Abstract:
Rice is one of the major cereals in the world and many African and Asia countries consume rice as a
staple food, including Sri Lanka. However, the existing rice yield is not enough to fulfil the
requirement. Because a considerable amount of yield lost has been reported every season due to the
lodging of the rice plants. Therefore, several breeding programs have been conducted to incorporate
the traits responsible for lodging resistance in rice. Dwarfism in rice is one such characteristic to
develop lodging resistant varieties. Changes in the genetic material of rice are responsible for
dwarfism, including genetic mutations and involvement of plant hormones. Since gibberellic acid
involves different developmental processes in plants, mutations in gibberellic acid biosynthesis and
signalling pathways are considered as the major reasons for dwarfism. This study is based on a white
seeded dwarf rice variety which was found among the progeny of CIC Tikiri. A comprehensive study
was conducted to find the causes of dwarfism based on the involvement of gibberellic acid in
dwarfism. Mutations were identified using a genetic identification process through PCR
amplification, and DNA sequence alignment of selected genes. PCR amplification was done using
OsGA3ox2 and OsSLR1 primers, targeting the genes that produce key components in the gibberellic
acid biosynthesis and signalling pathways; GIBBERELLIN 3BETA-HYDROXYLASE 2 and DELLA
genes, respectively. The amplified regions were aligned, and a base pair comparison was done to
identify the mutations in the respective regions. When compared with the mother plant “CIC Tikiri”
species, certain changes within the sequences have been observed. These changes cause the gain of
different amino acid sequences in DELLA and GIBBERELLIN 3BETA-HYDROXYLASE 2. As a result,
the functions of these proteins are altered. These changes might cause dwarfism in the white seeded
dwarf rice variety. However, phenotypic identification using a hormonal assay needs to verify the
involvement of gibberellic acid in dwarfism of the white dwarf rice variety.