چكيده انگليسي :
Begonia rex (Begonia rex putz.) is an ornamental plant from the Begoniaceae family In addition to conventional methods is propagated with the invitro methods nowadays. Modifying and increasing the genetic diversity in plants through physical or chemical mutagenesis is one of the common methods in the plant breeding field, and despite many studies in this field, there has been less focus on the breeding of ornamental plants.In the first part of this study, the optimization of the micropropagation protocol of three varieties of Begonia Rex (Silver dollar, Jurassic and Silver king) with nine treatments of different plant growth regulators (without plant growth regulator (T1), 0.5 mg/liter BA 0.2 mg/L TDZ (T2), 1 mg/L NAA 0.5 mg/L TDZ (T3), 0.2 mg/L NAA 0.2 mg/L BA (T4), 1 mg/L NAA 0.5 mg/L BA (T5), 1 mg/L NAA 1 mg/L BA (T6), 1 mg/L IBA 0.5 mg/L BA (T7), 1 mg/L IBA 1 mg/L BA (T8) and 1.5 mg/L IBA (1.5 mg/L BA (T9)) were investigated in MS media. In the second part of the experiments, calluses formed in two cultivars of Begonia rex (Jurassic and Silver king) were treated with gamma radiation (0, 10, 20, 30, 40, 50 and 100 Gy). In third experiment three Begonia rex cultivars (Silver dollar, Jurassic and Silver king) leaf explants were treated with colchicine in MS media (without colchicine (C1), 50 and 100 mg/liter of colchicine in the media for 15 and 30 days (C2, C3, C4 and C5). In the first experiment, the highest direct regeneration were occured in T2 treatment (21.11%) and the lowest callus formation observed in T1 treatment in three cultivars (0%) and in T6 treatment was observed in Jurassic and Silver king cultivars (55% and 33%). Also, regeneration occured in all calluses. The highest number of leaves was obtained with T8 treatment in Jurassic cultivar (180/66). In the Silver dollar cultivar T3, T4, T5 and T6 treatments showed the highest prolifration (100, 93.33, 91.66 and 91.66%) and the T6 treatment also showed the highest fresh weight (22.33 grams). In Jurassic cultivar, with T4, T8 and T9 treatments, highest prolifration (85, 100 and 95%) and high fresh weight (23.14, 22.98 and 24.50 grams) were obtained.The Silver king cultivar also showed the highest percentage of prolifration (91.66%) in the T3 treatment. According to the results of second experiment, increasing the gamma ray doses, cause the decreased in growth rate, root length, seedling height, prolifration percentage and the area of the largest leaf in the invitro seedlings. The lowest growth rates (1.73), root length (2.78 cm) and height of invitro seedlings (3.21 cm) were obtained in the 100 gray treatment. In Jurassic cultivar, 10, 30, and 100 grays treatments produced the lowest number of leaves (47.66, 48.33, and 27.33), and in Silver king cultivar, 20 grays treatment produced the highest number of leaves (85). In Jurassic cultivar, 40, 50 and 100 grays treatments (56.66, 36.66 and 15%) and in Silver king cultivar, 50 and 100 grays treatments (26.66 and 30%) showed the lowest percentage of prolifration. The lowest leaf area was observed in the Jurassic cultivar (172.60 m) and in the 100 gray treatment (124.45 mm2). The results of the third experiment showed that the lowest percentage of survival was obtained in the Silver king cultivar (82%) and in the C2 treatment (62.77%). The lowest height and prolifration percentage occure in Silver king cultivar (3.38 cm and 25.13%). C2 and C4 Treatments also showed the lowest height (1.8 and 2.65 cm) and the lowest prolifration percentage (11.77 and 15.66 cm). In the Jurassic cultivar, the highest number of leaves was obtained in the C5 treatment (93) and also the Silver king cultivar showed the highest number of leaves in the media that containing the C1, C3 and C4 treatments (57, 55.33 and 58.66). In the present study, due to the fact BA cytokinin is cheaper and also provides a better response to the characteristics studied in the regeneration of Begonia rex seedlings, it can be introduced as an effective and useful treatment in combination with IBA and NAA in the micropropagation of Begonia rex plants. The result of this study showed that the usage of gamma rays in the range of 10-100 Gy, cause significant changes in the morphological and physiological traits, which can be the basis for increasing the probability of mutation in the genomic content of two tested begonia varieties. Also, according to the results, less exposure of the samples to colchicine in terms of treatment duration, as well as lower amounts of this substance, causes more significant changes and increases the probability of genetic changes, especially in Jurassic and Silver king cultivars, in a way that Applying the treatment of 50 mg/liter of colchicine in the media and placing the samples for 15 days in this treatment, better results of the measured traits were obtained, like the other researchers results.
