S19 - Session O3 - Heat effect on highbush blueberry breeding lines in Oregon and Washington

Authors: Todd William Anderson *, Kim Hummer, Claire Luby

Innovative blueberry ( Vaccinium corymbosum. L ) growers in the Pacific Northwestern North America have successfully expanded production acreage into non-traditional growing regions. Breeding programs need to address this broader production area in their process to develop new cultivars. Four sites representing unique blueberry growing regions were chosen as trial locations for this study. Corvallis, Oregon, and Lynden, Washington, have a favorable maritime climate, tending to be moist with moderate temperatures for most of the year. Myrtle Creek, Oregon, and Prosser, Washington, generally have lower relative humidity with extreme air temperature fluctuations. Sixteen highbush blueberry breeding families, and their eight parental cultivars, were planted at these four sites. Our objective was to determine the response of the genotypes in our blueberry populations, considering the weather exposure within each site and if this response was heritable among sites. Contrary to the expected climate, in June 2021, a historic record-shattering heat event, termed by the press "a heat dome," occurred during the early or mid-ripening process of blueberry fruits on plants at our four locations and across the region. We monitored the effect of this event on fruit size, fruit weight, fruit texture, foliar tip burn, leaf scorching, and fruit sunburn at the four trial locations. We will present differences within and among the breeding families at the four locations in response to the high temperature and low humidity conditions experienced at the sites with data from 2021 and 2022. We explore the heritability of these traits to understand the implications of parental selection on improving highbush blueberries for adaptation to more extreme conditions and a changing climate.