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Broccoli phytochemical content

signiicant diferences in location, but for δ- and γ- tocopherol concentration

levels were higher in the fall compared to the spring, while for α-tocopherol,

concentration levels were higher in the spring compared to the fall. For the

carotenoids, there were no signiicant location diferences, however there was

a seasonal trend that all carotenoids were higher in spring compared to fall.

Ibrahim and Juvik (2009) found signiicant environmental variation among

24 broccoli cultivars for carotenoids and tocopherols which they attributed

to the stressful production environments. Factors explaining the genotype

and genotype by environment interaction components of variation in the

carotenoids and tocopherols could be clariied by the fact that environmental

stimuli are both up- and down-regulating genes associated with carotenoid

and tocopherol biosynthesis. There is evidence in the literature that there are

coordinated responses of the carotenoid and tocopherol antioxidants in vivo.

There was a reduction in rape seed (Brassica napus) tocopherol content in

response to increased carotenoid levels due to over expression of the enzyme

phytoene synthase (Shewmaker et al., 1999). This response could explain the

negative correlation between γ- tocopherol concentration and the carotenoids

observed in our trials.

5.4.2 Diferences in phytochemical content between diferent genotypes

and genotypic classes

The partitioning of variance indicated that genotype was an important source of

variation for all glucosinolates. The cultivar ranking and rank correlation analysis

demonstrated that there was a pattern in genotype content of glucosinolates

where cultivars with the highest concentrations of glucoraphanin had the

lowest levels for glucobrassicin (Supplemental Figure 5.1A-C). In our trials, the

range in glucoraphanin concentrations across cultivars was (1.15-7.02 μmol/g

DW, Supplemental Table 5.4), while glucobrassicin was 1.46-3.89 μmol/g DW,

Supplemental Table 5.5). Several of the cultivars with the highest concentrations

of neoglucobrassicin were those that had the highest concentrations of

glucobrassicin. Range in neoglucobrassicin concentrations across cultivars was

0.68-4.54 μmol/g DW, Supplemental Table 5.6). In earlier studies, glucosinolate

concentrations in broccoli have shown dramatic variation among diferent

genotypes. Rosa et al. (2001) studied total glucosinolate levels in eleven cultivars

of broccoli and found ranges from 15.2-59.3 μmol/g DW. Among 50 accessions

of broccoli Kushad et al. (1999) found glucoraphanin content ranges from 0.8-

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