by Dr. Desmond R. Layne, Peach Specialist, Dept. of Environmental Horticulture, Clemson University, 2010
Hey, I’m Desmond Layne, Peach Specialist at Clemson University. Welcome to the Clemson Tiger Peach Network.
Welcome back to “Everything About Peaches”! In our fourth episode we are going to be talking about the Clemson Peach Germplasm Evaluation Program. Today, we are at the Musser Fruit Research Farm in Seneca, South Carolina, where we have over 350 different types of peaches and nectarines from around the world and we are evaluating them to determine which ones will perform the best for the Southeastern fruit grower.
Today is July 7, 2010, and here at Musser Fruit Research Farm we have collected the varieties that we are going to evaluate today. You can see the great difference among these different cultivars – from nectarines, to white-fleshed peaches, to normal yellow-fleshed peaches. In just a couple of minutes, we will be going into the laboratory to perform our evaluations.
I have chosen six representative fruit for the sample that we are going to use for digital photography. We take two of the six fruit for the photograph and cut them in half. One is cut longitudinally and for the other one we make a cross-section. On the left, we have the longitudinal section and on the right we have the cross-section.
I arrange the fruit on a 1-inch grid for taking the digital photograph. The first thing I do is place the preprinted label at the bottom center of the grid. Then, I place the longitudinal section. Then, the cross-section. Then the non-suture side of the peach with the tip facing up. Then, the suture side of the peach with the tip also facing up. Then the stem end of the fruit with the suture facing down. Then the tip end of the fruit with the suture also facing down. In the laboratory, we use supplemental lighting for our digital photographs. Now you can see the fruit in the standard layout for a digital photograph.
These are the visual ratings for “Klondike White”. For shape, I will give it a 7.5. It is not a perfect shape because it has a bit of a suture bulge. For, pubescence, you can put down 4.8 because it is quite fuzzy. For red, 7.8, because the skin color is quite dark red, almost a purple in most of the spots. And then overall attributes, I’d say 7.5.
For each variety we have a 10-fruit sample - then we measure the diameter. For each fruit, we measure the diameter at the suture, 2.94 (inches), and the diameter perpendicular to the suture, 2.98 (inches), and then we take an average.
To measure firmness, we take the fruit and locate the suture. On sides adjacent to the suture, we take off a small amount of skin. Using a penetrometer, we measure the firmness in pounds. This side is 5 pounds and, after resetting the penetrometer, we measure the other side which is 2 pounds.
We also measure the brix, or sugar concentration, of each of our 10-fruit sample, by taking a small slice of the fruit and extracting a drop of juice on the glass surface of a refractometer. By looking through the refractometer, we can see a numeric scale that indicates the concentration of the extracted juice. This one was a 16 (brix).
We are at the farm of Mr. James Cooley up in Chesnee (South Carolina) where we have an on-farm grower trial and we are looking at about 87 different types of peaches and nectarines to see how they perform in the upstate of South Carolina.
This is our variety trial block where we’ve got these 87 different types of peaches and nectarines and Stephen here has got our map. We are going to walk through the orchard and determine today what is ripe – and that is the fruit that we are going to evaluate today.
The tree that we are at now is called “Galaxy”. It is a white-fleshed donut peach from California. Here you can see it actually on the tree and I am going to pick it off. So here we have it right here, a white, flat peach with good color, good size. Mmmm. Very tasty! We’re going to evaluate this one today.
Sometimes on the tree the fruit are beautiful - just like this one. But occasionally, we have fruit that have cracking on the end. This is undesirable! Look, you can see right through it!
This next tree that we are looking at is what we call an advanced selection. It is “BY93P4318”. It is from the breeding program of Dick Okie down in Byron, Georgia (USDA-ARS). We are looking good! It’s got that nice yellow background color. We’ve got some red blush coming on. We’ve got some good sugar and acid so we are going to evaluate this one today also.
You know that sometimes you have to “go out on a limb” to get a good peach! You’ve just got to go out a little bit, right Steve? There we go. Look at that! Beautiful! Sometimes the fruit are better closer to the top – like these! Mmm! This is the best part!
In the wintertime, when we have our peach grower educational meetings, there are no leaves, there are no fruit on the tree. So when we do our evaluations out in the field, we actually take pictures of the fruit on the tree so that growers will get a good idea of what they look like.
This is a representative sample of fruit that we picked from our variety trial block. This is a normal acidity, yellow-fleshed nectarine. This is a low-acidity, white-fleshed peach. This is a low-acidity, white-fleshed nectarine. This is a low-acidity, white-fleshed donut peach. This is a normal acidity, yellow-fleshed peach and another normal acidity, yellow-fleshed peach.
So now, I am going to prepare the fruit for our photograph. The reason that I am trimming them (the peaches) a little bit is so that they will sit properly on the grid and they won’t roll over. O.K., here we have fruit laid out for a photograph. As you can see, we’ve got our label with the name, the date and the location. And then the fruit are oriented a particular way so that we can see all different aspects of the fruit. This is the stem end of the fruit facing up. This is the tip end of the fruit facing up. This is the non-suture side and this is the suture side. You can see that line there. Then we have a cross-section of the fruit and a longitudinal section of the fruit. On the side we have a 2 and ½ inch standard (scale) so that you can see how this would compare with a 2 and ½ inch diameter peach.
Once I’ve got the fruit laid out the way that I want them laid out, then I’ll take my photograph and I’ll zoom in and take the picture. This is all under natural lighting outside which is different from the way that we do it at the laboratory at the Musser Fruit Farm.
Once we have picked our samples of fruit, we use a digital caliper to measure the average size of ten fruit per sample. Next, we measure the firmness of the peach using a penetrometer. We take one measurement from each side of the peach. The last thing that we measure out in the field is the brix or the sugar content of the juice. Each week we rate the fruit for various aspects such as the overall shape, the pubescence or the hairiness or the fuzziness of the fruit, the red skin color, and also the overall attractiveness of each the fruit.
For more information on peaches, and to view the results of our peach germplasm evaluation program, you can go to my Clemson peach website at www.clemson.edu/hort/peach. And to read my regular peach columns for the American Fruit Grower magazine, visit their website at www.growingproduce.com.
For more information on gardening, landscaping, insect and disease problems on your plants, visit the Home & Garden Information Center web site at www.clemson.edu/hgic.
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