Abstract
Success in inducing genetic variation through mutagenic agents is dependent on the source and dose of application. The objective of this study was to determine the optimum doses of a single and combined use of gamma radiation and ethylmethane sulfonate (EMS) for effective mutation breeding in sorghum. The study involved two concurrent experiments as follows: in experiment I, the seeds of four sorghum genotypes (‘Parbhani Moti’, ‘Parbhani Shakti’, ‘ICSV 15013′, and ‘Macia’) were treated using gamma radiation (0, 300, 400, 500 and 600 Gy), EMS (0, 0.5 and 1.0%), and gamma radiation followed by EMS (0 and 300 Gy and 0.1% EMS; 400 Gy and 0.05% EMS). In experiment II, the seeds of two genotypes (‘Macia’ and ‘Red sorghum’) were treated with seven doses of gamma radiation only (0, 100, 200, 300, 400, 500 and 600 Gy). Overall, the combined applied doses of gamma radiation and EMS are not recommended due to poor seedling emergence and seedling survival rate below LD50. The best dosage of gamma radiation for genotypes Red sorghum, Parbhani Moti, Macia, ICSV 15013 and Parbhani Shakti ranged between 392 and 419 Gy, 311 and 354 Gy, 256 and 355 Gy, 273 and 304 Gy, and 266 and 297 Gy, respectively. The EMS optimum dosage ranges for genotypes Parbhani Shakti, ICSV 15013, Parbhani Moti and Macia were between 0.41% and 0.60%, 0.48% and 0.58%, 0.46% and 0.51%, and 0.36% and 0.45%, respectively. The above dose rates are useful to induce genetic variation in the tested sorghum genotypes for greater mutation events in sorghum breeding programs.
Highlights
Use of climate-smart crop cultivars is a key mitigation strategy against the unpredictable impacts of climate change associated with threats such as drought and heat stress, flooding, soil erosion, and salinization [1]
Significant interaction effects (p < 0.01) were recorded between genotype and gamma radiation dosage on seedling emergence percentage and survival percentage (Table 1). This suggests that the optimum dose of gamma radiation in sorghum mutation breeding is significantly influenced by the genotype
Genotype Macia showed the lowest seedling emergence value of 2.4% at 600 Gamma ray dose (Gy), showing non-significant differences when compared with genotypes ICSV 15013, Parbhani Shakti and Parbhani Moti with values of 5.2%, 4.6% and 4.4%, respectively
Summary
Use of climate-smart crop cultivars is a key mitigation strategy against the unpredictable impacts of climate change associated with threats such as drought and heat stress, flooding, soil erosion, and salinization [1]. Sorghum (Sorghum bicolor [L.] Moench) is one of the key crops adapted to grow under arid and semiarid and harsh conditions where other crops fail to survive under similar environmental conditions This makes sorghum a crop of choice in sub-Saharan Africa (SSA), Asia and similar agro-ecologies. Plants 2020, 9, 827 plant breeders need to broaden the genetic variation of sorghum to develop high-performing cultivars with enhanced grain and biomass yields in SSA. Natural genetic variation is created via spontaneous mutation. Induced genetic variation using physical and chemical mutagens is an alternative method of creating the new genetic variation needed for the breeding of climate-resilient crop cultivars. Physical mutagens such as gamma irradiation result in deletion, translocation and aberrations of chromosomes [4]. Induced mutation increases the proportion of genetic variation multi-fold (1000 to a million times) [10,11,12]
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