Jenny Bolivar, WSU Extension discusses getting a good rootstock-scion-soil-system combination.

Jenny Bolivar is a WSU Tree Fruit Extension Specialist. Bolivar’s program focuses on tree fruit horticultural issues including apple rootstock evaluation, abiotic stress outreach programs and emerging industry needs. Her position is made possible through the Tree Fruit Industry Endowment.

This webinar was part of the 2021 Tree Fruit Days Webinar Series co-sponsored by WSU Extension, NW Cherry Growers, Okanogan Hort Assoc., Pear Bureau NW, NCW Fieldmen’s Assoc.

Link to YouTube video: Matching Rootstocks to Scions and Varieties

Text Transcript and Description of Visuals

Audio	Visual
Thank you, Tianna, for your kind words and welcome everybody to this presentation. For today, we will study rootstocks and scions, the combination of these two. We will learn or review some basic generalities and then we will share from the growers how is the experience.	Title slide. Presentation title: Matching Rootstocks to Scions and Varieties. Presenter information: Jenny Bolivar-Medina, Ph.D., Information and Technology Transfer – Extension, Tree Fruit Extension Team.
So my first 20 minutes, as I mentioned, I will go with some root characteristics, general characteristics and also describing what is the mainly rootstocks that we can find here in Washington nowadays. And basically giving the characteristics that these particular rootstocks have.	Slide titled “Outline” contains a bullet point list of the overall structure of the talk, including the time that will be spent on each section, as outlined in the audio.
Also, I will present with the data collected from the rootstock trials that Washington Tree Fruit Commission has established in Washington, provide some or illustrate how the rootstock and environment influence the figure and the characteristics of the varieties such as alternate bearing and production.	Bullet points appear in the outline as topics are listed in the audio
I will finish with some conclusions. And after that, we will have a video that is about 10 minutes where three growers from Washington will share with us the experience that they have using rootstock, one rootstock-scion combination that fits their goals in their orchards. We will finish with 10 minutes Q&A session.	Bullet points appear in the outline as topics are listed in the audio
Let’s see. So first of all, I want to make this comparison between what was an old orchard in the early 1900s and what we see right now in the orchards here in Washington. As you can see in the left picture, this is an orchard. typical tree that was present in those orchards. And as you notice, it’s really vigorous.	Slide titled “Evolution of apple production in Washington”. A horizontal arrow runs from”1900″ on the left to “Present” on the right. On the left is a black and white photo of a large apple tree from around 1900. On the right is a modern, color photo of small apple trees in an orchard row.
So the trees were huge. And because of that, just 50 or 70 trees could be planted in an acre. And then the growers have to wait about six to 10 years to get their first fruit production. And even then, the production was not good, like it was really low. And because of the tree architecture that these trees have, had very difficult maintenance of the orchards and also the labor was inefficient.	Text appears below the 1900 apple tree outlining the characteristic of the typical 1900’s apple orchard, as discussed in the audio.
So nowadays we see kind of the opposite situation where we have some small trees and because they have small trees, they can fit more trees in one acre, like about 1,500 or more. The time waiting for the first production, fruit production is reduced to four to five years and in some cases even less time to wait. And the production of the fruits is high with high efficiencies in their maintenance.	Text appears below the modern apple trees outlining the characteristic of typical modern orchards, as discussed in the audio.
So this transition from these old big trees to these small trees more easy to handle like simple has been given because of the rethinking in the orchard production as well in the need to increase the fruit production. So new systems, new technology and new plant materials with higher qualities has been put in place for getting to this moment. So part of the plant material that we needed for getting to highly productive orchards are the rootstocks.
So what are rootstocks? So I will go to the basics here and we know that sometimes we call it root, sometimes a stock or rootstock. And it is basically the lower part of a grafted tree or a composite tree as an apple tree in their orchards.	Slide titled “Rootstocks” contains one bullet point showing the definition of rootstock.
In the pictures that I am showing here from orchards here in Washington, taken in different times during the year, we can recognize the rootstock because it is the three or four inches of like a bigger stump of the stem or bigger part of the tree there.	Photos appear on the slide of orchards at different parts of the season. A yellow box highlights the rootstock, and a zoomed in image shows the larger part of the stump in greater detail.
