A comparison of four mutants induced by Beta radiation with the standard r, y, t and wf types.

Lesley, J. W. and Margaret M. Lesley.

Four mutants occurred in four R2 progenies of seed of L. esculentum treated with P^32 which closely resembled the three old standard fruit color mutants r, y and t and the white-flowered mutant wf discovered by P. A. Young. These four standard mutants are in three different chromosomes. Crosses of the induced mutants with the standard mutants gave types indistinguishable from the standard mutants. Accordingly, the old and new mutants are allelic in the original sense of this term. The yellow-fleshed and white-flowered mutants resulting from irradiation appear to be identical with the old mutants but tangerine and non-yellow skin show differences. The new tangerine contains neolycopene but is virescent and will be designated t^v. The hybrid t x t^v or t^v x t is non-virescent. F1 t^+ (wild type) x t^v backcrossed to t^v gave 57t^+ and 51t^v but no t plants from recombination. No difference in fertility or in meiosis in the pollen mother cells of the new tangerine were observed. A non-yellow skinned plant occurred in R2 of the variety Homestead. The fruit was unusually late in ripening but contained many good seeds. The new non-yellov skinned type had fewer trichomes than the parent type. A cross with an unrelated yy plant gave a non-yellow F1. For convenience the new mutation may be termed y^1. In F1, y^+^y^+ x mutant y^l^y^l, yellow skin and normal trichomes were dominant. A test of recombination between non-yellow skin and. reduced trichomes has not been made. The new non-yellow selfed gave, in the field in 1959, 16 plants like the parent excepting that only 3 or 4 set fruil@. This apparent loss of fruitfulness can hardly be attributed to climatic or to soil conditions. Smear preparations of anthers suggest that the new pink has fewer pollen mother cells and less pollen, but no irregularities in meiosis were found. In the tomato, ionizing radiations may produce mutations identical with known types or differing from but allelic with known types and behaving likewise as simple recessives. In conventional terms, overlapping but non-coincident segments of the chromosome have undergone changes. Only large backcross progenies will tell whether the multiple effects of the induced mutants are separable by recombination. In these instances, the additional effects not found in the standard mutants are more or less injurious but additional effects may conceivably be desirable in other cases.