Spontaneous mutation in OsABCI8 caused an albino rice mutant induced by transplanting.

Spontaneous mutations play a key role in plant evolution. In this study, we identified and characterized albino rice mutants in an F₂ population derived from a cross between the japonica elite line Hwaseong and the introgression line CR5029, which carries chromosome segments from Oryza grandiglumis. Among 440 F₂ plants, ten exhibited an albino phenotype after transplantation, which was not observed in the parental lines, suggesting that either novel allelic combinations or spontaneous mutations may be responsible. QTL-seq analysis identified a major locus, qALB11, on chromosome 11, with a 1-bp T deletion in the Os11g0490800 (OsABCI8) gene as the most likely causal mutation. This deletion resulted in a truncated protein lacking the ABC domain, potentially affecting its function. Protein structure modeling confirmed structural differences between the mutant and wild-type proteins. Further genome-wide screening identified 669 spontaneous variants in the progeny population, many of which were associated with repeat sequences. These findings not only elucidate the genetic basis of a conditional albino phenotype but also highlight the broader role of spontaneous mutations and genome instability in plastid development and environmental stress adaptation in rice.