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Rootstocks, canopy architecture and fruit quality of ANABP 01 apples

Research & Extension

This article was first published in Australian Fruit Grower Magazine – Autumn 2022

 

Scientists at Agriculture Victoria’s (AgVic) Tatura SmartFarm have been exploring the influence of different rootstocks on the quality of ANABP 01 apples (marketed as BravoTM).

The Advancing sustainable and technology driven apple orchard production systems (AP19003) project is part of the industry’s PIPS3 Program. Now in its second year of research activity, the project aims to determine adaptions and improvements growers may potentially consider in orchard design and management to combat the impact of increasing climate variability. In this experiment, the Tatura AgVic research team is investigating whether different rootstocks that alter tree canopy architecture, and consequently intercept sunlight, may inhibit or advance fruit ripening and cause variations in fruit quality.

The BravoTM apple, originating from Western Australia and known for its deep purple-burgundy overcolour, has no published research on its fruit quality response to different rootstocks. The study at the Tatura SmartFarm is being conducted in the Sundial Orchard, a unique multidirectional research orchard, on three dwarfing rootstocks: Bud.9, M9 and M26. Trees are grown at 1 m and 3.5 m tree and row spacing, respectively, and trained to spindles on vertical trellises.

 

Canopy architecture

The variation in scion vigour between the three rootstocks was visually evident from the kick-off of orchard planting and early growth. Bare rooted Bud.9 trees were notably “weaker” in appearance. Figure 1 shows the ‘ANABP 01’ scions in their third leaf and demonstrates the fuller canopies of the scions grown on M9 and M26 rootstocks. To quantify this, canopy radiation interception was measured with a custom-built three-metre-wide trolley equipped with light sensors. As expected, trees grown on Bud.9 intercepted significantly less light when compared to trees grown on M9 and M26 (see Table 1).

 

Figure 1. ‘ANABP 01’ trees at the Tatura SmartFarm in their third leaf grown on (A) Bud.9, (B) M9 and (C) M26 rootstocks.

 

Fruit quality

Fruit was harvested on 4 April 2022 at optimum storage maturity (i.e. 3–4 starch index). Between rootstocks, significant differences were found for background colour and overcolour, index of absorbance difference (IAD) and starch index (see Table 1). The classes for background colour and overcolour of ‘ANABP 01’ are depicted in Figure 2. Specifically, Bud.9 rootstock displayed advanced maturity in comparison to the other two rootstocks, with less green background colour, darker overcolour, lower IAD and higher starch index values. No significant effect of rootstock was evident for sunburn susceptibility, individual fruit weight, flesh firmness, soluble solids concentration and dry matter content.

RootstockEffective area of shade (%)Background colourOvercolourIADStarch index
Bud.930.42.53.10.993.6
M934.82.22.91.083.3
M2635.52.02.81.063.2

Mean values of significantly different (analysis of variance p < 0.05) parameters of ‘ANABP 01’ apple fruit grouped by rootstock in a randomised block design. Data represents combined 2020–21 and 2021–22 seasons.

‘ANABP 01’ colour classes (1–5) for (A) background colour and (B) overcolour. Adapted from Steele J, Lacey K, Sutton J (2017) Technical Information Dossier for Australia Apple Variety: ANABP 01.

What it means for growers

‘ANABP 01’ is performing well on all trialled rootstocks. The fruit grown on Bud.9 developed deeper overcolour and were advanced in their maturity, caused by a more open canopy allowing for increased sunlight penetration. A negative correlation (Pearson’s r = −0.271; p < 0.05) was discovered between EAS and overcolour, indicating that trees that fill more of the available space achieve less purple-burgundy colour development. The time taken by trees grown on Bud.9 to reach desired tree height and to fill out would be a drawback and could sacrifice early yields; however, the open canopy would be beneficial if growing ‘ANABP 01’ apples under netting. M26 has also demonstrated good performance in Western Australian trials (Steele et al. 2017). Long-term effects of rootstock on fruit quality and yield parameters will be investigated in the following seasons.

Acknowledgement: This project has been funded by Hort Innovation, using the apple and pear research and development levy, contributions from the Australian Government and co-investment from Agriculture Victoria. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

 

Further reading:

Technical Information Dossier for Australia Apple Variety: 1ANABP 01 (Steele J, Lacey K, Sutton J, 2014)

 

 

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