Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Ploidy reduction in blackberry.

Abstract

Polyploidy in blackberries and ploidy differences between Rubus species are obstacles to the efficient introduction of valuable germplasm, via both intraspecific and interspecific hybridization, into blackberry breeding programmes. Expansion of the germplasm base would be facilitated by reducing the ploidy level of blackberry cultivars to the diploid level. In this report, selection of twin seed, interspecific hybridization and pollen irradiation were compared as methods for the recovery of dihaploids from tetraploid blackberry cultivars (Shawnee, Cherokee, Raven, Blackstone, Chester, Navaho and Loch Ness). One dihaploid was obtained through selection of twin seed and several were obtained following interspecific hybridization. The infrequency of twinning and difficulties in detecting twin seed in Rubus reduced the efficiency of this method. The efficiency with which dihaploids could be obtained following interspecific hybridization varied with the pollen parent. Reduced seed set and seed quality following pollinations with, respectively, R. parvifolius [R. cuneifolius] and R. hirsutus could be used to advantage in the recovery of dihaploids from blackberries. Ploidy reduction in several tetraploid blackberry cultivars was obtained following pollinations with 100 and 150 kR γ-irradiated pollen. Most of the seedlings obtained via the 50 kR dosage were aneuploid. Pollen irradiation at 150 kR was the most efficient method of obtaining dihaploids from tetraploid blackberries, with some 20% of the seedlings obtained following this treatment being dihaploid.