Merging blackberry germplasm pools and moving previously unutilized species into commercially viable selections
The USDA-ARS blackberry breeding program, begun in the 1920s, was largely established from germplasm derived from Rubus ursinus (western US trailing dewberry) and its hybrids with R. idaeus (red raspberry) such as Loganberry. Over the decades, other species have been mixed in with varying levels of success. For example, the source of thornlessness primarily used in the mid-1900s was from Austin Thornless, an octoploid from a R. baileyanus × R. argutus hybrid. In the late 1980s, the thornless Lincoln Logan, began to be used. While the initial material derived from Lincoln Logan had some negative traits, within two generations Columbia Star was released. In the early 1990s, the USDA breeder naively crossed trailing higher ploidy types such as Kotata with eastern US tetraploid erect types such as Navaho; while most of the seedlings were largely sterile, a few were fully fertile. Selections from these populations were further backcrossed to erect/semi-erect types to produce Eclipse and Galaxy, which are 1/4 trailing and 3/4 erect/semi-erect blackberry. The USDA-ARS program has used many species over the past 25 years. While many species have been dead-ends in this program (e.g., R. canadensis, R. insularis), some still have promise (e.g., R. glaucus, R. caesius), and some have been highly successful leading to selections that will be released (e.g., R. caucasicus, R. georgicus). Finally, selecting for primocane fruiting in the cool climate Pacific Northwest from crosses among Arkansas and North Carolina genotypes has led to earlier ripening selections with commercial potential. The relationships between the various programs along with a strong belief in the value of new germplasm, has led to blending diverse germplasm that in just a few generations has led to commercially viable blackberry genotypes containing valuable traits not previously present in our USDA breeding material.
Finn, C.E., Peterson, M.E., Clark, J.R., Fernandez, G.E., Hall, H.K. and Worthington, M.L. (2020). Merging blackberry germplasm pools and moving previously unutilized species into commercially viable selections. Acta Hortic. 1277, 47-54
erect, semi-erect, trailing, thornlessness, primocane fruiting, Rubus allegheniensis, Rubus argutus, Rubus caucasicus, Rubus georgicus, Rubus idaeus, Rubus ursinus