S16 - Session P2 - Yellow kiwi fruit and high VPD – improving size since early development

Authors: Alexandra Boini *, Alessandro Bonora, Luca Corelli Grappadelli, Brunella Morandi, Luigi Manfrini

Actinidia chinensis is a highly profitable crop, however, the lack of information for management practices usually leads to poor fruit size and postharvest issues in Italy. One of the main reasons is the reference to the green deliciosa species, as a model for irrigation and management protocols. The current study compared the yellow and green species, from 2 different years' trials (2020 and 2021), in the highly productive Romagna region, in Northern Italy. The analyzed parameters were mainly physiological: fruit growth, leaf gas exchanges and water potentials, at different phenological stages. The VPDs of the experimental sites were also used to evaluate the sensitivity of the species. As in previous studies, the yellow species seems to prefer less stressful conditions and does not show marked linear trends, between plant water status and leaf gas exchanges. However, fruit water potential seems more influenced by environmental VPD ( A.chinensis : r=0.67, p=0.03; A.deliciosa : r=0.29, p=0.48) and fruit growth rates, compared to the deliciosa species, reach nearly 2.5 grammes per day in the very early season, with high VPDs (3.5 kPa). High fruit growth rates at early developmental stages will induce more cell division, generating a stronger sink and attracting more photosynthates along the season, probably explaining higher fruit size at harvest. Hence, the yellow species is able to reach bigger fruit dimensions, taking advantage of high spring VPDs and of water availability in such period.