Evaluationon Resistance To Stem Rotand Creation Of Germplasm Resource In Cymbidium

Cymbidium orchid has a high ornamental value,economic value and cultural value with broad market prospect.But the stem rot has become more and more serious,which has seriously hindered sustainable development of the industry.In order to develop new Cymbidium varietieswith resistance to stem rot,in this study,Cymbidium‘Yunv'were employed to study the method of evaluating on stem rot resistance in Cymbidium.Based on this,stem rot resistances of 100 germplasm resources were evaluated,and physiological and biochemical indexes were determinedin C.‘Yunv'and its mutants.In addition,the effects of heavy ion ¹²C⁶⁺on the rhizome of'Xiaofeng'.were studied.The main results were as follows:1.The effect of inoculation method,inoculation concentration and inoculation dose on stem rot disease occurrence in C.‘Yunv'were studied.The results indicated that injection method wasan appropriate vaccination method among matrix method,cotton ball method,spray method,injection method and paste method.The optimal inoculation concentration was 1.0×10⁶ per·mL^-1 among the tested concentrations of 1.0×10⁵ per·mL^-1,1.0×10⁶per·mL^-1 and 1.0×10⁷ per·mL^-1.At seedling stage,the best inoculation dose was 1.0m L,while the best inoculation dose was 3.0mL at mature stage.16 germplasm resources includingC.‘Yu xiang'?C.‘Yuye'?C.‘Yunv'Z50Gt?C.sinense×C.Bicolor-H2?C.sinense×C.Bicolor-H3?C.sinense×C.Bicolor-H4?C.‘Yunv'T2?C.‘Yunv'T3?C.‘Yunv'Z50G₂?C.‘Yunv'Z50G₃?C.‘Yunv'Z50G₄?C.‘Yunv'Z50G₅?C.‘Yunv'Z50G₆?C.‘Yunv'Z50G₇?C.‘Yunv'Z50G₃₃?C.‘Yunv'Z60G₂ had resistance to stem rot by using of injection method.2.1 After infection by pathogens,the changes of SOD,POD activity and MDA content in C.‘Yunv'T2 andC.‘Yunv'T3 were analyzed.The results showed that the activity of SOD in C.‘Yunv'T2 andC.‘Yunv'T3 was significantly higher than that of the control,whose maximum values were 48.78%and 44.77%,respectively,and the activity of POD was significantly higher thant hat in control,with the maximum valuesbeing 1.45 and 1.33 times more thanthe control,while MDA content was significantly lower than that in control.3.Heavy ion ¹²C⁶⁺irradiation had a significant inhibition effect on the proliferation and bud differentiation of the rhizome ofC.‘XiaoFeng',and the higher the dose was,the stronger the inhibition effect was.With the subculture going on,the growth and proliferation abilities grasually recovered,and the lower the irradiation dose was,the faster the recovery rate was.When the radiation dose exceeded 60 Gy,the rhizomes of'Xiaofeng'gradually lost the ability of proliferation and bud differentiation,and finally died.Through the above study,the technology system of evaluation on disease resistance to stem rot in Cymbidiumwas established,and 16 resistant germplasm resources were obtained.The irradiation effect of heavy ion ¹²C⁶⁺on the rhizome ofC.'Xiaofeng'was also clarified.These lay the foundation for breeding of new cultivar varieties with resistance to stem rot in Cymbidium in future.