MOLECULAR GENETIC DISSECTION OF CHILLING INJURY IN PEACH FRUIT

Abstract

Peach (Prunus persica L.), a member of the Rosaceae family is attaining a model status for fruit tree genetic studies. Fruit quality traits, including firmness, texture, stone adhesion, skin color, flesh color, sugars, acids, and flavor, determine usage and consumer acceptance. In many cultivars, such traits are negatively impacted by cold storage, a procedure used to extend fruit market life. The major symptoms of chilling injury are internal breakdown (flesh mealiness, browning, and bleeding) and loss of flavor. Understanding the genetic control of these traits, so that only cultivars free from chilling injury susceptibility are grown, promises to greatly benefit producers, shippers and consumers. A partial genetic linkage map was constructed for peach to locate genetic factors controlling fruit organoleptic traits and chilling injury symptoms. The map was developed from an Fl population derived from intraspecific crossing between the cultivars 'Dr. Davis' (clingstone, non-melting, bland-flavor, non-mealy, slight-browning, yellow-flesh fruit) and 'Georgia Belle' (freestone, melting, sharp-flavor, mealiness-prone, high-browning, white-flesh fruit). The linkage map, containing SSR, SRAP, RAF, candidate gene, and morphological markers and covering an estimated 90% of the genome, was used successfully to locate the Flesh color (Y) and Freestone-Melting flesh (F-M) loci. Major and minor QTLs controlling mealiness, browning, and bleeding were also localized, using phenotypic data collected for three harvest seasons. The endopolygalacturonase gene, at the F-M locus, is responsible for a major QTL controlling both mealiness and bleeding, while one of the minor QTLs for bleeding was located close to the Y locus. The goal is to develop molecular tools for efficient marker-assisted breeding of peach for improved postharvest fruit quality.