L. Giunchedi

A chemiluminescent immunoassay for the diagnosis of grapevine closteroviruses on nitrocellulose membrane

A dot-immunobinding assay was adapted on enhanced chemiluminescence (DIBA-ECL), which employs luminol, a cyclic diacylhydrazide, as substrate for horseradish peroxidase conjugated with a secondary antibody, for the diagnosis of grapevine closteroviruses I and III. The sensitivity of DIBA-ECL was also compared to other immunoenzymatic methods. DIBA-ECL proved to be at least 16 times more sensitive than the dot-immunobinding assay using chloronaphthol/diaminobenzidine mixture as a substrate, which was at least twice as sensitive as DAS-ELISA, DAS-indirect avidin-biotin complex ELISA, and dot-immunobinding assay, using alkaline phosphatase as enzyme. Optimisation of all parameters involved in the DIBA-ECL procedure and its advantages are discussed.

Transgenic tobacco plants expressing the bacterial mc gene resist virus infection

A bacterial rnc gene coding for a double-stranded RNA-dependent RNase III endoribonuclease and a mutant, rnc70, were expressed in tobacco plants. The RNase III protein produced in the transgenic plants was the same size as the bacterial protein. Expression of the wild-type gene could cause stunting in some plant lines, but not in others. Expression of the mutant protein did not affect normal growth and development of the transgenic plants. Transgenic plants of the R1 and R2 generations, expressing the wild type, as well as a mutant protein, were resistant to infection by three disparate RNA plant viruses with a divided genome but not against two viruses with a single-stranded RNA genome. Introduction of the rnc gene in crop plants may provide resistance to economically important virus diseases.

History and Current Status

Research into the etiology of the syndrome later called “rizomania” and measures to limit the considerable reductions in sugar yield required a large number of studies in different disciplines. The traditional methods for reducing the damages and the spread of the disease resulted without any effect or were too expensive. Since some degrees of genetic variability were soon observed in commercial varieties, the search of genetic resistance appeared the sole possibility of success. At this stage, the unofficial collaboration among universities and research institutes proved instrumental. Around 20 years after the first observations, it was discovered that the syndrome was caused by a virus, transmitted by the plasmodiophoral protist Polymyxa betae. The identification of the causal agents leads to considerable progress toward genetically resistant varieties and a satisfactory control of the economic consequences of rhizomania. Also in this case, the mentioned collaborations turned out decisive.

Peach Latent Mosaic Viroid in Temperate Fruit Trees Other Than Peach

Since 1997, research on the host range of peach latent mosaic viroid has been gradually extended outside peach and peach hybrids, to include: other stone fruits such as almond, apricot, cherry, Japanese apricot (mume), Japanese plum, European plum (prune); the pome fruits, apple, pear, quince, and wild pear; and a few nonrosaceous species. Geographically, it has been found in 20 countries in Europe, Africa, Asia, and North and South America. No clear data are available on the symptomatology and economic significance of peach latent mosaic viroid in these species.