Effects of Gamma Irradiation on Seedlessness and Fruit Quality of Ortanique Tangor

Abstract

The existence of a large amount of seeds in citrus fruits results as a major impediment to customer acceptability, even if the fruits have high organoleptic properties. Irradiation, which mainly reduces seed number of varieties, is a faster way than hybridization. The use of irradiation in citrus breeding programs is now quite widespread with most programs in the major citrus producing countries actively developing new selections. The present study reports the primarily results of gamma irradiation on seed number and fruit quality of Ortanique tangor mutant population. The shoots of scion were irradiated with gamma rays from 60Co at the dose of 50 Gy (gray) in April of 2014. All the treated buds were then immediately budded onto rootstocks and the survival rate was recorded as 60.34%. In order to stabilize the mutation, mV3 plants were developed by re-budding and plants at mV3 generation were transplanted in the orchard in 2017. Within the following year, 68 mV3 plants out of 852 grown in the field bore sufficient amount of fruit and were screened in terms of 19 fruit quality characters such as seed number per fruit, fruit diameter and ripening index. Fruit diameters of mV3 population varied from 56.72 mm to 84.79 mm, and fruit weight ranged between 90.00 g and 287.60 g. The number of seeds per fruit ranged between 0.6 and 13.1 whereas seed number of non-irradiated Ortanique tangor was recorded as 10.7 in the same fruit crop year. In general, fruit characteristics such as fruit weight, fruit height and fruit diameter which describe fruit size of a big part of the population, were similar to Ortanique tangor. According to primarily results, 18 plants have been described as low seeded (≤4). In addition, a cluster analysis was performed by using Euclidean similarity coefficient and similarity index ranged between 29.29% and 93.10% regarding variables related to fruit. The stability of mutations detected is being evaluated and new commercial field trials will be established with the selected materials.