ABSTRACT
Overall poor root color or irregular color development has been identified as a production defect that impacts postharvest marketability. California carrot production is affected by a variety of incompletely understood disorders that impact root color development or intensity. Divergent factors are believed to be responsible for roots with poor color (carotenoid) development as compared to light root syndrome (LRS). HPLC analysis showed that the total carotenoids are depressed in low color root tissue and LRS tissue. A significant shift in the ratio of key biosynthetic products is not detectable. No accumulation of compounds leading to β-carotene has been detected thus far. Although the total concentrations are variable for variety and sample data, the ratio of the compound phytoene to α and β carotene remain proportional and not significantly different between light and dark roots. Disruption of carotenoid production may occur at earlier steps in the pathway or at some other point of cellular dysfunction. An alignment of deduced amino acid sequences from ten phytoene syntheses in different crops was used to identify two conserved amino acid domains for the construction of degenerate PCR primers. A 519 bp cDNA fragment was derived by RT-PCR from carrot root RNA. DNA sequence analysis revealed that the predicted amino acid sequence is highly similar to the PSY from tomato and melon.
