Studies on mutation breeding in citrus: Improving seedless types of ‘Kozan’ common orange by gamma irradiation

Abstract

Abstract This study reports an induced physical mutation by gamma irradiation on a local sweet orange variety in order to develop new seedless varieties. Mature autumn shoots of seedy ‘Kozan’ common orange (Citrus sinensis (L.) Osb.) trees were irradiated with gamma rays from 60Co. The survival rate was 65 % for the dose of 60\u202fGy irradiation treatment of ‘Kozan’ common orange. In order to stabilize the mutation, mV3 plants were developed by re-budding and plants at mV3 generation were transplanted in the orchard in 2016. Observations in the present study were recorded for three consecutive years and trees which produced a sufficient number of fruits were evaluated for 19 fruit quality characters such as seed number, fruit diameter and maturity index. The seed number varied from 0 to 11, 0–10.82, and 0–10 per fruit in 2018, 2019 and 2020, respectively. Besides, high variations were observed in the mV3 population in terms of fruit weight and rind thickness. Through investigation of three years, two clones were completely seedless and selected as promising types. Vitamin C, total phenolic content and antioxidant activity in the fruit juice of the selected types were similar control. Furthermore, ploidy levels of the selections were investigated in order to explain the cause of seedlessness. Selected types were determined as diploid with the aid of flow cytometry. The selected lines were propagated in the field to confirm their stability and new commercial field trials have been conducted to evaluate the performances of the selections on different rootstocks.