Self and Cross-incompatibility of <i>Citrus depressa</i> Hayata (Shiikuwasha) and Its Relatives

Abstract

Self-incompatibility and compatibility ofCitrus depressa (Shiikuwasha) and its related species were determined by pollen tube growth within the style. Among the 30 accessions investigated, twelve C. depressa, two C. ryukyuensis (Tanibuta), and three species derived from C. depressa, C. keraji, C. oto, and C. tarogayo, were self-incompatible, while ten C. depressa, one C. tachibana (Tachibana), and two C. tachibana relatives showed self-compatibility. Of the self-incompatible accessions, some cross-incompatible relationships were discovered. All self-incompatible C. depressa except "Ishikunibu" were cross-incompatible with each other. Two C. ryukyuensis were cross-incompatible. This species showed cross-compatibility with C. depressa. C. depressa "Ishikunibu" was cross-compatible with all self-incompatible C. depressa and C. ryukyuensis. From the above, three genotypes determining incompatibility were found in C. depressa and C. ryukyuensis. In addition, all self-incompatible C. depressa and C. ryukyuensis accessions were cross-compatible with selfincompatible C. keraji, C. oto, and C. tarogayo which are related to C. depressa. The present study suggests that S (self-incompatible) alleles of C. depressa and C. ryukyuensis are derivatives of themselves and not from C. maxima (pummelo), major source of citrus S alleles.