Biology Reference
In-Depth Information
Evolution by stepwise mutation, as suggested
for the pathogen, justifies bringing additional
sources of resistance from wild
Cicer
into culti-
vated germplasm. Fortunately, various species of
annual wild
Cicer
possess a high level of resis-
tance to Foc (Rao et al. 2003). Indeed, Nene
and Haware (1980) reported resistance to Foc
in five of six annual wild
Cicer
species. All
C.
bijugum
tested accessions and some accessions
of
C. judaicum
,
C. reticulatum
,
C. echinosper-
mum,
and
C. pinnatifidum
showed resistance.
Moreover, some accessions of
C. bijugum
,
C.
judaicum,
and
C. reticulatum
were completely
free of wilt damage. Resistance to Foc was also
reported in accessions from the eight annual wild
Cicer
species (Kaiser et al. 1994; Infantino et al.
1996; Rao et al. 2003). Results showed that
most of the highly resistant accessions belong
to species of the first and second gene pools, and
this facilitates introgression of resistance genes
into cultivated chickpea.
Significant progress has been made in Foc
research and germplasm and cultivars are now
available that possess resistance to multiple
races. For example, WR315 is widely recog-
nized as possessing resistance to all known races,
while JG 74 is resistant to all races except races
2 and 5 (Haware 1998). Cultivars with stable Foc
resistance have been released in many countries
(Malhotra et al. 2007, Singh et al. 2009). Simple
genetic control of Foc resistance favors success
in the selection of resistant lines using marker-
assisted backcrossing methods (Dr. J. Gil, per-
sonal communication).
Fusarium Wilt (Foc)
Possibly because of climate change, particularly
the rise in soil temperature related to global
warming, Foc is becoming more significant even
in areas where it was not a severe problem in the
past. To design a breeding strategy for the devel-
opment of wilt-resistant varieties, knowledge of
genetic variations for virulence in the pathogen is
important. A number of resistant sources to Foc
have been reported under field and controlled
epiphytotic conditions in both cultivated and
wild chickpea germplasm (Haware et al. 1992;
Halila and Strange 1997; Sharma et al. 2005).
Cost-effective field, greenhouse, and laboratory
methodologies for resistance screening have
been developed (Gaur et al. 2007; Hamwieh et al.
in preparation;
http://icardanews.wordpress.
wilt-resistance-in-chickpea/).
Since develop-
ment of a wilt-sick plot for field screening is
comparatively easy, such plots are available
at many research stations around the world.
However, with time these sick plots become
contaminated with other soil-borne pests such
as nematodes and other root-rot pathogens,
thus the racial picture and availability of uni-
form inoculum is becoming a challenge when
evaluating materials in sick plots.
A collection comprising more than 8,231
germplasm and improved lines was evaluated
against a mixture of races of
F. oxysporum
at ICARDA, and 2,645 lines with less than
10% mortality (resistant) were identified (Imtiaz,
personal communication). Similarly, in coop-
erative research between INRAT, Tunisia, and
ICARDA, 650 lines were tested at Beja in
2011 in a wilt-sick plot infested by race 0.
In that test, 131 entries were found to be
resistant (less than 10% mortality), and 25 of
those resistant lines presented 0% mortality.
Haware and colleagues (1992) screened more
than 13,500 germplasm accessions from 40
countries for race 1 at ICRISAT and identi-
fied 160 resistant accessions (150 Desi and 10
Kabuli).
Other Diseases
Few accessions belonging to either cultivated or
wild
Cicer
are tolerant of BGM and the search
for higher levels of disease resistance is contin-
uing (Pande et al. 2006a). Higher levels of resis-
tance to BGM were identified in some accessions
of
C. judaicum, C. bijugum, C. echinospermum,
and
C. pinnatifidum
(Singh et al. 1982; Singh
et al. 1991; Haware et al. 1992; Haware 1998;
Rao et al. 2003). Moreover, at ICRISAT Pande
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