| Castor(Ricinus communis)is one of the most important industrial oil corps worldwide.Castor seed contains more than 50% fatty acids,of which the main component is ricinoleic acid,accounting for more than 80% of the total oil content.Ricinoleic acid has irreplaceable application value in aviation,chemicals,medicine and other fields due to its unique physical and chemical properties.With the development of economy in China,the demand for castor oil is huge,with about 400,000 tons per year.The resource gap is 50%.To meet the domestic demand for castor oil,a large number of castor oil is imported from India every year.At present,castor breeding in China relies on traditional methods,which is inefficient and lacks of varieties with advantageous traits.In recent years,genome sequencing has gradually entered the stage of high-throughput,high-precision and low cost,which provides a great impetus for crop breeding.In this study,based on the abundant germplasm resources of castor in China,we planned to make full use of genomics to assist castor genetic breeding to improve the efficiency of castor breeding.Therefore,we performed the whole genome sequencing for 405 castor varieties,including domestic local varieties,cultivated varieties and African wild varieties.We firstly identified all the genetic variations in these castor genomes,and carried out population genetic analyses.We identified the genomic regions and genes with selected signals during castor domestication.These results provide important genetic information for castor breeding and molecular biology research.The main contents of this paper are as follows:1.405 castor varieties,including 26 wild castor varieties from Africa and 386 local and cultivated species from 24 provinces in China,were sequenced and 2.02 TB original data were generated.2.Through sequence alignment and population variation detection,4,057,720 SNPs and 876,681 indels were obtained.The average number of SNPs per KB is 11.6,and the average number of reads per SNP is 9.5.3.According to the analysis of population structure,the castor varieties in China were divided into three subgroups,namely the southern subgroup,the central subgroup and the northern subgroup.The genetic background of the three subpopulations had been significantly differentiated.In addition,phenotypic analysis showed that the three subpopulations had also differentiated in seed size,ear height,pericarp dehiscence and other important phenotypes.4.Through the population genetic analysis,it was found that the wild castor population showed high genetic diversity,while the cultivated varieties were low.It is consistent with the expectation that the artificial domestication reduced the genetic diversity of the cultivated population.In the domestic cultivated population,the southern population had higher genetic diversity than the central and northern populations,and had a closer genetic distance with the wild population.In the process of transmission,the diversity of castor genome was reduced due to selection pressure.5.The genomic regions associated with artificial selection during the domestication of castor were identified,and the functional analysis of genes in these genomic regions was carried out.Combined with GWAS results,the mutation sites and genes controlling important agricultural traits were finally identified.6.The genomic regions and genes associated with geographical separation in China were identified in castor genome.It was found that the genes with selection signals were significantly enriched in the triglyceride lipase activation and abscisic acid response pathways,which may be related to the adaptability of castor to temperature during its transmission from south to north. |
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