Early Shoot Development Affects Carbohydrate Supply and Fruit Quality of Red-Fleshed Actinidia chinensis var. chinensis ‘Zes008’

Abstract

Fruit quality characteristics are highly variable across kiwifruit vines due to complex source-sink interactions. We investigated how variation in fruit quality of Actinidia chinensis (Planch.) var. chinensis ‘Zes008’ was influenced by different shoot types (short, medium or long) and rootstocks types (Actinidia chinensis (Planch.) var. deliciosa (A. Chev.) ‘Bruno’ or Actinidia macrosperma C.F. Liang). Short shoots had smaller leaves (−30 to −50%) and lower photosynthesis rates (−0.70 to −3.34 µmol m−2 s−1) in the first cluster of nine leaves (Zone 1) compared with leaves on medium or long shoots. Later in the season, photosynthesis rates in Zone 1 declined with leaf age, but photosynthesis rates were higher (+0.5 to +6.1 µmol m−2 s−1) in later developing leaves on medium or long shoots. Fruit from short shoots had lower dry matter (−0.3 percent units) and lower outer pericarp flesh red pigment scores than fruit from medium or long shoots. At harvest, fruit from vines on ‘Bruno’ rootstocks were larger (+3.7 g), had higher dry matter (+1.3 percent units), soluble solids concentration (+1.7° Brix) and firmness (+0.4 kgf) than fruit from vines on A. macrosperma rootstocks. Factors that prioritised early development of source leaves had a direct impact on the carbohydrate supply from photosynthesis to support flower and fruit development.