High Density Genetic Linkage Map Construction And QTL Indentification For Stone Cell In Pears

The stone cell contents of 88 pear varieties including 'Dangshansuli' and'Qiuyue'were determined by the Freeze separation method.In this paper,the genetic linkage maps of 'Dangshansuli' and 'Qiuyue' were constructed based on pseudo-testcross theory by GBS.QTLs were identified by KW(Kruskal-Wallis)and ICIM(Icimapping).The main results were as follows:The stone cell contents in mature fruits of 88 pear varieties from four species in were determined by the Freeze separation method.It showed that the mean value of stone cell contents of 88 pear varieties was 0.227g with a range from 0.032g to 1.024g,and the variation coefficient was 76%.However,the stone cell content in the fruits from ussurian accessions was the highest while that of interspecific hybrids was the lowest.Basing on the frequency analysis by stone cell contents,five cultivars with very low stone cell content were screened,which were 'Liuyuesu','Mantianhong','Longquanl9','Zhong1A3' and'Housui'.Also four varieties with very high stone cell content were screened,which were'Bayuesu','Jingchuanyeshengli 2','Baipisu' and 'Hongxiangsu'.The cluster analysis based on stone cell contents of ifferent accessions revealed that all the pear varieties could be divided into two groups,P.pyrifolia had a close relationship with P.ussurienisis,P.ussuriensis and interspecific hybrids shared common characteristics.The stone cell of hybrid F1 generation of 'Dangshansuli' and 'Qiuyue' were determination,and the clustering and frequency analysis was carried on it.Clustering analysis showed that 112 individuals can be divided into groups of male parent and female parent groups,the frequency analysis also showed its near normal distribution.In general,it suitable for QTL mapping.In this study,a high-density genetic map of pear was generated on 110 F1 individuals derived from the cross between pear cultivars 'Dangshansuli' and 'Qiuyue' by the rapid and robust technology of GBS.The linkage map consists of 2600 SNP markers distributed along 17 linkage groups,covering 1824.11 cM,with an average marker distance of 0.71 cM.The length of each chain group was 0.26?1.14 cM,with an average marker of 153.By using Kruskal-Wallis and interval mapping method,16 QTLs and 2 important regions for fruit stone-cell traits were detected.Basing on the analysis of KEGG and GO for gene being expanding areas,the pathway of phenylpropanoid biosynthesis was seeked out,and 16 genes and 3 candidate genes related to fruit lignin were screened.