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Morris Ingle and Edwin C. Townsend

Firmness, total soluble solids (TSS), starch concentration (starch index, SINDEX), and surface color (L*, a*, and b*) were measured for 18 `Delicious' apple strains (Malus ×domestica Borkh.) produced in a replicated, randomized planting at the West Virginia Univ. Experiment Farm, Kearneysville. There was a significant difference between 1991 and 1993 for firmness, L* on the blush or outer side (BL*), Bb*, BChroma, a* (nonblush side), hue angle, and Chroma. There were significant differences between strains in firmness and chromaticities and their derivatives, but not TSS or SINDEX. All measurements changed linearly with days after full bloom (DAFB). There were large chromaticity differences between the two sides of the fruit 130 DAFB, but the nonblush side changed more than the blush side, resulting in little difference at 158 DAFB. BL*(Ba*/Bb*) and L*(a*/b*) produced better separation of strains and sides than did Chroma, although the products were significantly correlated with hue angle and Chroma. The nonblush side of `Delicious' fruits should be monitored to obtain the highest percentage of fruit in the highest grades.

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Chon C. Lim, Rajeev Arora, and Edwin C. Townsend

Seasonal patterns in freezing tolerance of five Rhododendron cultivars that vary in feezing tolerance were estimated. Electrolyte leakage was used, and raw leakage data were transformed to percent leakage, percent injury, and percent adjusted injury. These data were compared with visual estimates of injury. Percent adjusted injury was highly correlated (0.753) to visual estimates. Two asymmetric sigmoid functions—Richards and Gompertz—were fitted to the seasonal percent adjusted injury data for all cultivars. Two quantitative measures of leaf freezing tolerance—Lt50 and Tmax (temperature at maximum rate of injury)—were estimated from the fitted sigmoidal curves. When compared to the General Linear Model, the Gompertz function had a better fit (lower mean error sum of squares) than Richards function. Correlation analysis of all freezing tolerance estimates made by Gompertz and Richards functions with visual LT50 revealed similar closeness (0.77 to 0.79). However, the Gompertz function and Tmax were selected as the criteria for comparing relative freezing tolerance among cultivars due to the better data fitting of Gompertz function (than Richards) and more descriptive physiological representation of Tmax (than LT50). Based on the Tmax (°C) values at maximum cold acclimation of respective cultivars, we ranked `Autumn Gold' and `Grumpy Yellow' in the relatively tender group, `Vulcan's Flame' in intermediate group, and `Chionoides' and `Roseum Elegans' in the hardy group. These relative rankings are consistent with midwinter bud hardiness values reported by nurseries.

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Suman Singha, Tara A. Baugher, Edwin C. Townsend, and Mervyn C. D'Souza

Fruit of 10 `Delicious' apple (Malus domestica Borkh.) strains were harvested 149 days after full bloom in 1988. Fruit color was measured at four locations on each fruit at the midpoint between the stem and calyx end with a Minolta CR-200b portable tristimulus calorimeter. Anthocyanin content of corresponding skin disks was determined spectrophotometrically. Significant differences existed among strains in both the amount and distribution of anthocyanin around the fruit. High-coloring strains had a significantly higher anthocyanin concentration at both the blushed and the nonblushed surface when compared to low-coloring strains. A linear regression of anthocyanin content on the ratio of (a*/b*)2 provided an R2 = 0.59; precision was enhanced by using a separate equation for each strain (R2 = 0.80). Regressing log (anthocyanin) on L* using two linear splines yielded an R2 = 0.78. These relationships allow the use of a portable calorimeter for rapid, nondestructive estimation of fruit anthocyanin content in situ.