ICARDA annual report 2004

ICARDA Annual Report 2004
10
the new drought-tolerant line. In
these cases, the new lines yielded
7-50% more than the local landraces.
In 2005, extension services
will disseminate more seed to farmers
in the province to allow them to
plant larger areas with these highyielding,
drought-resistant lines.
QTLs for straw traits
identified in recombinant
inbred lines of the cross
‘Arta’ x Hordeum
spontaneum 41-1
The objective of this study was to
identify trait-marker linkages in a
population of recombinant inbred
lines (RILs) of a cross between the
H. vulgare cv ‘Arta’ and H. spontaneum
41-1 using the QTL approach.
Of particular interest was to analyze
straw characteristics and determine
the locations of the genes
involved in their control.
One hundred and ninety-four
RILs were used to construct a
genetic linkage map (Fig. 2). Total
genomic DNA was extracted and
genetic mapping was carried out
using Amplified Fragment Length
Polymorphic (AFLP) markers and
microsatellite-based markers. The
linkage map based on the ‘Arta’ x
H. spontaneum 41-1 population orig-
Fig. 1. Grain yield
of new droughttolerant
barley
lines and local
checks in 10
farmers’ fields.
Because of
drought, the
local check
failed to produce
grain in six fields.
inally contained 189 marker loci,
including 1 morphological marker
locus (btr = brittle rachis). For the
purpose of the QTL analysis, a
reduced map was constructed containing
129 marker loci. The Join
Map v. 2.0 software package was
employed for map construction
and recombination fractions were
converted to centiMorgans (cM)
according to the Kosambi’s mapping
function. The QTL analysis
was performed using Windows
QTL Cartographer v. 2.0. The LRvalue
of the locus originates either
from Multi Trait Analysis or from
composite interval analysis. The
effect and the explained phenotypic
variance were estimated by Multi
Interval Mapping.
F7 RILs, derived by single seed
descent from the cross between the
H. vulgare cv ‘Arta’ and H. spontaneum
41-1, were planted with the
parents in the cropping seasons
1996/97 and 1997/98, at ICARDA’s
research stations located near Tel
Hadya and near Breda in Syria and
184 of the RILs evaluated for the
straw traits. Straw samples were
milled and analyzed by NIRS. The
traits measured were: acid detergent
fiber (ADF), neutral detergent fiber
(NDF), lignin (LIG), dry organic
matter digestibility (DOM), voluntary
intake (DMI), crude protein
(CP), and ash percentage (ASH).
Ten QTLs were detected for
ADL, but none of them was common
between the environments.
The QTLs detected in Br97
explained in total 18.6% of the phenotypic
variation and the ones
found in Th97 explained 19.2%. For
NDF, one QTL was detected being
common to two environments (1H-
1: Br98 and Th98). Eleven QTLs
were localized for LIG. One of
them was common to two environments
(6H-7 in Br97 and Br98). For
DOM, 12 QTLs were localized; one
of them was common to Br98 and
Th98 (on 5H-4). Twelve QTLs were
localized for DMI, one of which
common to Br97 and Th98 (on 1H-
8) and one to Br98 and Th98 (on
5H-5). Only for these two QTLs, the
H. spontaneum line contributed the
allele with the higher value, while
for all other QTLs detected for this
trait, the higher allele was found in
‘Arta.’ Specific QTLs for DMI were
detected in Br97, Br98, and Th98.
No QTLs were found in Th97. The
phenotypic variance explained was
about 30 %. For CP, no QTLs were
found in Br97, while one QTL was
common to Th97 and Th98 (on
5H-5) and three additional specific
QTLs were localized. Like in the
case of LIG, DOM and DMI, the
origin of the allele with the higher
value for the locus on 5H-5 was
opposite to the rest of the QTLs: in
this case, it was the only QTL
where the H. spontaneum line contributed
the allele leading to the
higher value of the trait. QTLs for
ASH were found only in Br98. Five
QTLs were identified, explaining
together 25.8 % of the phenotypic
variance. Some of the QTLs identified
would be good candidates for
exploitation by marker-assisted
selection.
The feeding value of barley
straw is of great importance. In
years with favorable rainfall the
feeding value is generally poor, but
high straw yields permit the straw