Determination of Median Lethal Dose and Effects of Gamma Radiation on Seed Germination in Viola cornuta L.

Effects of cobalt-60 gamma irradiation on seed germination and seedling survival of 7 cultivars of Viola cornuta L. were investigated. The results revealed that low doses of gamma radiation at 100 Gray (Gy) significantly stimulated germination in ‘Deep Blue Blotch’ and ‘Clear Purple’ and slightly enhanced germination in ‘Clear Yellow’ and ‘Victoriana’. In contrast, higher doses (> 400 Gy) significantly decreased germination across all cultivars. No germination was observed at 1,000 Gy in the ‘Deep Blue Blotch’ cultivar. Analysis of mean germination time (MGT) and coefficient of velocity of germination (CVG) showed delays in germination and decreased germination velocity with increasing irradiation dose. The seedling survival percentage also decreased with higher radiation doses, indicating sublethal effects on seedling establishment. The lethal dose for 50 % mortality (LD50) values ranged from 320 to 495 Gy for the Bel Viso series and from 430 to 640 Gy for the Grandissimo series. Our findings highlight the dose-dependent effects of gamma irradiation on seed germination and seedling survival and provide insights into irradiation tolerance and susceptibility among cultivars. Understanding these responses is crucial for optimizing irradiation-induced mutagenesis strategies and developing plant selection plans for crop improvement. HIGHLIGHTS Low cobalt-60 gamma radiation doses at 100 Gray (Gy) stimulated seed germination in Viola for ‘Victoriana’, ‘Deep Blue Blotch’, ‘Clear Yellow’ and ‘Clear Purple’ cultivars whereas higher doses (> 400 Gy) decreased germination across all 7 cultivars. Mean germination time (MGT) increases and coefficient of velocity of germination (CVG) decreases with higher gamma radiation doses, indicating delayed and slower germination. Seedling survival percentages decline significantly with increasing radiation dose, highlighting sublethal effects on seedling development. GRAPHICAL ABSTRACT