Rubus Hybridization

The blackberries and red and black raspberries are members of the diverse Rubus genus whose center of diversity is in China. The entire blackberry industry is dependent on cultivars that have multiple Rubus species in their backgrounds.  The blackberry cultivars developed in the eastern U.S. were derived from species native to that region (i.e. R. argutus, R. allegheniensis), however, the source of thornlessness in the modern tetraploid cultivars from the European R. ulmifolius.  The western blackberries are an even greater mix of species with eastern cultivars, red raspberry (R. idaeus), and a source of thornlessness from the lower Midwest that traces to a R. baileyanus ×R. argutus hybrid, in a background that is predominantly from the highly-polyploid, West-Coast-native R. ursinus. While the red raspberry cultivars were predominantly derived from the European R. idaeus, the North American R. strigosus has been a recent contributor of abiotic and biotic stress tolerance and other species including R. crataegifolius, R. occidentalis and R. spectabilis can be found in the pedigrees of recent cultivar releases.  Black raspberries have the smallest acreage of the three primary Rubus crops and they are nearly completely derived from R. occidentalis, although R. leucodermis and R. idaeus figure in the background of at least two commercial cultivars.  Many species have been evaluated in multiple programs for what they potentially could contribute to the breeding pool.  While in most cases these species have proven to be incompatible or do not exhibit any obviously valuable traits, there are several species or new germplasm sources within previously used species that hold great promise for improving these crop plants.