The ability of grapevine in vitro cultures to synthesise the phytoalexin precursor resveratrol in response to ultraviolet light irradiations is investigated in order to develop methods for screening for resistance to grey mould (Botrytis cinerea Pers.) in grapevines produced as a result of somatic embryogenesis. It is demonstrated that resveratrol formation can be reproducibly induced in leaves of in vitro plantlets. Differences in the production of resveratrol among the three varieties of Vitis vinifera tested (Pinot Noir, Chardonnay and Cabernet Sauvignon) were consistent with observations regarding their field susceptibility to grey mould. The use of phytoalexin induction and of in vitro methods as a tool for selection of Vitis resistant genotypes in early screening tests is discussed.

The production of resveratrol (3,5,4'-trihydroxystilbene) by grapevine in vitro cultures, and its application to screening for grey mould resistance

Tissue Culture: Its Prospects and Problems

Early infection stages of the downy mildew fungi Sclerospora graminicola and Peronosclerospora sorghi in plants and cell cultures

Soybean calli with nodular characteristics (nodular calli) and high regeneration potential were found to be induced by cocultivated with strains of bacteria Pseudomonas maltophilia in vitro. Upon subculture of the nodular calli, somatic embryos were regenerated. Unfortunately no complete plants have been obtained from the cultures so far because the somatic embryos were malformed to various degrees. Histological analysis revealed that the nodules were well organized. Young nodules possessed mostly small cells with densely stained nuclei, which are considered to have high potential to yield somatic embryos under improved culture conditions. Besides the cocultivated bacteria, the age and physiological state of the calli and ingredients of culture mediurn were also important factors affecting nodular callus formation. The findings on this experiment suggest that the cocultivtion system may be developed to solve the serious problems in regenerating plants from callus culture of soybean.

In Vitro Formation of Nodular Calli in Soybean (Glycine max L.) Induced by Cocultivated Pseudomonas maltophilia

Sugarcane plants of the cultivar B72 191 have been cultivated in tubes and inoculated with a pure culture of smut fungus (Ustilago scitaminea Sydow) in an otherwise microorganism-free environment. The parasite penetrates the tissues of the host. The plants thus infected produce symptoms of smut whip. The teliospores produced on these are viable and have retained their pathogenicity.

Inoculation of in vitro cultivated sugarcane with smut (Ustilago scitaminea)

Dual culture of sugarcane downy mildew fungus (Sclerospora sacchari Miyake) was established by placing a diseased sugarcane explant (shoot apex or spindle leaf) on a modified Murashige and Skoog medium containing 3 ppm 2,4-dichlorophenoxyacetic acid. After 3 weeks incubation, dense mycelia grew both on and in the callus which had developed. The use of different varieties or illumination periods did not affect the growth of the fungus. The hyphae ceased to grow when the infected callus was subcultured. A workable procedure was devised which enabled the hyphae to proliferate on a healthy tissue when diseased tissue was placed near it. Explants excised from either resistant or susceptible varieties could nurse the growth of the fungus, indicating that resistant genes may not be expressed in tissue culture. Histological studies revealed that the callus originated from mesophyll cells in leaf and parenchymatous cells of shoot apical tissue. Intercellular and intracellular hyphae were more concentrated in the p...

Chia-Yu Chao

Papers

The growth of sugarcane downy mildew fungus in tissue culture