Authors:

Abstract

Carica papaya L. exhibits monoecious and dioecious plants that usually take six months for phenotypic manifestation. Nursery culling aided by sex-specific DNA markers was envisaged to alleviate the unnecessary cost incurred by farmers for maintaining unproductive male plants that contribute to 40-50% of the population. The mechanism of sex determination in papaya has been described as a tri-allelic single gene system with alleles, M₁-dominant for maleness, M₂-dominant for hermaphrodism and m-recessive for femaleness with diploid zygotes; M₁M₁, M₂M₂ and M₁M₂ being inviable. Bulked DNA samples of male, female and hermaphrodite plants were amplified by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) using 100 random primers. Twenty of most promising of these were analyzed among individual sex types. Two sex-specific fragments, OPC09-1.7 and OPE03-0.4 were associated with maleness and hermaphrodism. The segregation of these two markers was analyzed in the F1 population obtained by self-pollinating a hermaphrodite plant. A linkage was detected between the RAPD markers, OPC09-1.7 and OPE03-0.4 and the male and hermaphrodite sex of papaya plants. These sex-specific RAPD fragments were cloned and sequenced for converting them to more authentic SCAR markers. The Southern blot hybridization of RAPD-PCR products obtained by amplification of female, male and hermaphrodite papaya DNA amplified by OPC09 primer using radio labeled recombinant plasmid detected a polymorphic fragment in male and hermaphrodite papaya sex types. The nucleotide sequence of OPC09-1.7 fragment showed the possibility of developing more authentic SCAR markers to enhance the accurate sex determination of Carica papaya at the nursery stage.

Keywords: Carica papaya, papaya, SCAR marker, sex linked polymorphism  

doi:10.4038/jnsfsr.v36i2.146

Journal of the National Science Foundation of Sri Lanka 36 (2) 145-150

Keywords: Carica papaya, papaya, SCAR marker, sex linked polymorphism