2017 ASHS Annual Conference

Apple fruit (Malus domestica) is one of the most consumed fruits in the world due to its flavor quality and nutritional value. The North America fruit industry is benefiting from increased production of a new cultivar ‘Honeycrisp’, which is economically profitable and has revitalized the apple industry. However, ‘Honeycrisp’ apple has been well known for its prone to soft scald, a storage disorder caused by the low temperature, which can cause significantly economical losses. Research has indicated that development of soft scald is influenced by many pre- and postharvest factors. However, the fundamental metabolism responsible for soft scald development in apples is not fully understood. In order to reveal the molecular mechanism of soft scald development, the effect of rootstocks on ‘Honeycrisp’ apple soft scald development was investigated employing a quantitative proteomic with stable isotope dimethylation labeling by peptides technique. ‘Honeycrisp’ apples on four different rootstocks (B70-20-20, G11, CG4214 and CG5078) were harvested at commercial harvest maturity and stored for three months. Scald incidence and fruit quality such as fruit weight, firmness, skin color, soluble solids and titratable acidity were evaluated. Apples on rootstock CG5078 showed significantly higher scald incidence as compared with B70-20-20 and other rootstocks. Quantitative proteomic analysis on stored fruit from scald sensitive and resistant rootstocks was conducted. In total, 780 common proteins were identified and quantified from two years as biological replicates. Among them, 130 proteins abundance were significantly higher, while 116 proteins abundance were lower in sensitive rootstock as compared with resistant rootstocks. The cluster analysis and protein function analysis revealed the significant increase in proteins abundance mainly associated with stress, signalling and cell function. Proteins in association with tricarboxylic acid (TCA) cycle, organic transformation and amino acid metabolism were decreased. The identities and quantities of the proteins found were linked with sensitivity to soft scald development. This study demonstrates that rootstocks play an important role in soft scald development in ‘Honeycrisp’ apples, which provides the evidences on molecular regulation on soft scald development and possible mechanisms.