| The formation of green tide is caused by the rapid growth and the rapid expansion of biomass of green algae detached from the auxiliaries in the eutrophic marine environment.It is a normalized marine disaster in the Yellow Sea in China.Its traceability problem,floating mechanism,prevention and control mechanism have always been hot issues.From the outdoor data of the floating green tide in the Yellow Sea in China from 2009 to 2018,we can see the dominant species of U Ulva prolifera can be divided into three subtypes(5S-I type,5S-II type and 5S-III type)based on the 5SrDNA spacer sequence.The emergence of ecological subtypes has shifted our research from morphological structure to algal species sequences and base changes.Hybridization can recombine the parental sequence,which can be an important means to study the emergence of ecological subtypes of U.prolifera,and can also as an important method to distinguish the species of Ulva,test the genetic relationship of algae.This paper establishes the technology of hybridization,which has guiding significance for the study of the emergence of ecological subtypes and cross breeding.The phylogenetic tree,genetic distance and hybridization test method were used to analyze the relationship between the U.prolifera from Japan and the dominant species in the Yellow Sea in China.The main results are as follows:1.The agarose gel electrophoresis,ITS sequence and 5SrDNA spacer sequence were used to monitor the floating green algae in the Yellow Sea from April 2018 to July 2018.It was found that among the 29 floating samples in 2018,there were 15 LPP(U.linza-procera-prolifera),13 strains U.flexuosa,1 strain U.compressa,.According to further analysis based on 5SrDNA spacer sequence,it was found that 15 LPP species were U.prolifera 5S-II.2.In 2018,from the species composition of floating samples in RD,DF,LYG and RZ we can know the sample of RD-May was the most abundant,and there were U.prolifera,U.flexuosa,and U.compressa.The floating species composition of RD-April and DF-May are U.prolifera and U.flexuosa.LYG and RZ are relatively single and all of which are U.prolifera.The genetic distances of U.prolifera based on 5SrDNA spacers of DF,LYG and RZ are similar.According to the floating time and the floating law from south to north,these floating U.prolifera may come from the same source.3.Establish technique of life history identification and hybridization for U.prolifera.According to the negative phototaxis of spores and the positive phototaxis of gametes,the asexual and sexual generations of U.prolifera were distinguished.Two successive generations identification results constituted the life history type of U.prolifera.Hybridization between female gametes of U.prolifera and male gametes of U.linza showed that has partial reproductive isolation.From the electrophoresis map,we can see hybrids both have the specific band of U.prolifera and U.linza.The sequence of hybrid is also similar to its parents.4.The ratio of male and female spores released by hybrids was 1:1.The female spores were 11.66 ?m long and the width was 5.20?m;the male spores were 9.27 ?m long and 4.15 ?m wide.Due to the meiosis,the hybrids F2 of U.prolifera and U.linza have the same sequence as their parents.5.By comparing neighbor joining tree and genetic sequence of U.prolifera come from Japan and Yellow Sea in China,we can find that the sequence AB298639.1-AB298646.1 and AB624461.1-QD208 belonged to the same branch evolution,and has small genetic distance.Hybridization test of U.prolifera AB29391.1 and AB624461.1-QD2008 showed that they could cross and reverse.It indicated that there have close genetic relationship. |
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