PLANT GENOTYPE AND GROWTH-REGULATORS INTERACTION AFFECTING IN-VITRO MORPHOGENESIS OF BLACKBERRY AND RASPBERRY

The morphogenic response of somatic (leaf and petiole) and de-differen tiated tissue (callus) of two blackberry (Rubus fruticosus) and one ra spberry (Rubus idaeus) cultivars have been studied in vitro. With the aim to induce regeneration the effect of two sets of plant growth regu lator (PGR) combinations (high cytokinin/auxin ratios and high auxin/c ytokinin ratios) in Murashige and Skoog basal medium, were analysed. T he three cultivars were characterised by a qualitatively different mor phogenic response to the PGR combinations. Raspberry adventitious shoo t regeneration from somatic tissue was improved by the 6-benzylaminopu rine (BAP)/indol-3-butyric acid (IBA) combinations. On the contrary, s hoot regeneration of both blackberry cultivars was reduced by high con centrations of BAP and completely inhibited by BAP/IBA combination. Me dia supplemented with high auxin/cytokinin ratios promoted callus prod uction and root differentiation according to genotype and type of auxi n. All the genotypes responded to media supplemented with IBA. 2,4-dic hlorophenoxyacetic acid induced good callus formation in blackberry, b ut was toxic to raspberry. Indirect shoot formation was observed only in callus of blackberry cultivar Hull Thornless cultivated on medium w ith 10 mu M BAP, the same concentration able to trigger efficient dire ct shoot regeneration from leaf explants of the same cultivar.