Yield affects qualitative kiwifruit characteristics and dry matter content may be an indicator of both quality and storability

A study was carried out to evaluate the relationship between the yield and the quality of kiwifruits. Yield and fruit from nine orchards of the cultivar 'Hayward' were investigated in 2007-2008. The two-year average yield ranged from 24 t/ha to 49 t/ha. Yield was negatively related (P <=0.01) to fruit dry matter content (DMC) and total titratable acidity (TTA) at harvest and total soluble solids (TSS) and flesh firmness after 5 months of storage. Fruit DMC at harvest was positively related to TSS (P<=0.001) and flesh firmness (P <= 0.01) after 5 months of storage. At harvest, fruit DMC was also positively related (P <= 0.001) to non-structural carbohydrate content (glucose + fructose + sucrose + starch); moreover, the non-structural carbohydrate content was positively related (P <= 0.05) to TTA and citrate and malate contents. Fruit DMC at harvest was also positively related (P <= 0.05) to the content of structural material, estimated as the difference between DMC and the measured non-structural carbohydrates and titratable organic acids.The content of fruit structural material at harvest was positively related (P <= 0.05) to flesh firmness after 5 months of storage. After 5 months of storage, also the TSS were positively related (P <= 0.01) to the flesh firmness. Finally, there was a positive relationship (P <= 0.05) between fruit starch content and flesh firmness after 5 months of storage. The results showed that a very high fruit load can have negative effects on fruit DMC and TTA at harvest and TSS and flesh firmness after storage. Moreover, a higher DMC, besides being correlated with a higher TSS in ripe fruits, was also associated with a higher TTA and organic acids content and the retaining of higher flesh firmness during storage. This indicates that fruit DMC may be an indicator of both eating quality and storability of kiwifruits.