QTL Mapping Of Traits Related To Lodging Resistance And Expression Of Key Gene In Lignin Synthesis In Brassica Napus L.

Lodging is a problem in crop production. It could cause not only the seed yield loss and seed quality reduction but also mechanized harvesting difficulty. To improving lodging resistance has become one of the most important goals in Canola breeding program.In this study, ZGF2:6-7, a RIL population in Brassica napus L. consisting of243lines was used in mapping QTLs of the traits related to lodging resistance (pressure resistant) The RIL population was deriving from a cross of Zheping1(lodging resistant) X Gaojie1(lodging susceptible). A genetic linkage map of Brassiea napus L. was constructed by applying SSR and SRAP markers. QTLs for lodging resistance were identified in populations of ZGF2:6and ZGF2:7at two locations (Nanjing and Lishui) within two years (2012and2013). QTLs for pod-setting layer were identified in ZGF2:6at two sites in one year. Quantitative real time PCR method was used to analyze the gene expressions in root collar and stem at bolting and silique-setting periods in B. napus. A comparison was made of the relative quantitative expression of the key genes (F5H,4CL and COMT) in lignin biosynthesis between Zheping1and Gaojie1.The main results from this study was summerized as follows:1. Genetic linkage map constructionA genetic linkage map of Brassiea napus L. was constructed by30SSRs and241SRAPs which was made up of21linkage groups covering2071.1cM in total with an average interval of8.6cM.2. QTLs analysis of lodging resistanceThere were16QTLs for pressure resistant identified by using inclusive composite interval mapping from the four trials. qRP2-1, qRP2-2and qRP16-1were located on LG2and LG16at Nanjing-2012with a phenotypic variation ranged4.68%～52.64%. qRPl, qRP4, qRP8-1and qRP16-1were located on LG1, LG4, LG8and LG16at Lishui-2012 with a phenotypic variation ranged of4.41%～15.36%. qRP8-2, qRP8-3, qRP16-1and qRP16-2were located on LG8and LG16at Nanjing-2013with a phenotypic variation ranged of6.29%～15.59%. qRPl, qRPS, qRP4, qRP8-1and qRP8-4were located on LG1, LG3, LG4and LG8at Lishui-2013with a phenotypic variation ranged of5.28%17.59%.Among them qRP16-1could be co-localized by three trials (Nanjing-2012, Lishui-2012and Lishui-2013). qRPl,qRP4and qRP8-1couled be co-localized by two trials (Lishui-2012and Lishui-2013). However qRP2-1, qRP2-2, qRP8-2, qRP8-3, qRP16-2, qRP3and qRP8-4were located by one trials only. QTLs for pressure resistant could be co-localized easily at any single location in each year.3. QTL analysis for thickness of pod-setting layer and its related traitsTwo QTLs, qTPL15and qTPL17, were identified on LG15and LG17explaining9.37%and5.35%of the phenotypic variation respectively at Nanjing-2012. qTPL15was identified on LG15at Lishui-2012explaining8.20%of the phenotypic variation. qTPL15could be co-localized on LG15by two trials.qSPS8and qSPS14(seeds per silique) were located on LG8and LG14at Nanjing-2012, which could explain5.65%and7.76%of the phenotypic variation respectively. qSPSl were located on LG1at Lishui-2012, which could explain6.25%of the phenotypic variation. qTSWl and qTSW8(thousand seeds weight) were located on LG1and LG8at Lishui-2012, which could explain7.65%and6.22%of the phenotypic variation respectively.There was no one QTL for number of siliqua per plant being identified at the two trials in this study.4. Disclosed the difference of expression patterns of the three key genes related to lodging trait between suceptable and resistant lines in B. napus.Results showed that at bolting and siliqua-setting stage the relative expression level of F5H,4CL and COMT in root collar of lodging suceptable line was higher than that of lodging resistant line in B. napus. At bolting stage the relative expression level of F5H,4CL and COMT in root collar of Gaojie1was11.48,35.46and21.18times higher respectively than that of Zheping1. At siliqua-setting stage that in root collar of Gaojie1was1.46,5.81and5.67times higher respectively than that of Zheping1. However the relative expression level of the three genes in stem of lodging suceptable line was much lower than that of lodging resistant line at siliqua-setting stage. At silique-setting stage, the relative expression level of F5H,4CL and COMT in stem of Zheping1was1.37,1.35and 1.76times respectively and significantly (P<0.05) higher than that of Gaojie1...