kiwi Zesy002: the earlier the flowering, the heavier the fruit

Zesy002 kiwifruit is a kiwi cultivar with yellow flesh (Actinidia chinensis var. chinensis) recently marketed as Zespri® SunGold. Its strong flavour is what makes it popular among consumers.

The researchers at the PFR Institute in Kerikeri (New Zealand): "We think that the variations of weight and quality of the fruit were determined during the flowering and that the moment of opening of the flower and the type of flower (terminal or lateral) were important indicators. Therefore, we studied whether the flowering period (early: 5% open flowers; average: 50% open flowers; late: 95% open flowers) and the type of flower (terminal or lateral) influenced the weight, ripening and composition of the fruit in two seasons of growth".

The fruits that developed from the terminal flowers with early opening weighed 12-13 grams more than those that developed from the terminal flowers with late opening. Second season measurements suggested that this kiwi weight difference was related to the weight of the ovary. Early opening flowers were produced on shoots smaller in diameter than the half-opening and late opening flowers. The soluble solids content, compactness and colour of the fruit flesh were linked to the period of development, so the late opening flowers produced less ripe fruit as the kiwifruit was harvested on a single date.

The terminal and lateral flowers with an early opening had a much more external pericarp than the one that developed from the terminal flowers with a late opening. This difference in tissue proportion was associated with both the fruit's dry matter content being 1-2 units higher and the higher sugar/acid ratios in ripe kiwi juice. The fruits produced by the side flowers with early opening were smaller, but had a degree of ripeness and a sugar/acid ratio similar to the fruits produced by the terminal flowers at the same precociousness.

"These results suggest that flowering in spring influences the weight and composition of the ovary and the characteristics of the fruit at harvest. Therefore, these characteristics of the Zesy002 kiwi could be managed by changing the development of the flowers in spring".

Source: Annette Richardson, Helen Boldingh, Peggy Kashuba, Georgia Knight, Deborah Ellingham, 'Flowering time determines the weight and composition of Actinidia chinensis var. chinensis 'Zesy002' kiwifruit', 2019, Scientia Horticulturae, Vol. 246, p. 741-748.

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