Projects / Programmes
Plant response analysis in multiple viroid infections and identification of plant resistance
| Code |
Science |
Field |
Subfield |
| 4.03.00 |
Biotechnical sciences |
Plant production |
|
| Code |
Science |
Field |
| B006 |
Biomedical sciences |
Agronomics |
| Code |
Science |
Field |
| 4.01 |
Agricultural and Veterinary Sciences |
Agriculture, Forestry and Fisheries |
Viroids, plant diseases, disease resistance, diagnostics
Researchers (13)
Organisations (2)
Abstract
Viroids are the smallest known plant pathogens, which cause severe to mild diseases in many herbaceous and woody plant species. In 2007, a severe and highly aggressive viroid disease was found in a hop garden in the Savinja valley, which caused stunting and death of infected plants. Extensive diagnostic analysis of symptomatic plants revealed the presence of two new viroids; Hop stunt viroid (HSVd) and Citrus bark cracking viroid (CBCVd), in addition to the generally present and widespread Hop latent viroid (HLVd). Both newly discovered viroids on hop plants were found here for the first time in Europe and, in the case of CBCVd, it was also the first known report of this viroid in hop plants. This new and uninvestigated multiple viroid disease, called »Hop stunt disease«, affected more than 70 ha of hop gardens in the period 2007-2013. Despite the eradication program, systematic disease monitoring and preventive control measures, the disease is still spreading, with some hop varieties showing high susceptibility and high infectivity of the disease. The presence of three different viroids in the diseased plants shows the complex nature of »Hop stunt disease«, which is still completely unexplored. In order to gain an insight into the complex nature of Hop stunt disease, we propose to perform controlled single and multiple viroid infections of viroid free plants. This approach will clarify the effect of each viroid (HLVd, HSVd and CBCVd) in single, double or triple viroid combination. The effects and interactions of viroids in the plants will be measured as visual symptoms expression and as changes of gene expression on the transcriptome level by using an RNA-seq approach. The results will be important for determining the status and for control measurements of both newly discovered viroids (HSVd and CBCVd) and for better understanding plant-viroid interactions on the cellular level. This will be the first such etiological viroid experiment in hops and, in addition, a new diagnostic method of multiplex real time RT-PCR for simultaneous detection of hop viroids will be developed. The second important goal of the proposed study will be to identify resistance/tolerance in hop to Hop stunt disease. Based on spatial and temporal analysis of the spread of the disease, it was discovered that some hop varieties, such as Savinski Golding and the newly breed variety Dana, have much slower disease progress, which may indicate potential sources of resistance or tolerance. Extensive disease resistance screening will be done by artificial infection of 30 different hop varieties and genotypes, representing European and North American genetic backgrounds. We expect to find differences in resistance or tolerance among hop genotypes and to use this knowledge in established breeding programs of new varieties. No such screening for viroid resistance in hops has been done to date.
Significance for science
In the frame of the project we performed the first scientific study of influence of hop viroids HLVd, HSVd and CBCVd in controlled conditions by using artificial inoculations in single, double and triple viroid combination. For comparing we include virus and viroid free hop plants. Based on assessments of disease symptoms of infected plants we found significant synergistic effect of viroid combination HLVd + CBCVd. This viroid combination present majority of infections in hop gardens with the most severe symptoms. In the same time we discovered that combination HSVd +CBCVd is less compatible in hop, despite that is stable in citrus plants. Chemical analysis of infected plants showed negative effect on alfa and beta acids, and xanthohumol content and until now undescribed accumulation of iron (Fe) in severely infected viroid plants. NGS transcriptome analysis revealed more that 100 differential expressed genes which are important in different biological processes. Part of these genes was common to all viroid combinations what is important contribution for understanding of viroid pathogenesis. The project was manage also extensive testing of 30 hop genotypes to CBCVd which revealed resistance/tolerance and low infection level in 7 genotypes. These results will significantly influence on future differential studies of resistant and susceptible varieties, since the mechanisms of tolerance are still unknown in viroid infections. In the frame of the project we developed new methods for artificial inoculation of plants and for detection of viroids in single and multiplex analysis based on real time RT-PCR. The new techniques have significant importance in future epidemiological studies of viroid diseases. The results of the project will have a significant impact on scientific groups involved in hop and viroids research, and phytopathology focused on plant-pathogen interactions.
Significance for the country
Hop production in Slovenia is an important agricultural industry, which is a leading export product of Slovenian agriculture, with more than 95% of the production being exported. Slovenia is the 6th largest hop growing country in the world, with 1500 ha of hop fields, which accounts for 3% of the world acreage. The appearance of severe hop stunt disease significantly threat Slovene hop production and causes high economic damage since the successful disease management is based on eradication of infected plants and hop gardens. In the frame of the project we clarify the complex nature of the disease inducers what will contribute to the development of new disease management actions and to the future sanitary status of severe hop stunt disease in Slovenia. We developed techniques which will manage better epidemiological studies in different technological procedures of hop production and consequently improvement of current management strategies. The project enabled testing and revealing resistant/tolerant varieties what already have influence on re-establishing of hop production on affected regions and influence to the strategy of disease outbreak avoidance. In addition on that way we got first candidate hop genotypes which will be used in the breeding process of new resistant varieties. The new knowledge will have long-term effect on reducing environmental pollution, lower energy consumption and a higher quality of sustainable development. The results will have an impact on gaining new knowledge in hop production and, consequently, on incorporating such knowledge in the transfer of new technologies in Slovenia, as well as in other European and other countries. The results of the proposed project reinforced and increase recognition of our work and thus indirectly contribute to the promotion of Slovene science. We increased international collaboration in order to have access to the knowledge of other laboratories and, at the same time, other laboratories will be interested in our participation in international projects. The project had significant indirect importance in the transfer of knowledge in educational processes at professional, undergraduate and postgraduate levels. On that way we contribute to gain the competitive personnel able to transfer the knowledge to the economy and thus contribute to creating added value.
Most important scientific results
Annual report
2014,
2015,
final report
Most important socioeconomically and culturally relevant results
Annual report
2014,
2015,
final report
