Comprehensive Evaluation On Landscape Application Of Azaleas Varieties And Preliminary Selection On Its Suitable Mutation Conditions

The azaleas?Rhododendron pulchrum?were crossed or varied by R.indicum and R.eriocarpum?Hayata?Nakai.They have numerous varieties,splendid color,high ornamental value and economic value.As one of the late flowering varieties in Rhododendron,they bloom from late May to June.At present,even though there are about 300 species of Rhododendron cultivars widely cultivated in China,R.pulchrum is the main variety used in the landscape.This would be give rise to some problems such as single cultivar,poor heat resistance,brief blossom and mostly blooming from April to May ect.,which is not benefit for the forming of the green landscape and colorful city in the summer.According to the materials of 83 azaleas introduced by ecological agriculture development CO.,LTD,the varieties source nursery of azaleas were built for annual cultivation and observation,thereafter,the analytic hierarchy process?AHP?was used to establish a comprehensive evaluation model for the application of azalea varieties,which were suitable to analyze and evaluate comprehensive value of azaleas,ultimately the varieties with good comprehensive characters were identified.Besides,the effect of physical mutagen on these three semi-hardwood azaleas cutting were studied,by using the material of three azaleas,namely of 'Hong wan chong','Ruo hui bi xu' 'Zi chen dian',and the different irradiation doses of electron beam;Besides,the effect of chemical mutagen on the buds of the 'G.G.Gerbing' were also studied,which were mutated by different time and different concentration of chemical mutagen,including EMS and NaN₃.The main objective of this study was to determine the difference of irradiation sensitivity between different azaleas and figure out the optimal irradiation doses and the suitable EMS or NaN₃ mutation conditions,according to the statistical analysis of the survival rate of shoots and the investigation of the morphological index of plants after mutation treatment.Which can be used to provide the guidance not only on the landscape application of azaleas varieties,but also on their mutation breeding.The main results are as follows:1.The new comprehensive varieties evaluation system for azaleas has been firstly established.According to the assessment value of the 14 indexes,the evaluation results are that all the 83 azalea varieties were classified into 3 grades,namely of excellent,fine and bad varieties for landscape usage,which includes:grade I?>4.00?,grade ??4.00?3.05?,grade ??<3.05?.And there were 8 varieties?'Xun feng','Shi yan du juan','Ruo hui bi xu',ect.?,48 varieties?'Tian zhang','Shang zong zi','Du he zhi chun',ect.?,and 27 varieties?'Zhao ying','Ren sheng zhi hua','Da bei',ect.?in this three grades respectively.2.The optimal irradiation doses of azalea varieties by grafting or cutting have been studied.In this study,the optimal dose of the electron beam irradiation with high energy was calculated by the value of 60%?70%of the control.The results showed that the optimal dose of azalea cuttings is between 60 Gy to 80 Gy,and their irradiation sensitivity from high to low is 'Zi chen dian','Ruo hui bi xu','Hong wan chong'.The optimal dose of azalea grafts is between 50 Gy to 70 Gy,and their irradiation sensitivity from high to low is 'Ruo hui bi xu','Zi chen dian','Hong wan chong'.3.The optimum treatment of EMS mutagen and NaN₃ mutagen on azaleas buds has been tested.The results showed that in EMS or NaN₃ treatment,the buds survival decreased,with the increase in concentration and the extension of process time.In addition,high concentration and long treatment significantly inhibited the growth of azaleas buds,which resulted in some variation phenomenon such as the slow growth of buds,shorten internode length of twigs,shrinkage and curly of leaves and so on.In EMS treatment,the suitable mutation conditions were that the concentration was between 30 mM to 60 mM and the duration of treatment was 1 d,or the concentration was 30 mM and the duration of treatment was 2 d,with the variation rate from 0.9 percent to 5.3 percent and the visual damage rating score of azalea buds was between 0.6 to 6.9;It is the lethal mutation treatment when the visual damage rating score of azalea buds is not less than 8.2.In NaN₃ treatment,the suitable mutation conditions were that the concentration was between 6 mM to 8 mM and the duration of treatment was 1 d,the concentration was 6 mM and the duration of treatment was 2 d,or the concentration was 2 mM and the duration of treatment was 3 d,with the variation rate was from 0.6 percent to 3.5 percent;The visual damage rating score of azalea buds was between 3.6 to 4.7.