Multi-year trends of retention of fruit firmness after storage and influence of cultivar representation among apple breeding selections

Abstract

Retention of fruit firmness, as an important component of fruit quality during cold storage, is one of three primary targets of Washington State University's apple breeding program. Fruit firmness is phenotyped with a penetrometer to obtain firmness measurements of outer and inner fruit cortices. Since the breeding program's inception in 1994, substantial records of fruit firmness from Phase Two selections have been amassed, as part of its routine breeding evaluation. From 2005 to 2019, firmness data from at-harvest and after-storage samples were analyzed to describe 15-year trends in fruit firmness (and its postharvest retention) of the selections. Genetic backgrounds of selections were estimated using average allelic representation to describe pedigree relatedness of selections to cultivars and to quantify the potential influence of cultivar representation on the selections' firmness traits. Results showed that the breeding program has been selecting for increased fruit firmness and retention capacity postharvest (especially inner cortex) of the selections. The selections' increased inner cortex firmness coincided with increasing average allelic representation of 'Cripps Pink', suggesting the cultivar's influence in firmness at harvest and firmness retention during storage. 'Honeycrisp', another important breeding parent (as noted from the increasing average allelic representation from 0.10 to 0.40) has likely positively impacted firmness retention in the selections. In summary, the 15-year trend analysis highlighted the influence of important cultivars, such as Cripps Pink, Gala, and Honeycrisp, in fruit firmness and/or firmness retention of breeding program Phase Two selections.

Keywords

• cortex
• cripps pink
• honeycrisp
• malus domestica
• storability