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W.R. Okie

`Black Ruby' is the newest plum released by the USDA stone fruit breeding program at Byron. This variety has large, firm fruit that ripens in early July, about 1 week after `Santa Rosa'. Fruit has reddish-black skin and yellow flesh. Eating quality is very good. `Black Ruby' has an upright tree similar to `Santa Rosa', except that tree health and vigor are much better than `Santa Rosa'. USDA has been breeding plums for the humid Southeast for 30 years. Goals are to combine large, firm, high-quality fruit with a disease-resistant tree that will live 8 to 10 years. Most plum varieties are short-lived in our area due to disease caused by Xanthomonas, Pseudomonas, and Xylella. Most existing varieties adapted to our climate have fruit unsuitable for commercial production. Previous USDA releases include “green plum” types `Robusto' (1980) and `Segundo' (1984); a yellow plum, `Byrongold' (1985); a black shipping plum, `Explorer' (1980); and the blood-fleshed, high-quality `Rubysweet' (1989).

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W.R. Okie and R. Scorza

Willow-leaf peaches, reported by Lesley (1957) as a product of inbreeding but also mentioned as far back as 1887 (Hedrick, 1917), are characterized by a narrow leaf shape. We received willow-leaf germplasm from Wayne Sherman (Univ. of Florida, Gainesville), who selected a peach seedling with unusually narrow leaves from a group of seedling rootstocks. His original willow-leaf tree bore very small, poor-quality fruit. In 1983, it was used in breeding at the USDA-ARS breeding program at Byron to develop willow-leaf peaches with improved fruit types. After four generations, current selections are approaching commercial fruit standards in size, color, firmness, and attractiveness. Inheritance studies indicate the character is at least partially dominant and is expressed in some F1 seedlings of crosses with wild-type parents. However, the precise mode of inheritance remains unclear as the ratios do not fit common patterns. Progeny show a range of leaf narrowness, complicating characterization of genotype. The character may be useful in standard-type trees to enhance spray penetration, speed drying of the foliage to reduce disease, improve light penetration and photosynthetic efficiency, and make the fruit more visible to speed picking.

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W.R. Okie and E.G. Okie

Check digit technology is frequently used in commercial applications such as shipping labels and credit cards to flag errors in numbers as they are used. Most systems use modular arithmetic to calculate a check digit from the digits in the identification number. Check digits are little used in horticultural research because the guidelines for implementing them are neither well known nor readily accessible. The USDA–ARS stone fruit breeding program at Byron, Ga., plants thousands of trees annually, which are identified using a 2-digit year prefix followed by a sequential number that identifies the tree location in the rows. Various records are taken over the life of the tree including bloom and fruit characteristics. Selected trees are propagated and tested further. To improve the accuracy of our records we have implemented a system which uses a check number which is calculated from the identification number and then converted to a letter that is added onto the end of the identification number. The check letter is calculated by summing the products of each of the digits in the number multiplied by sequential integers, dividing this sum by 23, and converting the remainder into a letter. Adding a single letter suffix is a small change and does not add much complexity to existing data collection. The types of errors caught by this system are discussed, along with those caught by other common check digit systems. Check digit terminology and theory are also covered.

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W.R. Okie and D.W. Ramming

The status of plum breeding around the world is reviewed. Two distinct types of plums are grown: Japanese-type shipping plums (mostly diploid hybrids of Prunus salicina Lindl. with other species) such as are grown in California, and hexaploid or “domestica” plums (P. domestica L.), which have a long history in Europe. In recent years there has been a resurgence of plum breeding outside the United States.

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W.R. Okie and Desmond R. Layne

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W.R. Okie and Desmond R. Layne

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Desmond R. Layne and W.R. Okie

White-fleshed peaches and nectarines are delicacies that have been enjoyed for centuries around the world. They are native to China and were introduced to the United States in the 1800s. Some white-fleshed peaches and nectarines are highly perishable and bruise easily, but are of very high eating quality. These are perhaps best suited for the local roadside market, where they can be sold and consumed more quickly. Others are much firmer at harvest, have a longer shelf life. and are suitable for long-distance transport to wholesale markets. White-fleshed peaches and nectarines may have some acidity or they may be very low acid with high sugar content (°Brix). Some novel flat (peento or donut) types also exist. Proximity to an urban market with a substantial Asian population is advantageous because Asians, in particular, often prefer the low-acid flavor and are willing to pay premium prices for high quality fruits. In our peach and nectarine cultivar evaluation program at Clemson University, we are currently evaluating 70 cultivars and advanced selections at four different locations in South Carolina. Several of these have been evaluated since 2000 and the “top performers” over the last six seasons by ripening date (earliest to latest) include the following: `Sugar May', `Scarletpearl', `Snowbrite', `Southernpearl', `White Lady', `Sugar Lady', `Summer Sweet', `Sugar Giant', `Stark's Summer Pearl', `Snow King', and `Snow Giant'. In general, most of the white nectarines and the flat/donut peaches and nectarines have serious problems with insect damage and brown rot. Complete details of our peach and nectarine (yellow- and white-flesh) evaluation work in South Carolina since 2000 will be noted by referring to my peach website (http://www.clemson.edu/hort/Peach/index.php).

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W. R. OKIE and D. J. WERNER

In the Southeast spring frosts often kill all or part of the flowers on peach trees. Increased flower bud density is one mechanism that increases the likelihood of enough flowers surviving to produce a crop. Mean buds per node in-North Carolina varied in 1986 from 1.6 for `Harko' to 0.4 for `Topaz'. The effect of environment on bud density was unknown. Therefore, for 3 years we compared the bud density of 25 peach and nectarine cultivars grown in completely randomized designs (4 reps per location, 10 twigs per tree) in Georgia and North Carolina. Genotypie variability was greater than that due to location or year effects. Cultivars selected for high bud density in one location can be expected to have high densities at other locations.