Bernardita Sallato explains nutrient composition differences between WA 38 apples with and without green spot, and how rootstock and growing systems can influence green spot development.
Acknowledgment: Pom Club for organizing the meeting and Garret Bishop, GS Long, for moderating the Q&A.
Text Transcript and Description of Visuals
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| My name is Bernardita | |
| My name is Bernardita Sallato and I’m a tree fruit extension specialist at Washington State University. | Bernardita appears on screen in a video call along with her contact information and title. |
| So, first of all, the WA38 trials, or Cosmic. The Cosmic apple trials we’ve done most of them at the Roza farm in Prosser. You may know this, but it was planted in 2013 with the purpose of evaluating a pruning system, training system, and rootstocks. So we have randomized two different rootstocks, the M9 Nic 29 and the G41, and we have three training systems: the spindle, planted 12 by 3 in V-trellis. And those are double line planted at 12 also by one and a half foot apart over the row. And we have the bi-ax which is 10 by 3. So it’s a very neat place for us to do research because it’s randomized in terms of the root stocks, and also one of the oldest blocks that we have with the Cosmic apples. | Slide titled “WA 38” contains a photo of an apple research orchard. The trees are trained on trellises in long rows. |
| So before I move on to all the results and trials, I need to thank my research assistant, Juan Munguia. He is a former student of Oregon State University, and now he is my research assistant and he’s applying for doing a masters with Washington State University. He’s been a tremendous help for all my trials. I also, for the WA38 trials, have a lot of support from growers, especially from Blyhl that manage all the IPM and Burrows Tractor, with Tyler that allows us to harvest the fruit like you see here in this bin. | Slide contains a photo of Juan Munguia, a large bin of apples, and the logos of the two mentioned companies. |
| Okay so now I’m gonna get more into the green spot. This is a work that I started. You’ve probably seen a publication that we released with Garrett Bishop last year with samples collected from different sites, and these results that I’m gonna show to you now are only taken from the Roza site. I did a very different type of analysis of the fruit. I will explain that later. This is what we selected as the disorder because there are different levels of green spot. There’s one that is more like a russet type. So we wanted to define this one, which is the very rounded, defined green spot, as you can see here. And it is at the level where you have the damage in the peel but you can also see the damage or necrosis or oxidation in the flesh of the fruit. | Slide titled “Green spot” contains two images of apples with green spot symptoms. The image on the right shows green, indented spots on the skin of the apple. In the image on the right, the skin has been peeled, showing that there are brown spots in the flesh as well. |
| So the way we’ve been doing it for two years–and we did it also this year and we haven’t included the data for the third year–but this is two years of data where we compare in the spindle, which is the one that we have more problems with the levels of green spot. And we also looked at, what was the mineral composition of this fruit, as you can see here. Before we move on, the fruit per tree in this were not statistically different in 2019, and the fruit size also was not different. | Slide shows an image of an apple orchard, which has been harvested. On the left side of the slide is a simple diagram of the spindle tree training system. A table at the bottom compares two rootstocks, M9-Nic29 and G41 by fruit per tree, fruit weight, and green spot incidence. |
| So the way we did it, we strip harvested the whole tree. We had three trees, multiplied by four replicates. So four blocks of each rootstock times three trees from each block were strip harvested. And we selected all the fruit. We evaluated all the defects, including green spot, of course, and only the healthy and green spot apples were then taken to the lab for further analysis. | Slide contains a photo of spindle trained apple trees which have many apples ready for harvest. |
| I’m gonna go right into the results. I know these are maybe too many tables, but uh I I felt that this was the best way to show results, because this is in relation of the balance between calcium and other nutrients. So in 2018, for G41 we observed in the peel, all the green spot apples had higher levels of nitrogen, potassium, and magnesium. Here you have the p-value, which indicates the significance in terms of a statistical analysis. So those were statistically different between the clean or healthy apple and the green spot | Slide titled “Results” contains a photo of an apple showing symptoms of green spot. To the left of the photo is a chart showing nutrient content in the peel of clean versus green spot G41 apples in 2018 along with their p-values. |
| In 2019, the same G41 in the peel, what we observed is that the potassium, calcium, and magnesium were not different, but nitrogen was significantly different again with higher levels in the green spot apples. And this was an analysis done only in the peel of the fruit. | An additional chart appears on the slide showing nutrient content in the peel of clean versus green spot G41 apples in 2019 along with their p-values |
| But there’s different ways of analyzing fruit nutrient content, composition, concentration, and this evaluation of nutrient contents in terms of milligrams take into account the peel and the flesh, and then we calculate in relation to the allometry or the proportion of the tissue of each nutrient. So here what we observed–and this was consistent in both years–is that calcium levels were always higher in the clean or healthy apple. | Slide titled “Green Spot – Nutrient” contains a photo of a bin of apples as well as a chart showing the nutrient content in milligrams of clean versus green spot G41 apples in 2018 along with their p-values. |
| The same was observed in 2019, calcium was higher in healthy apples. But also, we observed that green spot apples had higher levels of content of nitrogen. So the balance between those two elements are inadequate. | An additional chart appears on the slide showing nutrient content in milligrams of clean versus green spot G41 apples in 2019 along with their p-values |
| Okay, so besides the difference between the systems and root stocks and the conditioned healthy and green spot apples in terms of the nutrient composition, we wanted to see how the rootstock affects this nutrient composition in the fruit. | Slide appears with a close up photo of apple roots. |
| So the way we did it–we did it for also for the green spot apples–but the results that I wanted to show here are about the healthy fruit, just to see the difference between the two root stocks in terms of nutrient uptake or nutrient extraction, which also consider the amount of calcium or nutrients in the peel and in the flesh. And in here, you can see that statistically there were differences between G41 and M9-Nic 29, with all the elements being higher, with nitrogen, potassium, and magnesium for G41. And M9 was higher in uptake of calcium, which we believe it relates to that period of time where G41 stays growing for a longer period of time, especially in a period where we irrigate more, probably because it gets hotter. So there’s more chances for that rootstock to uptake water, nitrogen, and potassium. | A chart appears on screen showing the nutrient content in milligrams per 100 grams of fruit of healthy G41 versus healthy M9-Nic 29 apples in 2018 along with their p-values. |
| So I finished that with coming back to the system and the importance of managing that vigor. The rootstock has an influence, but when you do have a system that controls and you can manage the vigor, you can also manage the problem in the rootstock. So you have to balance and manage these many different factors. | Slide titled “Green Spot 2019” contains an illustration of three different ways of training apple trees as well as a chart showing the fruit per tree, fruit weight, yield, and rate of green spot for G41 and M9 based on those tree training systems. |
| There’s some green spot that looks very superficial, it’s really on the surface. Do you think that’s a mildew issue, or do you think that’s still a green spot and calcium related issue. | The name of the participant asking a question appears on screen. |
| Yeah, that’s a good question. I think this is something that we did discuss with Garrett when we started looking to these different symptoms. The first symptom article that we published, you probably see that initial states that we call green spot. I don’t like to call it green spot anymore, because I think it’s very distinct from the round spot that is green and remains green in the middle and also affects the flesh. So I’m not so sure if they are the same thing or different. But I do think that the mildew, especially the mildew that is early in the season, the effect–at least what I’ve seen in in Cosmic–is it doesn’t show a green flecking. It’s more of a white netting in the peel of the fruit. I think it is different from the mildew symptomatology , | Bernardita appears full screen. |
| Thank you everybody. | The name and contact info of the speaker appears on screen. |
| Thank you, Bernardita. Awesome presentation. |
Link to YouTube video: Nutrient differences in WA 38 apples with and without green spot.
