Effect of different irradiation sources and doses on haploid embryo induction in Altinbas (Cucumis melo L. var. inodorus) melons

In vivo induction of parthenogenesis using an irradiated pollen technique provides successful results in melon and accelerates breeding by shortening the time for obtaining 100% homozygous lines. Gamma rays (cobalt-60) are usually used for the pollen irradiation, although it is difficult to find a suitable source for irradiation. Haploid technology is widely used in melon breeding programs, so there is a need to find alternative sources for pollen irradiation. This study was performed to compare the efficiency of different irradiation sources to induce haploid embryos. One dose of cobalt-60 (300 Gy), two different doses (200 Gy and 300 Gy) of cesium-137, and two different doses (200 Gy and 300 Gy) of X-ray were used for the irradiation of melon pollen. All irradiation sources were efficient for fruit set, while the highest fruit set (60.38%) was obtained from 200 Gy cesium-137 and the lowest (20.01%) was obtained from 300 Gy X-ray. A total of 2294 haploid embryos were rescued, of which 2052 regenerated into plants. The number of rescued haploid embryos per fruit ranged between 8.77 (300 Gy cobalt-60) and 4.23 (200 Gy X-ray). The highest regeneration rate of haploid embryos into plants was 92.56% (300 Gy cobalt-60) and the lowest was 61.86 % (200 Gy cesium-137).