2006 Annual Report 4d.Progress report. This report serves to document research conducted under a reimbursable agreement between ARS and the University of California. Additional details of this research can be found in the report for the parent project, 1931-21000-011-00D, Genetic Improvement of Fruit Crops. Peach consumption in the U.S. is declining. Poor fruit quality in the market has been cited as a reason for this decline. Endopolygalacturonase (endoPG) has been shown to be at least partially responsible for fruit softening. If t This report serves to docuent research conducted under a reimbursable he gene for endopolygalacturonase could be regulated, it is possible that fruit could be tree ripened but maintain firmness for shipping and marketing. The objective of the project is to determine the genetic control of endopolygalacturonase in peach. To carry this out, over 60 BAC clones from two peach libraries and over 80 BAC clones from one plum library have been isolated that contain a fragment of the genome with at least one endoPolygalacturonase gene. All the peach and plum BACs have been analyzed by DNA blot hybridization to determine how many potential genes are present on each piece of DNA. Several of the endoPolygalacturonase genes have been sequenced in plum. In peach, over 40,000 bases of one BAC clone were sequenced and the ends of six other BAC clones were sequenced. These sequences, as well as, allele specific PCR primers were used to sort the BAC clones to determine which may be the most likely to contain the genes responsible for melting flesh texture, freestone properties, and wooliness traits. Specific alleles of several known endoPolygalacturonase were sequenced from several of the peach BAC clones.