Molecular Mapping of Complex Traits - Genetics, Genomics and Breeding of Crop Plants - page 166

The locations of QTLs identified for plant water status and osmotic
adjustment when compared with those controlling agronomic traits under
well-watered conditions reported by Rachid Al-Chaarani et al. (2004),
showed overlapping for some of the water status and agronomical traits.
The overlapping QTLs are located on: LG 2 for turgor potential and stem
diameter as well as for osmotic adjustment and sowing-to-flowering period;
LG 7 for relative water content and sowing-to-flowering period and for leaf
water potential and sowing-to-flowering period; LG 12 for leaf water potential
and percentage of oil in the grain and linkage group 17 for osmotic potential
and stem diameter (Poormohammad Kiani et al. 2007a). The co-location of
QTLs for water status traits and oil percentage as well as for agronomical
traits reported above suggests a clear biological link between plant water
status and yield-related traits.
5.2.7.2 Yield and Related Traits under Drought Conditions
The relationship between grain yield and related agro-physiological traits
was confirmed recently by an experiment conducted under different water
treatments using the same RIL population previously used for mapping
drought-adaptive traits (Poormohammad Kiani et al. 2007a, 2009; see Table
5-1 and Fig. 5-1 ). The authors evaluated days from sowing to flowering
(DSF), leaf number per plant (LN), leaf area at flowering (LAF), leaf area
duration (LAD), plant height (PH), total dry matter (BIO), head weight (HW)
and grain yield per plant (GYP) as major yield-related traits in the greenhouse
and field, under well-watered and water-stressed conditions. Two to seven
QTLs were identified depending on the trait and growth conditions with R 2
ranging from 4% to 40% ( Table 5-1 ) . Most of the QTLs were detected under
more than one growth conditions and interesting co-locations were found
between QTLs controlling grain yield per plant (GYP) and related agro-
morphological traits (see Fig. 5-1 ) .
Several QTLs were detected for DSF in four different growth conditions
and most of them were common across at least two growth conditions. The
most important QTL for DSF was located on LG 7 where several QTLs under
different growth conditions were co-localized ( Fig. 5-1 ) . The positive alleles
for these overlapped QTLs came from RHA266. Seventeen QTLs were
identified for LN under four growth conditions among which nine were
common across at least two growth conditions and eight were detected
under only one condition. Both the parental lines contributed almost equally
to the QTL expression. For LAF, 21 QTLs were detected under four growth
conditions, their number being from three to six depending on growth
conditions. Among 21 QTLs, nine were detected in only one of the growth
conditions and 12 were detected in at least two growth conditions. The
phenotypic variance explained by each QTL ranged from 5% to 19%, and