Somaclonal variation for some morphological traits, herb yield, essential oil content and essential oil composition in an Indian cultivar of rose-scented geranium

Somaclonal variation for plant height, plant spread, leaf shape, leaf size, leaf form, herb yield, essential oil content and 10 important constituents of the essential oil was studied in an Indian cultivar, ‘Bourbon’ of rose‐scented geranium (Pelargonium graveolens). Significantly larger variance was observed among in vitro‐regenerated plants of the SC1 generation (first generation following an in vitro phase) than among parental plants raised from stem cuttings for herb yield, plant height, leaf size, essential oil content, and for the contents of cis‐rose oxide, trans‐rose oxide, isomenthone and 10‐epi‐γ‐eudesmol in the essential oil. Plants of the SC₁ generation showing values beyond the higher or lower limit (depending on the trait) of the range observed among parental plants for different traits were developed into clones by their multiplication through stem cuttings, and evaluated again in the SC₂ generation (second generation following the in vitro phase). Somaclones selected for plant spread, and for the contents of linalool and trans‐rose oxide in their essential oils did not breed true in the SC₂ generation. However, for the remaining traits studied, 13–100% of the selected clones retained their selected traits in the SC₂ generation, suggesting that the changes in these somaclones were due to genetic causes.     

香叶天竺葵多倍体精油的化学成分研究

探讨香叶天竺葵(Pelargonium graveolens L'He'rit)染色体加倍后精油的香气特征,为香叶新品种选育提供理论基础。对香叶天竺葵扦插苗、组培苗和多倍苗的香叶油进行GC-9A分析,并与玫瑰香叶油、法国波尔蓬香叶油的主成分进行对比。这5种油的化学成分相同,但各成分的百分含量有差异。组培苗及多倍苗香叶油中香叶醇、甲酸香叶酯、芳樟醇的含量显著提高,而香茅醇、甲酸香茅酯、玫瑰醚的含量有所下降。其中,多倍苗香叶油含：香茅醇26.1%,香叶醇14.81%,β-古芸烯4.77%,这3个主香成分接近法国波尔蓬香叶油中的含量。香叶天竺葵染色体加倍后能改善其精油的品质,其精油中香茅醇、香叶醇的含量更接近法国波尔蓬等国外香叶油中的含量。     

Effect of meta-topolin on leaf senescence and rooting in Pelargonium × hortorum cuttings

Pelargonium (Pelargonium x hortorum) is grown as potted or bedding plants for their colourful, showy flowers and scented foliage. Absence of senescence symptoms in the leaves of Pelargonium cuttings, their capacity to initiate roots and continued growth of initiated roots is an important quality attribute. The effects of postharvest treatments with meta-topolin (mT) and thidiazuron (TDZ) to ‘Katinka’ Pelargonium cuttings were investigated. Leaves treated with mT or TDZ for 5 d had higher leaf chlorophyll contents than untreated controls. Exposing cuttings to mT had no effect on the rooting proportion (%) and average root diameter. Similarly, 0.05 mM mT had no effect on number of roots per cutting. However, mT slightly reduced root length, root surface area and total volume of the roots. TDZ severely inhibited adventitious root formation, thus it reduced all the root parameters investigated. In conclusion, mT is very active in retarding leaf senescence, and combined with the observed ease of rooting of cuttings after mT treatment, this treatment is a suitable alternative to TDZ in delaying the onset of leaf yellowing in ornamental crops.