University of Arkansas, Fayetteville Division of Agriculture


blackberries, molecular markers, PF2 performance, plant breeding


Typical blackberries (Rubus subgenus Rubus) have perennial crowns and roots and biennial canes. The first-year canes (primocanes) are usually vegetative, while second-year canes (floricanes) produce fruit. Primocane-fruiting blackberries produce fruit on first-year canes and are desirable to growers because they potentially allow for a longer harvest season in temperate regions and enable production in tropical areas where no natural chill hours are accumulated. The development of molecular markers for desirable traits can potentially increase efficiency in blackberry breeding. However, to date, there are no diagnostic molecular markers for economically important traits in blackberries. Primocane-fruiting is recessively inherited, and tetraploid blackberries must have four copies of the primocane allele for the trait to be expressed. A single locus strongly associated with primocane fruiting was recently identified on chromosome Ra03, and a new KASP marker (PF2) was developed within this locus. In this study, we validated the performance of the new PF2 marker in a seedling population (Population 1937) segregating for primocane-fruiting at the University of Arkansas System Division of Agriculture's Fruit Breeding Program. In 2022, 170 seedlings in the population were evaluated for primocane-fruiting. Of these seedlings, 68 were floricane-fruiting, 86 were primocane-fruiting, and 16 could not be phenotyped due to poor plant growth. The PF2 marker correctly predicted the phenotype for 146 of 154 progeny that were scored in the 1937 population. Some of the inconsistencies between the marker prediction and the observed phenotypes could have been due to weak plants shaded out by neighbors or human error.