INTEGRATING I_AD INDEX INTO THE CURRENT FIRMNESS-BASED MATURITY ASSESSMENT OF EUROPEAN PEARS

Harvest maturity is the most important factor affecting storage potential and eating quality after storage of European pears. Fruit flesh firmness (FF) is currently the only commercial maturity indicator for harvesting and predicting storage potential of European pears in the US Pacific Northwest (PNW). However, testing FF can be performed on only a few samples due to its destructive nature, and FF often remains constant while fruit continue to mature under high temperatures in certain production years. To study the possibility of fruit peel chlorophyll content as a maturity index, changes in chlorophyll content and I_AD index (an estimate of chlorophyll content) determined non-destructively by a portable DA meter were monitored in ‘Bartlett’, ‘Anjou’ and ‘Golden Bosc’ pears in two years. ‘Bartlett’ pear FF decreased linearly from ~89 to ~76 N in 2012, but remained constant at ~87 N for ~5 d and then decreased linearly to ~76 N in 2013 during 100-130 DFFB (days from full bloom). Chlorophyll content declined linearly (R²>0.99) from ~50 to ~25 µg g^-1 FW and I_AD index decreased linearly (R²>0.98) from 2.25 to 1.85 during 100-130 DFFB in 2012 and 2013. ‘Bartlett’ fruit harvested with IAD: >2.2, 2.2-2.1, 2.1-2.0, and <2.0 showed significant differences in FF, peel green color, and eating quality after 3 months of storage at -1.1°C. I_AD may be used as a complementary maturity index with FF for ‘Bartlett’ pears, but may not be appropriate for ‘Anjou’ and ‘Golden Bosc’ due to its small and non-linear decline during maturation or inconsistency between years.