Heritabilities and minimum gene number estimates of carrot carotenoids

Broad sense heritabilities and gene numbers were estimated for the production of total carotenoids and the major component carotenoids of carrot storage roots: phytoene, zeta-carotene, beta-carotene, alpha-carotene, and lycopene. Two crosses with different backgrounds were evaluated: orange B493 x white QAL and orange Brasilia x dark orange HCM. The HCM (high carotene mass selection), Brasilia and B493 parents had both alpha-carotene and beta-carotene, but HCM had proportionally more alpha-carotene. Carotene content in F (2) populations ranged from 522 ppm to 1714 ppm in Brasilia x HCM and from 0 to 695 ppm in B493 x QAL progeny. F (2) plants segregating for absence of alpha-carotene were identified in B493 x QAL. Broad-sense heritabilities ranged from 28% to 48% for all carotenes except lycopene and phytoene where estimates were 44% to 89% in the Brasilia x HCM cross, All heritability values exceeded 88% for the B493 x QAL cross, except one estimate for lycopene. The estimated number of genes was 4 conditioning alpha-carotene, 2 to 3 each for beta-carotene and total carotenes and one each for zeta-carotene, lycopene and phytoene in the orange x dark orange cross. In the orange x white cross, the estimates were 4 genes for alpha-carotene, 1 to 2 each for lycopene and total carotenes and 1 for each of the other carotenes. These results are in general agreement with QTL studies and they provided evidence for continuous inheritance of alpha-carotene, beta-carotene and total carotenoids in the orange x dark orange cross and discrete inheritance for beta-carotene and total carotenoids in the orange x white cross.