The agronomic performance of dwarfing, semi-dwarfing and vigorous rootstocks were compared at the Tatura Stonefruit Experimental Orchard on peach ‘September Sun’ and nectarine ‘Rose Bright’ (Table 1). The rootstock/scion study was established in 2013 on Shepparton fine sandy loam with tree spacing of 4.5 m x 2 m (1,111 trees per hectare), trained as open vase and drip irrigated.

Nemaguard is a very common and vigorous rootstock and represents the current industry standard for peach and nectarine in Australia.

Table 2 (Characteristics of rootstock) shows comparison of rootstock traits. Some key features of each rootstock are:

Nemaguard – prefers sandy soil,

Elberta – used in heavier soils,

Krymsk^® 1 – a new dwarfing rootstock,

Krymsk^® 86 – a new semi-vigorous rootstock tolerant to drought and wet soil,

Cadaman – prefers well drained soils, and

Cornerstone – tolerant of saline and high pH soils, new stock meant to offer greater vigour and disease resistance.

Table 1. Rootstock/scion combinations at Tatura Stonefruit Experimental Orchard

Early-season nectarine ‘Rose Bright’

Relative to Nemaguard, Krymsk^® 1 exhibited dwarfing characteristics, having reduced tree size and vegetative growth. Krymsk^® 1 trees produced less pruning biomass, smaller main branch size, a lower level of canopy light interception and reduced shoot length. From an orchard management perspective, Krymsk^® 1 grew an excessive level of suckers each season.

Krymsk^® 86 trees showed semi-dwarfing traits: lower canopy light interception compared to Nemaguard. Suckering on Krymsk^® 86 trees was greater than Nemaguard.

Elberta and Cornerstone rootstocks showed similar tree growth and development metrics compared to Nemaguard on early-season nectarine ‘Rose Bright’.

Late-season peach ‘September Sun’

Compared to Nemaguard, Krymsk^® 86 trees exhibited semi-dwarfing characteristics: less pruning biomass, smaller main branch size and less canopy light interception. Tree survival in establishment years was lowest on Krymsk^® 86. Suckering on Krymsk^® 86 trees was greater than Nemaguard.

Cadaman, Elberta and Cornerstone rootstocks showed similar tree growth and development metrics compared to Nemaguard on late-season peach ‘September Sun’.

Early-season nectarine ‘Rose Bright’

Cornerstone rootstock increased average fruit weight and fruit red skin coverage compared to Nemaguard. Krymsk^® 1 trees produced equivalent fruit weight and sweetness (°Brix) and improved skin red colour coverage relative to Nemaguard. Yield and fruit quality on Elberta and Krymsk^® 86 were similar to Nemaguard for nectarine ‘Rose Bright’.

Late-season peach ‘September Sun’

Relative to Nemaguard, Cornerstone and Elberta trees increased fruit weight and skin red coverage.

Krymsk^® 86 trees produced similar yield, fruit weight and sweetness (°Brix) to Nemaguard; however, fruit red skin coverage was improved. Yield and fruit quality on Cadaman trees were similar to Nemaguard for peach ‘September Sun’.

Tables 1 – 5 present production results (yield, fruit quality) for peach ‘September Sun’ in response to rootstock (‘Nemaguard’, ‘Cadaman®’, ‘Krymsk® 86’, ‘Elberta’, ‘Cornerstone’) and crop load (high, medium, low) treatments under a vase canopy system for seasons 2016/17, 2017/18, 2018/19, 2019/20 and 2020/21, respectively at Tatura, Victoria, Australia

Over the 5 seasons, the late season peach ‘September Sun’ produced large (≥ 199 g) sweet (≥ 14.1 °Brix) fruit when grown on the industry standard, ‘Nemaguard’ rootstock under a medium crop load (control treatment for rootstock x crop load study) regime.

Overall, high crop load increased final fruit number, reduced fruit weight, increased yield, lowered fruit sweetness and improved fruit skin redness coverage. Under low crop load regimes, the converse effect on yield and fruit quality occurred.

Overall, from a rootstock perspective, ‘Cornerstone’ and ‘Elberta’ fruit weight were larger and produced greater red fruit skin coverage compared to the industry standard (‘Nemaguard’). The semi-dwarfing rootstock ‘Krymsk® 86’ produced equivalent fruit weight, yield and sweetness to ‘Nemaguard’ and had greater red fruit skin coverage.

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Tables 1 – 5 present production results (yield, fruit quality) for nectarine ‘Rose Bright’ in response to rootstock (‘Nemaguard’, ‘Krymsk® 1’, ‘Krymsk® 86’, ‘Elberta’, ‘Cornerstone’) and crop load (high, medium, low) treatments under a vase canopy system for seasons 2016/17, 2017/18, 2018/19, 2019/20 and 2020/21, respectively at Tatura, Victoria, Australia.

Over the 5 seasons, the early season nectarine ‘Rose Bright’ produced medium sized (≥ 75 g) sweet (≥ 11.8 °Brix) fruit when grown on the industry standard, ‘Nemaguard’ rootstock under a medium crop load (control treatment for rootstock x crop load study) regime.

Overall, high crop load increased final fruit number, reduced fruit weight, increased yield, decreased fruit maturity (I_AD), lowered fruit sweetness (°Brix), and increased flesh firmness (kgf), and had no effect on fruit skin redness coverage (%). Under low crop load regimes, the converse effect on yield and fruit quality occurred.

Overall, from a rootstock perspective, the dwarfing rootstock ‘Krymsk® 1’ produced equivalent fruit weight and sweetness to the industry standard (‘Nemaguard’) but had the greater red fruit skin coverage. ‘Cornerstone’ fruit were the largest, had high red fruit skin coverage and maintained high levels of sweetness compared ‘Elberta’, ‘Nemaguard’, ‘Krymsk® 1’ and ‘Krymsk® 86’ rootstocks. The fruit quality characteristics on ‘Krymsk® 86’ and ‘Elberta’ rootstocks were similar to ‘Nemaguard’.

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Dr Mark O'Connell: I'm standing in a field orchard called the Stone Fruit Field Laboratory at Tatura. We have a rootstock experiment here, one on peach and one on nectarine. This is the Rose Bright Nectarine Field experiment. We're in the second year, trying to establish these trees. We didn't have much success in budding these trees last summer, so we've re-budded them this year and in future years we'll set up different crop load on each tree and look at five different root stocks. So this field experiment is on Rose Bright nectarine, early season nectarine. We have five different root stocks here. We have Krymps 1, Krymps 86, Cornerstone, Nemaguard and Cadaman. The trees will be trained as a four leader vase. They have two metre tree spacing, four and a half made a row spacing, and we'll set up different crop load, different fruit number pear tree in years three, third leaf on-wards. We'll have low, medium and high crop loads and we will look at the distribution of sugars, so bricks, high bricks content. And we would argue that the low crop load treatment and interactions with rootstock will help us understand the way the tree intercepts light and partitions those resources into the fruit to make high quality fruit.