Genetic and physiological analysis of tolerance to acute iron toxicity in rice

Abstract

BackgroundFe toxicity occurs in lowland rice production due to excess ferrous iron (Fe2+) formation in reduced soils. To contribute to the breeding for tolerance to Fe toxicity in rice, we determined quantitative trait loci (QTL) by screening two different bi-parental mapping populations under iron pulse stresses (1,000 mg L−1 = 17.9 mM Fe2+ for 5 days) in hydroponic solution, followed by experiments with selected lines to determine whether QTLs were associated with iron exclusion (i.e. root based mechanisms), or iron inclusion (i.e. shoot-based mechanisms).ResultsIn an IR29/Pokkali F8 recombinant inbred population, 7 QTLs were detected for leaf bronzing score on chromosome 1, 2, 4, 7 and 12, respectively, individually explaining 9.2-18.7% of the phenotypic variation. Two tolerant recombinant inbred lines carrying putative QTLs were selected for further experiments. Based on Fe uptake into the shoot, the dominant tolerance mechanism of the tolerant line FL510 was determined to be exclusion with its root architecture being conducive to air transport and thus the ability to oxidize Fe2+ in rhizosphere. In line FL483, the iron tolerance was related mainly to shoot-based mechanisms (tolerant inclusion mechanism). In a Nipponbare/Kasalath/Nipponbare backcross inbred population, 3 QTLs were mapped on chromosomes 1, 3 and 8, respectively. These QTLs explained 11.6-18.6% of the total phenotypic variation. The effect of QTLs on chromosome 1 and 3 were confirmed by using chromosome segment substitution lines (SL), carrying Kasalath introgressions in the genetic background on Nipponbare. The Fe uptake in shoots of substitution lines suggests that the effect of the QTL on chromosome 1 was associated with shoot tolerance while the QTL on chromosome 3 was associated with iron exclusion.ConclusionTolerance of certain genotypes were classified into shoot- and root- based mechanisms. Comparing our findings with previously reported QTLs for iron toxicity tolerance, we identified co-localization for some QTLs in both pluse and chronic stresses, especially on chromosome 1.

Genetic Improvement of Iron Toxicity Tolerance in Rice-Progress, Challenges and Prospects in West Africa

“…The expression level of ferritin genes, OsFER1 and OsFER2, were increased in leaves under Fe toxicity conditions (Silveira et al, 2009;Stein et al, 2009). A recent study revealed the presence of seven QTLs and three QTLs for leaf bronzing score in a F8 recombinant inbred population derived from IR 29/Pokkali and a backcross population derived from Nipponbare/Kasalath/Nipponbare, respectively (Wu et al, 2014). The effects of the QTLs on chromosomes 1 and 3 were associated with shoot tolerance and with Fe exclusion, respectively.…”

“…The effects of the QTLs on chromosomes 1 and 3 were associated with shoot tolerance and with Fe exclusion, respectively. The effects of these QTLs on chromosome 1 and 3 were confirmed by using CSSL carrying Kasalath introgressions in the genetic background on Nipponbare (Wu et al, 2014). Dufey et al (2012) have looked at the QTLs associated with yield components under Fe toxic field conditions in particular in West Africa.…”

Markers-traits association for iron toxicity tolerance in selected Indonesian rice varieties

“…121 RILs from IR29/Pokkali -nutrient solution, greenhouse (Wu et al 2014) Location of associated SNPs marker using 18 rice genotypes under hydroponic and field.…”

“…Introducing the traits of tolerant to iron toxicity from those varieties into the high yield popular varieties is the way to improved rice productivity in iron toxicity environment. Several study have been mapped on the rice genome related with traits involved in tolerance to Fe toxicity, under various environmental conditions and using different segregating populations issued from intra-specific populations (Dufey et al 2009(Dufey et al , 2012aShimizu 2009;Shimizu et al 2005;Wan et al 2003a, b;Wu et al 1997Wu et al , 1998Wu et al 2014) or interspecific (Dufey et al 2012b) crosses. These QTLs for traits directly or indirectly linked to iron toxicity tolerance have been localized but challenges of confident genomic localization remain huge, and with several hundred genes involved, their use in breeding programs is difficult.…”

Variability of Ground Water Table and Some Soil Chemical Carahteristic on Tertiary Block of Tidal Lowland Agriculture South Sumatera Indonesia

“…Under well-aerated soils condition , Fe is present as ferric hydroxides with low plant availability, However, in anaerobic soils condition and at low redox potential (Eh), Fe is moved to its soluble form Fe 2+ and can absorb excessively by crop. Iron toxicity occurs in swampy rice production due to excess ferrous iron (Fe 2+ ) formation in reduced soils (Wu et al, 2014). Some rice variety was tolerance till Iron pulse stresses (1,000 mg L −1 = 17.9 mM Fe 2+ .…”