作 者：
杨颖;段豪;郭金博;王紫阳;施钦;宣磊;於朝广
关键词：
落羽杉属;中山杉;扦插苗;生根;数量性状基因座(QTL);SLAF标记
摘 要：
【目的】探索中山杉硬枝扦插生根性状的遗传规律及机理,指导中山杉的育种实践。【方法】在[落羽杉×墨西哥落羽杉(墨杉)]×墨杉高密度遗传图谱的基础上对回交(BC1)子代硬枝扦插苗每穗生根率、发根数、根长(最长根长、次长根长、第3根长及前3根平均根长)、最大根粗、抽梢长度、抽梢地径9个硬枝扦插生根性状进行遗传分析及数量性状基因座(QTL)定位。【结果】9个指标在子代中的遗传变异系数为31.14%～63.67%。7个指标成功定位到7个QTL区间,包括每穗根长(最长根长、次长根长、第3根长及前3根平均根长)相关的3个QTL,生根率的2个QTL,发根数和抽梢地径分别定位到1个QTL,7个主效QTL的置信区间为0～2.784 cM,似然函数比值的对数值为2.01～4.51,可解释的表型变异为4.24%～12.78%。利用生物信息学分析预测了主效QTL区间内的候选基因。【结论】生根率和不定根长度在BC1子代中遗传变异显著,且与几个高强度的主效QTL相关,分子标记辅助育种应用于这两个性状的选择改良有较高的潜力。
译 名：
Genetic variation and QTL analysis of rooting traits of backcross progenies of(Taxodium distichum×T. mucronatum）×T. mucronatum hardwood cuttings steckling
作 者：
YANG Ying;DUAN Hao;GUO Jinbo;WANG Ziyang;SHI Qin;XUAN Lei;YU Chaoguang;Jiangsu Engineering Research Center for Taxodium Rich.Germplasm Innovation and Propagation,Institute of Botany,Jiangsu Province and Chinese Academy of Sciences;
关键词：
Taxodium;;Taxodium 'Zhongshanshan';;steckling;;rooting;;quantitative trait locus(QTL);;SLAF marker
摘 要：
【Objective】Explore the genetic variations and mechanism of rooting traits of hardwood cuttings stecklings of Taxodium'Zhongshanshan'and guide breeding practices.【Method】One-year-old lignified hardwood was harvested from130 backcross(BC1)strains for hardwood cutting,and 1 672 stecklings were achieved the next year. Nine rooting-related growth traits,i.e. rooting rate,number of adventitious roots,root length(the longest root length,the second root length,the third root length and average root length of the first three roots),the diameter of the largest root,shoot length and shoot diameter of BC1 progenies were measured. The variation law,genetic variation coefficient and the correlations among the growth traits were analyzed. Besides,the rooting ability of the 117 lines was classified according to the subordinate function values. QTL(quantitative trait loci)analysis was conducted based on the high-density genetic map of(T.distichum × T. mucronatum)×T. mucronatum using the rQTL method. Finally,to obtain the information of candidate genes in the main QTL interval,the 2 × 100 bp sequence information of each specific-locus amplified fragment(SLAF)marker within the major QTLs was blasted with transcriptome database.【Result】Except for the shoot diameter,the variation of the other eight phenotypic indices in BC1 population basically conformed to the normal distribution. All the 9 growth traits were widely separated. The variation range of genetic variation coefficient was 31.14%-63.67%. The variation coefficient of shoot length was the largest,followed by the rooting rate(54.61%),and the variation range of rooting rate among individuals was 3%-73%. A significant positive correlation was found between two of the diameters of the largest root,the longest root length,the second root length,the third root length,the average root length of the first three roots,the shoot diameter and the shoot length,that is,there was a significant correlation between the radial and longitudinal growth traits of the adventitious roots and shoots. However,there was no significant correlation between rooting rate and number of the adventitious roots with other growth traits. The 117 BC1 lines were divided into 4 groups based on the cluster result of subordinate function values. Forty seven lines were of low rooting ability type,33 lines were of relatively low rooting ability type,19 lines were of relatively high rooting ability type and 18 lines were of high rooting ability type. Seven major QTLs with logarithm of odds(LOD)values ≥2 located on 6 linkage groups(LG3,LG4,LG8,LG9,LG10 and LG11)were identified for the 9 growth traits,except for the diameter of the largest root and shoot diameter,and 102 SLAF markers were included. The longest root length,the second root length,the third root length and the average root length of the first three roots shared similar LOD profiles. The confidence interval of the 7 major QTLs ranged from 0 to 2.784 cM,the LOD ranged from 2.01 to 4.51,and the phenotypic variation explained(PVE)ranged from 4.24% to 12.78%. For the PVE of single QTL,the order was q3-1(12.78%)>q10-1(12.05%)>q4-1(8.72%)>q9-1(6.91%)>q11-1(6.68%)>q3-1(5.07%)>q8-1(4.53%). The highest values were associated with root length and rooting rate,both of which were above 12%. Unanimously,for the cumulative PVE of total QTLs,QTLs of root length were the highest with QTLs(q3-1,q8-1 and q9-1)that totally explained 24.22% of phenotypic variation. The second was rooting rate,with two major QTLs(q3-2 and q10-1)that totally explained 17.12% of phenotypic variation.Thus,there were several strong QTLs controlling a large proportion of the genetic variation of rooting rate and root length in Taxodium. Only one QTL(q4-1)was located for number of the adventitious roots,and the PVE was 8.72%. One QTL(q11-1)was located for shoot diameter with 6.68% PVE value. Only q4-1 had a negative additive effect,and all the other six QTLs had positive additive effects. Among the 102 SLAF markers within QTLs,25 had a high match with unigenes in transcriptome,among which encoding Ty1-copia long terminal repeat,ubiquitin binding enzyme,leucinerich repeat extensin and GDSL lipase genes were identified,all of which participate in the root development of plants.【Conclusion】The genetic variations of rooting rate and adventitious root length were both significant in the BC1 population,besides,they were both related to several strong QTLs. Thus,it is of high potential for the application of molecular marker assisted breeding in the selection and improvement of these two traits in T.'Zhongshanshan'.
