No abstract

In this study, the effect of gamma irradiation in inducing resistance/tolerance towards powdery mildew disease was investigated in Gerbera jamesonii cv. 'Harley'. In vitro shoot cultures were established through capitulum explants on Murashige and Skoog medium supplemented with 22.2 lM 6-benzyladenine (BA) and 2.53 lM indole acetic acid (IAA), followed by gamma irradiation of regenerated shoots (3-5 cm). Activity of four antioxidant enzymes i.e. superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase increased significantly as compared to the control and reached to highest level at the most stringent doses of mutagen. Ninety randomly selected irradiated plants (6 months old) and 100 control plants were inoculated with fungal conidial suspension, to screen for tolerance/resistance against powdery mildew. The severity of the disease was recorded on 0-4 scale with '0' indicating highly resistant; '1' indicating resistant; '2' indicating medium resistance; '3' indicating susceptible and '4' indicating highly susceptible. Three plants (3.33%) irradiated with 5 Gy were found to be tolerant to powdery mildew as these plants showed slight and delayed development of fungal colonies on the leaves. The random amplified polymorphic DNA characterization showed that the irradiated plants had DNA patterns that were different from the control and mother plants.

No abstract

No abstract

Gerbera (Gerbera jamesonii Bolus) is one of the most popular ornamental flowers worldwide and used both as cut flower and potted plant. Some of them show excellent agronomic characters such as color, floral diameter, stem length, and vigor, which make this plant of commercial importance. Conventionally, multiplication is done through seeds or rhizome cuttings. Rapid multiplication of elite cultivars of Gerbera, with improved agronomic traits, has been achieved by using both direct and indirect tissue culture methods. Direct shoot regeneration was accomplished from stem apices on MS medium supplemented with 1 mg/L 6-benzyladenine (BA) and 1 mg/L kinetin. Indirect shoot induction succeeded from callus differentiation has been achieved on MS medium containing 2 mg/L 2,4-dichlorophenoxyacetic acid, 0.5 mg/L indole-3-acetic acid, and 2 mg/L BA. The in vitro shoots, 4-5 cm long, were rooted by quick dipping the shoot bases for 3-5 s in 2,000 mg/L indole-3-butyric acid solution followed by transfer to the pots containing farmyard manure, soil, and sand (1:1:1 by volume). Initially, in vitro plantlets were covered with glass jars to maintain a high relative humidity (85-90%). As soon as new shoot growth begins, relative humidity is decreased by exposing them to the open environmental conditions prior transferring to the glasshouse. Indirect shoot regeneration increased the frequency of somaclonal variations. The selected somaclones were used in developing new and novel cultivars.