Molecular mapping of Quantitative Trait Loci (QTL) for heat tolerance of rice (Oryza sativa L.) during reproductive stage using microsatellite markers

Date

10-2008

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Rita P. Laude

Abstract

MOJICA, CHROMEWELL AGUSTIN ROSALES. 2008. Molecular Mapping of Quantitative Trait Loci (QTL) for Heat Tolerance in Rice (Oryza saliva L.) During Reproductive Stage Using Microsatellite Markers. University of the Philippines Los Banos. B.S. Biology Major in Cell and Molecular Biology.

Adviser: Dr. Rita P. Laude (UPLB)

Co-adviser: Dr. Edilberto D. Redoña (IRRI)

ABSTRACT

Microsatellite markers were utilized to identify possible locations of genes for heat tolerance of rice during the reproductive stage. One hundred fifty-six potential heat tolerance donors were first screened for pollen sterility in an experimental farm recommended for heat tolerance screening (after evaluation of the weather data from 2003 to 2006) during the dry season of 2007. N22, a known heat-tolerant variety was considered as control. Of the 156 rice accessions, 21 were re-examined for pollen sterility under chamber conditions (38 °C for 10 hours) during their reproductive stage having Kharsa Ratia as the tolerant check. Pollen sterility was correlated with spikelet sterility using the data gathered by INGER. A correlation coefficient of 0.43 was obtained implying a positive linear relationship between the traits. The mapping populations were then generated by crossing the heat-sensitive IR64 by N22, and selfing the F1 progeny. Phenotyping of the F2 intercross individuals exposed under chamber condition was done through pollen sterility evaluation. Only five individuals manifested tolerance and the heat-tolerant parent N22 gave a high pollen sterility value of 93%. A total of 73 of the 180 microsatellite markers covering the 12 chromosomes used for the polymorphism survey were employed in genotyping the F2 population. Through bulk segregant analysis, the DNA samples of the most tolerant and most sensitive individuals were pooled and allelic bands were scored using polyacrylamide gel electrophoresis. MapManager/QTX, QTL Cartographer 2.5 and GGT 32 2.0 were used to create linkage and graphical genotype maps. Eight chromosomes revealed potential locations of heat tolerance genes-chromosomes 2, 4, 5, 6, 8, 9, 10 and 12. In chromosome 2, the regions flanked by RM262, RM475 and RM482 may contain heat tolerance QTL. Regions on the side of RM273 (chromosome 4), RM178 (chromosome 5), RM400 (chromosome 6), RM433 (chromosome 8), RM205 (chromosome 9), RM474, RM222 and RM269 (chromosome 10), and RM235 (chromosome 12) also suggested possible heat tolerance QTL. Evaluating LOD scores, genotyping of the whole mapping population. fine-mapping of the regions identified by the graphical genotype maps and improved screening methods may facilitate better identification of QTL for heat tolerance.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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