Abstract

The Chilean strawberry (Fragaria chiloensis) is one of the wild parents of the commercial strawberry (Fragaria × ananassa) and is noted for its good quality. However, its fruits show a higher level of softening between the "large green" and the "turning" stages than that of F. × ananassa, a factor that could affect its shelflife and reduce its keeping quality. Fruit softening is certainly associated with the coordinated action of cell wall degrading enzymes. So far, we have investigated the role of key enzymes during softening, identifying potential candidate genes for selection. In order to broaden our knowledge of fruit softening, we have generated several suppression subtractive hybridization (SSH) libraries. By contrasting different developmental and ripening fruit stages of F. chiloensis, six SSH libraries were built containing 1809 differentially expressed cDNAs (ESTs). The expression analysis of interesting cDNAs during development and ripening of F. chiloensis fruit was carried out. As polygalacturonase (PG) and pectate lyase (PL) are probably involved in pectin metabolism, the expression of their genes was analysed. A considerable level of PG transcript accumulation was observed at the "large green" stage, while a similar level of PL transcript accumulation is reached at the "turning stage". In conclusion, the faster softening rate observed in F. chiloensis seems to be due to the early and high expression level of PG. Finally, the SSH strategy can provide new genes and could be a useful tool in strawberry breeding programmes.