Rubus upsets
The Rubus Stauche is a by phytoplasma Candidatus phytoplasma rubi disease caused by plants of the genus Rubus . It affects both cultivated and wild plants. The Rubus-Stauche is of economic importance for agriculturally cultivated blackberries and raspberries . The Rubus-Stauche is also known as broom growth or dwarfism disease of blackberries and raspberries . Its English name is Rubus Stunt .
Clinical picture
All types of raspberry ( Rubus idaeus ) and blackberry ( Rubus sectio Rubus ) as well as hybrids of these such as the Tayberry ( Rubus fruticosus x idaeus ) and the Loganberry ( Rubus × loganobaccus ) can be attacked by the Rubus compression .
After an incubation period of four to eleven months, symptoms appear on infected plants on canes, flowers and fruits, which persist until the infected canes die off after four to six years.
So-called witch brooms form on the rods . As a first symptom, numerous, thin, dense and upright growing rods grow out of the root buds, on which the axillary buds are increasingly sprouting. Whole tufts of up to ten compressed side shoots emerge from a single bud. The dense growth makes the rods look like witches' brooms. The leaves often appear chlorotically lightened.
Malformations also occur on the flowers of infested plants. The sepals become remarkably long and narrow, the petals green ( phyllody ). On individual flowers, instead of the ovary, the shoot continues to grow above the sepals and petals. Malformations also occur in fruits.
Plants weakened by a virus infection are significantly more susceptible to Rubus compression and also die faster after an infection. Although it is known that the different raspberry and berry varieties are differently susceptible to Rubus upsets, no variety has been found that shows long-term resistance. Some strains are able to regenerate after infection. These plants then no longer show symptoms, but remain infected and can thus transmit the infection. The blackberry variety Chester Thornless is considered less susceptible .
Biology and disease transmission
The distribution area includes Europe, Russia and the Middle East, so far it has not occurred in North America. Above all in Russia, the Rubus Stauche is an economically important plant disease, while it occurs only sporadically in Western Europe.
The phytoplasms only colonize the sieve tube part of the vascular bundle, in which they spread over the whole plant. Due to the lack of a cell wall, they are highly deformable, which is why they can overcome the sieve plates of the sieve tubes. They accumulate in high concentrations, especially in the plant roots.
The phytoplasms causing the disease are mainly transmitted from plant to plant by phloem-sucking insects. The phytoplasms are absorbed with the sap and can survive in the insects for a long time. An insect infected in the larval stage can remain a carrier of the disease until the adult stage. A transfer of the phytoplasms via the egg stage to the next generation is not possible.
So far the pathogen of the Rubus-Stauche could be detected in different species of cicadas, especially from the subfamily Macrospinae and the glass-winged cicadas (Cixiidae) , whereby other phloem-sucking insects cannot be excluded as carriers. The main carrier in Europe is the leafhopper Macropis fuscula . The cicadas of the subfamily of leaf cicadas (Typhlocybinae) (e.g. Edwardsiana rosae , Ribautiana tenerrima ) , which occur frequently and often in large numbers in Central Europe , suckle almost exclusively on the parenchyma of the plants and do not penetrate into the phloem when sucking, which is why they are called Carriers of phytplasmas can be excluded.
The Macropsis species that transmit the disease live mainly on Rubus species and form one generation per year. They overwinter in the egg stage in the bark of the host plants. The larvae that hatch in May to July can absorb the pathogens when they suckle on the plants. The adult, winged animals appear from August to September, which then spread the disease.
The transfer takes place both within a stand and between different stands, but also from wild Rubus stands to plants in production facilities. Furthermore, the disease can be introduced into stocks by infected seedlings and slips (in blackberries), which are not recognized as such due to the long incubation period, from which they are then transmitted to other plants by insects.
The disease can be transmitted experimentally through grafting. A transmission of the disease through cutting tools is excluded. A direct transmission from plant to plant through root growth, especially in closely spaced commercial areas, could not be completely ruled out so far.
diagnosis
The disease is macroscopically recognizable by the clear symptoms. Since less susceptible varieties no longer develop symptoms at a later stage of infection, a graft test or a laboratory diagnostic examination is necessary to reliably exclude an infection.
In a graft test, a rice of a variety that is considered highly susceptible, such as. B. the raspberry variety Malling Landmark or the blackberry varieties Thornless Evergreen and Loch Ness grafted. The phytoplasms from the test plant then migrate into the grafted rice, where the typical symptoms appear. However, it takes up to a year for the first symptoms to develop on the graft.
In laboratory diagnostics, the infection can be detected using a nested PCR from root material, in which the phytoplasms are particularly concentrated.
Control and preventive measures
A direct control of the phytoplasmas in infected plants is not possible. Combating the possible vectors does not make sense, since it does not capture all potential carriers, nor can the ingress of insects from outside be reliably prevented.
The prevention of infection is therefore of great importance. The exclusive use of proven, healthy, certified planting material is particularly important. New plants near infested plants should be avoided. Since wild populations are often infested and also harbor the vectors, acquisition facilities in their vicinity should also be avoided.
With a two to three hour thermal therapy at 45 ° C, the phytoplasms in infected plants can be destroyed and propagation and planting material can be made free of carriers.
In infested commercial areas, diseased plants must be removed immediately and the population must then be closely monitored for the occurrence of further diseases for at least eleven months. In the case of a more extensive infestation, all that remains is to clear the entire area, which must also be done to completely remove the roots if possible.
Individual evidence
- ↑ Sylvie Malembic-Maher, Pascal Salar, Luisa Filippin, Patricia Carle, Elisa Angelini, Xavier Foissac: Genetic diversity of European phytoplasmas of the 16SrV taxonomic group and proposal of 'Candidatus Phytoplasma rubi'. In: International Journal of Systematic and Evolutionary Microbiology (2011), 61, pp. 2129-2134
- ↑ a b c d e f g h i j k l m n o p q r E. Bosshard, H. Höhn, J. Rüegg, O. Viret: "Rubus-Stauche" with blackberry and raspberry. Agroscope Leaflet 832, 2002
- ↑ a b c Marlene Diekmann, EA Frison, T. Putter: FAO / IPGRI Technical Guidelines for the Safe Movement of Small Fruit Germplasm. International Plant Genetic Resources Institute Bioversity International, 1994, pp. 82f
- ↑ a b c d Georg Innerhofer: Rubus Stauche on blackberries. In: Haidegger Perspektiven 1/2009, Graz, p. 9
- ^ Richard C. Funt: Pest and Disease Management. In: Richard C. Funt, Harvey K. Hall: Raspberries. CABI, 2013, p. 137