Agriculture Reference
In-Depth Information
12.3.3 HOMOGENEITY OF THE VARIETIES
For quantitative criteria, levels of heterogeneity varied according to the
variety, but the F1 hybrid was not specifically less heterogeneous than the
other varieties. Except for the FD version of 'Eté de Rueil', which always
had a higher level of heterogeneity, differences of heterogeneity levels
between other farmers' versions and their respective original version were
observed, but without a systematic pattern. For qualitative criteria, levels
of homogeneity of the farmers' version were almost always comparable to
those of the respective original versions or to the F1 hybrid. No significant
differences were observed. Figure 6 gives an example of the results ob-
served for qualitative criteria.
There was no correlation between changes in mean values observed
in the varieties and their heterogeneity, or between changes in mean val-
ues and changes in the level of heterogeneity within versions of a variety.
Simpson's diversity index (calculated for qualitative traits) and the inter-
quantile range (calculated for quantitative traits) do not distinguish the
F1 hybrid from the other varieties tested. Furthermore, the farmers' ver-
sions of varieties appeared to have conserved their level of heterogeneity
whether they were selected or not.
When there was divergence in the mean values of different versions of
the same variety, the intra-varietal diversity may have increased even if
within each version, the same amount of phenotypic diversity exists com-
pared with the original version. Each version may have the same internal
level of diversity, but the global diversity represented by all the versions of
the variety may have increased. This has been demonstrated by Goldringer
et al. for phenotypic changes and diversity of agromorphological traits in
wheat populations subjected to selection pressure in contrasting environ-
ments [18]. This new diversity and the rapidity of the changes observed
indicate that population varieties may be good starting points for on-farm
selection and adaptation.
Farmer varieties are often said to be too diverse to meet the unifor-
mity criterion of registration in the European Union, however, our study
showed that the level of heterogeneity of the populations was often no
different from that of the hybrid for traits used in the DUS evaluation.
