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Major breeding objectives. Kiwifruit was initially not grafted in commercial orchards, but expansion of the industry to regions with poor soil or environmental features is essential for the future of this crop. Controlling excessive vegetative vigour and improving the percentage of fruit set are important. Italy has been utilizing the clonal rootstock ‘D1’ for calcareous soils (Vizzotto et al., 1999), and ‘Bruno’ and ‘Kaimai’ are important in New Zealand (Oliveira and Fraser, 2005). ‘Bruno’ seedlings have been used to support vines that grow rapidly and with greater productivity (Lawes, 1990). ‘Kaimai’, a clonal rootstock of Actinidia hemsleyana Dunn, stimulates doubling the number of flowers on each shoot of the scion (Wang et al., 1994b).

BREEDING ACCOMPLISHMENTS. Analyses of A. arguta and different rootstock–scion combinations of A. arguta have demonstrated that both rootstock and scion affect actinidin activity and free sugar and organic acid content in fruit (Boyes et al., 1996, 1997). Interspecific rootstocks of Actinidia can have a major effect on the amount of vegetative growth on A. chinensis var. chinensis ‘Hort16A’ vines, dramatically altering plant size, leaf area and scion vigour (Clearwater et al., 2006, 2007). Thorp et al. (2007) reported that interspecific clonal rootstocks had a substantial effect on the accumulation and concentration of inorganic nutrients in the fruit, leaves and stem sap of ‘Hort16A’ vines. The use of rootstocks of other species of Actinidia, e.g. A. hemsleyana, A. eriantha and Actinidia rufa, reduced the level of floral abortion and increased bud burst in ‘Hayward’ (Wang et al., 1994a). The flower-promoting rootstocks have more starch grains, more and larger xylem vessels and idioblasts with raphides and mucilage (Wang et al., 1994b). Powell and Santhanakrishnan (1986) showed that ‘Hayward’ on mycorrhiza-infected rootstocks had increased shoot length and fruit production.