The Major Salt-relative Gene Located By SSR Markers In Salt-tolerance Introgression F₂ Population Of Shanrong No.3 With Jinan 17

Common wheat (Triticum asetivum L.) is one of the most important cereals in the world. Therefore, it is important to accelerate wheat breeding, such as to increase its yield and quality, and to improve its stress tolerance, by using biotechnology. The edaphic salinization has turned to a very serious problem in the world recently. Thus, it is a main target in the world for scientist to work on the botanic salt-tolerant mechanisms; to clone salt-tolerant genes and to breed new salt-tolerant species. Because of the huge genome, the application of molecular marker technologies in the wheat drops is behind other crops, e.g. barley, maize and rice. Meanwhile, there are above 80% repeated DNA sequence in wheat genome, so that a high density genetic linkage map can be made by SSR molecular marks. Recently, the molecular marker technologies have a great application in the salt- tolerance of wheat because of the development of the molecular marker numbers and technologies.A novel salt-tolerant wheat variety Shanrong No.3(SR3) created by asymmetric somatic hybridization between wheat cultivar Jinan 177 and Agropyron elongatum, and salt-sensitive cultivar Jinan 17 was used as experimental material. The hybrid F₂ population between Shanrong No.3 and Jinan 17 has been constructed from sexual crossing. Salt-tolerances of the F₂ population were determined by microsatellite (SSR) and BSA (bulked segregant analysis) techniques in combination with the SSR map of wheat. It has primarily presented that salt-tolerance of this hybridization is likely controlled by a major gene which located on chromosome 5A by only one SSR locus in our early research. In this work, a F₂ population of 500 lines was constructed for further localization of the major gene of salt resistance. Among all of the 97 SSR marker pairs, 17 show polymorphism, with a polymorphic index 17.5%. Then PCR amplification has been carried out among the salt tolerance pond and sensitive pond with this 17 marker pairs. Of them, Xbarc 180, Xbarc 117, Xgwm 304, Xgwm 666 showed coherence to the parents. Analyzing by JoinMap3.0, we found that 4 marker pairs match to the linkage map published, but the genetic distances exhibit a few differences. The rank of the 4 SSR marker pairs on chromosome 5A is barcl80,barc117,gwm304 and gwm666, and the genetic distances are 11.6cM, 6.8 cM and 65.8 cM respectively, comparing with the published high density genetic linkage map with the similar rank and the genetic distances 6.0cM, 6.0 cM and 44.0 cM. And the major-gene was located on the position between gwm304 and gwm666 by software JoinMap3.0. In combination to the SSR high density genetic linkage map of wheat, the major gene for salt tolerance has been located on the 5A long arm of wheat chromosome, and the distance to the centromere is 15-25cM. This result makes us to localize the major gene in 10cM in the further study.