Physiological and biochemical changes in pre-bearing mutants of Kinnow mandarin (C. nobilis Lour × C. deliciosa Tenora)

Abstract

Impact of gamma (γ) irradiation and ethyl methanesulfonate (EMS) on leaf physio-biochemical parameters were studied in pre-bearing induced mutants of Kinnow mandarin budded on uniform Jatti Khatti rootstock. The mutants were developed by treating Kinnow bud sticks with different doses (5, 10, 15 and 20Gy) of gamma rays and EMS (0.05, 0.1, 0.2 and 0.5%). The Survival rate (%) of the mutants were recorded minimum at 20Gy (60%) and 0.5% EMS concentration (70.0%). The surviving mutants 24-month-old for each mutagenic dose were assessed for different parameters. Mutagenic treatments significantly reduced the leaf area in the surviving mutants at 20Gy and 0.5% EMS treatments. The mutants at these doses, however maintained high relative water content (RWC) with lower leaf membrane injury. Maximum chlorophyll breakdown in the mutants were observed due to 20 and 15Gy doses. The induced biochemical changes revealed enhanced proline accumulation in the leaves at 0.2% EMS followed by 0.5% EMS treatment, while elevated phenol contents were recorded in the mutants at 20Gy followed by 15Gy and 0.5% EMS doses. Mutagenic treatments at 20 and 15Gy upregulated superoxide dismutase, catalase and peroxidase enzyme activities. The study highlights that both physical and chemical mutagens at higher doses have the potential to generate much needed variation in ‘Kinnow’ mandarin with respect to physio-biochemical traits including antioxidant enzyme and should thus help in evolving desired mutants for economic traits including seedlessness and subsequent use in future breeding programmes.