I'm Mark O'Connell based at Tatura Smart Farm in Victoria, and today I'll present some experimental findings on project SF17006, which is the experimental stone fruit orchard. And the topic of today will be the rootstocks from peach and nectarine. I acknowledge the Summerfruit industry fund throught Hort innovation.

Quick background: We've just heard from Trevor that exports are increasing particularly Asia, Middle East. We also know in the industry that the quality and the variability in fruit quality does impact our sales and consumer preferences. The industry has a whole diversity of orchard systems and canopy designs, everything from their low density, traditional vase type freestanding trees, right through to the modern high-density two dimensional. Trellis type orchards are coming into production at the moment and worldwide in terms of rootstocks breeding programs in stone fruit there's very few of those compared to other tree crops like apple, for example. In Australia and Nemiguard's the main industry standard rootstock, and that's particularly pertinent to peach and  nectarine.

And overall in Australia, we have limited data on root stocks in stone fruit and information on tree survival at  growth of  development, et cetera, the yield, fruit number, fruit size components and the fruit quality aspects. So obviously rootstocks and the rootstock selection is a long-term strategy that needs to be decided before crop establishment. The vigour component of a rootstock is the, is a very important for orchard management at governs tree performance, it governs production, potential yield and fruit quality outcomes. And the main agronomic characteristics as we list there are tree survival and health of the tree, the vigor, the precocity, how early we can get into production, the adaptable to the soils, the climate, and to tolerance and resistance to stress, whether that's water stress, salinity, nematodes, pests, and diseases, et cetera.

Overall, the root stocks and systems provide important functions and they are access to water, nutrients, and barrier to soil stress, and a conduit for signals of plant growth and function. So what would expect to see if we have a dwarfing rootstock? What sort of behavior in the scion in the top of the part of the tree, this scion? Less decreased growth, and that comes around through decreased crown or canopy size. It comes, that in trunk size, reduced shoot growth, reduced water shoots. It also changes in tree architecture, more greater branching angles. You can more shoots that are short and spurs. And we also have changes in the flowering and behavior there as well with increased flowering and fruit set. So there are currently a number of mechanisms and theories out there that explain this behavior in, in, in a tree reduced tree size. due to dwarfing rootstocks and the three or four main theories are carbon and or nutrient exchange, the hormonal metabolic signaling theory or the water relations theory. Worldwide, there is no consensus, not one consensus overall, in all the work that's been done around the world on apples and other tree crops as well. Quickly carbohydrate theory, the nutrition theory suggests that there's a reduced available of carbon and carbohydrates from the root system, and that reserves, it limits what happens in spring, and the main outcome is decreased growth, in the scion in the tree. This, the hormone signaling theory, similar sort of story produced everything relates to this reduced growth, but basically ABA and cytokidens and gibberellins synthesis, are all decreased,  root growth's decreased, and that leads to changing tree behaviour, tree size.

The water relations theory is again, another one whether it's through the graph union or not, there's reduced water uptake and flux changes in what they call hydraulic conductance. Leads to mild water stress, changes the photo synthesis, and, or just see reduced tree growth. That's enough on the theory.

So our work at Tatura, it basically is looking at dwarf, semi-dwarf and vigorous rootstocks and looking at how they impact tree size. Have the rootstock affects yield of fruit quality and with an the  hypothesis is that the reduced growth and changing the production percentage. So we've set up two carefully design field experiments, and when basically keeping everything else, constant water management, nutrition pest and  disease management, soil type, everything else, except for the crop that we're growing. That's all the peach or  nectarine and the rootstock treatment, which is the genetics. That's the overview of the experimental site Tatura and the two crops and cultivars are peaches and nectarines, the block of peach here, and the block of nectarine. On Shep fine Sandy loam, planted in 2013, a vase canopy, four leaders per canopy, two metre  tree spacing, four and a half meter row spacing. And after the third leaf, we have been growing these trees and measuring things for the last five years. We've focused on the vegetation and yield fruit quality parameters.

So the focus is looking at these dwarf, semi-dwarf and or vigorous stocks on tree survivla, tree growth, tree development fruit yield and fruit quality. The root stocks are, Nemaguard, cornerstone Alberta, Krymsk 1, Krympsk 86 and Cadaman. Here's a snapshot of the trees in dormancy this winter. And you can see, as we, as I mentioned earlier, Nemaguard's to our control, our industry standard and we can see a tree size here and structure, and we can see a lot of suckers occurring on Krymsk 1 and also the reduced tree size.

