Effect of Seed Treatments with X-Ray and Phosphorus 32 on Tomato Plants of First, Second, and Third Generations.

ANY observers have reported an increase in variability following exposure of pollen or seeds to the effect of ionizing radiation. In several respects the tomato is favorable material for such studies. I t is self-pollinating, and recessive mutants can therefore be uncovered promptly. It is a perennial and can be propagated by cuttings, so that plants of a previous generation can be retained, and two generations can be grown in one year. The normal cytological and genetical behavior is well known. In a recent report (Tomato Genetics Cooperative Report No. 4, 1954) 108 mutant genes of the tomato are listed, and the number is increasing rapidly. LINDSTROM (1933), with radium, and ~IACARTHUR (1934), with X-rays, succeeded in inducing mutations in this species. Exposure of pollen to radiation has been much more used than exposure of seeds. The latter method seemed to offer certain advantages in using a radioactive isotope, since, when seeds are soaked in a solution containing P32, the radioactive isotope may enter the nuclei of the embryo before and during germination and the multicellular organism is exposed to decreasing amounts of beta radiation during a period of several weeks. The studies reported in this paper include a single experiment with X-rays and nine with phosphorus 32 during three generations of mature plants.