Amy Iezzoni, Project Director, Michigan State University

Blackberry canes typically have a biennial life span. Primocanes are first-year canes that normally do not bear fruit. Instead, fruit is produced in the early summer on second-year canes known as floricanes.

However, primocane fruiting is possible, in cultivars that carry the right alleles. Primocane fruiting in the late summer and fall is valuable as it allows growers to plant cultivars that target the late-season fruit market, increase the mechanization of their operation as the primocanes can be mowed down in the fall, and avoid winter injury as the canes are not overwintered (Clark 2008).

In blackberry, an important primocane-fruiting locus, named F, was identified on blackberry linkage group 7, where the recessive allele confers primocane fruiting (Castro et al. 2013).

With genetic knowledge of which blackberry parents are carriers for the desirable alleles and which seedlings will exhibit primocane fruiting, breeders can plan crosses to maximize the probability of obtaining cultivars that have this fruiting habit and select seedlings with this desired attribute before field planting. Such an approach helps redirectresources to other critically important consumer-related traits.

Therefore, because knowledge of the genetic region of the F locus will lead to more effective breeding of blackberry cultivars, it is chosen as one of RosBREED’s “Jewels in the Genome.”


Castro P, Stafne ET, Clark JR, Lewers KS. 2013. Genetic map of the primocane-fruiting and thornless traits of tetraploid blackberry. Theor Appl Genet 126 (10): 2521 – 2532.

Clark JR. 2008. Primocane-fruiting in blackberry breeding. HortScience 43: 1637 – 1639.