QTL Mapping Of Salt Tolerance During Germination And Seedling Stage Of Solanum Pimpinellifolium Using AB-QTL Analysis And Development Of Salt-tolerant Germplasm

Salinity is a major environmental constraint to tomato (Solanum lycopersicum) productivity around the world. Improving salt tolerance (ST) of tomato is an important target for tomato breeding program. It's an efficient way to improve ST of tomato by exploring favorable QTL from wild germplasms.The objective of this paper was to map salt-tolerant QTL in Solanum pimpinellifolium accession (LA722), and then obtain some salt-tolerant germplasm by large-saled screening under salt stress during germination stage and AB-QTL analysis. The main results were summarized as follows:1. Two hundred and eighty BC3S1 individuals were obtained by 9706×LA722 (9706 as recurrent parent) while the seeds were screened for germination at an intermediate salt-stress level (150 mmol?L-1 NaCl+15 mmol?L-1 CaCl2) in BC1 and BC2 genaration. The parental lines and 280 BC3S2 families were evaluated for germination and seedling stage at salt-stress, the results indicated that the BC3S2 population exhibited a continuous variation for germination under salt-stress , typical of quantitative traits.2. One hundred and eighty-three polymorphic markers were obtained from 466 CAPS, 54 RFLP, 330 SSR and 88 SRAP markers. A molecular genetic linkage map including 14 linkage groups was constructed, and composed of 26 CAPS, 66 SSR and 20 SRAP markers. The total distance of this map was 773.5 cM.3. MQM (Multiple QTL model) analysis was used to identify salt-tolerant QTL during germination. Eleven QTLs of salt tolerance were identified on chromosomes 1, 2, 3, 5, 8, 9, and 12. All QTLs accounted for 73.2% of the total phenotypic variance. Three QTLs derived from 9706, and the others derived from LA722.4. Fifty-eight lines were obtained which were the most salt-tolerant during germination stage. Nine lines of them were analyzed with two major QTLs including qST-8-1 and qST-9-2. The result indicated that 230-1 and 230-3 families contained qST-8-1,228-4 families contained qST-9-2, 231-6, and other families contained these two QTLs. Agronomic traits of these families were similar to 9706, they could be used as breeding materials.5. Eleven salt-tolerant QTLs during seedling stage were indentified for on chromosome 1, 2, 4, 7, 8, 9, 11, 12. They accounted for 20.4% of the total phenotypic variance. Five QTLs derived from 9706, and the others derived from LA722. QTLs for germination and seedling stages were compared. While the location of QTLs for germination was different from that for seedling grownth, there were no coincidences in QTL locations.6. Several agronomic traits QTLs were identified, including thirteen fruit weight QTLs, eight yield QTLs, seven biomass QTLs, five height QTLs, five early maturity QTLs.