Akbari, M. (2013) Investigation of disease severity and genetic diversity of Spiroplasma citri isolates, causal agent of citrus stubborn disease in Fars province. Masters thesis, University of Zabol.
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Abstract
Stubborn caused by Spiroplasma citri is one of the most important diseases of citrus in worldwide and in Iran. The main vector of S. citri in Iran is the leafhopper Circulifer haematoceps. In the research six isolates of S. citri (Fasa I, Fasa III, Darab I, Darab II, Darab III, and Darab IV), isolated from C. haematoceps, from Fars sesame fields and one isolate (Ghadimi isolate) from a stubborn affected sweet orange tree in Khafr region (Fars, Iran) affected to stubborn. A completely randomized design based on factorial experiment was performed to compare the disease severity. The main factors were season (winter and summer) and sub factors were Spiroplasma citri isolates including Fasa I, Fasa III, Darab I, Darab II, Darab III, Darab IV and Ghadimi. S. citri isolates were transmitted to young and of periwinkle plants by grafting and disease symptoms and other disease parameters such as wilting and yellowing periods (time between inoculation and initiation of wilting and yellowing) were compared, In general in winter experiment, the disease incubation period and duration of wilting and yellowing initiation were longer than those in summer season. Statistical analysis have shown that duration of disease incubation, wilting and yellowing was significantly (p<%1) different between summer and winter and in summer season duration of the disease parameters were significantly shorter than those with winter season. The interaction of season and isolates was significant at the (p<%1). Polymerase chain reaction (PCR) assay using P89-f/r, a primer pair specific for S. sitri, confirmed by infection of periwinkle plants S. citri grafted by infected plants to S. citri isolates. Total DNA was separately extracted from seven periwinkle plants infected by S. citri and were tested for S. citri genetic differences by short sequence repeat (SSR) PCR using 4 SSR primers (SSR20A f/r, SSR02 f/r, SS06 f/r and SSR20B f/r). Primer pairs SSR 20A f/r, SSR06 f/r and SSR 20B f/r amplified expected fragment of chromosome from all seven isolates .The expected fragment was amplified by primer pair SSR 02 f/r with Ghadimi, Darab III and Darab isolates but not with other isolates. Therefore, on the basis of SSR PCR amplification S. citri isolates fell into two groups: Group one consisted of Ghadimi, Darab III and Darab I, and group two consisted of Fasa I, Fasa III, Darab II and Darab IV isolates. SSRPCR products with SSR02 f/r and SSR20A f/r were directly sequenced where fragments were used for Blast search and phylogenetic analyses. Phylogenetic analyses using sequenced fragments and the same fragment from S. kunkelli as out group indicated genetic diversity of under investigated isolates of S. citri. Results of the research are useful to breed resistant cultivars. Genetic diversity of S. citri isolates using SSR primers is reported for the first time in the Fars province.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Spiroplasma citri, disease severity, SSR PCR, Genetic diversity |
| Subjects: | Q Science > QK Botany |
| Depositing User: | admin admin1 admin2 |
| Date Deposited: | 30 Oct 2016 07:24 |
| Last Modified: | 30 Oct 2016 07:24 |
| URI: | http://eprints.uoz.ac.ir/id/eprint/934 |
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