关键词: 水稻 , 白化转绿 , 叶绿体 , 叶绿素 , V

Abstract: 【Objective】 On the basis of phenotypic and physiological characteristics of a green-revertible albino mutant gra75, the mutant gene was finely mapped. 【Method】A green-revertible albino mutant was isolated from ethyl methanesulfonate mutagenesis. Phenotypes of the mutant were observed, and its physiological characteristics and main agronomic traits were analyzed. Genetic mapping of the mutant gene was conducted by using molecular marker and F2 mapping population of gra75/Zhefu 802 to identify this candidate gene. 【Result】 Under paddy ?eld conditions, gra75 mutant plants exhibited a normal green phenotype up to the third-leaf stage. Subsequently, it produce albino phenotype during the fourth to seventh leaf stage, but then it developed nearly normal green leaves from the eighth-leaf stage. At the mature stage, the gra75 mutant and its wild-type had no significant difference in major agronomic traits. On the other hand, chlorophyll and carotenoid content in albino leaves of the mutant obviously decreased at seedling stage. Electron microscopic observation revealed that the number of chloroplasts, thylakoid membranes, granums and starch granules significantly decreased in mesophyll cells of the albino leaves. Genetic analysis suggested that the mutant phenotype of gra75 was controlled by one recessive nuclear gene. The gra75 mutant gene was mapped between InDel markers HC1 and HC2 on the short arm of rice chromosome 6, with genetic distances of 0.06 cM and 0.6 cM, respectively, and with a physical interval of 120 kb. By analyzing and sequencing the candidate genes in this genomic region, it was found that there was a single nucleotide change (C716T) in exon 5 of LOC_Os06g07210 gene encoding RNRL1 (ribonucleotide reductase large subunit) in the gra75 mutant, which caused a missense mutation (Ala to Val) in the encoded product.【Conclusion】The gra75 mutant gene was allelic to V3 (Virescent3) gene. However, the green-revertible albino character of gra75 mutant could express steadily at seedling stage, and moreover, this albino phenotype did not affect significantly main agronomic traits at the mature stage. So the mutant gene of gra75 could be applicable in hybrid rice breeding as a leaf color marker gene.

Key words: rice , green-revertible albino , chloroplast , chlorophyll , V3 mutant