Genetic Diversity Analysis Of Chinese Bayberry (Myrica Rubra Sieb. & Zucc.) Based On AFLP And SSR Markers

Chinese bayberry(Myrica rubra Sieb.& Zucc.)is a subtropical fruit tree nativeto China and it is one of the most important fruit tree crops in south China.In Chinabayberry has a long history of cultivation and a lot of varieties and cultivars were developed.This study analyzed the genetic diversity and relationship of 101 commonly cultivatedbayberry accessions based on molecular markers of AFLP and SSR.The results willaid not only the classification and management of bayberry germplasms,but will alsobe useful for innovation and utilization the germplasms.The main results weresummarized as followings:1.Applications of AFLP technology in genetic diversity analysis of ChinesebayberryAs the bayberry leaves are highly rich in impurities including polysaccharides andpolyphenols,we used ultracentrifugation in CsC1 gradient to purify the genome DNAextracted from bayberry leaves.An improved AFLP protocol suitable for bayberrywas provided.Six EcoR I+2 bases/Mse I+3 bases primer combinations(EAA/M47,EAA/M54,EAC/M56,EAC/M50,EAG/M51å’ŒEAT/M61)were used.A total of 236bands were detected,of which 177 bands were polymorphic.The average percentageof polymorphic bands was 75.01.Nei's gene diversity was between 0.1332 and0.2464,Shannon's information index was between 0.2101 and 0.36000.An unweightedpair-group method of the arithmetic averages(UPGMA)was used to analyze thegenetic relationships.The Dice's similarity coefficient among the accessions rangedfrom 0.49 to 1.00,and 101 accessions were divided mainly into five groups.Group 1included a total of 29 accessions.Group 2 included a total of 63 accessions.Group 3included a total of 7 accessions.While group 4 included only one accession ofdayehuang and group 5 included one accession of Myrica cerifera L.The accessionsfrom the same origin did not completely belong to one cluster,which suggested thatthe accessions were not completely clustered by their origin,and an extensive geneticexchange existed among the accessions.And the clusters did not match with the ripefruit color,suggesting that the fruit color of bayberry were independent mutations. 2.Development and characterization of microsatellite markers for ChinesebayberryExpressed sequence tags(ESTs)have been increased rapidly in number recently,which are important resources for development of new SSR markers.In this study,395 Unigenes of Chinese bayberry fruit were screened and 21 SSRs were mined out,accounting for 5.31% of ESTs.Dinucleotide and trinucleotide repeats,with highfrequency and accounting for 57.12 % and 23.81% respectively in all SSRs.Whilethe frequency for other repeat type is below 20 %.In addition we found another twoSSRs as we cloning MYB related genes.We also designed primers and named themas MYBSSR1 and MYBSSR2.Under a optimize PCR amplification,11 polymorphicloci were generated.Polymorphism of these 11 loci was assessed in 32 individualsand the number of alleles(A)ranged from 3 to 12,observed heterozygosity(Ho)andexpected heterozygosity(H_E)ranged from 0.1250 to 0.9667 and 0.2359 to 0.8790respectively,polymorphism information content(PIC)ranged from 0.2285 to 0.8516.These microsatellite loci should be useful in the studies of genetic diversity of Myricarubra.3.Genetic diversity analysis of Chinese bayberry based on SSR markersEleven SSR loci(MRU11,MRU155,MYBSSR1,MYBSSR2,my0043,my0186,my0427,my0792,my0793,my0889,my0972)were used to evaluate the genetic diversity of 100bayberry accessions.A total of 122 polymorphic bands were detected and the averagenumber of polymorphic bands was 11 per locus.An unweighted pair-group method ofthe arithmetic averages(UPGMA)was also used to analyze the genetic relationships.The Dice's similarity coefficient among the accessions ranged from 0.73 to 1.00,and100 accessions were divided into five groups.Group 1 included a total of 56accessions.Group 2 included a total of 33 accessions.Group 3 included 5 accessions.Group 4 included 5 accessions too and group 5 included one accession of Myricacerifera L.The cluster results based on 11 SSR loci were not completely match withthat of AFLP markers.