Page 171 - Breeding and regulatory opportunities, Renaud

Broccoli phytochemical content

Tocopherols

For δ- and γ-tocopherol across all trials in both regions, the Season (S) main

efect accounted for the largest proportion of variance (Table 5.3). In contrast

the proportion of the variation associated with S for α-tocopherol across all

trials was minor. For all three tocopherols there was minor to no M efect, but

a large L main efect, being the greatest for γ-tocopherol. The G main efect

showed a similar pattern to L.

Carotenoids

For all three carotenoids across all trials in both regions, the G main efect

described a signiicant component of total variance and was of largest inluence

for lutein (Table 5.3). The S main efect played an important role for zeaxanthin,

and to a lesser extent for lutein but not for β-carotene. For all three carotenoids

the L efect was minor, but the L x S interaction for β-carotene was relatively

large and mostly associated with Maine (Supplemental Table 5.2a). There was

no M main efect; only for β-carotene was there a small efect of the G × M

interaction (mainly driven by Maine).

5.3.3 Repeatability, genetic correlation and ratio of correlated response

to direct response

Organic versus conventional

In the present study, we were able to estimate the proportion of the genotypic

variance relative to phenotypic variance, but because we did not have a

genetically structured breeding population, we apply the term repeatability

rather than broad sense heritability. Of the phytochemicals studied,

repeatabilities for concentrations of seven of the nine were comparable or

higher in organic compared to conventional systems (Table 5.4). Only for

glucobrassicin and δ-tocopherol was repeatability under organic conditions

lower than under conventional. In the analyses δ- and α-tocopherol had relatively

low repeatabilities. The highest repeatabilities were for glucoraphanin (0.82-

0.84), neoglucobrassicin (0.75-0.76), γ- tocopherol (0.72-0.75), lutein (0.83-0.85)

and zeaxanthin (0.76-0.77). Genetic correlations were high between organic

and conventional for the glucosinolates, γ-tocopherol and lutein (0.84-0.95),

while δ-tocopherol, α-tocopherol, zeaxanthin and β-carotene were lower (0.63-

0.77). The ratio of the correlated response to direct response for selection in the

organic system was less than 1.0 for all traits.

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