Identification Of QTL For Rice (Oryza Sativa L) Tolerance To Aluminum,Ferrous Iron And Cadmium Toxicity At Seedling Related Traits Using A Japonica Cv.02428/Changhui 891 BRILs Population

Rice(Oryza sativa L)is most important and staple food crop.Rice production has severe challenges owing to different abiotic stresses which significantly reduce the rice yield and quality.With japonica rice(cv.02428)and indica rice(Changhui 891)as parents,122 rice BRILs populations were cultivated and evaluated under hydroponic conditions to study the effects of Al,ferrous Fe,Cd toxicity on the seedling stage of BRILs populations and to identify the QTL controlling Al,Fe and Cd tolerance.A total of 3075 highly stable SNP markers were used for construction of bin map.A high-density Bin map constructed with high-quality SNPs was used to map QTL for Al tolerance,ferrous toxicity,and cadmium stress.The core results of the experiments are presented below.(1)Regarding Al toxicity tolerance experiment for estimation of Al tolerance in rice population,relative root length(RRL)was used as standard criteria.Current study identified 23 QTL for six seedling parameters.Regarding RL,three QTL,q CRL-6,q SRL-6,and q RRL-6 were found in three environments and they are stable and common QTL.The QTL,q RRL-6 showed higher estimates of heritability(H~2=96.59%)is new major QTL securing positive value of additive effect.Beside this other seedling traits like,SL,SFW,RFW,SDW and RDW were also used as tolerance index and,q SSL-11,q RRFW-1,and q RRDW-1 and q RRDW-8 were identified for these traits and these are newly reported QTL.In this study we have identified three QTL,q RRFW-1,q RSDW-1,and q RRDW-1 which are pleiotropic QTL and these QTL would assist to increase Al tolerance by MAS selection and QTL pyramiding.All of the identified QTL for Al tolerance across all experimental conditions revealed that these QTL are accountable for enhancing Al tolerance in population.Through use of markers assisted selection and QTL pyramiding these QTL can be transferred into elite cultivars for development of abiotic tolerant cultivars.The seedling stage is an ideal stage to investigate Al tolerance in population therefore the assessment of tolerance would lead to screening of potent lines which can used to carry out further investigation.(2)As a whole total of 23 QTL were identified for various seedling traits,3 under control with phenotypic difference ranging from 14.36%to 62.46%,11 QTL under stress with phenotypic difference ranging from 7.89%to 47.39%and 9 under stressed/control ratio with phenotypic variance ranging from 9.17%to 183.50%.LOD values of QTL ranging from 4.05 to 17.04 in control,2.64 to 11.46 in stress and 2.61 to 131.63 in stress/control ratio.SL,RL,SFW,RFW,SDW,and RDW were used to estimate the degree of Fe tolerance.Many stable QTL,q SSDW-4,q SSDW-6,q RSDW-4 and q RSDW-6affecting SDW were detected and beside this some new QTL,q RSFW-1,q RRFW-10 and q RRDW-1 were successfully identified significantly contributing to ferrous Fe toxicity tolerance in rice.These findings showed that the QTL can be transferred to develop Fe resilient rice cultivars by using marker assisted selection approach.All of the identified QTL for Fe tolerance across all experimental conditions revealed that these QTL are accountable for enhancing Fe tolerance in population.Through use of markers assisted selection and QTL pyramiding these QTL can be transferred into elite cultivars for development of abiotic tolerant cultivars.The seedling stage is an ideal stage to investigate ferrous Fe tolerance in population therefore the assessment of tolerance would lead to screening of potent lines which can used to carry out further investigation.(3)Current study identified 5 major QTL under various experimental conditions.Of them one QTL,q CRL-1 was mapped at chromosome 1 under control with LOD value2.91 and 10.67%of variance was contributed by this QTL.Two major QTL,q SRL-11and q SRDW-3 were mapped on chromosome 11 and 3 under Cd stress with LOD value of 2.53-2.59 and phenotypic variance 9.45%to 9.76.Under Cd stress/control ratio two QTL,q RRFW-1 and q RSDW-4 were identified on chromosomes 1 and 4.LOD value of2.82 and 2.74 and phenotypic variance of 0.81%to 9.85%was shown by these QTL.A total of six seedling trait SL,RL,SFW,RFW,SDW and RDW and their ratio were selected to determine Cd toxicity tolerance.Results of current study indicated that q SRL-11,q RRFW-1,q RSDW-4 and q SRDW-3 are major new QTL of seedling variables under condition of Cd stress in BRILs seedling which are beneficial for selection of breeding superior rice using QTL pyramiding.BRILs population would be more beneficial to identify the QTL for Cd tolerance.These results provide a ray of hope for future studies to identify the QTL and improve Cd tolerance.All of the identified QTL for Cd tolerance across all experimental conditions revealed that these QTL are accountable for enhancing Cd tolerance in population.Through use of markers assisted selection and QTL pyramiding these QTL can be transferred into elite cultivars for development of abiotic tolerant cultivars.The seedling stage is an ideal stage to investigate Cd tolerance in population therefore the assessment of tolerance would lead to screening of potent lines which can used to carry out further investigation.