So this is what we knew prior to the work. This is the evidence available at the time. Back in 2013, 2012, when the work for the study first started For Nemaguard, a very common vigorous root stock used in Sandy soils. Alberta typically use in heavier soils.Krymsk 86, another new rootstock considered vigorous, drought tolerance, high pH tolerance and wet soil potentially tolrant. Cadaman, new, another new rootstock alternative to GF677, prefers well-drained Sandy soils. Cornerstone, another new rootstock, high vigour, disease resistance in nematodes and crown gall. Krymsk 1, another new rootstock, cold and drought tolarant and water tolerant, water logging tolerant. So here's a a tree size graph, schematic and showing from zero to a hundred percent . And we are comparing ,we've got some here that, that we've captured in our Krymsk 86 Nemaguard and down here, Krymsk 1. So that suggests to me  that Krymsk 1 should be dwarfing, And we should have high vigor in Krymsk 86, Nemaguard, Cadaman. What we don't have information on is the cornerstone and Alberta.

Overall, what are we going to expect? We're gonna expect less vegetative growth in a dwarfing rootstock, reduced pruning biomass. That should occur. We would expect less internal shading that should lead to improve shoot quality and increase flower bud development.

Basic quick snapshot of some of our experimental designs and methods and approaches. And we're looking at phenology, light  interception trunk size, for example, pruning, tree survival and health, yield and fruit quality. And as we're doing today, webinars and presentations. At harvest time, measuring fruit number, fruit  weight  and internal and external fruit quality parameters. We've got a in-line grader here with quick sensors.

We have published on the websites, on the www.HIN.com.au throughout the years, each experimental treatment, each rootstock and a time series during the growth cycle each year. So there's a movie here, for example, on the nectarine. And there's one on Peach available on the website. So what we found, well when we look at tree performance and when we look at fruit behavior, all the things we've measured, whether that's true survival, phenology, the pruning weights, tree size,  light interception, branch diameter, the et cetera, shoot growth, that at harvest we're measuring leaf nitrogen, with the spag meter, for example, and suckering, and at harvest time, we measuring yield, fruit quality, everything we've measured with significant differences between rootstocks.

As an example, last season, 2020-21 in nectarine and in the peach, for the five root stocks under each crop, we're getting differences due to rootstock. So in, in nectarine, for example, we're getting reduced tree size, less light interception  under the dwarfing rootstock Krymsk 1. We had no differences in other tree rootstock treatments for in the nectarine. Everything was similar to Nemaguard  in this season. In that most current season in 2021 again we we measured light interception in the late season peach under the 5 different rootstocks. Compared the Nemaguard, we can see a slight reduction in tree size under Krymks 86.

What's been happening with pruning biomass over the last five winters and summers? So here's the cumulative pruning biomass that's winter and summer pruning for the first leaf, that's year three, year four, year five, year six, and year seven. For Rose Bright and for September Sun. And basically we're not getting much difference in pruning biomass, other than that, the dwafing rootstock having a large reduced amount of pruning material, being a smaller tree, in Krymsk 1. When we look at peach,  with comparing Nemaguard, Elberta, Krymsk86, Cadaman, Cornerstone, over time, that looks to be a drop-off in the Krympsk 86 biomass pruning rate over time.

In terms of yield, what are we seeing? This is a cumulative yield, fresh weight kilograms per tree in seasons 3, 4, 5, 6, and seven on the nectarine and 3, 4, 5, 6, 7 on the peach for each root stock. Then as you can see there's an order here, and that's the same order we can see in the graph in the data. And we can see cornerstone is basically out yielding most rootstocks, especially compared to our industry standard, Nemaguard, and Krymsk 1 obviously being the smaller dwarfing trees had low yield outcomes. In peach, the late season peach, we got cornerstone again at the top of the rankings and very close second, third ranking for Cadaman  and Nemaguard  and Alberta, and then the least yielding crop and rootstock is the Krymsk 86 under peach.

What's happening to fruit quality, fruit wight, fruit sweetness? So this is a five-year summary for averages for Rosebright nectarine. Compared to Nemaguard and fruit weight is in blue. The blue bars. So compare to Nemaguard over a five-year period, the five years at the study so far, fruit  size is increased  under  cornerstone on the Rose Bright trees.

