Comparative Analysis Of Pollen Vitality And Exploration Of Pollen Storage Technology Based On Different Lotus (Nelumbo) Germplasms

As the only aquatic flower among the top ten traditional Chinese flowers,Asian lotus(Nelumbo nucifera)has a long history of cultivation,and high economic,ornamental and cultural values.In this study,the pollens from 44 different lotus germplasms were used as materials to explore the culture media suitable for germination of lotus pollens and develope the methods that can quickly and effectively detect the vitality of lotus pollens,determine the lotus germplams with higher pollen vitality,and explore the conditions suitable for low temperature storage of lotus pollens,in order to provide a theoretical and practical guidance for parent selection in lotus cross breeding and improve breeding efficiency.The main results are as follows:(1)To explore an efficient method to optimize the in vitro culture medium for lotus pollens and to detect the pollen’s vitality.The results showed that the suitable liquid medium for lotus pollen germination was 10% PEG 4000 + 0.02% boric acid + 0.1% sucrose.The pollen staining rate detected by I2-KI staining method and TTC staining method was obviously inconsistent with the germination rate obtained by in vitro culture,and therefore,these two staining methods were not suitable but in vitro culture method was suitable for detecting the pollen vitality of lotus.(2)Pollen vitality of lotus showing difference at different flowering times.Through the obervation of changes in lotus pollen vitality in different flowering days and at different times on the second flowering day,the results showed that although the lotus flower can normally open for 4 days from the middle June to the middle August in Shanghai,the pollen vitality was the highest from 6:00 to 7:30 in the morning of the second flowering day,and then gradually decreased,but it was still at a high level on the third flowering day,with a slight decline trend during this season.Therefore,cross pollination for lotus should be better carried out from 6:00 to 7:30 am at the second flowering day.Of course,the time should be slightly adjusted according to the geographical differences between the north and the south and the different seasons.(3)Differences in pollen vitality of different lotus germplasms.In vitro culture method was mainly used to detect and compare the pollen vitality of lotus from different resources.Among the wild lotus,the lotus from Thailand and Vietnam had highest pollen vitality,while the wild lotus from Poyang Lake of Jiangxi province and from Tongjiang,Harbin and Jiamusi of Heilongjiang province had lower pollen vitality.Among the cultivars of lotus,the pollen vitality of N.nucifera ‘Guangmang Wanzhang’ is the highest and that of N.‘Suyi Cangcui’ is the lowest.For the cultivars with high-degreed double petalization,such as N.nucifera ‘Hongtai Lian’,N.‘Piaocheng Fanying’ and N.nucifera ‘Zhongshan Hongtai’,have low pollen vitality(except tropical lotus).(4)Effects of storage temperature,drying time and storage time on the vitality of lotus pollens stored at low temperature.The pollen vitality of different lotus germplasms stored under low temperature was tested by in vitro culture method.It was found that the pollens of N.lutea,N.nucifera Honghu Honglian,N.nucifera ‘Jianxuan 17’ and N.nucifera ‘Ju Yao’ were better stored at-40℃ and-80℃,dried for 24 hours,and had higher vitality when stored at shorter time(10 days).(5)Effects of different thawing methods on lotus pollen vitality after low temperature storage.The lotus pollens stored under low temperature was treated respectively by room temperature thawing,tap water washing thawing and 37℃ water bath thawing,and then the vitality was detected by in vitro culture method.The results indicated that thawing with running tap water was more suitable for the lotus pollens stored at-20℃,thawing in water bath at 37℃ was more suitable for the lotus pollens stored at-40℃ and-80℃,respectively.(6)Verification of lotus pollens vitality by cross pollination after low-temperature storage.The pollens of N.nucifera Honghu Honglian after being stored at low temperatures were taken out for cross pollination,some of which could make the lotus seeds set,which proved their vitality,and therefore verified the reliability of lotus pollen storage technology in this experiment.Lotus pollens can be stored at 4℃ for 10 days after drying for 24 hours in the early stage;After 6 hours and 12 hours drying treatment,the pollens can be stored for 60 days at-80℃,which significantly extended the pollen vitality.