Pedicel Characteristics Effects on Apple Fruit Size

Apple fruit size is one of the important quality parameters that determines fruit value. It is well known that many factors affect apple fruit size. These can be categorized as environmental, genetic, and cultural factors. Many studies have been conducted to determine the effect of these factors. The apple pedicel is not only responsible for the physical attachment of the fruit to the tree, but also provides the connection between the fruit and the source of water and nutrients, which are carried into the fruit throughout the pedicel via xylem and phloem. Previous work indicated that the amount of xylem area in the pedicel may play a role in fruit size regulation presumably by affecting regulation of water and nutrient movement through the pedicel. It seems reasonable to propose that the pedicel may have a role in regulating apple fruit size. Therefore we sought to determine the effect of apple pedicel size (length and diameter) and anatomy on final fruit size. We compared ten genotypes differing in fruit size potential in terms of pedicel size and anatomy. These comprised Crabapple, Gala, Gold Rush, Golden Delicious, Honeycrisp, Malus floribunda, Pink Lady, Pixie Crunch, Pristine, and Silken. Fruit size at harvest ranged from 5.4 g (crabapple) to 459 g (Honeycrisp). Among the genotypes, pedicel volume was positively correlated with fruit volume. However, pedicel diameter was more strongly positively related to fruit volume but pedicel length was negatively related. Therefore, genotypes with larger fruit size also had pedicels with larger diameter but shorter length. Such characteristics would be expected to offer lower resistance to flow than long, thin pedicels. Future work will examine pedicel anatomy and measure flow resistance directly.