| Salinity stress is one of the typical abiotic stress that seriously restricts crop production and quality. Recent years, with the reduction of arable land, development and utilization of saline land has become a major issue of the future of agriculture development. As the only winter rapeseed oil crops, Brassica competing for fewer conflicts with other crops, Among three types of rape, Brassica napus is the most widely cultivated area and relatively tolerant, Therefore, improving salt tolerance in Brassica napus is efficiency for improve the soil salinity land, which is of great significance to ensure oil supply in our country.In this study, three different salt tolerance of Brassica napus L. inbred lines(2205(strong salt-tolerant); 487(medium salt-tolerant) and 1423(sensitive))were taken as tested materials, to research the variation of several physiological index after salt stress, reveal the relationship between physiological changes and salt tolerance in the growth stage, providing methodological guidance and reliable material for rape salt resistant germplasm screening and breeding. The F2 population used in this study hybrids with 2205 and 1423, used SSR markers and AFLP markers analyzed its salt tolerance of parents and populations, to construct a genetic linkage map, and measured physiological parameters with F2:3 lines, detected QTL loci combined with molecular markers related to salt tolerance. The main results obtained in this study are as follows:1. Effects of Na Cl Stress on Physiological effects of Brassica napus L. Seedlings:Three different salt tolerance of Brassica napus L. inbred lines(2205,487 and 1423)were taken as tested materials, to research the variation of several physiological indexes(the contents of soluble sugar, MDA, chlorophyll and betaine) after Na Cl treatments(0,60,120,180 and 240 mmol·L-1) and its relationship with salt resistance in the 5-leaf stage, The results showed:(1) After 2 weeks with different Na Cl concentration stress, leaf soluble sugar content of three materials were reduced under Na Cl>120 mmol·L-1 compared with CK, 2205 leaf soluble sugar content always higher than 487 and 1423, and was the biggest increase above medium salt sress(31.69% and 34.60%), and significantly higher than 487 and 1423, 1423 is the lowest and the smallest increase.(2) After 2 weeks with different Na Cl concentration stress,leaf MDA content reduced and significantly lower than that of CK under Na Cl<120 mmol·L-1; while significantly increased when Na Cl<120 mmol·L-1(except 487), the MDA content in 1423 content was the highest and the biggest increase, increased 34.92% 53.35% compared with CK, respectively, 2205 and 487 were lower levels and the small increase.(3) After 2 weeks with different Na Cl concentration stress, leaf chlorophyll content of three materials were increased when Na Cl<120 mmol·L-1, but 2205 and 487 were significant difference with CK, 1423 and CK with no significant; while sharp decline under Na Cl>120 mmol·L-1, they were significantly lower than CK, 2205 leaf chlorophyll content less than 487 and 1423.(4) After 2 weeks with different Na Cl concentration stress, the betaine content increased with the increase of concentration of Na Cl stress comparied with CK, 2205 betaine content always higher than 487 and 1423, 1423 is the lowest.2. Salt genetic mapping and QTL mapping2.1 Construction of salt genetic map:In this study, 2205 and 1423 as a parent to build the F2 population(94 plants) as mapping population, used 194 SSR markers and 60 AFLP markers. A genetic linkage map was constructed by using Join Map 4.0, the map was made up of 19 linkage groups, including 173 SSR markers and 30 AFLP markers, covering 792.064 c M in total, the average interval distance was 3.9c M between makers. As for the different linkage groups, the length of linkage group varied from 18.276~87.283 c M, the longest LG12 was 87.283 c M, while, the shortest LG18 was 18.276 c M.2.2. QTL mapping of salt-tolerant gene:F2: 3 families were salt stress(200 mmol·L-1)at 3-leaf stage, 10 days after measured shoot height(SH), dry weight(SDW), fresh weight(SFW), root length(RL), chlorophyll(SPAD), electrical conductivity(EC), superoxide dismutase(SOD) and soluble protein(SP). Composite interval mapping method of Windows QTL Cartographer V2.5 was employed in QTL analysis of salt tolerance Physiology. A total of twelve QTLs were mapped on seven groups with LOD>2.5 except SFW and RL. Phenotypic variation explained by the single putative QTL varied from 13.35% to 58.17%, and the LOD sorce ranged from 2.6 to 4.8. specific results are as follows:one shoot height QTL(q SH) related to salt were detected in group six;two shoot dry weight QTLs(q SDW-1, q SDW-1) related to salt were detected in group one;five Soil and plant analyzer develotrnent QTLs(q SPAD-1~q SPAD-5) related to salt were detected in four different groups including LG1,LG4,LG5 and LG11;two electrolyte leakage QTLs(q EC-1and q EC-2) related to salt were detected in group twelve;one superoxide dismutase QTL(q SOD) related to salt were detected in group one;one soluble protein QTL(q SP) related to salt were detected in group sixteen. It showed that 12 QTLs loci were the main effect QTL control the salt tolerance genetic in rape. Besides, SDW and SPAD were overlapped on chromosome 1. |
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