Carotenoids of yellow-apricot and the tangerine-apricot tomatoes.
Jenkins, J. A. and G. Mackinney.
Apricot, a new recessive (TGC 2:6) is not markedly different from yellow either phenotipically or in carotenoid content. There is no major difference in xanthophylls, lycopene or in phytofluene. The beta- carotene content of apricot, however, is at a level characteristic of red. The apricot gene is not allelic to genes at the yellow, tangerine or beta orange loci. The F, red x apricot, yellow x apricot and tangerine x apricot were red, but their lycopene content was somewhat lower than that of typical reds. The F1 tangerine x apricot not only had the smallest lycopene content but in addition had an appreciable increase in beta-carotene and in phytofluene. Since the deviations of the F1 hybrids from typical reds could have been due to environmental effects, we are not stressing them.
The F2 yellow x apricot segregated 9 red to 7 non-red. Due to the similarity of yellow and apricot, the non-reds of the F2 could not be classified unequivocally into discrete classes. Backcrosses of F1 to yellow and to apricot both segregated in the expected 1:1 ratios. We have recovered what we consider the double recessive (r/r at/at) in the F3 and independently from the progeny of both backcrosses. It has a total carotenoid content toward the lower limit of the yellow parent, but the beta-carotene is below that characteristic of the yellow. In other words, the yellow-apricot differs from the yellow principally in its somewhat lower beta-carotene content.
The F2 tangerine x apricot also segregated 9 red to 7 non-red. Again the non-reds were difficult to classify. However, by a careful comparison of cut fruits in the later generations it was possible to isolate a type that was intermediate between tangerine and apricot. On testcrossing a number of the intermediates with both parents they proved to be double recessives, tangerine-apricot (t/t at/at). The latter has essentially the same pigments as the double recessive yellow-tangerine (Mackinney and Jenkins, 1952). Again the apricot gene behaves in hybrids essentially the same as yellow.