Page 231 - Breeding and regulatory opportunities, Renaud

General Discussion

often incorporated broccoli in their product assortment but are not located in

optimal regions where broccoli is mainly bred for, growers were concerned with

broccoli head development during hot summer periods (lack of vernalization,

leafy heads). Because broccoli develops uneven-sized lower buds on its

inlorescence when temperatures are above 24oC to 30oC (Heather et al., 1992),

therefore this should be a breeding priority for non-temperate environments

(Farnham and Björkman, 2011a and b).

Not all of the priority traits identiied were evaluated in the ield trial component

of this study e.g. leaf attitude, loret extension, ield holding capacity and post-

harvest quality were not studied. These traits should be prioritized in future

breeding, with speciic attention to their role in an organic production system

compared to conventional. What we did learn from our study through analysing

genetic correlations and GGE PCA Biplots (Chapter 4 and Chapter 5), was that

broccoli head yield trials were not positively genetically correlated to head

quality characteristics (head shape, bead uniformity). Therefore, if the goal is

to breed for head irmness or bead uniformity, this can be achieved without

relinquishing yield. As organic growers not only search for cultivars that it

in their management system but that also contribute to the resilience of the

organic system, root system research for nutrient eiciency in broccoli should

be explored.

Yield stability: the example of ‘Arcadia’

The results of the farmer surveys indicated that ‘Arcadia’ was the most

commonly used cultivar by both organic and conventional growers. In the

Oregon ield evaluations, the both sets of growers also selected this cultivar

as their preferred variety. When comparing these results to our own ield trial

results, we analysed trait performance and stability across trials to see why

this cultivar performed successfully in this speciic environment. Our results

indicated that Arcadia was not a top yielder (a mid-ranking cultivar of the 23

cultivars evaluated across trials, see Chapter 4), but in the top cluster for stability

and demonstrated a consistent yield performance across seasons, years and

management systems. The same trend was observed for the plant growth

traits head diameter, head thickness, uniformity, head height, and leaf height.

To dig deeper into why ‘Arcadia’ was a grower standard and to compare it to

the more recently grower selected cultivars, ‘Green Magic’, and ‘Gypsy’, we

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