QTL Analysis Of Salt Tolerance From Solanum Cheesmanii During Seed Germination And Seedling Stages Using Advanced Backcross Population

Salinity is a major environmental constraint to tomato productivity around the world. Therefore, breeding for salt-tolerant tomato is of great urgent. It's an efficient way to improve salt tolerance of tomato by introgression of favorable genes from wild germplasms into Solanum lycopersicum.In this study, the Solanum cheesmanii LA0317 (salt tolerant) and Solanum lycopersicum 9706(salt sensitive) were used to construct advanced backcross population. The objective was to map salt-tolerant QTLs in Solanum cheesmanii accession (LA0317), and to obtain salt-tolerant germplasm by large-saled screening under salt stress during germination stage. The main results were as followed:1. A total of 458 SSR markers and 551 CAPS markers were used to screen polymorphism among the parental lines and their F1 progeny. Eighty three SSR markers and thirty seven CAPS markers were found to be polymorphic, of which 87 markers were used for map constrction finally. A molecular linkage map consisted of 12 chromosomes was constructed using the mapping software Joinmap4.0. It covered approximately 964.7 cM of tomato genome.2. The performance for salt tolerance during germination and seedling stages of 130 BC2S4 families were identified and analyzed. Results indicated that the frequence distribution of germination rate, germination index, phytological traits value and salt survival value obeyed nomal distribution and could meet the requirement of QTL mapping.3. Using MQM mapping method, nine QTLs of salt tolerance during germination stage were identified, among which 5 QTLs conferring germination index located on chromosome 2,7,10,11 and 4 QTLs conferring germination rate located on chromosome 1,3,8,12. Fourteen families with high salt tolerance were obtained, which contained at least one of the major effect QTLs.4. In seedling stage, a total of 45 QTL for phytological traits of tomato were detected, and 2 QTL for salt tolerance were mapped to chromosome 3 and 6. Through comparative QTL analysis, it was found that QTL on chromosome 2,3 and 8 could only be detected under salt treatment, while QTL on chromosome 9 and 12 could only be detected under non-salt condition. QTL co-location among different traits was common in this study. Five lines of BC2S4 were found to be the most salt tolerant, and contained the major QTLs identified in this stage, thus these lines could be used as good breeding germplasm.