ASSESSMENT OF FLESH TEXTURE IN PEACH (PRUNUS PERSICA L. BATSCH)

The Italian peach compartment is nowadays experiencing a period of crisis. The cause of this crisis can be traced to a chain of production and distribution which is too attentive to the satisfaction of the individual components of the chain (e.g. large fruit size for the growers, fruit firmness for the packers, fruit color, size and texture for retailers) and not sufficiently focused on overall fruit quality at the end of the chain, on the table of the final consumers. The development of new cultivars belonging to the Slow Melting phenotype, characterized by a firmer texture even at full ripening and by softening more slowly (so that they can be harvested at a riper stage), definitely could help the fruit sector. Until now, the recognition of this new flesh phenotype was entrusted only to operator experience, which is not very reliable and allows flesh phenotype recognition only after obtaining the fruit, therefore some years after planting. An early determination, as it could be achieved through molecular markers, would lead to an early selection of fruit phenotypes, thus saving time, money and space. The objective of this research is to find possible physical or chemical differences in different flesh phenotypes, in order to characterize flesh texture. Accordingly, at the same time the expression profiles of the different flesh textures, in order to better understand which genes and pathways are involved in flesh firmness, were investigated. To reach these goals, three different approaches were performed: i) the characterization by a non-destructive approach. Time Resolved Spectroscopy (TRS) was performed on peaches belonging to different flesh phenotypes (Melting, Non Melting, Slow Melting, and Stony Hard). This technique gives information about fruit absorption and scattering properties. Scattering measurements in particular provide information concerning fruit structural characteristics, which could give useful information about the peculiar characteristics of the flesh. The results showed that this technique is able to discriminate only three flesh phenotypes (Melting, Slow Melting and Stony hard) out of the four that were tested. ii) The characterization by a traditional approach. Peaches belonging to M, NM, SM, and SH phenotypes were analyzed for weight loss, soluble solid contents (SSC), titratable acidity (TA), firmness, and expressible juice. Among all, expressible juice may be the key factor discriminating between the different flesh phenotypes. In fact it discriminated between all the flesh phenotypes in samples at physiological ripening in two consecutive years (2011 and 2012). Further studies are needed to determine whether this trait can be used as phenotyping method to be applied in QTL analysis, to the end of finding molecular markers associated with this character. iii) The characterization by gene expression analysis. Through this method, different gene expression peach profiles belonging to M, NM, SM, and SH phenotypes were compared at 2 different stages of ripening (fruit veraison and commercial ripening), in order to better understand which genes and pathways are involved in flesh firmness. The expression profile analysis gave partially unexpected results. In one of the most important contrasts of the experiment, M vs. SM, no differentially expressed genes were found, either in fruit veraison or in commercial ripening. On the contrary, differences were found in M vs SH and SH vs NM at varaison and again in M vs SH at commercial ripening.