Production of aroma volatiles in response to deficit irrigation and to crop load in relation to fruit maturity for 'Braeburn apple'

Aroma volatiles are important quality attributes for apples and there is not enough information on how their production is affected by deficit irrigation (DI) or by crop load. We investigated effects of irrigation, crop load, and their interaction on maturity-related quality attributes (aroma volatiles, total soluble solids (TSS), titratable acidity (TA), and firmness) and maturity attributes (internal ethylene concentration,'percent ripening fruit', and starch pattern index) for 'Braeburn' apple. Multivariate relationships between these two sets of attributes were also explored. Irrigation treatments were commercially irrigated control (CI) and DI applied throughout the season. Crop load treatments were commercial crop load (CCL) having six fruits per cm(2) of trunk cross-sectional area and light crop load (LCL) having four. There was no interaction between irrigation and crop load on any individual quality attributes. Control and DI fruit had similar maturity at harvest but DI fruit became more advanced in maturity during storage at 20 degrees C and after cold storage. DI enhanced volatile production during ripening and after cold storage. Firmness and TSS also increased in DI fruit but the increased firmness was lost during subsequent storage. Firmness and TSS increased in LCL in some occasions but crop load had no effect on maturity or aroma volatiles. Fruit TA was not affected by irrigation or crop load. Aroma volatiles poorly correlated with each individual maturity attribute. Canonical correlation analysis showed high multivariate correlation between maturity attributes and maturity-related quality attributes with two underlying dimensions that characterised their relationships. Quality enhancement in DI fruit was related, in part, to the advancement in ripening.