Identification Of QTLs Associated With Salt Or Alkaline Tolerance Under Salt Or Alkaline Stress Based On Recombinant Inbred Line Population In Rice

Salinization of soil is becoming worse and worse during these years, and it was becoming the greatly restriction to production of rice. In view of this, to do further studies on genetic mechanism of salt or alkaline tolerance in rice and then develop new rice cultivars which were resistant to salt or alkaline stress would be very important in extending rice planting area, improving rice production, ensuring safety of national foods, improving peoples’ living life and environment.The recombinant inbred line (RILs)population F8derived from a cross between two rice cultivars Yiai1and Lishuinuo was used for mapping. Based on this map, additive and epistatic QTL for traits associated with salt or alkaline tolerance were detected, so as to give a reference in fine mapping or clone of QTL associated salt or alkaline tolerance, and also in the SSR assisted breeding program to develop salt or alkaline tolerant cultivar. The results of this study as follows:1.Under salt stress RSDR of GE for the RILs population showed a continuous distribution but deviated to higher phenotypic values with2-3peaks at the same time; RSDR of GR and TRSDR of EGS for the RILs population showed a continuous distribution but deviated to higher phenotypic values; DLR for10or20days under salt stress showed a continuous near normal distribution, but DSR for10days showed a continuous distribution but deviated to lower phenotypic values; DSR for20days showed a continuous distribution but deviated to higher phenotypic values; under alkaline stress DLR for during10to60days showed a near normal continuous distribution, but DSR for55days with a larger variation of phenotype value, which showed a1continuous distribution but deviated to lower phenotypic values and with2-3peaks at the same time. The results showed that all traits above were controlled by a few major genes and many other micro-genes together.2. Under salt stress, three QTL for RSDR of GE, two QTL for RSDR of GR, two QTL for RSDR of EGS, five QTL for DLR and six QTL for DSR were detected Thirty-two QTL associated alkaline tolerance were detected under alkaline stress. qSGE12-land qSEGS12-2were located in RM7558-RM3739, on chromosome12; qSGR7-3and qSGR7-4were located in RM21201-RM5711, on chromosome7; qDLRs8-1for DLR with PEV of17.36%and qDLRs8-2for DSR with PEV of18.66% located in RM404-RM547, on chromosome8. These QTL which located in the same distance of the same chromosome were likely to be the same QTL, or one gene with multifunction or two QTLs with compact linkage, and then lead to the correlation among these QTL. RM404-RM547with the distance of10.6cM, were detected QTL for salt tolerance and alkaline tolerance at the same time.So these two marker distances could be used in the breeding program in rice to get salt or alkaline tolerance rice cultivars.3. Sixteen pairs of epistatic QTL were detected under salt stress. Of them, six pairs for RSDR of GE, ten pairs for TRSDR of EGS. Five pairs of epistatic QTL for DLR and five pairs of epistatic QTL for DSR were detected under salt stress. Fifteen pairs of epistatic QTL were detected under alkaline stress at germination stage. Of them, one pair for RADR of GE, twelve pairs for RADR of GR, two pairs for TRADR of EGS. Twenty-nine pairs of epistatic QTL were detected under alkaline stress at early germination stage. Of them, twelve pairs for RADR of SH, one pair for RADR of RL, fourteen pairs for RADR of RN and two pairs forT RADR of EGS. The results above indicated that epistatic QTL may play an important role in salt or alkaline tolerance in rice.4. At early seedling stage, QTL for DLR were epistatic QTL, but at late seedling stage QTL for DLR were additive QTL. The situation of QTL for DSR was opposite to QTL for DLR. Under alkaline stress, according to the total PVE value, QTL for DLR at10,20,30,45days were epistatic QTL; but at35and55days were additive QTL5. qSGR7-3for RSDR of GR, qSEGS7-4for TRSDR of EGS and qDLRa7-1for DLR which detected at55days under alkaline located in RM21201-RM5711,on chromosome7; qSGE12-1for RSDR of GE, qSEGS12-2for TRSDR of EGS and qDLRal2-1for DLR which detected at30days under alkaline stress located in RM7558-RM3739,on chromosome12. These QTL which located in the same distance of the same chromosome were likely to be the same QTL, or one gene with multifunction or two QTLs with compact linkage, and then lead to the correlation between salt tolerance and alkaline tolerance in rice.6. Efficient allele could not only from the "Yiai1", which was highly tolerant to salt-alkaline but also from "Lishuinuo", which was sesitive to salt-alkaline. The results indicated that excellent alleles could from any cultivars and never be abandoned for its poor phenotype.