QTL Mapping And Natural Variation Of Glucosinolates Content In Brassica Rapa

Brassica rapa (syn. campestris) is an important species of the Brassica genus, which includes a variety of vegetable and oilseed crops. Complex genetic basis of this crop makes it’s difficult to improve some important agronomic traits. On the other hand, lots of cultivar groups and abundant genetic diversity were formed due to long cultivation history, which provides expansive materials for improving some important agronomic traits. Recently quality breeding was attached importance with the improvement of standard of living, but many qulity traits such as glucosinolate lacked systematic researches in heritability. So genetic analysi of nutritional quality traits in B. rapa at metabolites and molecular levels will provide a genetic base for the improvement of quality, and this also will be used for exploitation and utilization to key genes in B. rapa.In the present study, we described natural variation for glucosinolates contents, which detected with HPLC method in B. rapa plant. It would be useful to exploit glucosinolate accumulation and genetics in B. rapa. Based on the selection of optimal parents, genetic research segeragation populations with abundant information were constructed and genetic linkage maps of B. rapa were developed. Furthermore, quantitative trait loci (QTL) analysis of glucosinolate traits has been performed. Main conclusions are listed as follows:1. Using the method of HPLC to determine the contents of8individual glucosinolate, and there has been shown that a great natural variation are present in B. rapa for glucosinolate contents in plants. The total contents and types of glucosinolates are both different, and during our five studied populations four groups contain more than80%aliphatic glucosinolates(only75%,Chinese Cabbage).Turnip held the highest proportion of the aliphatic glucosinolates,which was95%,and the average contention was6.98μmol/gDW. We can easily got the conclusion aliphatic glucosinolates are the main types during all glucosinolates in the B. rapa.The greatest difference is the content of NAP, Maximum variation in glucosinolate (NAP) levels in diffrent accessions was4372times, GBN was1053times, GBC was126times, NAS was57times,4ME was212times, NEO was174times and the total glucosinolates was141times. Otherwise, the total level of glucosinolates and types are different among each one in the same cultivar group. Like Chinese Cabbage, the variation range of aliphatic glucosinolates was13.6～98.9%, the indol-glucosinolate was0.8～80.4%and the Gluconasturtin was0.0～72.0%. And the variation level was different among or within different cultivar groups.2. The purpose of the work was to develop calibration equations use of NIRS for predicting the total glucosinolate content, as well as individual glucosinolates, Under the analyses of desulfur GS. NIRS calibrations resulted in coeffcients of determination and standard error of cross-validation of0.36and0.69for PRO;0.55and0.83for NAS;0.62and0.84for GBN;1.87and0.87for NAP;0.05and0.82for4OH;1.22and0.93for GBC;0.04and0.71for4ME;0.44and0.86for NEO;2.97and0.92for Total, respectively..Finally, the prediction ability of an NIR equation to predict unknown samples has been established. Especially, the equation for NAP、GBC、NEO and Total, which could be used to predict true value accurately and reliably. It was concluded that NIRS shows a high potential as an analytical method for total and individual glucosinolate routine analysis in Brassica rapa..3. Genetic linkage maps was constructed based on BILs population developed by crossing a Rapid cycling L144and a flowering Chinese cabbage variety L58.1093markers were organized into16main linkage groups covering a total distance of1326.1cM including85SSR markers,102SRAP markers and357DART markers. The average interval distance was2.44cM. Length of linkage groups varied from17.6cM to137.8cM and the number of markers to each group ranged from2to69.4. Interval mapping and multiple-QTL model mapping (MQM) methods were employed in mapping and analysis of QTL controlling glucosinolate contents.8putative QTL were detected in6linkage groups, including3for individual aliphatic glucosinolate,4for individual indole glucosinolate,1for aromatic glucosinolate. The percentages of variation explained were varied between16.7-82.0%. The explained variation of3QTL controlling aliphatic glucosinolate and indole glucosinolate was over40%and25%.