A virescent tangerine mutant in R2 from seed treatment vith radioactive isotope P32.

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

Fifty seeds of an inbred line of Canary Export r^+ r^+ were soaked for five days in aqueous acid phosphate containing initially 10.8 u C P32 per seed. R1 plants from treated seed were selfed. A total of 176 R2 plants were grown. One R2 contained a single plant with tangerine flesh color which was strongly virescent. A tangerine-fleshed type obtained from Dr. F. O. Holmes, Rockefeller Institute, New York, was almost as virescent as the mutant. The leaves of Burpee's Golden Jubilee tt are paler than those of Canary Export but are not virescernt. All three types have a characteristic faint reddish tinge of the corolla smd stamens.

Crossed with Golden Jubilee, the mutant gave F1 tangerine non-virescent and with Holmes' tangerine, virescent. A chromatographic test indicated identity of the flesh pigment in Holmes tangerine and the mutant. Backcrosses of the mutant with F\1 non-mutant X mutant Canary Export gave 19 non-virescent red-fleshed and 10 virescent tangerine but no recombinations. The virescent tangerine mutant is slightly less fertile than the parent type.

The following would account for the new mutation, listed in order of likelyhood. (1) Two closely linked gene mutations. Against this is the independent occurence of an almost identcal type, Holmes' tangerine; (2) Mutation at the t locus to a new pleiotropic allele causing tangerine-flesh and virescenzce (3) The t allele causes virescence in the genetic complex of Canary Export and Holmes' type but not in Golden Jubilee.