Rubus stunt is an economically important disease in the production of raspberries, blackberries, and loganberries. A fast, sensitive, and reliable diagnosis of phytoplasmas, the causal agent of the disease, is of prime importance to stop its spread by vegetative propagation and by insect vectors. Therefore, multiplex qPCR assays using TaqMan probes with different kinds of fluorophores in one reaction were developed, allowing the detection of phytoplasmas in general as well as a more specific detection of phytoplasmas belonging to group 16SrV and host DNA (either plant or insect). This assay now provides a practical tool for the screening of motherplants and monitoring the presence and distribution of phytoplasmas in Rubus plants of different geographic origins, cultivars, and cultivation systems, as well as in putative insect vectors like leafhoppers.
Phytoplasmas are cell wall‐less phytopathogenic bacteria which are associated with a disease in Rubus species known as Rubus stunt. Symptoms range from stunting, witches’ broom, small leaves, short internodes, enlarged sepals, phyllody and flower proliferation to fruit malformations. Phytoplasmas can be spread by vegetative propagation and by phloem‐feeding insect vectors. However, little is known about the spectrum and distribution of putative Rubus stunt insect vectors. In this study, a screening of putative insect vectors of Rubus stunt in raspberry plantations in southern and northern Germany was carried out during two successive years (2014 and 2015) with multiple sampling dates throughout the growing seasons. A total of 2,891 hemipteran insects were sorted, identified to family, genus or species level when possible, and a subset of 319 DNA samples containing a sum of 932 selected individuals representing all identified species, sampling locations and sampling dates were tested for phytoplasma DNA using qPCR. Altogether, eight DNA samples were positive for phytoplasma DNA, among them species from the genera Euscelidius, Macrosteles, Euscelis, Anaceratagalliaand Psammotettix. These data will form the basis for choosing and timing appropriate control measures against Rubus stunt and also for potential insect vector transmission experiments.
Phytoplasmas are plant-pathogenic bacteria that cause a disease in Rubus species which is referred to as Rubus stunt. As phytoplasmas can be spread by vegetative propagation and latency periods of Rubus stunt can be up to one year, the use of pathogen-free Rubus propagation material in plant nurseries is important in order to stop the spread of this disease. Even though heat therapy has been commonly applied against viruses in many plants, its potential for phytoplasma eradication has been much less explored. Here, the efficacy of heat therapy with subsequent tissue culture to eliminate phytoplasmas from infected raspberry and blackberry plants is evaluated. Heat therapy was performed on 25 phytoplasma-infected raspberry and 33 infected blackberry plants, out of which 100 raspberry and 65 blackberry plants were regenerated via subsequent tissue culture. All plants were negative for the presence of phytoplasma DNA by qPCR at the end of cultivation periods of 481 to 565 days for the treated raspberry plants and 231 to 337 days for the treated blackberry plants. These results show the suitability of heat therapy combined with tissue culture as a routine tool to ensure the presence of phytoplasma-free Rubus mother plants in nurseries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.