Page 189 - Breeding and regulatory opportunities, Renaud

Broccoli phytochemical content

of the carotenoids are associated with the outer surfaces of the inlorescence,

smaller broccoli heads with a greater surface area to volume ratio should show

higher concentrations of these compounds., (4) Because carotenoids have high

G main efect good germplasm sources as indicated in Figure 5.1 have high

concentrations of carotenoids and demonstrated stability across environments.

As all three carotenoids are highly correlated with one another, selecting for

one should efectively select for all., (5) Selection for darker green colour more

widely distributed throughout the tissues of the head should allow the breeder

to relatively eiciently increase carotenoid content in broccoli.

In closing, we want to address the question of selecting in an organic or

a conventional environment. The argument commonly used to support

selecting in productive environments is that heritabilities are higher compared

to resource poor environments (Ceccarelli, 1994; 1996). Organic is often

considered a low-external input environment, resulting on average in 20% less

yield compared to conventional production (De Ponti et al., 2012). Nevertheless,

in our trials repeatabilities for some phytochemicals were higher or comparable

to conventional (Table 5.3). Narrow sense heritabilities would be expected to

be signiicantly lower. For those traits where repeatabilities were higher or

comparable, direct selection under organic systems could enhance selection

gain. In all cases, the ratio of correlated response to direct response was less

than one suggesting that direct selection would allow more rapid progress than

correlated selection. Our data on phytochemicals did not show a wider range of

levels under organic conditions as we found for horticultural traits in the same

trials (Renaud et al., 2014), however, in several cases, repeatabilities in organic

production were higher than in conventional.

To maximize eiciency in a breeding program, commercial breeders may

seek to combine breeding for both conventional and organic markets, and a

combination of strategies can be proposed. Some studies that utilized highly

heritable (agronomic) traits, where cultivar yield performance ranked similarly

between organic and conventional management systems and which had

high genetic correlations, suggested that early breeding be conducted under

conventional conditions, with the caveat that advanced breeding lines be tested

under organic conditions for less heritable traits (e.g. Löschenberger et al., 2008;

Lorenzano and Bernardo, 2008). In studies where cultivar yield performance

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