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W.R. Okie

Peach breeders need rapid, non-destructive methods to rate fruit quality changes after picking in order to select genotypes that can be delivered to the consumer with the maximum quality. Changes in ground color and firmness over time can be quantified by use of a bouncemeter (which measures coefficient of restitution) in conjunction with a colormeter. During 1991 and 1992, the ripening patterns of over 100 peach and nectarine varieties and selections were measured, allowing comparisons between different genotypes. Ten fruit, picked when firm ripe, were measured both before and after storage for 5 days at 5°C followed by 2 days at 20°C. Soluble solids (%) for each fruit were then measured with a refractometer, followed by determination of titratable acidity on 2 pooled samples. In general ground color changed from green to yellow and firmness decreased over time, but genotypes varied widely in the relationship of ground color and firmness. There also appeared to be differences in rates of change of these parameters.

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W.R. Okie

“Peach and Nectarine Varieties” is a self-contained computer program describing more than 600 varieties and their performance in the southeastern United States. The information can be accessed in various ways, including searching for any word or name. A Master Index of names and synonyms lists more than 6000 names used in the United States, plus many foreign names. This index includes pedigree, origin, and a coded description. General information is included regarding peaches and nectarines. All North American breeding programs are chronicled. The program is available for MS-DOS computers with an EGA or VGA monitor, and may be freely distributed.

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W.R. Okie

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W.R. Okie

Plumcots are hybrids of plums (usually Japanese-type) and apricots. In recent years, several new plumcots have been released, but most of these have been unreliable croppers and tree health of those tested in the Southeast has been poor. Some do have very high quality fruit, combining the best features of both parents. BY88Z1092 appeared as a chance hybrid in a lot of open-pollinated seedlings from the plum selection BY8111-6, which was a hybrid of BY4-601 (=`Queen Anne'*`Santa Rosa')*`Frontier'. BY8111-6 was a high-quality, midseason plum with black skin and amber flesh. BY88Z1092 blooms about with 750 chill hour peaches, and appears to be somewhat self-fertile. Cropping is heavy at Byron in absence of severe spring frosts. Tree health is good, comparable to local adapted plums such as `Black Ruby'. Trees are upright in growth habit. Fruit of BY88Z11092 ripen in late May, when quality of other adapted plums is insipid. It has firm yellow-orange flesh and a purple-black skin with light pubescence. Flavor is acidic until the fruit begins to soften, at which time it is very good. Fruit size will reach 4 to 5 cm in diameter if properly thinned. BY88Z1092 is in the final stages of testing and will likely be named within the next year.

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W.R. Okie

Pubescence in peach fruit is controlled by the Gg locus, with the homozygous recessive being the glabrous-skinned nectarine. The roughskin character in peach causes the loss of all long hairs on the epidermis of the fruit. Under a microscope short stubs are visible. The fruit is rough to the touch and appears dull rather than shiny as a nectarine would appear. A pleiotropic effect is lack of hairs on the dormant leaf and flower buds, making them noticeably shiny to the naked eye, unlike normal peaches and nectarines. The roughskin character appeared in 3 of 70 seedlings from the cross of Pekin × Durbin. The remaining seedlings all produced normal peaches. Sibling F2 progenies segregated for peach and nectarine, and in one case, for roughskin as well, indicating the cross was valid. Results from numerous crosses and F2 populations indicate this character is controlled by a single recessive gene, which is hereby designated rs. Nectarines homozygous for this gene have glabrous buds, but otherwise appear normal. The origin of the mutation is unclear. Selfed seedlings of Pekin and Durbin have not expressed the recessive form of the gene. Possibly a limb of the Pekin tree (now gone) used for the crosses had mutated to the recessive form at one or both loci. The homozygous roughskin progeny would have then been inadvertent self-pollinations rather than hybrids, since none of them segregated for nectarine.

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W. R. Okie