Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Genetics

Squash leaf curl virus (SqLCV) is a bipartite begomovirus affecting squash plants. In the last decade, SqlCV has been widely spread in the Middle East and caused huge yield loss in Egypt. It transmited by whitefly bemisia tabaci biotype B causing severe leaf curling, vein banding, molting ending by stunting as a late symptom. In this study posttranscriptional gene silencing (PTGS) has been induced to develop virus resistance. Two gene fragments from SqLCV were introduced in sense and antisense orientations using pFGC5941 vector to be expressed as a hairpin RNA (hpRNA). The first fragment was 348 bp at the 3' end of the replication associated protein gene (Rep or AC1), which had 50 bp overlapping with the transcription activation protein gene (TrAP or AC2). The second fragment was 879 bp representing the full sequence of the movement protein gene (BC1). Agrobacterium LB4404 was used in transient expression employing the syringe spotted technique in squash plants (cucurbita pepo L. cv. eskandarani). The infilterated plants harbouring the construct containing the Rep/TrAP fragment proved to be the best region for initiating PTGS

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