Thompson, A. E.
The author previously postulated (Science 121:896-897, 1955) that two nonallelic recessive genes are necessary for the production of high total carotenoid pigments in tomato fruits. They were tentatively named high pigment 1 and 2 (hp\1 and hp\2). Kerr reported in TGC5 that two recessive genes dark red (dr) and black shoulders (bs) conditioned the dark internal flesh color and the intensely dark green shoulders of the Black Queen (Webb Special) variety.
The association of dark green plant and fruit color and the high carotenoid content of the fruits has never been observed to be broken. Environmental factors greatly influence ultimate pigment production under field conditions, thus necessitating adequete sampling procedures. If shaded samples are taken at the turning stage and ripened for 12 days under optimum temperature conditions and then analyzed for pigment content, an accurate estimate of the pigment potential will be made.
Only the Webb Special X Orange King (r^+r^+^tt) cross has given a segregation indicating that high pigmentation is conditioned by two recessive genes. Crosses of Webb Special and the following: Snowball (rr t^+^t^+), Golden Queen (rrt^+^t^+), University of Illinois Acc. 36 (rrtt), and Garden State (r^+^r^+^t^+^t^+) all segregate on a monogenic basis.
High pigment lines homozygous for red, tangerine, yellow, and light tangerine have now been isolated. The high pigment light tangerine has not as yet been checked genetically, but were classified on the basis of their visual apperance and the nature of their absorption spectra. Photolometer readings of hexane extracts of their total pigments were converted to relative density for ready comparison. It is of interest that the high pigment genes condition increased carotenoid production in both pigment systems and all four color classes. It appears logical to conclude that the high pigment genes exert their influence early in the biosynthetic pathway of carotenoid pigment production.
Average relative density of total pigments
Color Normal High pigment Red r^+^r^+^t^+^t^+ .603 1.000 Tangerine r^+r^+^tt .554 .885 Yellow rr t^+^t^+ .022 .051 Light tangerine rrtt .125 .310