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Exploring novel genetic sources of salinity tolerance in rice through molecular and physiological characterization.

ABSTRACT: BACKGROUND AND AIMS:Agricultural productivity is increasingly being affected by the build-up of salinity in soils and water worldwide. The genetic base of salt-tolerant rice donors being used in breeding is relatively narrow and needs broadening to breed varieties with wider adaptation to salt-affected areas. This study evaluated a large set of rice accessions of diverse origins to identify and characterize novel sources of salt tolerance. METHODS:Diversity analysis was performed on 107 germplasm accessions using a genome-wide set of 376 single-nucleotide polymorphism (SNP) markers, along with characterization of allelic diversity at the major quantitative trait locus Saltol Sixty-nine accessions were further evaluated for physiological traits likely associated with responses to salt stress during the seedling stage. KEY RESULTS:Three major clusters corresponding to the indica, aus and aromatic subgroups were identified. The largest group was indica, with the salt-tolerant Pokkali accessions in one sub-cluster, while a set of Bangladeshi landraces, including Akundi, Ashfal, Capsule, Chikirampatnai and Kutipatnai, were in a different sub-cluster. A distinct aus group close to indica contained the salt-tolerant landrace Kalarata, while a separate aromatic group closer to japonica rice contained a number of traditional, but salt-sensitive Bangladeshi landraces. These accessions have different alleles at the Saltol locus. Seven landraces - Akundi, Ashfal, Capsule, Chikirampatnai, Jatai Balam, Kalarata and Kutipatnai - accumulated less Na and relatively more K, maintaining a lower Na/K ratio in leaves. They effectively limit sodium transport to the shoot. CONCLUSIONS:New salt-tolerant landraces were identified that are genetically and physiologically distinct from known donors. These landraces can be used to develop better salt-tolerant varieties and could provide new sources of quantitative trait loci/alleles for salt tolerance for use in molecular breeding. The diversity observed within this set and in other donors suggests multiple mechanisms that can be combined for higher salt tolerance.

SUBMITTER: Rahman MA

PROVIDER: S-EPMC4866315 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Exploring novel genetic sources of salinity tolerance in rice through molecular and physiological characterization.

Rahman M Akhlasur MA Thomson Michael J MJ Shah-E-Alam M M de Ocampo Marjorie M Egdane James J Ismail Abdelbagi M AM

Annals of botany 20160410 6

<h4>Background and aims</h4>Agricultural productivity is increasingly being affected by the build-up of salinity in soils and water worldwide. The genetic base of salt-tolerant rice donors being used in breeding is relatively narrow and needs broadening to breed varieties with wider adaptation to salt-affected areas. This study evaluated a large set of rice accessions of diverse origins to identify and characterize novel sources of salt tolerance.<h4>Methods</h4>Diversity analysis was performed ...[more]

PMID: 27063367

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Project description:BackgroundFe toxicity occurs in lowland rice production due to excess ferrous iron (Fe(2+)) 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 Fe(2+) 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 Fe(2+) 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.

Project description:Salinity is one of the most severe abiotic stress in the world. Also, the irrigated lands have been treated with second salinity. Canola is one of the most important industrial crops for oil production all over the world which is affected by salinity. Salt stress causes imbalanced ion hemostasis (Na+ and K+) and interrupted mineral absorption in canola. Also, salinity stress leads to oxidative stress (production and accumulation of reactive oxygen species (ROS). Accumulation of ROS is extremely dangerous and lethal for plants. As a consequence, canola production is reduced under salinity stress. So, a suitable approach should be found to deal with salinity stress and prevent the loss of production oilseed. Plant growth-promoting rhizobacteria (PGPR) can colonize on the plant root surface and alleviate the salt stress effect by providing minerals like nitrogen, phosphate, and potassium. Also, they alleviate salt stress by phytohormones like auxin (IAA), cytokinin (CK), and abscisic acid (ABA). This study focus on physiological parameters like leaf area (LA), root length (RL), shoot length (SL), chlorophyll fluorescence indexes (Fv/Fm and Fv/F0), relative water content (RWC), electrolyte leakage index (ELI), photosynthesis pigments (chlorophyll a, b, and carotenoids), Na+, and K+; and biochemical parameters like malondialdehyde (MDA) content, hydrogen peroxide content (H2O2), total protein content, proline, antioxidant capacity, and antioxidant enzyme activities in canola through the inoculation with Enterobacter sp. S16-3 and Pseudomonas sp. C16-2O. This study showed that LA, RL, SL, chlorophyll fluorescence indexes, RWC were significantly increased and ELI was significantly decreased in bacteria inoculated treatments. Also, MDA, H2O2 were decreased, and antioxidant capacity, proline, and antioxidant enzymes were increased due to inoculation with these bacteria. Besides, the amount of K+ as an index of salinity tolerance significantly increased, and leaf Na+ content was significantly decreased.

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Exploring novel genetic sources of salinity tolerance in rice through molecular and physiological characterization.

Publications

Exploring novel genetic sources of salinity tolerance in rice through molecular and physiological characterization.

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