Page 187 - Breeding and regulatory opportunities, Renaud

Broccoli phytochemical content

‘OSU OP’ was explicitly bred for a dark green stem and head color, not only for a

darker green dome surface but also for a dark green interior color between the

lorets of the dome and in the stem (personal communication, Jim Myers 2013).

‘OSU OP’ was the highest in overall carotenoid concentrations across trials as it

is known that carotenoids are correlated with chlorophyll concentrations and

the intensity of green pigmentation (Khoo et al., 2011).

5.4.3 Perspectives on breeding broccoli for enhanced phytochemical

content speciically for organic agriculture

Our study included predominantly broccoli cultivars selected for broad

adaptability in conventional production systems and not purposely bred for

high phytochemical content nor for adaptation to organic agriculture. What

we can conclude from our data is that there has been little change in levels

of several phytochemicals over three decades of breeding. This may indicate

genetic variation for phytochemicals is limited in elite germplasm, or it may be

the result of the lack of selection tools for these traits. This may be changing

with recent eforts to introgress high glucoraphanin from B. villosa to produce

the high-glucoraphanin Fcultivar ‘Beneforté’ (Faulkner et al., 1998; Mithen et

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al., 2003; Traka et al., 2013). The seed industry needs to exploit known sources

of variation in the genus Brassica to enhance levels of other health-promoting

phytochemicals and to broaden the genetic diversity of commercial broccoli

germplasm. Our inding of a strong correlation between dark green color

and high carotenoid levels provides breeders with a simple and eicient

means of increasing carotenoids. The three groups of phytochemicals studied

contribute to health promotion in diferent ways. As these groups are related

to diferent metabolic pathways selecting for one compound does not

necessarily inadvertently improve the other compounds, and may even result

in negative correlation as we have seen in our data between glucoraphanin

and the carotenoids. Although these compounds belong to diferent metabolic

pathways, their production may be coordinated through regulatory feedback

loops, or the structural and/or regulatory genes controlling these pathways

may be genetically linked.

Designing a breeding program for broccoli high in glucosinolates would require

the following considerations generated from our research: (1) Glucoraphanin

is a highly genetically determined compound with minor location and season

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