Effects Of Heavy Ion Irradiation On Tissue Culture And Mutagenesis In Hybrid Cymbidium

Hybrid Cymbidium is a new type of Cymbidium with big bright-color flowers and a long-lasting flowering period,which inherit from Cym.hybridum,and pleasant fragrance and graceful gesture,which come from Chinese Cymbidium.It has very high ornamental value,economic value and broad market prospect.Heavy ion irradiation breeding has been widely used in flower breeding because of the characteristics of short breeding cycle,high mutation rate,wide mutation range,novel variation types and so on.In this study,the rhizomes of Cym.‘Xiaofeng'and protocorm-like bodies?PLBs?of Cym.‘Junhong'were employed to study the effects of heavy ion irradiation on the survival and differentiation of hybrid Cymbidium and analyze the genetic diversity of Cym.‘Xiaofeng'test-tube seedlings after heavy ion irradiation;Micropropagation characteristics of Cym.‘Xianyiunhao'obtained by heavy ion irradiation was also investigated.The main research results are as follows:1.Effects of heavy ion irradiation on the survival and differentiation of intermediate propagule of hybrid Cymbidium.Heavy ion irradiation caused the death of Cym.‘Xiaofeng'rhizomes and Cym.‘Junhong'PLBs.The mortality of rhizome in one to six generation was 8.89%,46.67%,53.33%,84.45%,95.56%and 100%respectively in Cym.‘Xiaofeng',and 6.67%,53.33%,71.11%,77.78%,82.22%and 100%in Cym.‘Junhong',which indicated that the irradiation of ¹²C⁶⁺heavy ions with 50 Gy dose and 10 Gy/min dose rate was not suitable for mutation breeding of Cym.‘Xiaofeng'and Cym.‘Junhong'by using of intermediate propagule as mutagenic materials.Heavy ion irradiation completely inhibited the differentiation of Cym.‘Xiaofeng'rhizome and Cym.‘Junhong'PLBs,and the inhibition effect did not recovered until sixth generation.2.Diversity of test-tube seedling of Cym.‘Xiaofeng'after heavy ion irradiationBoth seedling height and leaf length of the 50 Gy radiation were significantly higher than that of 0 Gy and 60 Gy.The number of leave and root of the 50 Gy and 60 Gy radiation was all significantly less than that of the 0 Gy.SSR marker analysis showed that no polymorphic bands were amplified from test-tube seedlings of the 0 Gy and 50 Gy radiation,but there were two polymorphic bands appeared in test-tube seedlings of the 60Gy,with the polymorphism rate being 2.0%.3.Mcropropagation characteristics of Cymbidium‘XianyiJunhao'Variegated leaf of Cym.‘XianyiJunhao'created by heavy ion irradiation was stable.The formation time of rhizome from Cym.‘XianyiJunhao'stem apex was shorter and the induction rate was higher than that of Cym.‘Junhao'.Cutting treatment prolonged the induction time of rhizome,but increased the induction rate of rhizome,the induction rate was 90%when the stem apex being longitudinally cut in Cym.‘XianyiJunhao'.There was no significant difference in absolute proliferation rate of rhizome between Cym.‘XianyiJunhao'and Cym.‘Junhao',the proliferation multiple of Cym.‘XianyiJunhao'rhizomes was 1.59 on MS culture,which was significantly higher than that on the medium of MS+6-BA 2.0 mg·L^-1+NAA 0.5 mg·L^-1+AC 0.3 g·L^-1.The initiation time of bud differentiation of Cym.‘XianyiJunhao'was obviously earlier than that of Cym.‘Junhao',and the bud differentiation rate,seedling differentiation rate,average number of bud differentiation,average number of seedling differentiation were also higher than those of Cym.‘Junhao',however,the differentiation rate of bud and seedling with the height being more than 2 cm had not significant difference between Cym.‘XianyiJunhao'and Cym.‘Junhao'.Through the above research,the effects of ¹²C⁶⁺heavy ion irradiation on survival and differentiation of the rhizomes of Cym.‘Xiaofeng'and protocorm-like bodies of Cym.‘Junhong'and micropropagation characteristics of Cym.‘Xianyi Junhao'were clarified,two mutation plants were identified by SSR molecular marker analysis.These laid a solid foundation for establishing effective technology system of mutation breeding by heavy ion irradiation and creating breakthrough new cultivars?lines?in hybrid Cymbidium.