Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2003
Publication Date: March 1, 2004
Citation: Callahan, A.M., Scorza, R., Bassett, C.L., Nickerson, M., Abeles, F. 2004. Endopolygalacturonase genes in melting and nonmelting peach cultivars. Functional Plant Biology 31:159-168 2004. Interpretive Summary: Peaches that are used for fresh-market generally have a melting flesh characteristic, while those used for canning are non-melting flesh. This textural difference allows the canning fruit to ripen longer on the tree because they are less susceptible to the damage from handling and shipping. The trait for texture type, M, appears to be a single gene and has been thought to represent a gene for endopolygalacturonase, a cell wall softening enzyme. This cell wall softening activity is absent in non-melting flesh peach fruit and reports in the literature suggest the gene is also absent or rearranged in non-melting flesh peaches. Eight different cultivars of non-melting flesh peaches were examined; all were found to be lacking one or more endopolygalacturonase genes and also to have none or very low levels of mRNA for endopolygalacturonase during fruit ripening. This information can be used to identify the non-melting trait in seedlings instead of fruit, by looking for the deleted genes. This will aid breeding programs in early selection as well as further the understanding of what determines flesh texture and keeping properties.
Technical Abstract: Endopolygalacturonase activity during peach fruit softening is thought to be responsible for the melting flesh texture. A cDNA, PRF5, was previously identified as a fruit-related endopolygalacturonase that may be involved with the texture differences. We found that all eight of the nonmelting flesh cultivars in this study had at least one of their fruit ripening-related endopolygalacturonase genes deleted or rearranged while none of the melting flesh cultivars did. One source of nonmelting flesh resulted in a complete deletion of PRF5 related genes while other sources had deletions of a subset of those genes. All of the nonmelting flesh cultivars in this study in contrast to the melting flesh cultivars, had greatly reduced or undetectable mRNA levels of endopolygalacturonase during fruit softening. Using PCR techniques, it was determined that either the PRF5 gene, or more likely an unidentified peach polygalacturonase, is responsible for texture determination.