Page 138 - Breeding and regulatory opportunities, Renaud

Chapter 4

4.3.3 Repeatability and genetic correlations

The repeatabilities for head weight, head diameter, hollow stem and overall

quality ratings were higher for organic compared to conventional across trials

(Table 4.5). For maturity, head color and head surface, repeatability levels in

organic were equal or near equal to those in conventional. For head shape,

bead size, bead uniformity and plant height repeatabilities were higher in

conventional compared to organic. The genetic correlations between organic

and conventional for most traits were generally high with the exception of

bead uniformity, which showed the lowest genetic correlation (0.66). The ratio

of correlated response to direct response for all traits was below 1 with the

exception again of bead uniformity. When repeatabilities were calculated for F
1
hybrids only, repeatabilities and correlated response were smaller in most cases,

but the trends were similar (with the exception of overall and head diameter).

4.3.4 Comparison of cultivar rankings for head weight and other traits

per cultivar

Spearman’s Rank Correlation

We wanted to investigate the comparison between organic and conventional at

the most ine grained level and looked at correlations between the genotypic

means for the eight location by trialing period combinations. For head weight,

conventional and organic genotypic means were highly correlated. However,

when the Fhybrid genotype class was analyzed separately (minus the OPs
1
and inbred lines), most M pairs were not signiicant, indicating change in rank

between M in any given Y, L, S. Genotype rank was signiicantly correlated

between management systems in Maine Spring 2008, and Oregon Spring 2007

and 2008 but genotypic rank was not correlated in fall environments (Table 4.6).

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