Two DNA fragments of a Potato leafroll virus full-length cDNA which comprised parts of the PLRV ORF2 sequence were amplified by PCR. Both fragments were exactly the same except that they had the restriction sites for the enzymes XbaI and KpnI at the opposite ends.Therefore insertion of the two fragments into the same binary plasmid transformation vector would take place in the opposite orientations (sense or antisense). Using an Agrobacterium tumefaciens-mediated plant transformation procedure, leaf discs of Nicotiana tabacum were transformed with either of the fragments and regenerated into whole plants. Using PCR and RT-PCR, the transgenic plants that expressed mRNA transcripts of the transgenes were identified. Six lines of the plants transformed with sense and six lines of those transformed with antisense were crossed and the remaining was allowed to self-fertilise. The seeds obtained from these were grown to produce seedlings used in resistance tests. The resistance tests were done by aphid inoculation of seedlings with PLRV. Two weeks later the inoculated seedlings were tested for infection with PLRV by ELISA. Of the lines transgenic for sense and antisense only 28.5% and 23% were resistant to PLRV accumulation, respectively, whereas 50% of the lines obtained from crosses between sense and antisense plants were resistant. It seems that the simultaneous expression of sense plus antisense mRNA could have triggered post transcriptional gene silencing more effectively than expression of either sense or antisense mRNA alone.

Potato leafroll, the disease caused by potato leafroll virus (PLRV), is one of most important diseases of potato. Yield of infected plants may be reduced by as much as 90 %. Since the disease is important at potato seed production program and its symptoms (such as inward curling of the upper and lower leaves) were observed in Khorasan, the virus was detected by DAS-ELISA test and its distribution was determined during the course of the investgation. To determine the distribution of the virus in khorasan, from 86 fields of Bojnoord, Chenaran, Torbat jaam, Fariman, Torbat-e-Heidarieh (Jolgeh Rokh) and Torogh (Khorasan Agricultural and Natural Resources Researche Center), 2298 plants were randomly samples and DAS-ELISA test was used for detection 8.1, 16, 5.2, 8.6, 6.1 and 5.5 respectively. Also the geographical distribution of Myzus persicae (the vector of the virus) was surveyed. According the result of the survey, the population of the aphid is very low. Also, according the survey it seems that the aphid has very low role in the virus transmission and the most important manner of PLRV transmission in Khorasan is potato tubers.

Potato leaf roll disease is one of the most important and widely distributed viral diseases of potato. Like other plant viruses, the use of resistant cultivars is the most effective control measure of this disease. In this study, the reactions of some potato cultivars and genotypes to Potato leafroll virus (PLRV) were evaluated in a field trial experiment. The experiment conducted as a randomized complete block design with 12 treatments and three replications. Each plot of the experimental design included a planting row of five potato plants of each cultivar/genotype. The experimental plants were then inoculated with the virus by putting 10 PLRV-carrying green peach aphids on each plant. One month after inoculation, the plants were examined for PLRV infection by observing symptoms development and using enzymelinked immunosorbent assay (ELISA) test. The results revealed significant differences between the PLRV-infection rates of the potato cultivars/genotypes tested. The potato genotype 803970/13 with having no infected plant was evaluated as highly resistant to PLRV. The cultivar “ Sante” was resistant, the cultivar “ Lady Rosetta” and the genotype “ 397015/31” were moderately resistant, cultivar “ Diamant” was moderately susceptible and the rest of genotypes or cultivars were found susceptible or highly susceptible. The results also showed a significant correlation (79%) between the infection rates of the test plants based on symptom development and those of the ELISA tests.

Potato is the world's fourth-largest food crop after maize, wheat, and rice. Potato is seriously affected by both single and mixed viral infections because of vegetative propagation. In plants, RNA silencing is a protective mechanism against viral infections. Some researchers have been used RNA silencing technique to silence viral genes, but ultimately, due to the activity of viral RNA silencing-suppressor proteins, the resistance of plants is broken down and the virus can replicate and make the damage. The purpose of this study was to provide simultaneous resistance to three important viruses including Potato X Virus, Potato Leafroll Virus, and Cucumber Mosaic Virus. From genes corresponding to proteins of suppressoer of RNA silencing in these viruses (P0, P25 and 2b, respectively), a fragment was amplified with specific primers by PCR and ligtaed to each other. The recombinant final fragment was cloned in the form of sense and antisense orientations with an intron between them, in pFGC5941 plasmid under 35S promoter to produce a hairpin RNA after transcription in plant. The T-DNA of recombinant hairpin vector was transformed into potato (cv. Agria) genome by Agrobacterium. The obtained transgenic plants were screened by PCR to confirm the presence of the transgenes. The resistance of selected tansgenic lines will be assessed against three viruses.

In this study the PLRV transmission efficiency of five major genotypes of Scottish M. persicae) were analysed. The genotypes denoted as types A, B, C, J, and I. In virus transmission experiments detached leaves of PLRV-infected Physalis floridana and virus-free seedlings (2-3 leaf) of the same plant were used as virus source and test plant, respectively. Both acquisition and inoculation access periods were 3 days at 18oC with a 16 h photoperiod. One viruliferous aphid per seedling was used for inoculation and 24 seedlings for each genotype were inoculated. Three weeks after inoculation and based on symptoms or ELISA tests, the numbers of infected plants in each set of inoculated seedlings were determined. The transmission experiment was repeated five times. To reveal the factors underlying the differences in PLRV-transmitting abilities of the genotypes, transmission efficiency of PLRV and closely related virus, Beet mild yellowing virus (BMYV), by genotypes A and J were compared. Significant differences in PLRV transmission efficiency of the genotypes were observed. Genotypes A, B and C transmitted PLRV to more test plants. The comparison of the PLRV and the BMYV transmission efficiency showed that genotypes A and J transmitted BMYV almost with the same efficiency whereas genotype A transmitted PLRV more efficiently than did genotype J. These results suggest that such differences are likely to be caused by small variations within the aphid's receptors that recognize PLRV particles and assist their circulation and stability within the aphid's body. It has been shown that the genotypes A and B also carry all three known insecticide-resistance mechanisms and therefore can potentially increase the spread of PLRV.

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Potato virus Y (PVY), Potato virus X (PVX), Potato virus S (PVS) and Potato leaf roll virus (PLRV), are the most important viruses of potato and can cause serious diseases and significantly reduce the yield and quality of potato crops. The incidence of these viruses is reported from almost all main potato growing regions in Iran. Therefore, application of a sensitive, rapid and inexpensive procedure for simultaneous detection of potato viruses is very important for management of their control. In the present research, a sensitive and reliable multiplex RT-PCR technique for the detection of PVY, PVX, PVS, PLRV and 18S rRNA as internal control was employed and compared with ELISA, the method used routinely to assay potatoes for virus infections. Total RNA was extracted from virus infected potato leaves. Then cDNA for above viruses and 18S rRNA was individually synthesized using their specific reverse primers and single RT-PCR for each virus and 18S rRNA. Subsequently, multiplex RT-PCR was carried out with five primer pairs in a single reaction. As a result, five different fragments (145-342 bp) specific to the viruses and the internal control were simultaneously amplified and were identified on the basis of their molecular sizes. The sensitivity of our optimized system also was compared with that of commercial DAS-ELISA for detection of PVY, PVS and PLRV. The results showed that the sensitivity of multiplex RT-PCR was 100-fold greater for detection of PVY, PVS and PLRV and the duplex RT-PCR was 1000-fold greater for detection of PVY than that of commercial DASELISA.