A New Whitefly Transmitted Geminivirus Infecting Tomato Plants in Egypt
A New Whitefly Transmitted Geminivirus Infecting Tomato Plants in Egypt
A-New-Whitefly-Transmitted-Geminivirus
ABSTRACT
Whitefly transmitted Geminiviruses cause severe damage to different crops in Egypt. Geminiviruses often occur in mixed infections, and it is difficult to diagnose such mixtures by biological properties. Two types of yellow leaf curl symptoms were collected from tomato plants grown at different locations in Egypt. The collected plants were subjected to biological analysis, the viral causal agent vector of the two types of symptoms was found to be Bemisia tabaci (Gennadius). Based on diagnostic host species and back inoculation assay two different types of symptoms were found. The first consists of identical Tomato yellow leaf curl virus (TYLCV) symptoms such as severe leaf chlorosis and distortion on tomato plants. named TYLCV-Giza isolate, and the other one showed yellow mosaic symptoms on tomatoes, named Tomato yellow mosaic virus (TYMV)-Qalyubia isolate. The genetic diversity at the molecular level for the two isolates showed that the coat protein and the replicase genes of putative TYMV-QaIubia are not identical to TYLCV resembled genes, at least at the flanking regions of each gene. According to the results obtained from the PCR products and indicator host plants, it can be concluded that they are two different Geminiviruses. Based on host range and symptomatology, the TYMV-QaIubia appeared to cause infections only to some species of the family Solanaceae, in contrast to TYLCV. It was indicated that TYMV could be mechanically transmitted to several species of the family Solanaceae with the aid of a special buffer as well as by grafting and whitefly transmission. Electron microscope studies of TYMV showed geminated virus particles with about 18-20 x 30 diameters nm. The molecular weight of the viral capsids was estimated to be 28 KDa for TYMV. Serological analysis also proved that the putative TYMV belongs to whitefly- transmitted geminivirus by ELISA analysis using the whitefly transmitted-geminivirus (WTG) antiserum [immunogenic oligopeptides coat protein (Cp-3)]. Based on the previous results, the isolated virus TYMV is confirmed to be a whitefly transmitted geminivirus belonging to genus Begomovirus or the Geminiviridae family.
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