Like many plant RNA viruses, infection by potato spindle tuber viroid (PSTVd) is known to lead to RNA silencing and a marked reduction in visible disease. To examine the relationship between RNA silencing and this recovery phenomenon in greater detail, we have carried out time-course analyses of viroid-specific small RNA accumulation using several viroid—host combinations. These analyses reveal...

The potato spindle tuber disease was first observed early in the 20th century in the northeastern United States and shown, in 1971, to be incited by a viroid, potato spindle tuber viroid (PSTVd). No wild-plant PSTVd reservoirs have been identified; thus, the initial source of PSTVd infecting potatoes has remained a mystery. Several variants of a novel viroid, designated Mexican papita viroid (M...

The detection of a viroid in Coleus blumei species in Brazil (1) has prompted us to search for viroids in C. blumei cultivars (cvs) commercially propagated by cuttings for more than 50 years in Germany. 'Return' PAGE (2) of nucleic acid extracts from the cv 'Bienvenue' revealed a band of circular viroid-like RNA molecules. Northern blot analysis (3) with radioactive probes specific for viroids ...

A viroid-like disease causing mosaic leaves and dwarfism was found on mulberry plants in Zhejiang, China. Grafting of stems from infected plants onto healthy plants resulted in the same symptoms on the healthy plants. A circular small RNA (Mmd-v RNA1) was isolated from the infected plant leaves and caused identical symptoms after more than two years. Nucleotide sequencing indicated that the Mmd...

In autumn 2006, a new disease was observed in a glasshouse-grown crop of sweet pepper (Capsicum annuum L.) in the Netherlands. Fruit size of the infected plants was reduced up to 50%, and plant growth was also slightly reduced. Here we show that the disease is caused by a previously non-described viroid. The pepper viroid is transmitted by both mechanical inoculation and pepper seeds and, when ...

Viroids are small, circular, single-stranded RNA molecules that, while not coding for any protein, cause several plant diseases. Viroids rely for their infectious cycle on host proteins, most of which are likely to be involved in endogenous RNA-mediated phenomena. Therefore, characterization of host factors interacting with the viroid may contribute to the elucidation of RNA-related pathways of...

The effect of carrageenans on tomato chlorotic dwarf viroid (TCDVd) replication and symptom expression was studied. Three-week-old tomato plants were spray-treated with iota(ɩ)-, lambda(λ)-, and kappa(κ)-carrageenan at 1 g·L-1 and inoculated with TCDVd after 48 h. The λ-carrageenan significantly suppressed viroid symptom expression after eight weeks of inoculation, only 28% plants showed distin...

Recent experience using 23 oligonucleotides to diagnose avocado sunblotch viroid (ASBV) is described. In a number of field collected samples with sunblotch symptoms, the probe was unsuccessful in detecting the viroid. The sunblotch viroid varies greatly from branch to branch in a tree. Tree to tree variation is also common. However, the probe can be used with a reasonable measure of success to ...

The tomato (Solanum lycopersicum) callose synthase genes CalS11-like and CalS12-like encode proteins that are essential for the formation of callose, a major component of pollen mother cell walls; these enzymes also function in callose formation during pathogen infection. This article describes the targeting of these callose synthase mRNAs by a small RNA derived from the virulence modulating re...