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Mapping Qtls for Salinity Tolerance of Horkuch at Seedling Stage

Md. Sazzadur Rahman
Senior Scientific Officer (SSO)
Plant Physiology Division, Bangladesh Rice Research Institute (BRRI)

Sabrina M. Elias
Ph.D. student
Deapartment of Biochemistry and Molecular Biology, University of Dhaka

Sumaiya F. Khan
Ph.D. student
Deapartment of Biochemistry and Molecular Biology, University of Dhaka

Taslima Haque
Research Associate
Deapartment of Biochemistry and Molecular Biology, University of Dhaka

Samsad Razzaque
Research Associate
Deapartment of Biochemistry and Molecular Biology, University of Dhaka

Rumena Yasmeen
Chief Scientific Officer (additional charge)
Plant Physiology Division, Bangladesh Rice Research Institute (BRRI)

Abstract/ Executive Summary:

The concentration of Na⁺ and K⁺ was found significantly higher for the tolerant parent Horkuch than IR29 but the ratio of K⁺/Na⁺ was significantly higher for Horkuch. These give the clues of possible physiological mechanisms governing the tolerances of Horkuch. Here, two physiological mechanisms could be hypothesized for the tolerances of Horkuch i.e. (i) tissue tolerance (Horkuch maintained higher Na⁺ concentration) and (ii) better K⁺ absorption/uptake (higher K⁺ improves the healthy K⁺/Na⁺ratio). For comparing populations, most of the trait showed transgressive segregation. ICIM method identified a total of 24 putative QTLs for 5 traits i.e. K⁺/Na⁺ ratio, chlorophyll a/b ratio, root relative water content, root length and root dry weight. But the QTLs identified for the 5 traits were not directly linked to the tolerance of Horkuch. But for the important trait ‘K⁺/Na⁺ ratio’, ICIM method identified only 4 QTLs in chr.8, 11 and 12. The LOD and R-square values of the identified QTLs ranging from 3.01-7.44 and 18.30%-30.62% respectively, which are indicative of major QTLs for salinity tolerance at seedling stage.

Keywords: Salinity tolerance, QTL, Na+/K+ ratio, LOD

Location: Plant Physiology Division, BRRI and Department of Biochemistry and Molecular Biology, University of Dhaka

Start Date: 00-05-2013

End Date: 00-08-2013

Program Area: Variety and Species

Commodity: Rice

Objectives:

To find out the physiological mechanisms contributing tolerance of Horkuch at seedling stage.
To map QTLs for salinity tolerance of Horkuch at seedling stage.

Methodology:

For developing mapping populations hybridization was made between Horkuch (IRGC 31804) and IR29 (IRGC 30412) at IRRI in 2011, the cross registration number is IR102583 (Horkuch/IR29). F₁’swere confirmed by a well-known and robust SSR marker RM493. Confirmed F₁’s were advanced to F₂ in the field of Plant Physiology Division of BRRI in 2012. F₂ progenies were again advanced to F₃ in the field at Plant Physiology Division of BRRI during 2012-2013. Leaf samples from 100 F₂ progenies were collected and DNA was isolated through CTAB-method (Doyle and Doyle, 1990). Forty-nine well polymorphic SSR markers were used for genotyping of 100 F₂ populations through standard protocol for SSR in PAGE system at Plant Biotechnology Laboratory of the Department of Biochemistry and Molecular Biology, University of Dhaka. The coverage of 49 markers was about 957.92 cM with an average genetic distances between markers are 19.55 cM with the range of 10.64 to 29.54 cM. Penotyping of 100 F₃ progenies for seedling stage salinity was carried out according to the IRRI standard protocol described by Gregorio et.al 1997 in the Plant Physiology Net House of BRRI, Gazipur during May to August 2013. Phenotypic traits such as SES score, Na⁺& K⁺ concentration and ratios, relative water content of shoots & roots, chlorophyll a & b content and ratios of leaves, stomatal conductance, seedling height and root length, dry mass of shoot and root were recorded and computed for judging seedling stage tolerance. All recorded phenotypic data were analyzed for summary statistics and correlations through Breeding View 1.1 (GCP) and JMP 10 (SAS Inc.) software, respectively. Linkage analysis and QTL mapping were done through ICIMapping v 4.0 software (http://www.isbreeding.net). Inclusive Composite Interval Mapping method was used to map QTLs. Significant QTL was declared when LOD value exceed the threshold LOD 3.0.

Source of Information: Proceedings of the BRRI Annual Internal Review for 2013-2014

Article Link (Online Journal):

Funding Source:

1.	Budget:
2.	Budget:
3.	Budget:
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Total Budget (Tk.) :

Achievement/Findings:

Phenotypic data of parents and populations revealed the donor Horkuch could possesses physiological mechanisms ‘tissue tolerance’ and ‘higher absorption of K⁺’. Four QTLs in chr. 8, chr. 11 and chr. 12 for the trait K⁺/Na⁺ ratio could be the potential genomic regions contributing tolerances of Horkuch at seedling stage. Further characterization of these genomic regions and narrowing down the interval of respective QTLs would involve identification of more polymorphic markers facilitating to use in marker-assisted introgression for the development of high-yielding salinity tolerant variety.

Knowledge Management: Report/Proceedings