Chromosome Variation from Sect.Chinenses (Rosa L.) through Chinese Old Garden Roses to Modern Rose Cultivars

摘要

Contributing recurrent flowering and tea scent to modern roses, wild Rosa resources from China especially Rosa chinensis and R.odorata complex, and Chinese Old Garden Roses have played very important roles in the formation history of modern roses.In order to understand the chromosome variation in the formation process of modern roses, karyological studies of 6 species/varieties from Sect.Chinenses, 9 Chinese Old Garden Roses and 5 modern roses were carried out by traditional squashing and pressing.Their molecular cytogenetic characters were analyzed with FISH using 45S rDNA as probes.The results were the following:1) species/varieties from Sect.Chinenses were all diploid with 14 chromosomes,except the triploid R.ododrata var.erubescens from Lijiang.Except for R.chinensis 'Tiebahong' with a karyotype of 2A, all the others belonged to 1A.Two 45S rDNA hybridization sites were observed in the pro-metaphase and interphase cells of diploid plants, while three sites were found in those of triploid R.odorata var.erubescens; 2) there were 3 pioidies, namely diploidy, triploidy and tetraploidy, and 4 karyotypes, namely 1A, 2A, 1B and 2B, in the Old Garden Roses.Their 45S rDNA hybridization sites were also coincident with their ploidy, but the intensity of hybridization signals differed much among cultivars; 3) all the studied modern roses were tetraploid, but they had only three 45S rDNA hybridization sites.Their FISH signals were unanimous in size and intensity.The results showed that Chinese Old Garden Roses got more variable in chromosome number and structure and became more diverse in number, size and intensity of 45S rDNA FISH signals than their original progenitors from Sect.Chinenses.However, modern roses got more homogenous in cytogenetics because of the repeated hybridization and inbreeding among cultivars.It is necessary to introgress wild species and Old Garden Roses into modern roses for improvement.