Softening Rate and Ethylene Fruit Production of Different Flesh Textures of Arkansas Peach and Nectarine Germplasm

The peach industry requires new cultivars that meet high standards of fruit quality and postharvest potential. The fresh-market industry needs peaches firm enough to be shipped long distances without affecting flesh quality. Peach growers often harvest unripe fruits to achieve firmness at the final market, but this practice can lead to fruits with flesh disorders and poor flavor resulting in a bad eating experience. The action of different enzymes and hormones determine peach flesh texture. The enzyme endopolygalacturosase (EndoPG) is involved in the ripening and softening processes and determines if a peach will be melting (MF), non-melting (NMF), or non-softening flesh (NSF) depending on the allelic combination controlling this trait expression. Ethylene is the primary hormone involved in the ripening and softening processes of peach fruits. Currently, an endoPG DNA marker is available allowing breeders to determine on a juvenile peach tree if its flesh will be MF, NMF, or NSF facilitating marker-assisted breeding (MAB). However, there is another flesh texture present in the University of Arkansas peach breeding program that differs from these flesh types, the slow melting flesh (SMF), which is not differentiated by the endoPG marker. This texture is crispy and firm, with outstanding postharvest potential. Its melting rate is slow with the fruit maintaining firmness for a long period until completely ripe when melting occurs as in a normal MF peach. The objective of this study was to characterize the softening rate and ethylene production of different flesh textures to ultimately design a DNA test for SMF. During 2013, softening and ethylene production rates were measured daily for 6 d after harvest on fruits from a range of flesh textures. Non-softening and SMF fruits showed a slow rate of ethylene production; however, SMF individuals reached ethylene levels similar to MF during the final storage day. Flesh firmness was high for NSF and SMF individuals, but SMF fruits at the end of the period were soft and their firmness was similar to MF. Preliminary results indicate a quantitative trait loci (QTL) associated with SMF and an interaction of this QTL with the maturity date QTL, both located on linkage group 4. Currently, DNA tests are being developed and validated for both traits, and will be combined with endoPG markers to provide a single DNA test to accurately predict flesh type in peach.