a rain occurs prior to harvest. Breeders often aim to produce cultivars that germinate uniformly and establish quickly in order to have strong and healthy plants prior to the winter months. This goal may have resulted in cultivars being developed with lower levels of dormancy which has led to cultivars that are more susceptible to PHS. Post-harvest dormancy has often been seen to be reduced in wheat that experience nutrient deficiencies, high temperatures, drought, short days and other stress factors that can occur during grain fill. The objective of this study is to determine the degree of post-harvest dormancy that is expressed in older commercial soft white winter wheat cultivars and compare them to recently released cultivars to see if post-harvest dormancy has been slowly bred out of soft white winter wheat or how strongly it was present to begin with. This research will look at 39 different varieties released from the 1940’s to 2014 as well as 6 experimental crosses. The varieties were planted in two different locations, Corvallis, OR and Pendleton, OR to compare how different ripening environments impact seed dormancy expression. Germination trials were run at four different temperatures (4C, 10C, 20C, 30C) to determine the optimal temperature in which grain dormancy is expressed the highest. This study mainly focuses on how different temperatures during grain maturation and seed germination impact dormancy expression. The results of this research will demonstrate the direction wheat breeding programs should be working towards in whether they should be preserving or introducing post-harvest dormancy into soft white winter wheat.