Assessment of efficacy of mutagenesis of gamma-irradiation in plant height and days to maturity through expression analysis in rice

Abstract

Introduction of semi-dwarfism and early maturity in rice cultivars is important to achieve improved plant architecture, lodging resistance and high yield. Gamma rays induced mutations are routinely used to achieve these traits. We report the development of a semi-dwarf, early maturing and high-yielding mutant of rice cultivar ‘Improved White Ponni’, a popular cosmopolitan variety in south India preferred for its superior grain quality traits. Through gamma rays induced mutagenesis, several mutants were developed and subjected to selection up to six generations (M6) until the superior mutants were stabilized. In the M6 generation, significant reduction in days to flowering (up to 11.81% reduction) and plant height (up to 40% reduction) combined with an increase in single plant yield (up to 45.73% increase) was observed in the mutant population. The cooking quality traits viz., linear elongation ratio, breadthwise expansion ratio, gel consistency and gelatinization temperature of the mutants were similar to the parent variety Improved White Ponni. The genetic characterization with SSR markers showed variability between the semi-dwarf-early mutants and the Improved White Ponni. Gibberellin responsiveness study and quantitative real-time PCR showed a faulty gibberellin pathway and epistatic control between the genes such as OsKOL4 and OsBRD2 causing semi-dwarfism in a mutant. These mutants have potential as new rice varieties and can be used as new sources of semi-dwarfism and earliness for improving high grain quality rice varieties.

Characterization and Genetic Analysis of the Selected Rice Mutant Populations

“…Mutation breeding has a unique position in breaking the bottleneck of germplasm resources. Thought to create more beneficial resources than cross-breeding, it confers higher yields in rice (Tiwari et al, 2018;Kato et al, 2020;Andrew-Peter-Leon et al, 2021). Induced mutations are valuable sources of genetic variability (Oladosu et al, 2016).…”

“…Reports stated gamma rays had created mutants tolerant to abiotic stress, such as salinity and drought-tolerant mutants in rice (Song et al, 2012;Joshi et al, 2016;Huang et al, 2019). Further reports said variations in terms of different agronomic traits, such as plant height, tiller number, shoot and root weight, total biomass, and panicle length, occurred due to γ-irradiation (Oladosu et al, 2014;Joshi et al, 2016;Sharifi, 2019;Kato et al, 2020;Andrew-Peter-Leon et al, 2021).…”

Loss of Function of OsFBX267 and OsGA20ox2 in Rice Promotes Early Maturing and Semi-Dwarfism in γ-Irradiated IWP and Genome-Edited Pusa Basmati-1

“…In the earlier study, we identified that WP-22-2 was highly sensitive to gibberellin ( Supplementary Material 4 ) compared with IWP (Andrew-Peter-Leon et al, 2021 ) ( Figure 2 ). Therefore, the effect of the exogenous application of GA 3 (50 μM) was studied through foliar spray on WP-22-2.…”

“…Earlier, we reported the high sensitivity of WP-22-2 to 50 µM gibberellic acid (Andrew-Peter-Leon et al, 2021). This was tested by raising WP-22-2 along with IWP (wild-type) in a completely randomized design and spraying the 10-day-old seedlings with 50 µM of GA 3 .…”

“…The previous study showed that the WP-22-2 mutant is sensitive to gibberellic acid (Andrew-Peter-Leon et al, 2021). Responsiveness to exogenous gibberellin (as measured by the reversal of internode elongation in dwarf mutants) indicates a defective gibberellin pathway in rice (Ashikari et al, 2002), and the famous mutant sd1allele is also sensitive to gibberellin.…”