Page 188 - Breeding and regulatory opportunities, Renaud

Chapter 5

main efects but with substantial G×L×S interaction., (2) Comparatively,

glucobrassicin and neoglucobrassicin are more impacted by location and

season and L×S interaction with highest glucobrassicin concentrations and

largest range in our Oregon Fall trials and neoglucobrassicin highest in Oregon

Spring trials., (3) Cultivar performance for glucoraphanin and glucobrassicin

and neoglucobrassicin was negatively correlated indicating that there may be

a trade-of between glucoraphanin on the one hand, and glucobrassicin and

neoglucobrassicin on the other hand., (4) Selection for glucoraphanin without

consideration of horticultural traits would probably result in larger headed

and later maturing cultivars. Conversely, selection for smaller headed, early

maturing cultivars would favor glucobrassicin and neoglucobrassicin at the

expense of glucoraphanin.

A breeding program for broccoli for high tocopherol content would require: (1)

Overall the tocopherols were more season, location and L×S dependent and

had lower overall repeatabilities compared to the glucosinolates. In a structured

genetic population where additive genetic variance could be partitioned,

narrow sense heritability would likely be low, and increasing tocopherol content

would best be conducted with breeding methods suited to low heritability

traits., (2) δ- and γ-tocopherols were both season dependent and fall grown

broccoli had higher concentrations of these compounds across trials and a

wider range of content levels, whereas levels of α-tocopherol were higher in

spring but the range was comparable under both seasons. Thus, fall would be

the preferred environment for breeding for these compounds., (3) There were

no signiicant diferences for location for δ- or γ-tocopherol, but the average

levels of α-tocopherol levels were signiicantly higher in Oregon than Maine,

suggesting greater potential for genetic gain in the Oregon environment.

If the goal is to design a breeding program for broccoli enhancing the levels

of carotenoids it would require the following considerations: (1) For all three

carotenoids studied, genotypic variation, particularly for lutein, was relatively

more important than location and season., (2) However, zeaxanthin exhibited

a large S (spring) and L×S interaction. For both β-carotene and lutein, spring

grown broccoli had signiicantly higher levels than fall produced. Thus, selection

for carotenoids would probably be more efective in spring than in fall., (3) Early

maturing and small headed cultivars had higher levels of carotenoids. Since most

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