Direct shoot organogenesis from petiole and leaf discs of Withania somnifera (L.) Dunal

An efficient and reproducible procedure is described for direct shoot regeneration using petiole and leaf explants of Withania somnifera (L.). The shoots were mainly induced from the distal end of the petiole, whereas in leaf explants, shoot regeneration was initiated from the basal part and wounded tissue. The regeneration medium that induced the highest numbers of shoots in the petiole and leaf explants was Murashige and Skoog (MS) medium supplemented with 2 mg/l N6-benzyladenine (BA) alone or with 0.1 mg/l a-naphthalene acetic acid (NAA). The frequency of shoot regeneration was greatly influenced by the type of explant, the carbon source, the orientation of the explant, and the basal medium used in the regeneration medium. Explants produced shoot buds and adventitious shoots within four weeks. Histological analysis of the regenerating shoots showed that the shoot buds emerged from sub epidermal parenchymal cells, with no intermediate callus formation. Plantlets were rooted on MS alone or MS containing different concentrations of 3-indolebutyric acid (IBA). The addition of 1 mg/l IBA to the medium was most effective in inducing root formation. The regenerated plantlets were acclimatized in the greenhouse and successfully transferred to the field, with a 90% survival rate. The acclimatized plants showed normal flowering and were not morphologically different from the seed-derived mother plants.Key words: Histology, medicinal plant, plant growth regulator, plant regeneration, Withania somnifera

Effects of Colloidal Silver Nanoparticles on Sclerotium-Forming Phytopathogenic Fungi

Effects of silver nanoparticles on the phytopathogenic fungal growth were investigated. Fungal phytopathogens, especially for sclerotium-forming species Rhizoctonia solani, Sclerotinia sclerotiorum and S. minor, were selected due to their important roles in survival an disease cycle. Tests for the fungal hyphal growth revealed that silver nanoparticles remarkably inhibit the hyphal growth in a dose-dependent manner. Different antimicrobial efficiency of the silver nanoparticle was observed among the fungi on their hyphal growth in the following order, R. solani > S. selerotiorum > S. minor. Tests for the sclerotial germination growth revealed that the nanoparticles showed significant inhibition effectiveness. In particular, the sclerotial germination growth of S. sclerotiorum was most effectively inhibited at low concentrations of silver nanoparticles. A microscopic observation revealed that hyphae exposed to silver nanoparticles were severely damaged, resulting in the separation of layers of hyphal wall and collapse of hyphae. This study suggests the possibility to use silver nanoparticles as an alternative to pesticides for scleotium-forming phytopathogenic fungal controls.clos

Effects of Colloidal Silver Nanoparticles on Sclerotium-Forming Phytopathogenic Fungi

Effects of silver nanoparticles on the phytopathogenic fungal growth were investigated. Fungal phytopathogens, especially for sclerotium-forming species Rhizoctonia solani, Sclerotinia sclerotiorum and S. minor, were selected due to their important roles in survival an disease cycle. Tests for the fungal hyphal growth revealed that silver nanoparticles remarkably inhibit the hyphal growth in a dose-dependent manner. Different antimicrobial efficiency of the silver nanoparticle was observed among the fungi on their hyphal growth in the following order, R. solani > S. selerotiorum > S. minor. Tests for the sclerotial germination growth revealed that the nanoparticles showed significant inhibition effectiveness. In particular, the sclerotial germination growth of S. sclerotiorum was most effectively inhibited at low concentrations of silver nanoparticles. A microscopic observation revealed that hyphae exposed to silver nanoparticles were severely damaged, resulting in the separation of layers of hyphal wall and collapse of hyphae. This study suggests the possibility to use silver nanoparticles as an alternative to pesticides for scleotium-forming phytopathogenic fungal controls.clos

Control Efficacy of Nano-silver Liquid on Oak Wilt Caused by Raffaelea sp. in the Field

In other previous in vitro tests, the hyphal growth of Raffaelea quercivorus was inhibited by the treatments of various concentration of nano-silver. In this field tests, treatment of different concentrations of nano-silver to oak trees in Cheolwon and Hongcheon sites showed the inhibition effects against wilt disease caused by Raffaelea quercivorus. However, nano-silver-treated oak tree in Chuncheon site showed mild wilt symptoms with no phytotoxicity. Scanning electron microscope (SEM) observation confirmed that the spore and hypha of Raffaelea sp. inside the vessels were damaged by nano-silver. This result indicates the application of nanosilver is effective for control of Raffaelea quercivorus in the field

An In Vitro Study of the Antifungal Effect of Silver Nanoparticles on Oak Wilt Pathogen Raffaelea sp.

In this study, we investigated the antifungal activity of three different forms of silver nanoparticles against the unidentified ambrosia fungus Raffaelea sp., which has been responsible for the mortality of a large number of oak trees in Korea. Growth of fungi in the presence of silver nanoparticles was significantly inhibited in a dose-dependent manner. We also assessed the effectiveness of combining the different forms of nanoparticles. Microscopic observation revealed that silver nanoparticles caused detrimental effects not only on fungal hyphae but also on conidial germination.close212