So this is the part that we see from the rootstock, but it also includes all the root system that is anchoring the tree. We have here then the scion, so the apical part, the portion that we see in the orchard.	The cursor points to the part of the trunk above the bump of the rootstock.
So we have the rootstock and the scion, and we can recognize it because of the more wider stems on the base.	The cursor points to the thicker bump of the rootstock.
Since, a grafted tree, it is basically a combination of two plant materials to make one composite tree. There’s a lot of complex interaction that has to be in carrying out to get the results that we want, to get differences in vigor, high productivity, tolerance to specific diseases or environmental conditions.	Slide contains a diagram of an apple tree labeled “Scion” above ground, and “Rootstock” below ground. Arrows show the movement of nutrients, water, hormones, and proteins through the xylem and phloem. Boxes to the left list factors affecting crop productivity and quality.
For selecting this type of rootstocks, there has been breeding programs that has been established around the world. And for Washington purposes, most of the rootstocks that are planted currently are coming from the Geneva Rootstock Breeding Program in New York, the East Moline Research Station in England, and the Budagovsky Institution in Russia.	Slide titled “Apple Rootstock Breeding Programs” contains a map of the world with stars indicating the locations of apple rootstock breeding programs.
Most of the breeding programs look for different characteristics, but among the main ones are they looking for dwarfism, rootstocks that gives precocity to the orchard. So precocity is charting the time that you have to wait since you plant the tree to get the first fruit production. Productivity, also rootstocks that are modifying the tree architecture, conferring resistance to diseases and tolerance to different environmental conditions depending on the region.	Bullet points appear below the map outlining the characteristics that the apple rootstock breeding programs look for in their varieties.
The Rootstock-scion combination with these kind of complex interactions that we still don’t know very well, they will give results related with these traits in higher or lower proportion depending on the plant, on the genetic component. But there’s also an important component in this interaction.	Slide titled “Rootstock-scion combination” contains a diagram of desirable characteristics in apple such as dwarfism and productivity and indications that these traits can be high or low depending on the rootstock and scion combination.
And it is the environment. The environment plays a big role in how these two plants interact to make a composite tree and the characteristics that we will see in your chart.	A circle is drawn around the desirable characteristic diagram, labeled “Environment”.
In Washington, currently, in the orchards, we have noticed that there are more than 30 rootstock types that are planted. Most of them are belonging to the (indistinct) clones, more specifically the M9 clones. following by the Geneva series. Those are the rootstocks that are being produced by the Geneva Breeding Program. And also from Russia, from the Budagovsky Institution, particularly the B9 and B10. Because there is a lot of rootstocks and information that we can get from there, I was just trying to compress in the main characteristics that most of the time are looking for.	Slide titled “Rootstocks in WA” contains a chart of the top rootstock types planted in Washington State along with the percentages that these rootstocks make up.
And it is in this graph where, sorry, where in the left side, we can see characteristics that are dwarfism, precocity, yield, disease resistance cold hardness, and the arrows will indicate if the rootstock has higher or low impact or show high or low these characteristics. For example, the M9 clones that includes the M9T337, as well as the Pajam II that it is popular here too. we can see the following. So this rootstock is in the dwarfing section, has high precocity, good yield, but the disease to resistance is somehow limited. It is very susceptible to fire blight and it is fairly to crown and rot roots.	Slide contains a diagram of characteristics in the M-9(T337) rootstocks. Arrows are shown for each of the listed characteristics, with one side of the arrow indicating high levels and one side indicating low levels. A green bar is drawn on each arrow to denote the level of each characteristic in M-9.
For the Geneva series, we have also the G41. This is also a dwarf rootstock with again, high precocity, yield. This is resistance and cold hardiness. So this is good. The only thing, the big issue with this rootstock is that not all the varieties are compatible with this rootstock. Some like Honeycrisp and Gala, we have seen that there are problems in the union, in the grafting. Meanwhile, other cultivars like JAS get better results.	Blue bars appear on the diagram denoting the level of each characteristic in G-41.
Another one is the G 935 dwarf, high precocity, high yield, really cold hardy. The biggest problem with this one is that it is highly sensitive to viruses. So if you are planning to use the 935, be sure that your scion is virus-free.	Grey bars appear on the diagram denoting the level of each characteristic in G 935.
