Vegetative (nonflowering) spur characteristics of `Granny Smith', `Lawspur Rome', and `Redchief Delicious' apples (Malus domestics Borkh.) at two canopy positions (1 and 2 m heights) were examined on eight dates throughout a growing season. `Granny Smith' had a greater leaf number/spur (LNO/SP) at each date than `Rome' and `Delicious'. Area/leaf (LA) and dry weight/leaf (LDW) for `Delicious' were substantially less than for `Granny Smith' and `Rome'. Area/leaf increased rapidly after full bloom (FB) until FB + 21 days for `Delicious', FB + 35 for `Granny Smith', and FB + 56 for `Rome', after which no further changes occurred. For each cultivar, leaf area/spur (LAMP) and leaf dry weight/spur (LDW/SP) increased rapidly from FB until FB + 35 days and then more gradually until FB + 104 days. From FB + 21 onward, `Granny Smith' had greater LA/SP and LDW/SP than `Rome', which, in turn, was greater than for `Delicious'. At harvest (FB + 160), LA/SP was 2.5-fold greater for `Granny Smith' and 1.7-fold greater for `Rome' than for `Delicious'. Cultivar differences for leaf dry weight/leaf area (LDW/LA) were small and canopy position differences were large. LDW/LA declined from 7 days before FB to FB + 7, then gradually increased to the end of the season. Dry weight of the vegetative spur buds (with leaves removed) was lower for `Delicious' than for `Rome' or `Granny Smith'. Total spur dry weight (bud + leaves) was, from FB + 21 onward, greatest for `Granny Smith', intermediate for `Rome', and lowest for `Delicious'.
Bruce H. Barritt and Bonnie J. Schonberg
Soon Li Teh, Lisa Brutcher, Bonnie Schonberg, and Kate Evans
Fruit texture is a major target of apple (Malus domestica) breeding programs due to its influence on consumer preference. This multitrait feature is typically rated using sensory assessment, which is subjective and prone to biases. Instrumental measurements have predominantly targeted firmness of the outer region of fruit cortex using industry standard Magness–Taylor-type penetrometers, while other metrics remain largely unused. Additionally, there have been limited reports on correlating sensory attributes with instrumental metrics on many diverse apple selections. This report is the first to correlate multiyear historical fruit texture information of instrumental metrics and sensory assessment in an apple breeding program. Through 11 years of routine fruit quality evaluation at the Washington State University apple breeding program, physical textural data of 84,552 fruit acquired from computerized penetrometers were correlated with sensory assessment. Correlations among various instrumental metrics are high (0.63 ≤ r ≤ 1.00; P < 0.0001). In correlating instrumental outputs with sensory data, there is a significant correlation (r = 0.43; P < 0.0001) between the instrumental crispness value and sensory crispness. Additionally, instrumental hardness traits are significantly correlated (0.61 ≤ r ≤ 0.69; P < 0.0001) with sensory hardness. Outputs from two versions of computerized penetrometers were tested and shown to have no statistical differences. Overall, this report demonstrates potential use of instrumental metrics as firmness and crispness estimates for selecting apples of diverse backgrounds in a breeding program. However, in testing a large number and diversity of fruit, experimenters should perform data curation and account for lower limits/thresholds of the instrument.