The vitamin C content of tomato fruit is significantly increased by the genes high pigment (hp) and dark green (dg) which also have undesirable pleiotropic effects, including smaller fruits (Jarrett et al., 1984) and smaller, less productive plants (Wann et al., 1985). I have noticed that uniform ripening, dark green lines appear to develop more vigorously, produce larger fruit, and yield more than corresponding lines with u+ and dg.
To test this, a homozygous stock (u+u+ dgdg BB) was crossed with the cultivar Burgis (uu dg+dg+ bb). The F2 progenies were classified for the three segregating genes, and two ripe fruits of each plant were tested for ascorbic acid (vitamin C) content by the technique of Wann et al. (1985).
Vitamin C content (mg/100 g fresh fruit) were as follows: u+-: 30.0 mg, uu: 27.1 mg; dg+-: 25.2 mg, dgdg: 31.8mg; B-: 27.6 mg, bb: 28.2 mg.. These data suggest that dgdg increased vitamin C by an average of 26% in progenies heterozygous for many other genes. The data also suggest that uu decreased vitamin C an average of 9.6%. They do not implicate the Beta gene in vitamin C content.
When the effects of the genes were compared in pairs, the interaction of uu in decreasing and dgdg in increasing vitamin C are apparent. In the presence of u+, dgdg increased vitamin C content 48%, but in the presence of uu there was no increase.
The implications are that while uu may overcome the pleiotropic effects of dgdg, it negates the ascorbic acid increase for which the gene dg is of interest. Furthermore, uu appears to decrease vitamin C content when compared to u+ even in normal lines.
Jarrett, R.L., H. Sayama, and E.C. Tigchelaar. 1984. J. Amer. Soc. Hort. Sci. 109 (6) :873-87 8.
Wann, E.V. and E.L. Jourdain. 1985. J. Amer. Soc. Hort. Sci. 110(2):212-215.