| Ferrous iron toxicity is the main factor limiting the productivity of rice in gleyic paddy soils. Rice genotypes differ widely in resistance to Fe2+ toxicity, which makes it possible to develop rice cultivars with enhanced resistance to Fe 2+ through breeding program .In the present study, we have constructed a linkage map including 101 SSR markers using F2 and F3 from a cross of Longza8503/IR64 as a mapping population and identified QTLs associated with ferrous iron toxicity tolerance using this linkage map. Meanwhile, Mapping quantitative trait loci (QTLs) controlling ferrous iron toxicity tolerance has been carried out among backcross inbred lines, recombinant inbred lines and chromosome segment substitution lines using molecular markers. The results were as follow: 1. Mapping of QTL controlling ferrous iron toxicity tolerance in riceQTL analysis was performed according to the method of interval mapping using MAPMAKER/ QTL 1.1 in BILs and RILs populations.For CSSLs population, statistical analyses were performed on the JMP Version 3.1 software package for Macintosh. Mean values of the parameters measured for the tested genotypes were compared to the appropriate control genotypes using the "Fit Y by X" function and "Compare with control" with an alpha level of 0.05. The minimum number of p < 0.05 significant QTL affecting a trait was calculated on the basis of the following assumptions: l)each IL affecting the trait carries only a single QTL.2)two overlapping introgressions with a significant effect on the trait (in the same direction relative to the control) carry the same QTL.3)a QTL is counted only if the IL or its hybrid is significantly different from the corresponding control, regardless of the significance of a and d . The mean degree of dominance for each trait(d/[a]) was calculated from the mean dominance deviation for all ILs divided by the mean additive effect.1) A mapping population of 96 BC1F9 lines (Backcross Inbred Lines: BILs), derivedby a single-seed descent method from a backcross of Nipponbare/KasalauV/Nipponbare, was used to detect quantitative trait loci (QTLs) for leaf bronzing index (LBI), stem dry weight (SDW), tiller number (TN) and root dry weight (RDW) under Fe2+ stress condition in seedling rice. Two parents and 96 BILs were phenotyped for the traits by growing them in Fe2+ toxicity nutrient solution. A total of eight QTLs were detected on chromosome 1 and 3, respectively, with LOD of QTLs ranging from 3.17 to 7.03. One QTL controlling LBI, SDW, TN and RDW was located at the region of C955-C885 on chromosome 1, which may be important to ferrous iron toxicity tolerance in rice. Comparing with the other mapping results, the QTL located at the region of C955-C885 on chromosome 1 was identical with the results reported previously. In addition, the QTLs for SDW, RDW located at the region of C955-C885 on chromosome 1 and at the region of C25-C515 on chromosome 3 were simultaneously detected under Fe2+ stress in seedling rice, which coincided with the previous reports that the QTLs for SDW and RDW were simultaneously detected under Potassium deficiency stress and Phosphorus deficiency stress in rice.2)A mapping population of 81 Fu lines ( recombinant inbred lines: RILs ), derived from a cross between a japonica variety Kinmaze and an indica variety DV85 by the single-seed descent methods, was used to detect quantitative trait loci ( QTLs ) for leaf bronzing index ( LBI ) and plant height ( PH ) under Fe2+ stress in seedling rice. Two parents and 81 RILs were phenotyped for the traits by growing them in Fe2+ toxicity nutrient solution. A total of three QTLs were detected on chromosome 3 , with LOD ranging from 3.79 to 5.89. Two QTLs controlling LBI was located at the region of XNpb279-C25 and XNpbl44-XNpb362 , and their contributions to total variation were 17.38 % and 22.07 %, respectively. Comparing with the other mapping results, the QTL for LBI located at the region of XNpb279-C25 on chromosome 3 was identical with the QTL for chlorophyll content on a rice f...
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