The lemon cultivar ‘Jeramon’ is a nucellar seedling obtained through controlled pollination, with ‘Frost Lisbon’ as the seed parent and ‘Meyer’ as the pollen parent. ‘Jeramon’ had its first fruit set in 2012 and was selected in 2015 after evaluating its characteristics for three consecutive years. The ‘Jeramon’ tree was vigorous, upright-spreading, and flowered three times a year (mid-May to Early June, late June to early August, and early September). The average fruit weight was 120 g. The rind thickness was approximately 5 mm, which was thicker than that of common citrus cultivars, including Satsuma mandarin and late-maturing cultivars. The rind and pulp were pale yellow at full maturity. Total soluble solid ratio and acidity were 8.5% and 11°Brix, respectively, which were higher than that of ‘Frost Lisbon’. ‘Jeramon’ is self-compatible, producing approximately 10 polyembryonic seeds per fruit (Registration No. 9060).

In this study, we investigated the variety-dependent survival of citrus seedlings and analyzed the pomological characteristics of fruits and thorn lengths following irradiation with gamma rays. Scions from the seedlings of the following citrus varieties, ‘Yuzu’, ‘Noeulhyang’, ‘Sarahyang’, ‘Namgam’ (nucellar), and ‘Meiwakumquat’ irradiated with gamma rays at 0, 60, 80, and 100 Gy were grafted onto trifoliate orange. At 6 months after grafting, the survival rates of ‘Yuzu’ and ‘Noeulhyang’ exposed to 100 Gy were 49.5% and 34.8%, and that of ‘Sarahyang’ and ‘Namgam’ (nucellar) exposed to 80 Gy were 51.6% and 46.8%, respectively. ‘Meiwakumquat’ exhibited the lowest survival among the varieties used in this study. Therefore, we classified ‘Meiwakumquat’ as highly susceptible to gamma radiation; ‘Noeulhyang’, ‘Sarahyang’, and ‘Namgam’ (nucellar) as intermediately susceptible; and ‘Yuzu’ as the least susceptible. We assessed the effects of gamma radiation on the pomological traits in irradiated ‘Tambit1ho’ and ‘Yuzu’. Among the 72 irradiated ‘Tambit1ho’ seedlings, the average seed number (number of seeds per fruit) varied between 0 and 18.6, whereas that in the unirradiated seedlings was between 8 and 18. Among the irradiated seedlings, the average seed number was less than 1.0 in eight seedlings. In addition, we observed variations in weight, rind and segment hardness, and sugar and acid contents. The thorn length of the flush in unirradiated ‘Yuzu’ was between 1.3 and 6.0 cm, whereas that of flush in gamma-irradiated seedlings was between 0.1 and 6.1 cm. Among the irradiated ‘Yuzu’ seedlings, the thorn length was less than 0.1 cm in two seedlings.