INHERITANCE OF BETA-CAROTENE IN TOMATOES

Abstract

ETA-carotene is the principal vitamin A active carotenoid found in to-B mato fruits. This pigment, however, constitutes only about 5 percent of the total carotenes present in commercial red-fruited varieties. Almost all of the remaining 95 percent of carotene is lycopene. In spite of the relatively small percentage of beta-carotene occurring in red-fruited varieties, tomatoes are classified, nevertheless, as a "good" source of vitamin A for the human diet (HEINZ 1942). In 1942 a study aimed a t increasing the vitamin content of tomato selections by breeding was initiated a t this station. Progress toward the production of varieties genetically constituted to produce high concentrations of provitamin A and ascorbic acid has been reported (LINCOLN et al. 1943, 1949; KOHLER et al. 1947). It also has been reported that selections were made during the course of this work in which beta-carotene constituted 95 percent of the total carotenes (KORLER et al. 1947). This paper reports the results of studies of the inheritance of beta-carotene in crosses between high lycopene (low beta-carotene) and high beta-carotene tomato selections. PREVIOUS LITERATURE The results of several studies on the inheritance of tomato flesh and skin color have been summarized by BOSWELL (1937). Most commercial varieties are red fleshed with yellow skin and therefore carry the dominant alleles RTY of yellow flesh (r), tangerine, orange flesh (t) and colorless skin (y). LE ROSEN et al. (1941) have shown that flesh and skin color are genetically and chemically unrelated. The R gene for red flesh color affects only the red and yellow plastid pigments, chiefly lycopene, but to a smaller extent other carotenes and xan-thophylls, while the Y gene for yellow skin has no effect on plastid pigments but causes a tenfold increase in an alkali soluble epidermal pigment. Recently LESLEY and LESLEY (1947) presented evidence that three or more genes determine the red-yellow color series in subgeneric crosses of Lycopersicon. I n the initial paper, LINCOLN et al. (1943) reported obtaining a selection containing 67.5 y/ gm of beta-carotene or nine times as much as the content of the highest commercial variety. The same group, KOHLER et al., (1947), later reported individual plant fruits containing as much as 115 y/gm of beta-carotene (95 percent of total carotenes), while others of commercial fruit size contained