Résumé
Key message
The genetic variation of
Beta
section
Beta
is structured into four taxonomic and spatial clusters. There are significant associations between molecular markers and environmental variables.
We investigated the genetic diversity of
Beta
section
Beta
, which includes the wild and cultivated relatives of the sugar beet. The taxa included in the study were:
Beta vulgaris
subsp.
maritima
,
B. vulgaris
subsp.
adanensis
,
B. macrocarpa
,
B. patula
and
B. vulgaris
subsp.
vulgaris
(garden beet, leaf beet and swiss chards). We collected 1264 accessions originating from the entire distribution area of these taxa and genotyped them for 4436 DArT markers (DArTs). We showed that the genetic variation of these accessions is structured into four taxonomic and spatial clusters: (1) samples of
Beta macrocarpa
, (2) samples of
Beta vulgaris
subsp.
adanensis
, (3) Mediterranean and Asian samples and (4) Atlantic and Northern European samples. These last two clusters were mainly composed of samples of
Beta vulgaris
subsp.
maritima.
We investigated in deeper detail the genetic structure of
B. vulgaris
subsp.
maritima
, which constituted the majority (80 %) of the wild samples. This subspecies exhibited a clinal genetic variation from South-East to North-West. We detected some markers significantly associated to environmental variables in
B. vulgaris
subsp.
maritima
. These associations are interpreted as results of natural selection. The variable most often involved in the associations was annual mean temperature. Therefore, these markers can be useful for the development of frost-tolerant winter beets and drought-tolerant rain-fed beets.