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ISHS Acta Horticulturae 572: XX International Eucarpia Symposium, Section Ornamentals, Strategies for New Ornamentals - Part II

FUNDAMENTALS FOR INTEGRATION OF SOMATIC HYBRIDIZATION IN ROSE BREEDING

Authors:   A. Schum, K. Hofmann, R. Felten
Keywords:   protoplast regeneration, blackspot resistance, Rosa wichuraiana, Rosa multiflora, Rosa roxburghii
DOI:   10.17660/ActaHortic.2002.572.2
Abstract:
With the intention to exploit new sources of disease resistance in rose breeding, the feasibility of introgression of genes by means of somatic hybridization is evaluated. Protocols have been established for (I) regeneration of protopasts in a variety of rose genotypes, (II) PEG mediated fusion, and (III) preferential regeneration of heterologous fusion products. Protoplasts isolated from non embryogenic source material gave rise to callus in R. canina, R. caudata, R. corymbifera 'Laxa', R. multiflora (two accessions), R. roxburghii, R. spinosissima, R. wichuraiana (two accessions), as well as in R. x hybrida 'Elina' and 'Pariser Charme'. Protoplasts isolated from embryogenic cell suspensions of 'Heckenzauber' and 'Pariser Charme', as well as from non embryogenic suspensions of the hybrid R. persica x R. xanthina were regenerated into plants. In order to suppress sustained cell divisions of non-fused protoplasts or of homologous fusion products, protoplasts were pretreated with either rhodamine 6G (0.1 mmol) or iodoacetate (0.5 1 mmol) for 15 minutes as well as with X-rays (300 Gy) at a dose rate of 3 Gy/min. Induced defects are mostly complementary, thus corresponding pretreatment of protoplasts prior to fusion allows preferential regeneration of the heterologous fusion products aimed at. Specific genotypes of different wild species within the genus Rosa were identified to carry resistance genes against Diplocarpon rosae, the causal agent of blackspot (von Malek-Podjaski, 1999). For introgression of resistance into cultivars by means of somatic hybridization, experiments concentrate at the time being on diploid accessions of Rosa multiflora, Rosa wichuraiana and Rosa roxburghii. Putative somatic hybrid callus lines were obtained from 'Heckenzauber' + Rosa wichuraiana or Rosa multiflora as well as from 'Pariser Charme' + Rosa wichuraiana, Rosa multiflora or Rosa roxburghii, respectively. Shoots were regenerated from the combination of 'Pariser Charme' and Rosa wichuraiana. The hybrid character of some selected regenerates was exemplarily confirmed by flow cytometry and AFLP-analysis.

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