Endopolygalacturonase and the Melting Flesh (M) Locus in Peach

Abstract

Southern analysis of two ripening-related polygalacturonase (PG) genes of peach [Prunus persica (L.) Batsch] detected a restriction fragment length polymorphism (RFLP) in one that had been previously identified as encoding the endoPG enzyme of melting flesh fruit. This RFLP distinguished the melting flesh cultivars Flavorcrest and Flordaking from the nonmelting flesh cultivars Carolyn, Early Gold Queen, Fla. 86-28C, and Fla. 9-26C. Complete deletion of endoPG-related genomic sequences was demonstrated in the nonmelting flesh variety Fla. 9-20C. In a blind trial, segregation of the endoPG RFLP was followed in relation to the melting flesh trait in a population of 20 trees from `Fla. 86-28C' × `Springcrest' in which the trait was segregating 1:1. Cosegregation of the RFLP with the trait occurred for 17 out of 20 trees. Practical aspects of scoring the melting flesh trait in a genetically variable population may account for incomplete segregation. EndoPG protein was detected by western blotting in fruit of the melting flesh cultivars Flavorcrest and Fragar, but not in fruit of the nonmelting flesh cultivar Carolyn. Results from this study and earlier work are used to discuss the hypothesis that the endoPG gene corresponds to the melting flesh (M) locus of peach.