Phylloquinone (Vitamin K) Variation, QTL Identification, and the Correlation with Carotenoids in Broccoli (Brassica oleracea var. italica)

Phylloquinone (vitamin K) is important for bone metabolism, blood coagulation, and contributes to the carboxylation of vitamin K dependent proteins. This fat soluble vitamin is also associated with decreased risk of age related chronic disorders and in the plant acts as a cofactor in Photosystem I. Little information is available concerning the genetic control of this compound in Brassica vegetables or in the related model crop, Arabidopsis. The purpose of the experiment was to quantify phylloquinone in the broccoli population in order to identify QTLs associated with variation.  Florets from 125 F_2:3 broccoli families derived from the cross 'VI-158 x Brocolette Neri E. Cespuglio (BNC)' were harvested in 2009 and 2010 in Salisbury, NC. Tissue extracts were analyzed for phylloquinone, carotenoids and tocopherols to evaluate variability among the families.  Three-fold variation in phylloquinone concentration was observed in both years with significant genetic and environmental effects. Genotype x Environment interaction was not significant. Moderate to high correlations were observed (r = 0.28 to 0.53) with all carotenoids and α-tocopherol (except epoxy lutein). These correlations were all positive suggesting that breeding for enhanced lutein, β-carotene, α-tocopherol and phylloquinone can be accomplished in the same genetic background. Two significant QTLs were observed that impacted phylloquinone variability. A single QTL on chromosome 7 co-segregated with the major carotenoid QTL that impacts lutein and β-carotene while the second QTL is independent of carotenoids or tocopherol accumulation. The results suggest that phylloquinone concentrations in broccoli are moderated by a relatively small number of genes that can be used in developing broccoli with higher levels of vitamin K.