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Broccoli phytochemical content

5.3.7 Principal component biplot analysis: correlation between phyto

chemicals and cultivars by production system

In the principal component analysis the irst PC axis accounted for similar

amounts of the total variation in both conventional and organic production

systems (43.5% vs. 39.6%). The second PC axis showed a similar trend with

17.02% for conventional and 16.93% for organic (Figure 5.4A and 4B). The irst

two PC axes together accounted for 60.53% and 56.57% of total variation for

conventional and organic, respectively. The PCA biplot analysis supported

our indings that carotenoids were highly associated across systems, while

tocopherols were highly associated in conventional, but not in organic

(tocopherols demonstrated the largest shift between production systems).

Glucoraphanin and neoglucobrassicin were associated with one another,

but not with glucobrassicin across production systems. Glucoraphanin was

associated with α-tocopherol in organic, but not in conventional treatments.

Glucobrassicin was associated with δ- and α- tocopherol in conventional, but

not in organic treatments. δ-tocopherol had a higher association with the

carotenoids in organic than conventional. The biplots show response of both

cultivars and phytochemical traits to environment. Those cultivars close to the

origin reveal little about the relationship of cultivars and trait vectors, whereas

those located near the extremes of trait vectors are those with the highest (or

lowest) values for those traits.

5.4 Discussion:

5.4.1 Impact of organic management system compared to environmental

factors on phytochemical content

Few studies have speciically compared the levels of health promoting

compounds in Brassica vegetable species grown under organic and conventional

production systems (Meyer and Adam, 2008; Naguib et al., 2012; Picchi et al.,

2012). To our knowledge, this investigation is the most comprehensive study

with the broadest range of phytochemical compounds (9) and a diverse set

of broccoli cultivars (23) over regions (2), and management systems (2), with

Fall and Spring season trials (2 each). In this study organic versus conventional

management systems contributed the smallest source of variation compared

to genotype, region and season. Within the phytochemicals studied individual

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