توصيفگر ها :
فلفل دلمه اي , ويروس پژمردگي لكه اي گوجه فرنگي , ژنوتيپ , مقاومت , ژن Tsw
چكيده انگليسي :
Bell pepper (Capsicum annum L.) is a vegetable crop with high economic and nutritional value, belonging to the Solanaceae family. Tomato spotted wilt virus (TSWV) as one of the devastating viruses infecting bell pepper annually causes both quantitative and qualitative losses. The virus is transmitted in nature by different species of thrips, especially Frankliniella occidentalis. TSWV control is challenging due to the wide host range of the virus and its vector and the rapid acquisition of resistance to insecticides. One of the most effective tools for controling the disease in bell pepper is to use resistant cultivars harboring the Tsw resistance gene. In this study, bell pepper genotype screening for the Tsw gene using the SCAC568 marker and phenotypic analysis using mechanical inoculation method under greenhouse conditions were performed. To detect the Tsw gene, total DNA from 40 bell pepper genotypes was extracted and subjected to PCR method using the SCAC568F/SCAC565R primer pair. The PCR products were subsequently digested using XbaI restriction enzyme. In molecular analysis, the Tsw gene, tightly linked to the SCAC568 marker, was detected in Bachata, Darsena, SV99082 and Simpity genotypes as homozygous and in Aranica, H127-1, H300, H414, H253, H124-1, Tormes and Lorca genotypes as heterozygous. To prepare a source of TSWV, samples showing chlorotic and necrotic ring spots were collected from greenhouse bell pepper in Isfahan province. Total RNA was extracted from the leaves or fruits of bell pepper and RT-PCR was performed using FJJ200274/FJJ200275 and Tobamo-F/Tobamo-R primer pairs. The expected 810 bp fragment was amplified using FJJ200274/FJJ200275 primer pair, while no fragment was amplified with the Tobamo-F/Tobamo-R primer pair. To biologically purify the virus, extracted leaf or fruit tissue which had been tested by RT-PCR, mechanically inoculated on the leaves of Nicotiana glutinosa at the 4-5 leaf stage. After 7-10 days, symptoms of local ring spots and mosaic symptoms appeared on the leaves. For phenotypic analysis, 35 bell pepper genotypes were mechanically inoculated with TSWV at the 4-5 leaf stage and scored at 14, 21 and 28 days post inoculation (dpi), based on the symptom severity. In phenotypic analysis, Sanston, Cassiano, Paramo, Lemonchelo and Tarento genotypes were evaluated as resistant at 28 dpi. The Tsw gene was not detected in any of these genotypes. In all genotypes the expected 810 bp fragment was amplified using FJJ200274/FJJ200275 primer pair in RT-PCR. These finding suggest that these genotypes are tolerant to TSWV. The susceptibility of H300, H253, H414, Tormes, Lorca, Darsena, Bachata, Aranica, Simpiy, SV99082, H124-1 and H124-1 genotypes, despite having the Tsw gene indicates a breakdown of resistance to the TSWV Iranian isolate. Additionally, the absence of the Tsw gene in some resistant genotypes highlights the presence of new sources of resistance. The identification of the involved gene(s) in these genotypes expands our knowledge of the resistance mechanisms to TSWV disease in bell pepper.
Keywords: Bell pepper, Tomato spotted wilt virus, Genotype, Resistance, Tsw gene
