Characterization of a Collection of Brassica carinata Genotypes for in vitro Culture Response and Mode of Shoot Regeneration

Brassica carinata , a natural alloploid formed between B. oleracea and B. nigra , is a potential oil crop for the Mediter- ranean area in which genetic transform ation could help to breed. In vitro culture and shoot regeneration are key fac- tors in developing an efficient transformation method in the genus Brassica. However, the studies for in vitro culture and shoot regeneration in B. carinata are limited to only a few genotypes. The aim of this study was to evaluate the in vitro culture response and shoot regeneration in a collection of B. carinata accessions to identify promising genotypes with high shoot regeneration for genetic transformation experiments. Cotyledonary explants from 51 genotypes were cultured in vitro and callus formation and swelling as well as the mode of shoot regeneration evaluated. A highly posi- tive response to in vitro culture , i.e. callus formation or swelling , was observed in all the genotypes tested. Tissue blackening occurred only in eleven genotypes. Parameters li ke callus formation and swelling and number of shoots per explant were highly variable among genotypes. Fourteen genotypes regenerated only via callus formation , whereas only one regenerated only via swelling. Most genotypes showed a higher percentage of callus formation than swelling. The average number of shoots regenerating per explant among genotypes was the most variable factor measured. Six genotypes regenerated more than 6 shoots per explant via callus phase. These genotypes have been identified as having a high regeneration potential and can be used in genetic transformation via Agrobacterium.The authors acknowledge fund ing by the Spanish Comi- sión Interministerial de Ciencia y Tecnología (C.I.C.Y.T.), project AGL2004-03361-C02-2 and to the Regional Plant Introduction Station (Iowa St ate University, Iowa, U.S.) for supplying seeds. Javier Gil-Humanes acknowledges the CSIC for a pre-doctoral I3P fellowship and to Dr. Penelope Sparrow from the Crop Genetics Department of John Innes Center (UK) for the critical reading of the manuscript.Peer Reviewe