Abstract:
Gibberellic acids (GA) are a family of tetracyclic diterpenoid phytohormones, whose regulation of
biosynthesis and signal transduction are crucial for key characteristics in plant growth and
development. Plants that lack these elements exhibit unique phenotypes, including delayed
germination, dwarfism, small and dark green leaves, and retarded root development. Dwarfism, in
particular, is a desirable trait in crop breeding, as it enhances the plant's ability to withstand lodging
damage caused by heavy rain and wind, resulting in increased yields. Rice is a major crop plant
grown worldwide including in Sri Lanka. Similar to all the other plant types, gibberellic acids play a
prominent role in dwarfism in rice. Hence, this research was carried out to study the involvement of
a few genes in GA biosynthesis and signaling pathways on the dwarfism of black seeded dwarf rice
variety. Therefore, this study was conducted to identify and characterize mutations responsible for
the dwarf phenotype of a novel black seeded dwarf rice variety which is a spontaneous breeding
outcome of a locally available rice variety CIC Tikiri. A genetic analysis was performed through DNA
extraction and Polymerase Chain Reaction using two selected molecular markers, OsSLR1 and
OsGA3ox2. They are accountable for amplifying segments of SLR1 and GA3ox2 genes in the rice
genome, which encode for the production of DELLA protein and GIBBERELLIN 3BETA HYDROXYLASE 2, which are critical in the conductance of gibberellic acid signaling and biosynthesis
pathways, respectively. This process was followed by a sequence alignment with the associated
mother plant variety, CIC Tikiri. The results revealed some variations of a few base pairs in the
amplified regions of the genes. The differences that appeared to be nonsense mutations and INDELs
could be concluded as possible causes of dwarfism of the considered mutant rice variety. However,
a phenotypic analysis through a gibberellic acid hormonal treatment assay is recommended to
further clarify the involvement of the identified mutations for the respective phenotype.
