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Premunization (cross protection) as a new strategy to control phytoplasma diseases in fruit production: Apple proliferation as case study
Project
Project code: 2811NA062
Contract period: 01.10.2012
- 31.01.2016
Budget: 307,749 Euro
Purpose of research: Applied research
In Europe the fruit tree phytoplasmas, apple proliferation (AP), pear decline (PD) and European stone fruit yellows (ESFY) cause considerable economic losses. Due to the lack of resistant plant material and problems in controlling the insect vectors the management of the diseases is unsatisfactory. Breeding phytoplasma-resistant plants is a long time endeavour and not suited to meet the present needs. An alternative approach is the use of non-virulent phytoplasma strains as a premunizing or cross protection agent. Observations in ESFY-affected orchards in France and Italy demonstrated the presence of hypovirulent graft transmissible pathogen strains with protective properties. Identical results have been obtained in Germany with an AP strain. The isolate 1/93 has been observed since 1993 and infected trees never showed disease symptoms. Within the proposed research project we want to corroborate field data on premunization results on a larger scale with the non-virulent AP strain and examine the molecular and histochemical background for the cross protection activity. In graft inoculation studies with different apple rootstocks and cultivars we want to demonstrate the general applicability and protective nature of the procedure. Comparative genomics between the non-virulent and virulent strains will lead to the identification of discriminatory genes putatively responsible for cross protection. The mechanism underlying this phenomenon will be studied with graft-inoculated periwinkle plants. Transcription analysis of candidate genes and immuno-histological in situ examination will give a better understanding of the cross protection phenomenon. The project is supposed to show that premunization is a new, stable and reliable procedure to control AP in the field and a model for other fruit tree phytoplasmoses.
Workpackage 1 (grafting experiments). Two grafting experiments with Malus domestica and three greenhouse trials with Catharanthus roseus have been initiated after experimental inoculation with different combinations of weakly and strongly virulent apple proliferation strains to observe the plant reaction upon infection.
Workpackage 2 (monitoring). In C. roseus trials the weakly virulent strain dominated after a few months and reduced the number of virulent phytoplasmas increasingly. To assess the situation in the field plants more sampling results are needed.
Workpackage 3 (genome sequencing). All sequencing results for the apple proliferation strains 1/93 and 12/93 were obtained. The assembly of the reads was performed in guided reference assembly mode against the fully sequenced strain AT. Thirteen contigs were obtained for strain 1/93 and 20 contigs were obtained for strain 12/93. Gap closure and verification of contig arrangement is ongoing.
Workpackage 4 (antisera production). Two antisera were produced and tested for their specificity in immunoblot experiments for the phytoplasma strains 1/93 and 12/93. Both antisera showed strong reactions with plant proteins. Therefore the IgGs from one serum (anti 12/93) were monospecifically purified. First analysis with the monospecific IgGs showed a clear reaction with the pathogen strain in immuno-histological experiments.
Workpackage 5 (transcriptom analysis). C-DNA libraries of the mRNA from 1/93-, 12/93-infected plants and a healthy control were established and sequenced. Due to disease symptoms samples were taken at different times of the year. The number of significantly different expressed genes between the samples was greatest in November. In March and August only one gene was differentially expressed between 1/93 and 12/93 infected plants.
Section overview
Subjects
- Crop Protection
- Arboriculture
- Organic Farming
Framework programme
Federal Organic Farming Scheme and other forms of sustainable agriculture (BÖLN)
Funding programme
Excutive institution
Institute for Plant Protection in Fruit Crops and Viticulture - Fruit Cops (JKI-OW)
