Construction Of Genetic Linkage Map And QTL Detection In Saccharina

Saccharina is an important large economic algae, which own the most part inboth yield and scale among all the aquatic plants, and was used in many ways. Atpresent, molecular quantitative genetics research on Saccharina has just started, andthe constructed genetic linkage maps and the found QTLs do not enough for breeding.The genetic linkage maps reported was constructed mainly with amplified fragmentlength polymorphism (AFLP) marker, and only18SSR markers (the co-dominantmarker) was used, so these maps could only be applied in some limits.Contemporarily, the traits inclusive in QTL analysis were only frond length and frondwidth, and the QTLs linked to some trait were found only five (Three were linked toblade length and two were linked to blade width.), and it was far from enough toexplore the quantitative genetics of Saccharina.In this research, Saccharina longissima and Saccharina japonica were selectedas the parents to construct the F2populations, and102unbroken sporophore wereselected randomly as the mapping population. AFLP, SRAP and SSR were usedsimultaneously in the research, and two different methods were adopted in geneticlinkage maps construction. In addition, apart from blade length and blade width, thewidth between the two longitudinal grooves, blade thickness, fresh weight and themorphology of blade-stipe joint were also analysed to find QTLs. In addition, CIMand IM two different methods were used to analyse the QTLs. The summary of theconclusions were as follows:(1) Six hundred and thirty-two loci were obtained in thisresearch, consisting of221loci of AFLP,133loci of SRAP and278loci of SSR.(2)Two hundred and ten loci, out of632were detected to be distorted segregation,possessing33.23%. The percentage of dominant markers was45.20%, and it washigher than the percentage of co-dominant markers, which was only17.98%.(3) Fourhundred and twenty-two loci without the loci showing distorted segregation, including137loci of AFLP,57loci of SRAP and228loci of SSR, were used to construct the genetic linkage map.(4)The map was totally2233.1cM, with an average markerdistance of7.92cM, consisting of327loci and45linkage groups, which was0.9cMto175.3cM.(5) Twenty-nine QTLs were detected, and they could explain thecorresponding trait from1.06%to64.00%. Three QTLs were linked to blade length,and the contribution rate were2.93%~20.17%; five QTLs were linked to blade width,and the contribution rate were15.56%~44.91%; two QTLs were linked to the widthbetween the two longitudinal grooves, and the contribution rate were28.18%~64.00%;two QTLs were linked to blade thickness, and the contribution rate were13.63%~16.95%; three QTLs were linked to fresh weight, and the contribution ratewere3.01%~24.53%; fourteen QTLs were linked to the morphology of blade-stipejoint, and the contribution rate were1.06%~10.11%.The constructed map and the detected QTLs will be helpful to molecularquantitative genetics of Saccharina. If it could be used in breeding, the foreseeabilityand veracity on selecting elite genotype will be improved, and it will expedite theprocess of breeding. This research could be employed in MAS breeding, molecularaggregation breeding and cloning of the major gene, and it will be a new andconstructive strategy to breeding new Saccharina varieties.