Study On Polyploid Breeding Technology Of Hybrid Cymbidium Based On 2n Male Gamete Pathway

Hybrid Cymbidium is a new type of Cymbidium cultivar developed from the combination of Chinese Cymbidium and Cymbidium hybridium,it has both the fragrance and elegent plant-type of Chinese Cymbidium and the large flower with bright color of Cymbidium hybridium and a broad market prospect.Polyploid breeding is the main breeding method of Cymbidium,but few articles on developing polyploid varieties by the use of 2n gamete pathway have been reported in hybrid Cymbidium now.In this study,Accessions such as Cymbidium’44-58’,Cymbidium’Xiaofeng’,Cymbidium’Junhao’and Cymbidium’Gongfenjiaren’were employed to study the technique of breeding new polyploid varieties of hybrid Cymbidium by using 2n gamete.The main results are as follows:1.2n male gametes were identified in Cymbidium sinense‘Jinzui’,Cymbidium’Taipingyang’,Cymbidium’Xiaofeng’,Cymbidium’Junhao’and Cymbidium’Gongfenjiaren’.The result showed that different Cymbidium varieties had different 2n male gamete incidence rate,the occurrence rates of 2n male gametes in Cymbidium’Junhao’and Cymbidium’Gongfenjiaren’was high.2.The seed germination rate of the hybrid offspring of Cymbidium’44-58’×Cymbidium’Xiaofeng’was 100%,and a total of 1226 lines were obtained,of which two were candidate polyploids.The seed germination rate of Cymbidium’Junhao’×Cymbidium’Gongfenjiaren’was 98.00%,and a total of 231 lines were obtained;morphology of the propagule included rhizomes（56.71%）,protocorms（23.38%）and intermediate type（19.91%）,and the plant type of the regenerated plantlets included the Chinese Cymbidium type accounting for 20.78%,the hybrid Cymbidium type accounting for 77.49%,and Cymbidium hybridium type accounting for 1.73%.The proliferation and differentiation characteristics of intermediate propagules in different lines were significantly different.3.There was a significant difference in the ornamental traits of flowering plants between sexual triploid and diploid from the same combination.Plant width and the number of flowers of Cymbidium‘Huanghe’were significantly higher than that of diploid DH.Plant height and the diameter of pseudobulb of Cymbidium’Yutao’were significantly higher than that of diploid ZJ-3-88.Plant height and the number of leaves of F410 were also significantly higher than that of diploid F103.Cymbidium’Huanghe’had compact plant-type with large,yellow,lotus-type and fragrancy flowers,while Cymbidium’Yutao’had compact plant-type with round,pink and fragrancy flower.4.Cymbidium’Huanghe’and Cymbidium’Yutao’had higher micropropagation efficiency compared with the counterpart diploid,respectively,and the rhizome induction rate,proliferation coefficient,differentiation rate,rooting and strengthening and test-tube seedling transplanting survival rate of the triploid were all significantly higher than that of diploid,but seedling height and root length of the diploid test-tube seedlings were significantly higher than that of the corresponding sexual triploids.Micropropagation characteristics varied with the cultivar of sexual triploid,plant regeneration rate and the number of plantlet regenerated from rhizomes of Cymbidium’Huanghe’were significantly higher than that of Cymbidium’Yutao’,but the mean number of root of Cymbidium’Yutao’was significantly higher than that of Cymbidium’Huanghe’.5.The initial dedifferentiation time of shoot tip with transverse cutting was earlier and the induction rate was higher than that with longitudinal cutting in sexual triploid hybrid Cymbidium’Huanghe’.The length of rhizome,combination of exogenous hormone,light intensity and organic additives had significant effects on rhizome proliferation,and when rhizomes with 0.50 cm in length were inoculated on MS+6-BA 1.00 mg·L^-1+NAA 0.20mg·L^-1+potato 80.00 g·L^-1+sucrose 30.00 g·L^-1+AC 0.30 g·L^-1and cultured at 26℃under 1000 Lux light intensity for 40 d,the proliferation coefficient was the highest（3.18）.Combination of exogenous hormone significantly affected rhizome differentiation,and when rhizomes in 1.00 cm length were inoculated on MS+6-BA 1.00 mg·L^-1+NAA 0.20mg·L^-1+sucrose 20.00 g·L^-1+AC 0.02 g·L^-1and cultured at 26℃under 2000 Lux light intensity for 40 d,the bud and seedling differentiation rates were 60.00%and 57.50%,respectively.When seedlings with 4.00 cm high were inoculated on 1/2MS+6-BA 0.10mg·L^-1+NAA 0.50 mg·L^-1+Sucrose 20.00 g·L^-1+AC 0.50 g·L^-1and cultured at 26℃under 2000 Lux light intensity for 50 d,the average seedling height and mean number of root were 7.32 cm and 3.56,respectively.The transplantation survival rate of seedlings in April and October was 98.67%and 99.67%,respectively by using of moss as culture substance.Through the above research,the effects of sexual polyploidy on micropropagation characteristics and major ornamental characters were clarified,and a new technical system for breeding new polyploid varieties of hybrid Cymbidium using 2n gamete pathway was preliminarily established,factors influencing on micropropagation efficiency of sexual triploid hybrid Cymbidium’Huanghe’were discovered,and its micropropagation technological system was established,which laid a solid foundation for further creating and micropropagation of polyploid hybrid Cymbidium.