Study On The Interspecies Relations And Origins, Evolution Of Cultivated Hawthorn (Crataegus Spp.) And Related Species In China

The genus Crataegus,a member of the Rosaceae family and has very long cultivation history because of the high economically,ecologically and ornamental value.There are some studies have examined intraspecific and interspecific relationships of Chinese Crataegus,but there is no systematic research at present.This study included all of the four cultivated species and three related wild species of China Crataegus,the first time to analyze the origins and evolution of cultivated Crataegus and related species in China based on the morphological,interspecific hybridization compatibility,molecular marker and the whole genome molecular information.The main results were as follows:Through to analyze the leaf,fruit morphological characteristics and the biological characteristics of the Crataegus species,this research found that the leaf blade lobes,the average weight of fruits and the phenological period can be used as the basis for Crataegus classification.The leaf blade lobes of Crataegus have non-dissected lobed,shallowly lobed,moderately lobed and deeply lobed three types;The phenological period have early,moderate and late three types;The fruit of Crataegus has small fruit,medium-sized fruit and large fruit.Based on the leaf blade lobes,the average weight of fruits and the phenological period,the Crataegus species of this study were separated into the following groups: plants with non-dissected lobed or shallowly dissected leaves and medium-sized fruit(C.hupehensis);plants with non-dissected lobed or shallowly dissected leaves and small fruit(C.maximowiczii and C.sanguineae);plants with moderate lobed or deeply lobed leaf and early phenological period(C.bretschneideri);plants with moderate lobed or deeply lobed leaves and late phenological period(C.pinnatifida and C.pinnatifida var.major).Chose one accessions from every species formed 25 interspecies hybrid combination,the average fruit setting rate is 45.5%,the average kernel percentage is 48.9%.The fruit setting rate and kernel percentage revealed the C.pinnatifida var.major and C.hupehensis,the C.sanguineae and C.maximowiczii are closely related;the C.sanguineae and C.pinnatifida,the C.brettschneideri and C.sanguineae are far related.Three exotic taxa collected from abroad were used in SSR analyzed,this study the first time selected 40 pairs of SSR primers from hawthorn transcriptional data.In the dengrogram which constructed based on the SSR data,when similarity values in 0.72 the seven Crataegus species been clustered into 5 groups,?: C.scabrifolia;?: C.brettschneideri and C.hupehensis;?: C.pinnatifida var.major and part accessions of C.pinnatifida;?: C.maximowiczii;?: C. sanguineae and part accessions of C.pinnatifida,this classification is different from above.The unknown germplasm ZWSLH,GSSZ,RR3 H and RR5 H were clustered with the accessions of C.maximowiczii and C.sanguineae in the SSR dendrogram and have nearly related to C.sanguineae.This study the first time used the SLAF-seq to investigate the origins and evolution of Chinese Crataegus,used Rsa?+ Hae ? for digestion and got the high quality sequencing data which mean Q30 is 91.83%.The average sequencing depth of the SLAF tag was 12.31-fold,got 803,196 SLAF tags and 933,450 SNPs.The STRUCTURE analysis showed that the seven Chinese hawthorn species have two different speciation events.The first speciation event occurred in the north.The second speciation event originated in southwestern China and then progressed northward and eastward to northeastern China diverged the C.pinnatifida then hybridization with the C.maximowiczii which native to northeastern China and gave rise to new species C.brettschneideri.Four unknown accessions(ZWSLH,GSSZ,RR5 H,and RR3H)in the SSR dendrogram and ML phylogeny tree,these accessions showed higher similarity to the northeastern species C.maximowiczii and C.sanguineae.