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

• Higher doses of irradiation and EMS concentration reduced leaf area, fresh and dry mass and chlorophyll fractions in the developed mutants.
• Increasing doses of irradiation and EMS concentration exhibited linear increase in the RWC% and decrease in MII.
• Leaf proline and antioxidant enzymes were up regulated in the mutants at higher mutagenic doses.
• From R2 value, γ-ray was found to be more efficient over EMS to bring gross changes in plant traits.

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 20 Gy) of gamma rays and EMS (0.05, 0.1, 0.2 and 0.5%). The Survival rate (%) of the mutants were recorded minimum at 20 Gy (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 20 Gy 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 15 Gy 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 20 Gy followed by 15 Gy and 0.5% EMS doses. Mutagenic treatments at 20 and 15 Gy 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.