Other important characteristic that has been noticed in the rootstock trials here in Washington is that the size of the tree will depend, will change with the variety. For example, with having the G935s with Delicious, get a tree that is a little smaller than M9, but if it is combined with Fuji, it will be taller. So now we are seeing the interaction of these rootstock size combinations.	Text bubbles appear on the diagram showing three examples of rootstock-scion interactions in G935.
We have the G11, and this is now getting into the semi-dwarf rootstocks area. Even though it’s a semi-dwarf, still has a lot of precocity, good yield, but the resistance to diseases are variable. So for some of the, for the replant tolerance, it is good. Have some issues with fire blight, and does not like at all the aphids. It is really cold hardy one.	Orange bars appear on the diagram denoting the level of each characteristic in G 11. Three orange bars appear on the disease resistance arrow, showing how it can be variable in this trait based on different factors.
The other one, semi dwarf, but more vigorous is the G890. The precocity has been, it is not so precocious as the previous ones, but it still has a good yield, good disease resistance and hardy one. Since it has a big vigor, so there could be some issues with the bitter pit, This, it is, since also the vigor and has a big root system, so has good anchorage, so that could be a freestanding tree. Or it can be used with scions, cultivars that have low vigor.	Red bars appear on the diagram denoting the level of each characteristic in G 890.
Similar situation is happening with the 969. Their characteristics are very similar to the 890, that it could be worked as a freestanding tree, highly vigorous, not so precocious with high yield, high resistance and high cold hardiness.	Green bars appear on the diagram denoting the level of each characteristic in G969.
In Washington, it has been observing the rootstock trials that even though it seems that it is not as precocious as the other ones, in the central area of Washington has reported higher yields than other rootstocks, even in the second or third year of being planted.
Now we go to the Budagovsky series where we have the B9. That is the smallest tree that we have right now. It is the…but even though it is a small has high precaution, it is very precocious doing good yields. The resistance is kind of, Yes and no, it’s highly resistant to crown rot, but it is vulnerable to fire blight. Most of the time happens that they are very susceptible when they are very young, but once the trees get older, they get more tolerance to this disease. It is a really good cold hardiness one.	Silver bars appear on the diagram denoting the level of each characteristic in B9.
And the final in these examples is the Budagovsky 10, the B10. It is still a dwarf, but it’s not as small as the B9. With good precocity, with yield, with good resistance to fire blight in contrast to the B9. And also, but it is susceptible to the aphids. I really cold hardy one too.	Gold bars appear on the diagram denoting the level of each characteristic in B10. Two gold bars appear on the disease resistance arrow, showing how it can be variable in this trait based on different factors.
So as you can see with this, in summary, you can see in this slide is that the rootstocks in Washington goes from dwarf to semi dwarf, and they have been planted because they have good precocity, yield, and cold hardiness characteristics. Most of the time they have good disease resistance, but depending on the rootstocks, you will have more resistance or more tolerance to certain diseases than to other ones.
And now I will change topics to show with data how the rootstock and the environment affect the growth of the plant. So just keeping in one variety consistent that in this case is Honeycrisp and taking the data from two rootstock trials here in Washington, one in the north area of the state and the other in the central part of the state where more than 14 root stocks were evaluated.	Slide titled “Effect of the rootstock vigor in plant growth and fruit production – WTFREC rootstock trials contains text outlining the variety and site information for the rootstock trials.
And for simplicity, I am just taking as an example, six or seven here in these graphs. And in these graphs, I’m showing the vigor and the fruit production.	Four bar graphs appear on the slide, showing the vigor and fruit production vs the rootstock for each of the two sites used in the trial.
When the rootstocks or in the rootstock trials that has been planted in the north area, we can see that the Geneva series G210, it is the one more bigger by this trial. And this figure, with this figure, they have a low fruit production compared with the rest of rootstocks evaluated.	A red arrow is used to indicate the bar representing the G210 rootstock vigor and fruit production at the Northern site.
In the opposite, in contrast, we have the Budagovsky, the B9, which is the dwarf, that low vigor and the productivity is high.	A black arrow is used to indicate the bar representing the B9 rootstock vigor and fruit production at the Northern site.
