PEACH FRUIT ESTS - ANNOTATION AND MAPPING

Many physicochemical changes occur during fruit development and ripening that determine its final organoleptic and nutritional properties. These changes concern notably colour, increase in the sugar/acid ratio, softening and allergenic components. To better understand the different processes involved in peach fruit development and ripening, we sequenced fruit ESTs. The aims were to advance knowledge of fruit physiology and the generation of genomic tools for molecular assisted selection. Two cDNA libraries were obtained from fruits of ‘Fantasia’ peach at two stages of development (30 and 80 days after bloom). Two thousand five hundred and seventy five ESTs were sequenced from the 5’ end. The primary goal was to identify and map new candidate genes involved in fruit quality. On one hand, a bio-computing pipeline was built in order to develop an automated method for SNPs detection from the dataset assembled into contigs. ESTs were clustered in 355 contigs and annotated using a bio-informatic pipeline in which initial automated annotations are manually investigated and curated using a web-based annotation tool. Search for SNPs was performed on contigs containing more than 10 ESTs. Eight contigs were selected and 10 SNPs were detected. On the other hand, 1,730 unigenes were obtained in which 34 SSRs (2%) were detected by using Sputnik software with selection criteria of motif including 2 to 5 nucleotides and minimum size of 18 bp. From these SSRs, 27 primer pairs were designed and 21 SSRs were mapped by using the selective mapping strategy on 6 hybrids of the ‘Texas’ x ‘Earlygold’ F2 progeny that has been used for the construction of the saturated reference Prunus map. The ESTs annotation is available in a public database.