The Effect of Rice Chromosome 1 on Traits Associated with Drought and Salinity Tolerance at Germination and Seedling Stages

In this research, the chromosome 1 of rice was studied to identify QTLs controlling traits associated with drought and salinity tolerance at germination and seedling stages using F2:4 population derived from a cross between two cultivars, Gharib (tolerant to drought and salinity) and Sepidroud (sensitive to drought and salinity). Two hundred and thirty six polymorph markers (105 AFLPs and 131 SSRs) were used to construct genetic map of the rice chromosome 1. Thirteen SSR and seven AFLP markers with length of 216.1 cM were mapped on chromosome 1 and average distance between adjacent markers was 10.8 cM. In total, 17 QTLs controlling germination rate, germination percentage, radicle length, plumule length, coleoptile length and drought and salinity tolerance indices at germination stage under four different conditions (drought stress induced by PEG and sorbitol, salinity stress induced by NaCl and non-stress conditions) and four QTLs controlling shoot potassium concentration, root/shoot length ratio, root dry weight and standard tolerance ranking at seedling stage under salinity stress induced by NaCl were identified on chromosome 1 using composite interval mapping. Seven major QTLs associated with drought and salinity tolerance were mapped in adjacent of RM212 and RM1287 markers at two growth stages. The major QTLs qGR-1 and qSV-1 were detected under both stress and non-stress conditions showing the stability of these QTLs under diverse environmental conditions. Furthermore, the same locations of the QTLs qSKC-1 and qRL/SL at seedling stage with the QTLs of germination related traits showed the same genetic control of these traits at both germination and seedling stages, associated with drought and salinity tolerance controls by the same genomic regions. Also, the location of the QTLs associated with salinity tolerance were very near to the QTLs associated with drought tolerance which indicated that drought and salinity tolerance in rice controls by pleiotropic or tight linked genes. It seems that the rice breeding for one of these stresses can be successful to the other stress.