Vegetative growth and water use efficency characterization of durum wheat near isogenic lines for the QTL Qyld.idw-3B
Résumé
The study of the genetic basis of grain yield is one of the major challenges of the scientific
community because of both its complex genetic control and the strong interaction with
environment and management practices. Furthermore, such interactions may affect yield during
the entire life cycle of the plant. It is therefore crucial to consider yield as the result of multiple
simpler traits and thus study their genetic control separately. In this study, we used the phenotyping
platform PhenoArch in order to identify growth and water use related traits that may explain the
segregation for yield and plant height observed at the QTL Qyld.idw-3B by Graziani et al. (2010).
Four pairs of durum wheat near-isogenic lines (NILs) for the QTL Qyld.idw-3B were grown at three
levels of drought stress: no stress (soil water potential > -1 bar), mild stress (soil water potential of
-5/-8 bar) and severe stress (soil water potential ≈ -13 bar). The stress was applied at the beginning
of stem elongation until the end of the experiment (late milk stage, Zadok 77) on eight replicates
per genotype per treatment. We recorded two main types of phenotypic data: (i) canopy images
and (ii) weight measurements: every night, digital RGB images were collected. From these images
we estimated several growth related phenotypes like biomass, leaf expansion and plant height;
every plant was weighted to estimate the evapotranspiration at least once per day. Combining these
data, it was possible to evaluate key physiological parameters like water use efficiency (WUE) and
leaf transpiration. The QTL seemed to not affect vegetative behaviour and water use of plants during
the early vegetative stages while majorly differentiating the NILs couples during the reproductive
and earl ripening stages. This explains the segregation for final plant height previously observed by
Graziani et al (2010). These results may provide useful information for further phenotypic as well as
physiological and genetic characterization of the QTL Qyld.idw-3B with a main focus on mid to late
stem elongation and reproductive/maturity stages.
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