Determination of Effective Mutation Dose on Walnut (Juglans regia L. cv. Chandler) Budwoods

Abstract

Walnut (Juglans regia L., 2n=2x=32, Juglandaceae) is a deciduous temperate fruit species with an increasing economic importance and health benefits. The effective mutation dose (EMD) was not determined for ‘Chandler’ budwoods. The objective of this study was to determine the radiosensitivity of walnut budwoods to cobalt-60 gamma ray. One-year-old budwoods of ‘Chandler’ walnut cultivar carrying 4-5 buds in 20 cm in length were irradiated with cobalt-60. The gamma irradiation and chip budding were performed three different times. The budwoods were irradiated (1) with 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 Gy gamma doses on Apr 2017, (2) with 0, 20, 25, 30, 35, 40 Gy gamma doses on Sep 2017, and (3) with only 42 Gy gamma dose on Apr 2018. Then, gamma irradiated budwoods were chip budded on seedling rootstocks. Mutation 1 Vegetation 1 (M1V1) plants were obtained. The humidity content of the budwoods was determined after gamma irradiation. The bud take ratio, shoot length, and chlorophyll density of M1V1 plants were measured. From the shoot length of the plants, EMD was calculated as 42.1 Gy after the first irradiation on Apr, 2017, and that was calculated as 20.9 Gy in the second irradiation on Sep, 2017. The main plant population was obtained by previously calculated 42.1 Gy dose in the third irradiation on Apr, 2018. The survival rates of budded plants in three irradiation experiments were 21.6%, 54.8%, and 32.0%, respectively. According to the results, the most suitable gamma ray dose is 42.1 Gy.