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Roses are one of the economically most important groups of ornamental plants. The internal transcribed spacers (ITS) of the nuclear ribosomal DNA and the chloroplast gene matK were used to investigate the genetic diversity and genetic relationships among Rosa germplasm including 39 wild species, 21 old garden roses, and 29 modern cultivars. Three dendrograms based on ITS and matK clustering data indicated that 1) 39 wild genotypes were consistent with their classification into botanical sections with only a few exceptions; 2) most of the wild genotypes were separated from rose cultivars. However, three sections, Synstylae, Chinenses, and Rosa, that contributed to the modern roses generally gathered together with almost all old garden and modern roses on the molecular level; and 3) the relationships between cultivated roses as inferred by ITS and matK sequences do not correlate with horticultural groups. Results demonstrated that both sequence techniques can contribute to clarifying the genetic relationships of rose accessions and germplasm conservation to enhance the ornamental and economic value of rose.
The aim of this study was to establish a regeneration system of watermelon. Watermelon W1 was selected as the experimental material using seedling shoots as a receptor. The effects of different concentrations of 6-Benzylaminopurine (6-BA) on the shoot-tip of watermelon seedlings were studied. Number of shoots at the stem tip were counted every other day until the new buds reached 2 cm. The new stem tip was cut, and the effect of different concentrations of Murashige and Skoog (MS) medium on the number of regenerated roots and root length of shoots were studied. The results showed that the differentiation rate was highest when the 6-BA concentration was 0.7 mg/mL to 0.8 mg/mL. The optimum concentration for root regeneration was 1/8 MS. At this concentration, the number rooted was the highest, and root length was also promoted.
Rose (Rosa L.) is an economically important ornamental genus that has been cultivated for its scent for the perfume industry since antiquity. However, most modern roses have lost their fragrance during the later stages of the breeding process. Here, 59 species of Rosa, including 24 wild Rosa species, 20 Chinese old garden roses, and 15 modern roses, were examined by headspace solid-phase microextraction and gas chromatography–mass spectrometry. Fifty-three volatile organic compounds (VOCs), including terpenoids, benzenoids/phenylpropanoids, and fatty acid derivatives, were detected with qualitative and quantitative analyses. Thirteen common components, including geraniol, citronellol, 2-phenylethanol, 3,5-dimethoxytoluene, 1,3,5-trimethoxybenzene, germacrene D, and cis-3-hexenyl acetate, were found. Furthermore, different wild species or cultivars showed different characteristic compounds. 3,5-Dimethoxytoluene and 1,3,5-trimethoxybenzene were the main compounds in Rosa odorata and Rosa chinensis, which are the original parents of modern roses. 2-Phenylethanol, citronellol, and geraniol were the main aromatic compounds in Rosa damascene and Rosa centifolia. Methyl salicylate, eugenol, methyl eugenol, and benzyl acetate were lost during domestication and breeding of wild Rosa species to Chinese old garden roses and then to modern cultivars. Geranyl acetate, neryl acetate, and dihydro-β-ionol were gained during this time and showed higher amounts across the rose breeding process. Natural and breeding selection may have caused volatile compound gains and losses. These findings provide a platform for mining scent-related genes and for breeding improved ornamental plants with enhanced flower characteristics to develop new essential oil–producing plants.