Dissecting the all-hermaphrodite phenomenon of a rare X chromosome mutant in papaya (Carica papaya L.)

Abstract

Sex form is one of the most important characters in papaya cultivation in which hermaphrodite is preferable sex form. However, sex determination is impossible until flowering. This study has developed SCAR markers derived from the SVP-like gene and can truly discriminate the three sex forms: female, male, and hermaphrodite papaya. Molecular markers were applied to study the mechanisms responsible for the all-hermaphrodite phenomenon in the self-pollinated progeny of “H*-TSS No.7,” an inbred line derived from a rare X chromosome mutant SR*. This study has provided evidence to support that “H*-TSS No.7” contained a recessive lethal allele, ml, on the X chromosome, and the X*X* homozygous genotype (ml/ml) was detected only in seeds but not in seedlings. Consequently, lost germination ability rather than seed abortion was responsible for missing female progeny in the selfed “H*-TSS No.7” population. The lethal effect in genotypes of YY, YYh, and YhYh papaya could be explained by at least one functional X chromosome being necessary for seed development. This study has demonstrated that “H*-TSS No.7” with a lethal allele (ml) on its X* chromosome is the cause of the defect of germinating ability in its homozygous female progeny.