Discovery Of Candidate Genes Of Starch In Tuber Of Tetraploid Potato And Molecular Marker Assisted Breeding

Potato is an important food crop,vegetable crop and industrial raw material,which plays an important role in guaranteeing food security in China.However,potato processing varieties with high starch content are still lacking,and starch yield can not meet the market demand,which seriously restrict the sustainable development of its industry.Therefore,it is urgent to breed new potato varieties with high yield,high quality and strong disease resistance.In this study,F₁ and F₂ populations from the cross between tetraploid potato YSP-4（female）and MIN-021（male）were used as test materials.Super BSA technique was used to locate the candidate regions and preliminary determine candidate genes related to starch content trait.Based on the different sections,SNP-CAPS and SSR markers were developed.The overlapped regions from Super BSA and QTL were selected to in-depth discover candidate genes.In addition,the developed molecular markers closely linked to starch content trait were used in assisted breeding to screen new strains with high starch.This study will lay a foundation for functional analysis,cloning and breeding of related genes associated with potato starch content.The main research is as follows:1.Super BSA method was used to locate the candidate regions of starch content trait in the 0-5.62 Mb region of potato chromosome 2.A total of 86 candidate genes were annotated,including 41 non-synonymous mutant genes between parents.2.A total of 85 pairs of primers（45 SNP-CAPS and 40 primers for SSR）were designed based on candidate gene section of starch content,and 12 polymorphic markers were developed.Four molecular markers,CAPS6-517,CAPS21-387,SSR14-246 and SSR22-231,which were closely linked with potato starch content traits,were identified and verified by the potato F₁ extreme plants,some extreme individuals in 240 F₂ population and potato varieties（strains）.3.The detection results of these four markers in F₂ population and tetraploid varieties（strains）were counted and the correlation analysis was conducted respectively.The detection result and phenotype corresponding degree of marker CAPS6-517 were 83.43%and75.00%,respectively.The detection result and phenotype corresponding degree of marker CAPS21-387 was 81.07%and 79.17%,respectively.The correlation between SSR14-246marker and phenotype was 89.35%and 79.17%,respectively.The correlation between SSR22-231 and phenotype was 92.90%and 83.33%,respectively.The correlation analysis was carried out between the results of four markers and starch content,and the correlation coefficients（r）were all greater than 0.5 and extremely significant at 0.01 level（P<0.01）.The results showed that the four markers developed in this study were closely linked with starch content trait and could be used for marker-assisted selection of new potato varieties with high starch content.4.Twelve polymorphic markers（2 SNP-CAPS markers and 10 SSR markers）developed in this study were used to construct a genetic linkage map.The map covered 71c M and contained 7 markers with an average spacing of 7.1 c M.Base on the genetic map,combined with starch trait determination results,the QTLs for starch content were identified.The target QTLs were detected between SSR14-246 and SSR22-231 markers,corresponding to position 299405 bp-2085470 bp on chromosome 2,explaining 41.9%of the phenotypic contribution rate.5.The overlapping regions from Super BSA and QTL were selected for study,and the target interval located at position 299405 bp-2085470 bp on chromosome 2.Function prediction of candidate genes and RT-q PCR fluorescence quantitative analysis were conducted in this region.PGSC0003DMG400037470 and PGSC0003DMG400036840 were identified as candidate genes for the regulation of high starch accumulation,and their bioinformatics analysis was conducted.6.Two SNP-CAPS and two SSR markers developed in this study were used to detect528 isolated individuals from F₂ population,and 102 high-starch genotypes were obtained.Combined with field observation,10 disease-resistant and robust plants were selected,and the yield and quality traits were determined after the potato tubers were harvested in autumn.Finally,strains NO.37 and NO.186 were determined to be the new strains with high starch and excellent comprehensive characters.7.The plant phenotypic characteristics,tuber characteristics and growth period of the new high-starch lines 37 and 186 were observed and recorded,and pollen fertility and chromosome pairing configuration were studied.It was confirmed that the new high-starch lines 37 had high pollen fertility（77.63%）and should be used as male material for further hybridization.The fertility of the new high-starch strain 186 was the opposite（43.11%）,which could be used as female material for cross improvement.