However, this pattern is different in the central area of Washington. As we can see here, the vigor is consistent, just the G210 is the highest and B9 is small and has the similar tendency to rootstocks.	A red arrow is used to indicate the bar representing the G210 rootstock vigor and fruit production at the central site.
But the fruit production in the central part of Washington was not as affected as it was in the north. Basically it is similar to the rootstock that is a dwarfing rootstock, that’s the B9. So small vigor, but still the fruit production is similar to the one that has the highest vigor in the trial. So we can see here that environment is having an effect on them. And with environment, not just the weather, not just the soil, but also the maintenance of the orchard here could have an impact on them.	A black arrow is used to indicate the bar representing the B9 rootstock vigor and fruit production at the central site.
Other parameter that shows this relationship between the rootstock and the environment is the alternate bearing. So alternate bearing, as all of you know, is the alternation between seasons of high production with seasons of really low production. And in this experiment where they were evaluating treatments for replanting, with the rootstock trials in the South region of Washington where they evaluated 14 rootstocks. And for simplicity, I am taking just four and the more representative here. I calculated the alternate bearing index using the fruit production from the second year of planting to the fifth production year of being planted to analyze this index.	Slide titled “Effect of Rootstocks on Alternate Bearing (WTFRC) contains bullet points outlining the location, rootstocks, and other factors of this trial. The representative rootstocks are listed: Bud9, M9, M26, and G214.
So the treatments were controlled where the ground was the same with no pesticide and where the ground was treated with two different pesticides for replanting diseases.	Text appears below the bullet points outlining the three treatments used in the trial: No pesticide, Telone, and Metam.
The ABI index that was calculated that goes from zero to one. If the index go to zero, it means that it is non-alternate bearing, so it doesn’t have this alternation in fruit production. If it is one, it is a strong alternate bearing cultivar. At least with this set of trial, none of the root stocks get to the non-biennial part, but there’s some differences.	An arrow labeled “ABI” appears on the slide. The left end of the arrow is labeled “0, no biennial” and the right end of the arrow is labeled “1, Biennial”.
If we take B9, we observe that with no pesticide in the control. So in the control ground, the index was in the middle.	An arrow appears beside the “No pesticide” text. A green bar labeled “0.64” appears on this arrow indicating the alternate bearing index of B9 in the control treatment.
But then when the pesticides were put in place, the alternate bearing trait was affected, like it was more drastic.	Arrows appear beside the “Telone” and “Metam” text. Green bars appear on each of these arrows indicated the alternate bearing index of B9 in these two pesticide treatments. B9 has a value of 0.71 in the Telone treatment and 0.86 in the Metam treatment.
M9 is a strong alternate bearing and the treatments didn’t make too much of the change.	Pink bars appear on the arrows indicating the alternate bearing index of M9 in the three treatments. M9 has a value of 0.89, 0.79, and 0.89 in the no pesticide, Telone, and Metam treatments respectively.
But with the M26 and the G214, they became stronger alternate bearing when they were planted in the treatments for replanting. So now we can see that even the soil and how it is treated could affect the traits of our plants in the orchards.	Blue and grey bars appear on the arrows indicating the alternate bearing index of M26 and G214 in the three treatments. Each of these rootstocks showed a higher alternate bearing for both of the pesticide treatments.
As some conclusions from or take home points from this presentation is that the rootstocks are interacting with the science and meaning the cultivars and provides the different characteristics that we are looking for in the orchard, such as resistance, such to tolerance, resistance to diseases, tolerance to environmental conditions, fruit production, precocity, among others.	Slide titled “Conclusions” contains a bullet point list of key messages which appear on screen as they are read aloud.
Also with these previous examples that I was presenting the performance of the rootstock can vary based on the environment that they grow. In Washington, most of the rootstocks that are planted are coming from the M9 clones, the Geneva series and B9 and B10 rootstocks.
One thing that I maybe forgot to mention, but I think that it is important. There’s not an ideal rootstock. Unfortunately, like not all the desired traits can be found in a single rootstock. So because of the interaction with the scion and with environment.
With this, I give you some references that I use for this presentation.	A reference slide appears.
And then I will let Tianna help us put on the video. Thank you so much.