Improvement of in vitro donor plant competence to increase de novo shoot organogenesis in rose genotypes

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English. A procedure was developed for in vitro propagation of Rosa genotypes along with an efficient de novo shoot organogenesis (DNSO) method. We tested, on one genotype (hybrid of Rosa wichurana), the effects of MS basal medium complemented with two growth regulators to achieve either shoot elongation or shoot multiplication of plants. These media were complemented with carbohydrate concentrations from different sources. Then, the impacts of various carbohydrates (fructose, glucose, maltose, sorbitol, sucrose) on the growth and development of several rose genotypes during donor plant subculturing were studied on SMM. The results showed high variability in growth and development between genotypes. Contrary to other members of the Rosaceae family, no correlation was found between the shoot size and number when the amount of sorbitol was increased.Murashige and Skoog medium supplemented with 3.0 mg L-1 BAP and containing fructose or glucose at 30 g L-1 was chosen to induce leaf explants for the DNSO experiments. MS basal medium complemented with TDZ/IBA at three ratios and the same range of carbohydrate sources were tested for DNSO. Significant genotypic variations with regard to the percentage of regeneration was demonstrated with six genotypes. For two genotypes, a hybrid of Rosa wichurana and Rosa 'White Pet', we defined the conditions required to obtain 100% DNSO. For Rosa chinensis 'Old blush' and the rootstock genotype Rosa 'Natal Briar', we obtained 74 and 87.5% DNSO and only 56.67% and 37.5% for Rosa GUY SAVOY (R) ('Delstrimen') and Rosa Felicite et Perpetue' respectively. This adventitious shoot regeneration method may be used for large-scale shoot propagation and genetic engineering studies in Rosa.Keywords