Comparison of cell wall components between Fragaria × ananassa and Fragaria chiloensis grown in Chile

Fruit firmness and cell wall composition were compared among five cultivars of F. × ananassa (‘Chandler’, ‘Seascape’, ‘Tudla’, ‘Hokowase’ and ‘Reiko’) and two land races of F. chiloensis (‘94BAU-1A’ and ‘97PUR-1A’) grown in central Chile. Fruits of F. chiloensis were smaller than those of F. × ananassa. Firmness of epidermal tissue did not differ significantly between F. × ananassa and F. chiloensis. Firmness of cortical tissue, however, was significantly lower in F. chiloensis than in F.× ananassa and as a result, difference in the firmness between epidermal and cortical tissues was significantly greater in F. chiloensis than in F. × ananassa. Calcium concentration was low in ‘Reiko’ and ‘Hokowase’ while high in the other varieties of F. × ananassa. F. chiloensis showed intermediate values between these two groups. Higher levels of total uronic acid and neutral sugars in cell wall fractions of F. chiloensis as compared with F. × ananassa were mainly due to its high concentration in the water soluble fraction. Total uronic acid in cell wall fraction was significantly higher in F. chiloensis than in F. × ananassa, mainly due to significantly higher concentrations in the water-soluble fraction. Non-cellulosic neutral sugars, especially arabinose in the water, CDTA, and Na₂CO₃-soluble fractions were significantly higher in F. chiloensis than in F. × ananassa. On the other hand, galactose in the CDTA-, Na₂CO₃-, and KOH-soluble fractions was significantly lower in F. chiloensis than in F. × ananassa. Moreover, cellulose concentration of F. chiloensis was also significantly lower than that of F. × ananassa. Results obtained from cell wall analysis suggest that softer cortex in F. chiloensis might be due to either lower cellulose content, higher solubilization rate of pectic substances, and/or compositional differences in the branching of neutral sugars.