| Tomato (Solanum lycopersicum) originated from middle-south America, it was grown around the world, and can be used as fresh and processing products marketing. Soil salinization is a key factor of land degradation, leading to falling crop yields. Breeding for salt-tolerance (ST) cultivars have been recognized as an effective way to improve tomato productivity in salt-affected soil. In this paper, the introgression line population (ILs), which was developed from a salt-sensitive parent S. lycopersicum M82and a ST wild species S. pennellii LA716, was employed to identify QTLs conferring ST during seed germination and vegetative stage respectively. Meanwhile the genetic effect and interaction of some QTLs were also analyzed. The fine mapping of one major ST QTL during vegetative stage and the trial of the ST germplasm and hybrids were conducted. The main results obtained in this thesis were concluded as follows:1. Identification and Effect Analysis of QTLs Conferring ST during Seed Germination Through salt tolerance identification in seed germination, ten unambiguous QTLs (Stq1, Stq2a, Stq2b, Stq2c, Stq4, Stq5, Stq6, Stq8a, Stq8b and Stq12) located on Chrom.l,2,4,5,6,8and12were identified, which were responsible for controlling ST during seed germination and derived from wild relative S. pennellii LA716. The germination index decreased about21.52～36.22%as compared to the control M82under salt stress.Comparing these10QTLs with other3QTLs derived from S. lycopersicoides LA2951ILs, the results showed that only QTL Stq2c and QTL St2b (from S. lycopersicoides) sitting at the same position on Chrom.2.Genetic analysis of4QTLs (Stql, Stq2c, Stq5and Stq8b) showed a significant dominant effect, and6QTLs (Stq2a, Stq2b, Stq4, Stq6, Stq8a. and Stq12) showed a recessive effect. The interaction of QTLs presented a typically less-than-additive effect. 2. Identification and Effect Analysis of QTLs Conferring ST during Vegetative StageThrough salt tolerance identification in vegetative stage, seven unambiguous QTLs (Stq2a, Stq2b, Stq6a, Stq1a, Stq7b, Stq8and Stq10) located respectively on Chrom.2,6,7,8and10were identified, which were responsible for controlling ST during vegetative stage and derived from wild relative S. pennellii LA716. The survival percentage increased by18.9-83.8%as compared to the control M82under salt stress. One QTL possibly involved in IL6-4and IL6-3needed to be confirmed in the further experiments.Comparing these7QTLs with other7QTLs derived from S. lycopersicoides LA2951ILs, QTL Stq2a and QTL St2, as well as QTL Stq6a and QTL St6, sat at the same position on Chrom.2and Chrom.6respectively.Genetic analysis of some QTLs showed a significant dominant effect with the exception of Stq6b. The interaction of QTLs presented a typically less-than-additive but two QTLs located on Chrom.7gave a reduced effect.3. Fine Mapping of Major ST QTLStq7b during Vegetative StageScreening with PCR polymorphism molecular markers based on the ST differences between M82and IL7-5-5,6molecular markers (3CAPS,1SSR and2AFLP markers) were confirmed, which were closely linked with major ST QTLStq7b and can be used for fine mapping.1338F2individuals were derived from a cross of M82×IL7-5. The recombinant population of255individuals was selected via screening the1338F2individuals by SSR285, then screening the recombinant population of255individuals by others5markers. Finally, the fine mapping of QTLStq7b on IL7-5-5segment was constructed. The length of the introgressed segment was measured at0.9cM which is approximately the same as the length of IL7-5-5, and with an average genetic distance of0.15cM. ST QTLStq1b was identified in the fine mapping, its genetic distance to the maker U231219and TG418was0.36and0.16cM respectively, and co-segregating with the maker C2_At4g30580. The contribution of individual QTL to phenotypic variation was7.34%, the additive effect was5.45, and the LOD was2.24.Prediction of candidate genes involved in the genome sequence of Stq7b was carried out by bioinformatics based on the fine mapping and the published complete genome sequence of S. lycopersicum H1706. The candidate gene (Solyc07g005440) and (Solyc07g005520) contained a typical NAF domain and BTB domain in terminal region respectively, the former may have a positive effect on responds to abiotic signals, and the latter may have a positive effect on responds to salt stress, which play an important role in protecting cell against abiotic stress by maintaining cell turgor.4. Trial of the ST ILs and Hybrids in Salt-affected SoilComprehensive evaluation the salt-tolerance of ILs, six ILs were selected, IL7-5showed good ST, high yield and fruit weight. IL6-2, IL6-4and IL7-1presented good ST but lower yield and fruit weight. IL2-2-2and IL2-6-5presented not best ST but high yield and fruit weight. Comparing to the M82and others3controls,4combinations performed good ST with high survival percentage and high yield were selected from26hybrids. |
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