Genotypic and Maturity-related Variation in Anthocyanin Quantity and Quality in Crucifer Vegetables

Crucifer vegetables comprise a unique family of commercial market classes based on harvestable plant morphotypes.  Several classes contain genotypes with anthocyanin expression in their tissues, including market classes of Brassica oleracea (cabbage, kale, Brussels sprouts), Raphanus sativus (radish), Brassica juncea (mustard), and Brassica rapa (pak choi, bok choi).  Anthocyanins in crucifer vegetables have antioxidant activity giving a wide range of health benefits and also provide novel aesthetics that can be utilized for cultivar development. The  HPLC and MS protocols were utilized to provide insight into anthocyanin variations among different species and genotypes.  These were coupled with microscopy to determine cellular localization of anthocyanins among the different species. The ratios of anthocyanin species differed within market classes, and among market classes themselves, as did the localization of anthocyanins on a cellular level.  The anthocyanin profiles differed between mature and juvenile plants of the same genotype, especially in those exhibiting a different plant morphotype at maturity such as cabbage and Brussels sprouts.  Total anthocyanin content ranged from 0.2 mg/g to 22.11 mg/g (dry weight, cyanidin 3,5-diglucoside equivalent) in germplasm accessions of mature red cabbage evaluated, indicating that there is significant genetic diversity to select and develop crucifer vegetables high in anthocyanin content.  The types of anthocyanins also varied considerably among different crucifer vegetable species with cole crops containing primarily cyanidin based anthocyanins and radish producing primarily pelargonidin based anthocyanins. While B. oleracea morphotypes produce cyanidin based anthocyanins, chromatograms show that the profile of these anthocyanins can vary due to different glycosylation and acylation possibilities. Imaging shows the ability of R. sativa species to be able to produce anthocyanins in all tissue types while B. oleracea has only been able to produce anthocyanins within the epidermal, outer mesophyll layers, and vascular xylem and phloem tissue only. This information is being used to develop crucifer vegetables high in desirable anthocyanins that are expressed in tissues with aesthetics that are appealing to consumers.