MUTATIONS IN APPLES INDUCED BY X-RADIATION

Abstract

Dormant scions of the diploid apple varieties Yellow Bellflower, Cortland, Sandow and Golden Russet were treated with 3500–4000r of X-rays and grafted into grown trees by the framework method, inserting 100 to 200 scions per tree. Typical abnormalities in the leaves and bifurcation of the branches were observed in the early growth from the scions. The X-rays also caused an abnormal short thick shoot development and induced early formation of the flower buds. During the second season, grafting these buds produced a total of about 200 apples, many of them of giant size and irregular in shape. Of 150 apples carefully examined when picked, nine were found to be sectorial color chimaeras. Color changes were observed in the direction of both more and less red color. A comparison of the picked fruit from the X-rayed scions with a sample of 150 apples from non X-rayed trees showed both more and wider sectors in the fruit from the X-rayed scions. The results indicate that X-rays may be used as an artificial method of inducing color gene mutations in apples.