Phsiology Of Cold Tolerance And QTL Mapping Of Related Traits In Brassica Napus L.

Cold stress is one of the typical abiotic stress that seriously affect crop growth,yield and quality.Recently,under the background of global climate warming,some extreme weather even also occur frequently,such as cold winter and spring cold.Meanwhile,with the change of rape planting structure in recent years and rapeseed were planted in north and hills,stronger cold resistance becomes more vertical for rapeseed.Hence,studying the gene mapping of Brassica napus.L.cold tolerance,screening strong cold resistance plant resources and cultivating new product with high cold resistance has important significance.In this study,cold-tolerant GZhui and cold-sensitive 10B were taken as the test parental materials,F2 plant and F2:3 families were as the test materials were planted at three points in two years.Cold injury investigation,physiological indexes,SSR markers correlation analysis of six physiological indexes were analyzed and the linkage map,QTL loci were studied.The main results of this study are as follows:1.The DL of F2 population(GZhuix10B)was surveyed and F2:3 families were detected with DL and other five physiological indexes(RWC,EC,SP,MDA,SPAD).The results showed that the DL average of GZ hui and 10B in Yangling were 2.10 and 3.30;The DL average of GZhui and 10B in yongshou district were 2.79 and 3.67,and the difference between the two parents' frostbite levels was extremely significant.The DL of F2 plants ranged from 1.00-4.00 which has a transgressive separation between the two sites,and conforms to the normal distribution rule.The DL of F2:3 raged from 1.50-4.20 and 2.42-3.79 in Yangling and Yongshou respectively.Both has a transgressive separation between the two sites,and conforms to the normal distribution rule.Therefore,it is more reliable when the F2:3 families were used to measure the cold tolerance of F2 plants.2.The DL of F2 population were detected with F2:3 families's DL and other five physiological indexes(RWC,EC,SP,MDA,SPAD)and their correlation were analyzed.The results showed that the DL in F2 population represented extremely significant or significant correlation to DL,MDA,SPAD and SP in F2:3 families at Yangling,correlation coefficient were 0.621,0.601,0.338,0.326 respectively.The DL in F2 population represented extremely significant or significant correlation to DL,EC,RWC,MDA,SP in F2:3 families at Yongshou,correlation coefficient were 0.505,0.482,0.560,0.456,0.295 respectively,and weak to SPAD.Correlation analysis of six physiological indexes in F2:3 families at two locations showed that the correlation among the indexes in Yongshou was above Yangling.DL with RWC,EC,SP represented extremely significant,correlation coefficient were 0.542,0.402,0.459;RWC with SP,MDA,EC also represented extremely significant,correlation coefficient were 0.393,0.459,0.624;MDA with SP and EC also resented extremely significant,correlation coefficient were 0.593 and 0.523.The DL with RWC,SPAD and SP represented significant in F2:3 families at Yangling,correlation coefficient were 0.206,-0.216,0.190;the correlation coefficient betwween SPAD and EC was 0.293.The five physiological indexes of parents both in Yangling and Yongshou show significant difference and that in F2:3 both are accord with normal distribution and transgressive segregation and it's suitable for QTL mapping studies.3.1030 SSR primers in A and C genome were used to screen cold-tolerance GZhui and cold-sensitive 10B.221 pairs of SSR primers were detected to show polymorphism between parents.Using these 221 pairs of primers to screen 150 F2 plants,among them there were 177 pairs of primers were detected to show polymorphism with total of 333 markers.333 SSR markers which had polymorphism between 147 F2 plants were analyzed using JoinMap4.0.290 SSR markers were clustered into 19 linkage groups spanning 1317.7cM in lengthwith a mean distance between the adjacent markers of 4.54cM.The total number of markers is 290,of which 43 are not included in the linkageThe number of markers ranged from 5 to 42 on different linkage group and the chain length changed between 17.00 and 145.70cM.4.The phenotypic value of F2 population were represented by F2:3 families in Yangling and Yongshou.Composite interval mapping method(LOD ? 2.5)using WinQTLcart 2.5 was implemented to detect QTL combined with average physiological index in F2:3 families.20 QTLs related to cold tolerance in Brassica napus L.were detected,and the LOD score ranged from 2.54 to 5.87.Phenotypic variation explained by the single putative QTL varied largely from 0.005%(qECYL-8)to 42.501%(qMDAYS-6).Hot spots were detected both on A7,A8 and A10 chromosome.The data showed that the region BrgMS587-BnGMS488 on A7 were common regions shared by SPAD in Yongshou and MDA in Yangling;the region BrgMS653-BrgMS5339 on A8 were shared by SPAD in Yangling and MDA in Yongshou;and the SPAD and SP in Yangling were controlled by the region of BrgMS321-Na12A06 on A10.5AT5G30510 was searched in NCBI database then the gene sequence was homologous blast in Brassica napus database,that Bra010018 and Bra036120 were got.They are located in the A5 chromosomes,11611983-11634456 bp,A6 bp between 3122514-3138050.This study also found the corresponding QTL,but due to the density of genetic linkage map,the localization of QTL with no overlap area between genes,but within easy reach of both,the latest marker on A5 chromosome with Bra010018 was BrgMs70-2 with a distance of 0.577 M;The latest marker of the A5 chromosome with Bra036120 was BnGMS280-2,with a distance of 0.588 M.