The Characteristics Of Flowering And Karyotype Analysis Of Xanthoceras Sorbifolia Bunge

Yellow horn(Xanthoceras sorbifolium Bunge)is a unique woody oil tree species in China.The seeds of Yellow horn are rich in fat and protein.Fatty acids not only contain nervous acid,oleic acid,linoleic acid and other substances which are beneficial to human health,but also approximate to the reasonable proportion of fatty acid in edible oil.Besides,Yellow horn can also be used as biodiesel,ornamental tree species in gardens and so on.It has high application value.In order to speed up the breeding of Yellow horn and the investigation of genetic information,the flowering characteristics,karyotype analysis and genome size were studied in order to provide scientific basis for the research of Yellow horn breeding and genetic evolution.The main results of this study are as follows:(1)To observe the phenology of Xanthoceras sorbifolia in Tai'an city.The results showed that WF19 first entered flowering stage on April 3.The latest flowering stage was CB,which was April 14.13 superior lines of Xanthoceras sorbifolia entered flower bud germination stage on March 16,early flowering stage on April 3,full flowering stage on April10,late flowering stage on April 12,ovary expansion stage on April 26,fruit maturity stage on July 2,fruit setting stage on July 11 and fruit setting stage on October 23.The single flowering period is 5-7 days,and the total flowering period is about 30 days.(2)The flower size,fertile flower rate and flower color of Yellow horn were measured and analyzed.The results showed that the differences in flower length ratio and petal width/petal length ratio between different superior lines reached significant levels;The pregnant rate of the superior lines was between 9.25% and 21.43%.The highest proportion of pregnant flowers was WF6(37.44%),the lowest proportion of pregnant flowers was CB(10.76%)and the average pregnant rate was 25.32%.Most flower petals had obvious differences in inner and outer color,with white outer petals.The inner part changes with the number of flowering days,and the color changes are yellow-green,yellow-green/yellow,yellow/light pink,pink and pink-purple in turn.The color of GFWF1 and GFWF2 are specific.The color difference between inner and outer petals is not significant with the number of flowering days.The color change is yellow-green,yellow-green/yellow,light pink,pink-purple and purple in turn.The relationship between flower color and flowering days was analyzed.It was found that there was a linear correlation between flower color and flowering days.(3)Observation of the meiosis process of Yellow horn and karyotype analysis of the cells at the terminal stage showed that the number of chromosomes was 2n=30.The karyotype formulas were WF12=2n=30=12sm+18m,WF18=2n=30=18m(2SAT)+12sm,WF4=2n=30=8sm+22m,WF6=2n=30=10sm+20m,WF15=2n=30=8sm+22m,and WF15=2n=30=8sm.It consists of two types: the central centromere(m)chromosome and the subcentral centromere(sm)chromosome;the chromosome size is between 1.46 and 9.38 ?m;the karyotypes of the superior lines WF18,WF4 and WF6 are all type 2B.The karyotypes of WF12 and WF15 are 2C;the karyotype asymmetry coefficients are between 50% and 60%.During the meiosis of Xanthoceras chinensis,most of the pollen mother cells had normal chromosomal behavior,but there were a few abnormalities such as unsynchronized,unequally split,and multi-divided.(4)The genome size of Xanthoceras sorbifolia was estimated to be 442.51 M by k-mere method and 442.33 M by modification.The heterozygosity rate was 0.81% by formula calculation.