Agriculture Reference
In-Depth Information
Table 8.2
Principal sources of genes used to breed wheat for resistance to root-lesion nematodes
Pratylenchus neglectus
(
Pn
) and
P. thornei
(
Pt
).
Cultivar or
Line
Response to
Pathotypes
b,c
Cereal Species
Origin
Resistance Gene(s)
a,b
Use in Cultivars
Triticum
aestivum
GS50a
Australia—
reselection from
cv. Gatcher
Major QTL mapped
to 6D
Australia
AUS4930
=
Iraq
QTLs mapped to 1B,
2B, and 6D
R to
Pt
but also
portrays R to
Ha
Australia,
CIMMYT—under
investigation
Iraq 48
Reselection of
Excalibur
Australian cv.
Excalibur
QTL mapped to 7AL
R to
Pn
(
Rlnn1
),
on chromosome
7AL
Australia, CIMMYT
Croc_1/
Ae.
tausch
.
(224)//Opata
Primary synthetic
QTLs mapped to 1B
and 3B
R to
Pt
CIMMYT
CPI133872
Primary synthetic
QTLS mapped to 2B,
4D, 6A, 6D
R to
Pt
and
Pn
Australia
W-7984
Opata 85
×
QTLs mapped to 2B
and 6D
R to
Pt
Australia
AUS4926
Middle eastern
landrace
QTLS mapped to 1B,
2B, 3B, and 6D
R to
Pt
Australia
AUS13124
Middle eastern
landrace
QTLs mapped to 2B,
3B, 6D, and 7A
R to
Pt
Australia
Aegilops
tauschii
CPI 110872
R to
Pt
and
Pn
Aegilops
geniculata
MZ10, MZ61,
MZ96,
MZ144
Middle East and
West Asia
pR to
Pt
, several
also portray R
to
Ha
a
Sources:
Reviews and references in Rivoal and Cook (1993), Cook and Rivoal (1998), McDonald and Nicol (2005), and
Nicol and Rivoal (2007).
b
Characterized QTLs associated with multigene resistance to root-lesion nematodes.
c
R
=
resistant, pR
=
partially resistant,
Ha
=
Heterodera avenae
.
Other management practices are less effective
in managing
Pratylenchus
populations. Field sani-
tation during the fallow phase is as important as
during the in-crop phase, because
Pratylenchus
species multiply on many weed species in the
genera
Avena
,
Brassica
,
Bromus
,
Carrichtera
,
Emex
,
Heliotropium
,
Hordeum
,
Malva
,
Raphanus
,
Rumex
, and
Tribulis
(Vanstone and Russ 2001a,b)
and on volunteer cereals including oat, wheat, and
triticale (Forge et al., 2000). The presence of sus-
ceptible weeds or crop species between planted
crops allows
Pratylenchus
to increase population
density over a greater interval of the cropping
system (Smiley et al., 2004b).
Tillage has reportedly increased, decreased, or
had no effect on populations of
Pratylenchus
in
wheat (Smiley et al., 2004b). In North America it
appears that the greatest impact of conservation
cropping systems will be associated with the
frequency of host crops or weeds rather than the
presence, absence, or intensity of tillage. While
cultivation and fallow have appeared to reduce
populations of
P. neglectus
and
P. thornei
(Orion
et al., 1984; Thompson 1992; Nombela et al.,
1998; Smiley et al., 2004b; Strausbaugh et al.,
2004), these interpretations were based mostly
upon soil samples collected at shallow depth.
Shallow samples accurately characterize
Prat-
ylenchus
populations in shallow soils but not in
many deep soils where these nematodes may be
found as deep as 150 cm and where peak popula-
tions may vary from shallow to as deep as 60-
