Rootstock effect on growth, branch morphology and flowering precocity of young monoaxis and biaxis trees of ‘Scilate’ and ‘Fuji supreme’ apple cultivars

ABSTRACT The New Zealand Institute for Plant and Food Research has developed three semi‐dwarfing apple rootstocks: PFR2, 4 and 5 with pest and disease resistance/tolerance. Nursery performance and flowering of ‘Scilate’ and ‘Fuji Supreme’ grafted onto PFR rootstocks and grown as monoaxis or biaxis trees were evaluated in comparison with ‘Malling 9’ (dwarf) and ‘G.202’ (semi‐dwarf) at Hawkes' Bay research centre. For monoaxis ‘Scilate’ trees, PFR rootstocks promoted primary, axillary and total shoot length/scion by (11–15%), (54–76%) and (22–37%), respectively compared with ‘M.9’, but the same were lower by (4–11%), (25–62%) and (17–42%) compared with ‘G.202’. On PFR2 and PFR5, ‘Scilate’ produced 6 axillary shoots/tree, compared with ‘M.9’ (4) and ‘G.202’ (7). ‘Scilate’ on PFR2, 4 and 5 produced 74%, 62% and 93% of axillary shoots with moderate (30°–45°) crotch angle compared with ‘M.9’ (30%) and ‘G.202’ (79%). On biaxis trees, the total shoot length was higher on PFR2, 4 and 5 compared with ‘M.9’, but not different from ‘G.202’. Flowering precocity was not affected by rootstocks. Overall, PFR2, 4, 5 and ‘G.202’ produced high‐grade young trees expressing greater potential for early canopy development.