Page 233 - Breeding and regulatory opportunities, Renaud

General Discussion

indicated was a top performer (see Chapter 4). ‘Green Magic’ is a hybrid cultivar

for which seed is generated using a cytoplasmic male sterility, therefore it

cannot be reproduced unless one has the maintenance inbred for the maternal

parent nor is the genotype accessible to plant breeders. Comparatively, the

OP cultivars in our trial were poorer performers than the hybrids studied in

terms of horticulture trait performance (yield, stability and quality traits), but

demonstrated value for select phytochemicals (e.g. carotenoids, glucobrassicin,

neoglucobrassicin). OP cultivars are reproducible and can be used as crossing

parental material in breeding programs. There is a desire within the organic

sector to have access to reproducible seed. It was apparent from our study

that attention to the improvement of OPs for horticulture traits has not been

a priority for many years, but that they are of use as base for the development

of nutritionally enhanced cultivars. An opportunity for future breeding could

focus on improved OPs for horticultural traits and health promotion.

6.3.4 Genetic variation is a requirement to develop optimized cultivars

Genetic variation

Genetic variation is a requirement for efective plant breeding. Most of the

cultivars included in this project were those used by growers at the onset of

this research project. They were known to be predominantly cultivars selected

for broad adaptability in conventional production systems and not purposely

bred for high phytochemical content nor for adaptation to organic agriculture.

Horticultural and phytochemical trait performance diferences of the early

maturing versus late maturing cultivars and between open pollinated and F
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hybrids demonstrated some clear patterns. When these analyses were restricted

to the Fhybrids only, the patterns were not as distinct in the phytochemical
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analysis. This leads to the conclusion that there has been little change in the

concentrations of phytochemicals over three decades of breeding (the time

span of cultivar release for the set of cultivars studied) suggesting that genetic

variation for phytochemical content is limited in elite germplasm, or likely the

result of a lack of selection for these traits. This may be changing with recent

eforts to introgress high glucoraphanin content from the wild brassica species

B. villosa to produce the high-glucoraphanin Fcultivar ‘Beneforté’ (Traka et al.
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2013). However, the genetic diversity introduced into‘Beneforté’ is not generally

available to any breeders apart from the company that holds the exclusive

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