INTERSPECIFIC HYBRID KIWIFRUIT ROOTSTOCKS HAVE POTENTIAL TO MODIFY SCION ARCHITECTURE AND VIGOUR OF YOUNG 'HAYWARD' VINES

Abstract

Knowledge of how rootstocks affect scion architecture and vigour in kiwifruit is limited, unlike for some fruit crops. For example, in apple, scion dwarfing by ‘Malling 9’ (‘M9’) rootstock can be measured within the first two years following grafting. Architectural modifications imposed by ‘M9’ on the scion include early shoot termination and therefore less node neo-formation, and fewer sylleptic shoots. Currently in kiwifruit, there are no vigour-controlling rootstocks that reduce scion vigour in ways similar to those in apple. To elucidate the potential of Actinidia rootstocks on vigour control and altered scion architecture of kiwifruit, ‘Hayward’ scions grafted onto thirteen hybrid rootstocks were assessed at 8 and 14 months following grafting. Inter-specific hybrid rootstocks affected the early growth and altered initial shoot architecture of the ‘Hayward’ scion. For example, rootstocks modified the trunk cross-sectional area and proleptic budbreak of the ‘Hayward’ primary shoot. The lengths of long and short proleptic shoots of the scion from particular rootstocks were also slightly reduced, thus reducing the total length of proleptic shoots on grafted scions. Based on this promising evidence, selected Actinidia rootstocks show some potential to modify scion architecture and vigour during initial vine development. Vine architecture and components of yield will be further assessed in subsequent years as these vines mature.