Vigor-controlling rootstocks affect early shoot growth and leaf area development of kiwifruit

Abstract

Patterns of shoot development and the production of different types of shoots were compared with scion leaf area index (LAI) to identify how eight clonal Actinidia rootstocks influence scion development. Rootstocks selected from seven Actinidia species (A. chrysantha Merri., A. deliciosa (A. Chev.) C. F. Liang et A.R. Ferguson, A. eriantha Benth., A. hemsleyana Dunn, A. kolomikta (Maxim. et Rupr.) Maxim., A. kolomikta C.F. Liang and A. polygama (Sieb. et Zucc.) Maxim.) were grafted with the scion Actinidia chinensis Planch. var. chinensis 'Hort16A' (yellow kiwifruit). Based on an earlier architectural analysis of A. chinensis, axillary shoot types produced by the scion were classified as short, medium or long. Short and medium shoots produced a restricted number of preformed leaves before the shoot apex ceased growth and aborted, resulting in a 'terminated' shoot. The apex of long shoots continued growth and produced more nodes throughout the growing seasons. Mid-season LAI of the scion was related to the proportion of shoots that ceased growth early in the season. Scions on low-vigor rootstocks had 50% or less leaf area than scions on the most vigorous rootstocks and had a higher proportion of short and medium shoots. On low-vigor rootstocks, a higher proportion of short shoots was retained during pruning to form the parent structure of the following year. Short parent shoots produced a higher proportion of short daughter shoots than long parent shoots, thus reinforcing the effect of the low-vigor rootstocks. However, overall effects of rootstock on shoot development were consistent regardless of parent shoot type and nodal position within the parent shoot. Slower-growing shoots were more likely to terminate and scions on low-vigor rootstocks produced a higher proportion of slow-growing shoots. Shoot termination also occurred earlier on low-vigor rootstocks. The slower growth of terminating shoots was detectable from about 20 days after bud burst. Removal of a proportion of shoots at the end of bud burst increased the growth rate and decreased the frequency of termination of the remaining shoots on all rootstocks, indicating that the fate of a shoot was linked to competitive interactions among shoots during initial growth immediately after bud burst. Rootstock influenced the process of shoot termination independently of its effect on final leaf size. Scions on low-vigor rootstocks had a higher proportion of short shoots and short shoots on all rootstocks had smaller final leaf sizes at equivalent nodes than medium or long shoots. Only later in the development of long shoots was final leaf size directly related to rootstock, with smaller leaves on low-vigor rootstocks. Thus, the most important effect of these Actinidia rootstocks on scion development occurred during the initial period of shoot growth immediately after bud burst.

Modified CAROTENOID CLEAVAGE DIOXYGENASE8 expression correlates with altered branching in kiwifruit (Actinidia chinensis)

“…, 1994). Low‐vigour rootstocks ( Actinidia polygama and Actinidia kolomikta ) have also increased the proportion of short shoots on the scion and increased the fruit load relative to total leaf area compared with the scions on high‐vigour rootstocks (Clearwater et al. , 2004, 2006).…”

“…Different Actinidia rootstocks, such as Actinidia hemsleyana, have been shown to increase the percentage bud burst and the number of flowers produced per shoot on the scion (Wang et al, 1994). Low-vigour rootstocks (Actinidia polygama and Actinidia kolomikta) have also increased the proportion of short shoots on the scion and increased the fruit load relative to total leaf area compared with the scions on high-vigour rootstocks (Clearwater et al, 2004(Clearwater et al, , 2006. The mechanism of this effect is not clear, but a recent investigation in cherry has revealed differential expression of genes involved in brassinosteroid signalling, flavonoid metabolism and cell wall biosynthesis between the scions grafted to dwarfing or semivigorous rootstock (Prassinos et al, 2009).…”

“…In kiwifruit, both the shoot architecture and yield can also be influenced by the rootstock (Wang et al. , 1994; Clearwater et al. , 2004, 2006), suggesting that root‐derived signals, such as strigolactones, may be important for controlling kiwifruit branching.…”

“…The development of shoots and the potential to produce flowers and fruit are influenced by low winter temperatures, which increase the proportion of buds that break dormancy (McPherson et al, 1994(McPherson et al, , 1995. In kiwifruit, both the shoot architecture and yield can also be influenced by the rootstock (Wang et al, 1994;Clearwater et al, 2004Clearwater et al, , 2006, suggesting that root-derived signals, such as strigolactones, may be important for controlling kiwifruit branching.…”

Apple Rootstock-Induced Dwarfing is Strongly Influenced by Growing Environment

“…Another way of interpreting this is that the primary axes on dwarfing rootstocks terminate growth earlier in the season and therefore have a shorter duration of growth in warmer growing seasons than those on ' M793 ' . Low vigour or dwarfing rootstocks in kiwifruit and cherry are also associated with earlier termination of the primary axis [46,47]. Earlier termination on dwarfing rootstocks was consistent across all sites, suggesting that this trait is largely under genetic control.…”