GENOMIC STUDIES AND IDENTIFICATION OF SEX AT SEEDLING STAGE IN SOME DIOECIOUS PLANTS THROUGH PCR BASED DNA MARKERS

RAVIKUMAR C BARATAKKE
Department of Botany, KARNATAK UNIVERSITY, DHARWAD
November, 2011
 

Abstract
In dioecious plants sex identification is challenging task for the plant breeder. As
the sex of the plant cannot be identified in many dioecious plants at pre-flowering
stage, because of absence of morphological markers. In the absence of morphological
markers, molecular markers like RAPD (Random Amplified Polymorphic DNA),
SCAR (Sequence Characterized Amplified Region) play an important role for sex
identification at pre-flowering stage. Therefore development of an ideal tool to
identify the sex at seedling stage is worth exploring.
Two dioecious plants namely Momordica dioica Roxb. (Cucurbitaceae) and
Simarouba glauca DC. (Simaroubaceae) were studied during my Ph.D. work as both
the taxa have sex specific economic value. The main objectives of my Ph.D work are;
to assess the existence of heteromorphic chromosomes in these two taxa, development
of sex linked RAPD marker, Sex specific SCAR marker in both the taxa and probable
role of these markers in sex determination.
Present investigation revealed that both taxa exhibited homomorphic
chromosomes, which reveals that, in these two plants sex cannot be identified based
on karyomorphological analysis. In S. glauca chromosome number was found to be
2n=30 in both male and female accessions. Present study was the first report of
chromosome number in S. glauca. In M. dioica RAPD marker OPA-151500 was
developed to identify male sex at pre-flowering stage. Based on RAPD analysis,
further SCAR marker named as SCAR-SDSM was developed to identify male sex at
pre-flowering stage. It was submitted to GenBank (Accession number: GQ980260).
Similarly in S. glauca RAPD marker OPA-181100 was developed to identify male sex
at pre-flowering stage. Based on RAPD analysis, further SCAR marker named as
SCAR-MSSMS was developed to identify male sex at pre-flowering stage. It was
submitted to GenBank (Accession number: HM240852). Both SCAR-SDSM and
SCAR-MSSMS genomic sequences exhibit homology with these two repetitive
sequences RAYSI and RAE180 of Rumex acetosa. Existence of repetitive sequences is
the key information as it helps for designing probes for identification of sex
chromosomes in both M. dioica and S. gluaca as both taxa exhibit homomorphic
chromosomes.