---

Grapevine viruses cause significant losses in the yield of grape. This study describes applying silver nanoparticles (AgNPs) to produce virus-free grapevine plants and compares it with chemo and thermotherapy. Preliminary molecular analysis proved the presence of Grapevine fanleaf virus (GFLV) and grapevine leafroll-associated virus-1 (GLRaV-1) in the ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ cultivar samples, then single node explants were cultivated in the MS medium. Thermotherapy at 35 ± 1 ºC and cycles of 35/38 ± 1 ºC, chemotherapy with ribavirin 0, 20, 25, and 30 μg.ml^-1 and using AgNPs at 0, 10, 15, and 20 ppm in medium and 40, 50, and 60 ppm sprayed during acclimatization stage were applied to obtain virus-free explants. The results indicated that using 20 ppm AgNPs in medium and AgNPs combined treatment (15 ppm AgNPs in medium and sprayed with 50 ppm AgNPs in the acclimatization stage) were the most effective treatments for the elimination of viruses. The best treatment led to 100% eradication of GLRaV-1 and 67% of GFLV in ʻAsgariʼ, 100% eradication of GLRaV-1 and GFLV in ʻPeykaniʼ and 100% eradication of GLRaV-1 and 67% of GFLV in ʻShahaniʼ. Furthermore, applying of AgNPs improved plant growth parameters, including plant height, which in infected plantlets was (18.06, 12.36, and 14.92 cm in ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively) less than virus-free plantlets. Leaf number was 45, 34, and 27 in virus-free plantlets of ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively, but in infected plantlets, it was 24.40, 19.80, and 12. Leaf area increased from 5.34, 5.50, and 5.94 cm² in infected plantlets to 9.56, 11.43, and 12.33 cm² in virus-free plantlets of ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively. Complementary results proved that chlorophyll content in virus-free is significantly higher than in virus-infected plantlets, which explains and confirms the change in growth parameters after virus removal.
 

---

 Two experiments were performed for in vitro establishment, proliferation and shoot growth in axillary bud explants of Sebri pear cultivar. In the first experiment, the effect of different concentrations of IBA(Indole-3-butyric acid) on explants’ establishment was evaluated. In a second experiment, the influence of several combinations of PGRs (Plant growth regulators)on shoot proliferation and shoot growth was investigated. IBA at 0 and 0.1 mg L^-1 concentration led to successful bud establishment. At higher IBA concentrations, callus was induced, but fewer explants were successfully initiated. BAP increased shoot proliferation, while TDZ(Phenyl-N'-(1, 2, 3-thiadiazol-5-yl) urea) did not show any effect on shoot proliferation. BAP, at 3 mg L^-1 was more effective than 2 mg L^-1 on the number of proliferated shoots. Maximum shoot length was obtained for the medium containing BAP(6-benzylaminopurine) (2.0 and 3.0 mg L^-1)+IBA (0.1 mg L^-1) and BAP (2.0 and 3.0 mg L^-1)+IBA (0.1 mg L^-1)+GA₃ (0.5 mg L^-1). IBA in BAP combinations induced lateral bud swelling, while GA₃ (Gibberelic acid) inhibited it. Maximum leaf number was obtained for MS medium with 2.0 mg L^-1 TDZ and 0.5 mg L^-1 GA₃. Moreover, medium supplemented with 2.0 mg L^-1 BAP+IBA (0.1 mg L^-1)+GA₃ (0.5 mg L^-1) and 2.0 mg L^-1 TDZ+GA₃ (0.5 mg L^-1)produced maximum shoot length. Vegetative growth habit varied with different combinations and BAP concentrations, being the highest in BAP (2.0 mg L^-1)+IBA (0.1 mg L^-1) treatment. The combination of BAP at 2 mg L^-1 and 0.5 mg L^-1 of GA₃ is finally recommended for a proliferation of Sebri pear cultivar.

---

Production of virus-free stocks is crucial for efficient management of plant viruses in cultivation of pome fruits. Regarding the importance of producing the pre-basic stocks of valuable fruit trees, pear cultivar ʽNatanzʼ, an important local pear cultivar in Iran, was selected for virus eradication. In the present study, tissue culture combined with in vitro thermotherapy and thermo-chemotherapy techniques were used for elimination of Apple Stem Pitting Virus (ASPV) and Apple Mosaic Virus (ApMV). In thermotherapy approach, in vitro shoots were initially incubated for 55, 60, 65, and 70 days in alternating temperatures (32/38°C), then, meristems were cultivated on meristem medium. In thermo-chemotherapy approach, in vitro shoots were incubated for 50 days at 32/38°C, and then meristems were cultivated on a medium containing ribavirin. Virus detection by RT-PCR using specific primers was carried out after rooting and adaptation of the regenerated shoots. The percentage of survived shoots and meristem establishment were depended on thermo-duration. After 55 days, 83.33% of shoots survived, while it decreased to 33.33% after 70 days. Both ASPV and ApMV were eliminated after 60 days of thermotherapy. Ribavirin at 10 and 20 mg L^-1 reduced the percentage of meristem establishment to 50 and 37%, respectively, compared to the control (88.88%). Thermo-chemothery was also effective for ASPV and ApMV eradication from pear shoots.