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`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).
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.
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.