Relationship of apple vitamin C and antioxidant contents to harvest date and postharvest pathogen infection

A surprisingly strong correlation between the date of commercial harvest and the mean vitamin C (L-ascorbate, L-AA) contents of fruits from Belgian-grown Malus x domestica cultivars was reported recently (Davey MW and Keulemans J, J Agric Food Chem 52:8031-8038 (2004)). The study has been extended to show that this correlation remains consistent over different production years and that harvest date is also significantly correlated with fruit L-AA and total antioxidant activities but not with glutathione (GSH) levels or other physiological parameters of fruits. L-AA concentrations were also found to be negatively correlated with mean preharvest daytime temperature; however, since preharvest temperature and harvest date themselves are closely linked, it was not possible to definitively separate the relative contributions of genetic and environmental factors to these traits. It is also shown that the susceptibility of fruits of different apple genotypes to postharvest infection with Botrytris cinerea decreases with increasing harvest date and that this susceptibility is correlated with fruit vitamin C but not GSH levels. There is no such relationship underlying the susceptibility of fruits to postharvest infection with Gloeosporium fructigenum. These results are discussed in the context of low-input breeding for improved fruit quality and disease resistance via selection of fruits with improved antioxidant defence capabilities.