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Single Nucleotide Polymorphisms in a Gene for Translation Initiation Factor (eIF4G) of Rice (Oryza sativa) Associated with Resistance to Rice tungro spherical virus

¹Department of Functional Crop Science, National Institute of Crop Sciences, Rural Development Administration, 1085 Neidong, Milyang, Gyeongnam, 627-803, Republic of Korea; ²Plant Breeding, Genetics, and Biotechnology Division, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines; ³Plant Genome Research Unit, Division of Genome and Biodiversity Research, National Institute of Agrobiological Sciences, Kan'non dai 2-1-2 Tsukuba, Ibaraki 305-8602, Japan; ⁴Research Team for Vector-borne Plant Pathogens, National Agricultural Research Center, Tsukuba, Ibaraki 305-8666, Japan.

Rice tungro disease (RTD) is a serious constraint to rice production in South and Southeast Asia. RTD is caused by Rice tungro spherical virus (RTSV) and Rice tungro bacilliform virus. Rice cv. Utri Merah is resistant to RTSV. To identify the gene or genes involved in RTSV resistance, the association of genotypic and phenotypic variations for RTSV resistance was examined in backcross populations derived from Utri Merah and rice germplasm with known RTSV resistance. Genetic analysis revealed that resistance to RTSV in Utri Merah was controlled by a single recessive gene (tsv1) mapped within an approximately 200-kb region between 22.05 and 22.25 Mb of chromosome 7. A gene for putative translation initiation factor 4G (eIF4G^tsv1) was found in the tsv1 region. Comparison of eIF4G^tsv1 gene sequences among susceptible and resistant plants suggested the association of RTSV resistance with one of the single nucleotide polymorphism (SNP) sites found in exon 9 of the gene. Examination of the SNP site in the eIF4G^tsv1 gene among various rice plants resistant and susceptible to RTSV corroborated the association of SNP or deletions in codons for Val^1060-1061 of the predicted eIF4G^tsv1 with RTSV resistance in rice.