Résumé
Drought strongly affects cereal yield in several regions of the
world. Plant growth and plant water status in
response to soil water deficit play an important role in tolerance to drought
and in yield stability. In order to
investigate the relationship between plant growth and water relations,
187
barley (Hordeum vulgare L.)
recombinant inbred lines from a cross between two Mediterranean varieties,
Tadmor and Er/Apm, were studied
in a growth chamber for RWC, number of leaves on the main tiller (NL),
number
of tillers (NT) and total shoot
fresh and dry biomass (TSFM and TSDM). Measurements were made at the beginning
of tillering on well
watered plants and at a soil moisture content of 14% of field capacity.
A
negative phenotypic correlation between
RWC and growth parameters was obtained in both treatments. Under water
stress,
a negative genetic correlation
was also found between the same characters. QTLs involved in RWC, NL and
TSFM
variation were positioned
on a RFLP-RAPD genetic map. Different DNA regions involved in constitutive
and
water stress responses were
detected. In the stress treatment, one region on chromosome 1 was involved
in
RWC and NL variation giving a
genetic basis to the phenotypic correlations found. Separated map positions
were also found for RWC and NL.
Epistatic interactions between several QTLs and between QTLs and other
markers
were detected only in the
water stress treatment, suggesting that some chromosomal regions might
be
involved in the regulation of the
expression of the traits under water stress. This work suggested that even
if some parameters are strongly
correlated, finding QTLs for only one trait is not sufficient to detect
all
the candidate regions which might be
involved in the control of the correlated traits. The results of localization
and co-localization of QTLs are physiologically interpreted.