Introgression of spine-free and primocane fruiting from red raspberry (Rubus idaeus L.) to black raspberry (R. occidentalis L.)

C.A. Weber
At the V International Symposium on Rubus and Ribes in 1989, Jennings and McNicol described efforts at the SCRI to develop black (Rubus occidentalis L.) and purple (R. hybrid) raspberries that are spine-free and tetraploid. However, since this report, further development has been intermittent, and it has also become apparent that primocane fruiting is required to increase the availability of fruit in order to develop and expand a market for fresh black and purple raspberries. A significant hurdle in the development of such raspberries is the recovery of the black raspberry fruit phenotype including flavor and pigmentation aspects after interspecific hybridization for transfer of these traits. Interspecific hybrids between red (R. idaeus) and black raspberry produce fruit with intermediate characteristics of color and flavor, that may have utility but are unacceptable in the black raspberry market. Multiple generations of interspecific hybridization and backcrossing has been utilized to transfer spine-free and primocane fruiting from red raspberry into black and purple raspberry germplasm with comparable flavor and pigment profiles. Fruit phenotypes approaching the black raspberry phenotype have been rarely selected in germplasm containing a minimum of 75% black raspberry parentage when selection for dark fruit was done in the previous generation. More commonly, black phenotypes could be selected at 87.5% or greater black raspberry parentage, although hybrids with intermediate phenotypes could still be observed at these percentages. Primocane fruiting is more challenging, being reduced at higher percentages of black raspberry parentage due to the floricane nature of most black raspberry genotypes. Analysis of pigmentation and other fruit quality traits of hybrid genotypes for comparison to black raspberry has been done to guide selection and population development. The development of tetraploid germplasm for further breeding work has been initiated to potentially improve fruit size and quality aspects in future populations.
Weber, C.A. (2020). Introgression of spine-free and primocane fruiting from red raspberry (Rubus idaeus L.) to black raspberry (R. occidentalis L.). Acta Hortic. 1277, 17-24
DOI: 10.17660/ActaHortic.2020.1277.3
anthocyanins, breeding, brix, interspecific hybridization, everbearing, fall bearing, tetraploid, colchicine

Acta Horticulturae