| A solution culture experiment was conducted to study the effects of K+ on plant height, root length, fresh weight of shoot or root, leaf bronzing index and chlorophyll content of three rice genotypes, Asominori (Fe2+ tolerant genotype), IR24 (sensitive genotype) and Line22 of CSSL under 250 mg · L-1Fe2+ stress. The results showed that the growth of rice shoot and root was inhibited by Fe + stress compared to control. After 250 mg ? L"1 Fe2+ treatment, the chlorophyll content was decreased and leaf bronzing index (LBI) could be observed clearly. Along with the concentration of K+ treated, the inhibition of the growth of rice shoot and root by Fe2+ stress was decreased, the chlorophyll content in the leaves increased, and leaf bronzing index reduced in three rice genotypes. The amelioration of K+ was more pronounced on the sensitive genotype (IR24, Line22) than that on tolerant genotype (Asominori), which indicates the different genotype existed in the amelioration of K+ on Fe2+ stress. It suggested that K+ could play an important role in increasing rice resistance to excessive Fe2+ stress.Recently, more and more evidences indicated that NO also play important roles in plants, and involve as a stress signal in adaptive response and mediating growth regulation. However, the function of NO on plant root growth processes under Fe2+ stress is still unclear.In this study, a solution culture experiment was conducted to study the effects of NO on plant height, maximum root elongation, shoot fresh weight and root fresh weight of two genotypes, Asominori (Fe2+ tolerant genotype), IR24 (sensitive genotype) under 250 mg · L-1 Fe2+ stress. The results showed that the growth of rice shoot and root was inhibited by Fe2+ stress compared to control. Along with the concentration of NO treated, the inhibition of the growth of rice shoots and root by Fe2+ stress was decreased. It suggested that NO could play an important role in increasing rice resistance to excessive Fe2+ stress.There were widely different among rice genotypes in resistance to Fe2+ toxicity, which made it possible to develop rice cultivars with enhanced resistance to Fe2+ through breeding program.In this study, quantitative trait loci (QTLs) controlling ferrous iron toxicity tolerance had been carried out using chromosome segment substitution lines (CSSLs). We have constructed a linkage map including 5 SSR markers (on chromosome 11) using F2 from a cross of Line57/IR24 as a mapping population and identified QTLs associated with ferrous iron toxicity tolerance. The results were as follows:1. Mapping of QTL controlling ferrous iron toxicity tolerance in CSSLsA mapping population of 66 japonica chromosome segment substitution lines (CSSLs ) in indica genetic background, derived from a cross between a japonica variety Asominori and an indica varietyIR24 by the single-seed descent, backcrossing and marker-assisted selection, was used to detect quantitative trait loci (QTLs) for leaf bronzing index (LBI), root dry weight (RDW), plant height (PH), maximum root length (MRL) and chlorophyll content under Fe2+ stress in seedling rice. A total of 12 QTLs were detected on chromosome 3, 6, 7, 9, 10,11 and 12. Four QTLs for LBI was located at the region of C515, R2638-C1263, X37-R1877 and X257-C950 on chromosome 3, 9, 10 and 11. Comparing with the other mapping results, the QTL for LBI located near to C515 on chromosome 3 was identical with the QTL for chlorophyll content on a rice function map.2. Mapping of QTL controlling ferrous iron toxicity tolerance in F2 population from Line57/IR24QTL analysis was performed according to the method of interval mapping using MAPMAKER/ QTL 3.0 in F2 population. A QTL for leaf bronzing index was detected at the region of RM2110-RM3605 on chromosome 11 (LOD=6.48). The detected single QTL could explain 29.4% of variation in LBI in F2 population. Comparison of QTLs in different populations showed that the different populations shared few common QTLs, reflecting multigenic control of ferrous iron toxicity tolerance. |
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