ASHS 2015 Annual Conference

In 'Honeycrisp' (Malus domestica Borkh.) the establishment of harvest times is crucial to maintain good quality fruit and determining an optimum maturity is hard to gauge, since a) 'Honeycrisp' maturation is strongly dependent on crop load and b) commercial quality/value is primarily determined via percent of red color formation. The DA meter is known to offer a fast, non-destructive way to monitor maturity progression of fruit and we hypothesized that I_ADvalues if correlated to any other common maturity parameter in 'Honeycrisp' might be useful to determine optimal harvest points. Correlations to common destructive maturity indices were made on 200 fruit each from two orchards in 2014, utilizing an average DA value of 2 readings (front, back)/fruit. Orchard 1 was picked Sept. 10 (single pick of 100 fruit from range of canopy positions). DA values recorded ranged from 0.09 to 1.55. A large spread in background and red color was visually observed, and verified with laboratory readings. DA values correlated in the field to background color, but regression analysis showed only a weak actual correlation. Fruit on sun side looked very similar in 0.31-1.2 range. Fruit in commercially harvestable range (based on visual clues) had DA-values between 0.5-0.7. A linear regression analysis was performed for all maturity indices. Background color and starch exhibited the strongest relationship with the I_AD index (r² = 0.43 and 0.46). Firmness and fruit weight presented the weakest correlation (r² = 0.08 and 0.04). Fruit in the second orchard had a very narrow range in DA readings, with 70% of the fruit falling within I_AD of 0.61-0.9 and no readings below 0.3. Regression analysis revealed red color to be the strongest correlated to the I_AD index (r² = 0.26), while all other values had weak correlations below r² of 0.1. Further studies need to be conducted to determine a specific model for this cultivar with the goal to establish stronger correlations and maintain reliability when using the I_AD index to non-destructively assess 'Honeycrisp' maturity and quality.