When we look at fruit sweetness compared to Nemaguard, our industry standard, we're getting big significant increases in fruit brix under Krymsk one, that the dwarfing rootstock. What's happening, what's the picture look like for September Sun? We have Nemaguard fruit size, that's getting bigger fruit on Alberta, we're getting bigger fruit or cornerstone, and we're getting bigger fruit Cadaman over a 5 year average.

In terms of fruit sweetness, there's not a lot of statistical differences in fruit sweetness among the five root stocks in peach.

Another way we're looking at the data is looking at the distributions of all the fruit that we measure across the rootstock treatments and what we're wondering, whether we can see a shift to the right of the curve. That means we're getting a higher mean value at the same sort of variation, the same sort of uniform. We might also argue that we might get a more uniform outcome, but at the same the same mean value where we get the best of both worlds, where we are shifting the profile of quality and we're getting a higher mean value and more uniform.

So here's some data for the first season of nectarine Rose Bright under the four root stocks in that year. Nemaguard is the purple line here. Cornerstone, and krymsk 86 do look like there's a shift to the right in fruit size. So there's a huge range in fruit size outcomes here, but the distribution of fruit in the fruit size, is suggesting the beginning in that season, a shift.

When we look at, in that same season, Rose bright fruit sweetness, bricks, where you're getting no significant differences between the profiles, the distributions under the different root stocks.

These are a summary from  last season, Rose Bright under the five root stocks. Nemaguard*, Elberta, Krymsk86, Cadaman, Cornerstone. We can see in fruit number per tree we're getting small, but smaller trees, the Krymsk,  the Krymsk one trees don't have the capacity to carry large fruit number. Hence the yields are low, fruit numbers low. However, their fruit weight in this season was maintained very similar, statistically similar to the Nemaguard. However, they were sweeter fruit but more firmer fruit so less mature, but they had a higher percentage red skin color. So they were sweeter fruit, more red fruit, but the yields were down.

So in summary, what have we found? For tree growth metrics we found in the nectarine, the Krymsk 1 showed dwarfing traits. We saw that in reduced tree size and vegetative growth, whether that was everything from pruning biomass, main branch size, light interception , shoot length. We did see excessive levels of suckers under Krimsk 1. We continue to see that. We did have some suckering on Krymsk 86  as well, and it was greater than the standard Nemaguard. Krmsk 86 also showed some semi dwarfing traits in the light interception data  across many years. Alberta and cornerstone had similar growth and development compared to Nemaguard. We've got the summary here for peach, with tree survival in establishment years was lowest under Krymsk 86 and Cadaman. Krymsk 86 did show semi- dwarfing traits. There was some suckering in Krymsk 86. The other three Alberta, Cornerstone and Cadaman had similar tree growth and development. In terms of the yield and fruit quality, the main messages are cornerstone increased average fruit weight, and in color compared to Nemaguard. Krymsk one produced low yields, good fruit size and sweetness and improved color. Yield and quality under Alberta, Krymps 86 were similar to Nemaguard. For peach, Cornerstone and Alberta increased fruit weight and  red skin coverage. Krymsk 86 produced similar yield, fruit weight and Brix, however, did have increased red skin coverage. Yield, and quality under Cadaman was similar to Nemaguard.

I've covered that off earlier, so the main conclusions is that we looked, examined our peach and nectarines using dwarf, semi dwarf and high vigour stocks and found that we did induce vigour effects on tree growth, tree development, yield, and fruit quality.

In summary, Cornerstone - high vigour, large sweet fruit, and high yeild.

In summary, Krymsk 86, semi dwarfing,

and Krymsk 1, low yield, dwarfing, and excessive suckering.

Further information: we can refer to the latest issue of the Australian tree crop magazine. Also posted on the www.hin.com.au. We've developed production protocols and a grower information there on the HIN. We've got published scientific literature and summary tables of yield and quality for each experiment on the HIN. You can contact me directly or researchgate. I acknowledge the funding body and the project team members.

mark.oconnell@agriculture.vic.gov.au

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 – 6 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 six consecutive seasons: 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

Over the 6 seasons, the late season peach ‘September Sun’ produced large (≥ 189 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’). Most seasons, 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 – 6 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 6 consecutive seasons: 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

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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