The vines they are a-changin’: QTL in grapevine acclimation across environments

Grapevine (Vitis spp.) dormancy acclimation is defined by a suite of critical traits essential for winter preparation, survival through extreme climatic events, and continued productivity in challenging environments. An association panel composed of ten sub-populations was created to examine dormancy acclimation in the context of applied grapevine breeding. Five distinct parents (E.S. 10-18-58, ‘Frontenac’, ‘King of the North’, ‘Marquette’, and ‘Sabrevois’) were intercrossed to form a half-diallel without selfing or reciprocal crossing. Seedlings were maintained in a growth chamber simulating the progression from the active growing season to the end of the year via a fluctuating temperature regime in conjunction with a photoperiod reduced by 0.5 h each week. Visual phenotyping was conducted for five traits, and from these traits multiple metrics were calculated including a new trait, area under acclimation progress curve, based upon the commonly used metric, area under disease progress curve. Additionally, low temperature exotherms (LTEs) for buds were examined at the conclusion of growth chamber phenotyping. From these cumulative phenotypic responses, a total of 284 distinct QTL were identified across all linkage groups at a LOD threshold of 3.0; this number was refined to 113 QTL after adjusting the LOD threshold to 4.59 to account for marker density. Significant QTL occurred on 13 linkage groups. The influence of parentage was observed for LTE values, yet no significant QTL were identified for LTE traits. The breadth of QTL identified across multiple phenotyping environments emphasize the quantitative nature of grapevine environmental responses. These populations were subsequently field planted to allow for continued field- and growth chamber-based phenotyping of dormancy acclimation responses in conjunction with future planned work toward understanding fruit and wine composition in the context of cold-hardy grapevine breeding populations for the purposes of GWAS and refining methods for future genomic selection.