Virus resistance by gene silencing

Squash production fields sustain significant yield losses due to viral infections. Fruits that develop on infected plants become highly distorted or discoloured. Infected plants show shortening and leaf deformation. The economic loss due to mosaic viruses in the case of infection is frequently more than 50% yield loss. The most damaging viruses world-wide are the Zucchini Yellow Mosaic Virus (ZYMV), the Watermelon Mosaic Virus-2 (WMV-2), the Cucumber Mosaic Virus (CMV) and the Papaya Ringspot Virus (PRSV). As in most production areas, in the Palatinate approx. 80% of virus infected plants are infected by ZYMV and WMV-2. There are virus-tolerant cultivars produced by conventional breeding, but these virus tolerances break down on the field when mixed infections or infections with aggressive virus strains occur.

The aim of the project is to produce virus-resistant green squash material by genetic engineering. The resistance gene will be introduced via Agrobacterium-mediated transformation in commercially acceptable cultivars, which were provided by European breeding companies. The resistance strategy used is based on the phenomenon of post-transcriptional gene silencing (PTGS). Short viral sequences were incorporated as inverted repeats under the control of a constitutive promoter into the plant cell. The inverted repeat transcripts form double strand RNA, which triggers a plant defence mechanism leading to sequence-specific degradation of virus RNA and consequently to virus resistance. In this way, multiple virus resistance should be achieved for both WMV-2 and ZYMV.


Virus infected Zucchini plant	Embryogenic calli: starting material for Agrobacterium-mediated tranformation

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