Relationships between ‘Hayward’ kiwifruit weight and dry matter content

The relationship between fruit weight and dry matter content (DM) of ‘Hayward’ kiwifruit was studied. Measurements were made on 3.62 million individual pieces of export grade fruit from 36 different orchards across four consecutive harvests (2001–2004) using near infrared grading technology. The objective of the study was to determine whether grading kiwifruit populations into weight classes also segregates on the basis of DM. It was postulated that fruit size and DM are positively correlated across seasons and among orchards. Statistical analyses showed that there was a general trend of increasing DM with increasing fruit weight between fruit within fruit populations. However, within any given season a proportion of fruit populations displayed a negative correlation between fruit weight and DM, and the proportion of populations with such a negative correlation varied between seasons. It is concluded that no general correlation exists between fruit size and DM across all fruit populations, as the correlation is dependent on cultural and seasonal conditions. However, overall, the practice of grading fruit into count sizes can also segregate for DM, and large fruit (lower count size) will often have higher DM than small sized fruit (higher count size).