INITIATION OF PROEMBRYOGENIC CELL SUSPENSIONS IN NINE INTERSPECIFIC GRAPEVINE HYBRIDS
Petioles, taken from in vitro grown plants of nine interspecific grapevine hybrids: rootstocks Berlandieri x Riparia 'Kober 5BB' and Riparia x Rupestris '101-14' and cultivars (cvs):1 'Bianca', 'Zigfridrebe', ′Podarok Magaracha', 'Pervenets Magaracha', 'Tsitronnyi Magaracha', ‘Intervitis Magaracha' and hybrid form 'Magarach 100-74-1-5' were cultured on solid NN medium supplemented with different levels of 2,4-D and BA at various concentrations. In order to initiate cell suspensions, proembryogenic calluses were subcultured to liquid NN medium supplemented with 1.0 mg/L 2,4-D and 0.2 mg/L BA. Subculturing these suspensions to liquid NN medium supplemented with 2 mg/L NAA and 0.1 mg/L BA led to the development of embryo aggregates while subculturing to liquid NN medium supplemented with 0.5 mg/L BA resulted in development of single globular and heart-stage embryos. Proembryogenic cell suspensions consisting of prevailing single cells can be used in gene transformation and cell selection with the aim of decreasing the probable formation of chimeric plants.