ASHS 2015 Annual Conference

Cultivar development has allowed commercial wine production in North Dakota.  Among the most grown cultivars in the region are Frontenac Gris, Marquette, and St. Croix.  Though these cultivars have been adopted, some uncertainty exists in their year-to-year reliability.  A key factor in determining reliable performance is fall acclimation to winter conditions.  In a three year study, vine acclimation response was tract at two locations in North Dakota for the three cultivars.  Seven acclimation predictors were evaluated at each location for each half-hour decrease in photoperiod (15 – 12 hours daylight).  Principal components analysis was used to reduce the seven predictor variables to four latent variables contributing 45.41%, 33.57%, 7.54%, and 6.62% of the total variability of the dataset respectively.  Through correlations with the original predictors, it was determined that Factor 1 was positively associated with tissue maturation and tip abscission, Factor 2 was positively associated with stem growth and lateral shoot development, Factor 3 was positively associated with stem maturation and negatively associated with tip abscission and number of nodes, and Factor 4 was positively associated with lateral shoot formation and negatively with stem growth.  All factors were evaluated using ANOVA as a randomized complete block design with three replications, six environments, three cultivars, and seven repeatedly measured photoperiods.  Factors 1 and 3 were significant for genotype by environment by photoperiod interaction.  Factors 2 and 4 were found to have genotype by environment interaction.  Eberhart and Russell (1966) stability analysis was used to determine the relative stability of each cultivar.  For factor 1, within photoperiod, stability slopes tended to differ based on the ability of the cultivar to mature tissues when conditions were less conducive to maturation.  This caused positive slopes to be attributed to cultivars showing below average maturation in environments not favorable to maturation.  While St. Croix’s stability slope remained near the mean across photoperiods, Marquette’s stability slope tended to increase as the season progressed demonstrating the cultivar’s reduced maturity in unfavorable environments compared to the mean of all cultivars.  Alternatively, Frontenac Gris’s stability slope tended to decrease as the season continued demonstrating it’s higher than average maturity of tissues in unfavorable environments.  The difference in slope between the two cultivars grew as the season progressed. The data from this study suggests that the relative differences in year-to-year survival may be partly explained by the relative stability in acclimation response of cultivars across differing environments.