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Mapping of quantitative trait loci associated to Fe stress tolerance in the rice seedling
Thesis Abstract:
Rice (Oryza saliva L.) demand is on the rise worldwide due to population growth, which has forced several countries to increase their production. Excessive iron (Fe) as abiotic stress, which often occurs in several countries, proved to be one of the obstacles in rice production. Screening for varieties tolerant to Fe toxicity would be critical for breeders to identify the varieties with the most desirable performance as donor parents in the breeding program, and for a researcher to develop molecular markers used in the selection process. The first step that needs to be done is to look for the chromosomal region related to Fe toxicity defense mechanism. To search for this region, QTL analysis was carried out. In this experiment, 104 RILs derived from IR64 and Nipponbare were treated with 400ppm Fe2SO4.7H2O for 11 days. Phenotyping was conducted by using two evaluating systems to inspect the leaf bronzing level. The first method is to analyze the Red (R) and Green (G) color channels of the scanned leaf images using Adobe Photoshop CS3, the other is to visually assign bronzing score according to the scale described in Shimizu A. (2009). These two independent phenotyping results were combined with 41,256 SNP markers for QTL analysis. The result from single marker analysis showed a peak marker at 8.98Mb on chromosome 8 and two peak markers at 1.06 Mb on chromosome 1 and 6.01Mb on chromosome 3 for R/G index and leaf bronzing score, respectively. Gene function annotation indicates that two genes in these regions are linked to Fe tolerance through ROS scavenging and two genes are linked to Fe transport.