Non-invasive 3D Quantitative Imaging Of Lipids In Different Tissues Of Seeds And QTL Analysis For Seed-related Traits In Brassica Napus

In China,rapeseed is the first major oil crops.Increasing seed oil content is one of the most important goals in rapeseed breeding.Seed oil content is a typical quantitative trait and is easily affected by environment.QTL mapping is an effective method to explore the genetic mechanism.At present,the method for determining seed oil content is either destructive or can not quantitatively reveal the distribution of oil in the seed,and the QTL related to oil content of different tissues of the seed is not known.The results showed that there was a significant correlation between seed oil content and seed color,and it was of great significance to improve the seed oil content though explore seed-related traits.In this study,based on KN DH population,using nuclear magnetic resonance imaging(MRI)and seed phenotypic analysis method,to reveal the formation mechanism of oil content of rapeseed seed through observe lipids distribution in seed and QTL mapping for oil content in different tissues of seeds and seed-related traits.The main results are as follows:1.Non-invasive 3D imaging of lipids in rapeseed seeds.Through the analysis of different oil content seeds of rapeseed with MRI,found that lipids exist in all tissues of rapeseed seeds,but the lipids distribution is not uniform,and the lipids was gradually reduced from the outer cotyledon to inner cotyledon,radicle and seed coat.The lipids distribution is also not uniform within tissues,and there is a dark band in the middle of cotyledon with the oil content is very low.The quantitative analysis showed that nearly90% of the seed oil content from the cotyledon,approximately 3% from seed coat,about6% from the radicle.In addition,the cotyledon,the seed coat and the radicle in the seed were account for ~70%,~20%,~10% of seed volume.2.Correlation analysis between fatty acids components and different tissues of rapeseed seeds.Using GC to analysis oil content in different tissues of different oil content seeds,found that there is no significant correlation between the oil content ratioand seed oil content,also found total oil content of low oil seeds sometimes over high oil seeds with the same number of rapeseed seeds.There is no significant correlation between the fatty acid composition and seed oil content,but there is significant correlation between the fatty acid composition and tissues of seeds.3.Correlation analysis between oil content and oil-related traits in different tissues of rapeseed seeds.Based on the KN DH population,a total of 24 groups of oil content and oil related traits were obtained,and the phenotypic data of each trait tended to be normal distribution.The correlation analysis showed that the total oil content,mean oil content between seed and tissues has very significant positive correlation,and the correlation is outer cotyledon > inner cotyledon > radicle > seed coat,oil contribution of tissues in seed is outer cotyledon > inner cotyledon > radicle > seed coat and seed volume contribution of tissues is outer cotyledon > inner cotyledon > radicle > seed coat.There is a significant positive correlation between total oil content,mean oil ontent and volume of tissues,the relationship between outer cotyledon and inner cotyledon,radicle and seed coat is stronger than other tissues.4.QTL analysis for oil content and oil-related traits in different tissues of seeds in Brassica napus.Based on high density genetic map,we detected 84 identified QTLs for seed oil content and oil-related traits in different tissues of seeds,the number of QTL is1-24 on each linkage and the largest is A9.The number of QTL is 1-7 for each trait,the phenotypic variation range is 5.22%-15.00%.Next,84 identified QTLs were integrated to 48 unique QTLs,17 of which were pleiotropic.Further analysis revealed that eighty-six candidate genes within QTLs were identified to be orthologous with A.thaliana genes associated with lipid metabolism,many of which are tissue specific candidate gene of rapeseed seeds.5.Correlation analysis of seed-related traits of rapeseed seeds.The total of 12 traits,including seed color,size,roundness,grain weight,oil content,oil and mass densitydensity,were obtained.The phenotypic values(except for seed color)trend to normal distribution,,and seed color traits with two peaks.The correlation analysis showed that the seed weight and seed size related traits,seed color have a significant positive correlation,seed color and oil content,grain weight,grain size have significantly positive correlation,oil content and seed color,seed roundness have significantly positive correlation.The resulted indicated we can cultivate high oil rapeseed varieties through the breeding of both round and large yellow seeds.6.QTL analysis for seed-related traits in Brassica napus.Based on a high density genetic map,we detected 117 identified QTLs for seed color,seed roundness,seed size,seed weight and other traits,these QTL distribution on the 14 linkage groups,except A1,A3,A10,C4,C7.The number is 1-23,among them,the number are largest on A9,C5.The number of QTL for each trait is 7-18,explained 4.09%-41.12% of phenotypic variation.117 identified QTL were integrated to 64 unique QTL,with 28 are unique QTLs(pleiotropy or close linkage),we found that the main effect QTL for control oil content,seed color,uqA9-5,which is co-locate QTL of qOC-14DL9-1(9.49%),qOC-13DL9-4(17.36%),qSC-14DL9-2(41.12%),qSC-13DL9-2(37.48%),the QTL contains 70 rapeseed candidate genes,uqA9-9 which is co-locate QTL of qOC-13DL9-3(15.31%),qSC-14DL9-1(27.04%),the QTL contains 21 rapeseed candidate genes.