Biology Reference
In-Depth Information
This locus was mapped between STMS mark-
ers TA18 and TA180 (3.9 cM apart) in the same
genomic region of the QTL (Table 11.1). These
STMS markers are close enough to
Uca1/uca1
to
allow reliable marker-assisted selection for rust
resistance.
ing three annuals were assigned to the tertiary
gene pool.
The cultivated chickpea has a narrow genetic
base, and sources of resistance to several stresses
are often lacking within cultivated germplasm
(Abbo et al. 2007). Diversification and broad-
ening of the genetic base through the use of
wild relatives and primitive landraces is there-
fore pivotal for making progress in the devel-
opment of new cultivars. Some efforts have been
made in the past to screen germplasm collections
under field and controlled conditions in order to
identify useful genes for resistance to AB, Foc,
BGM, rust, and other diseases. These efforts have
resulted in identification of valuable sources of
resistance for these key diseases (Table 11.2).
However, concerted efforts are needed to mine
these collections further to identify new sources
for resistance.
GeneticResources and Breeding
Progress
To make progress in breeding against evolv-
ing biotic stresses, it is imperative for chick-
pea breeding programs worldwide to search
and deploy new sources of resistance for these
stresses. These sources can be mined from wide
collections of chickpea landraces and wild rela-
tives. The two CGIAR (Consultative Group on
International Agricultural Research) centers -
ICARDA (International Center for Agricultural
Research in the Dry Areas) and ICRISAT (Inter-
national Crop Research Institute for the Semi-
Arid Tropics) - conserve more than 34,085
accessions, in addition to those available in
the USDA-ARS (United States Department of
Agriculture-Agricultural Research Service) and
the ATFCC (Australian Temperate Field Crops
Collection). Of the CGIAR centers' collections,
578 accessions are of wild relatives, which are
a rich reservoir of useful genes/alleles unavail-
able in the cultivated gene pool (Kumar et al.
2011). The
Cicer
genus encompasses one cul-
tivated species - chickpea (
C. arietinum
)-34
wild perennial and 8 wild annual species. The
8 wild annuals include
C. reticulatum
,
C. echi-
nospermum
,
C. pinnatifidum
,
C. judaicum
,
C.
bijugum
,
C. cuneatum
,
C. chorassanicum,
and
C. yamashitae
(Singh et al. 2008; Kumar et al.
2011). Basing their work on crossability, molec-
ular diversity, and karyotype analyses, Croser
and colleagues (2003) classified the annual
Cicer
species into three major gene pools. The primary
gene pool consists of the cultivated species (
C.
arietinum
), the wild progenitor
C. reticulatum
,
and the closely related
C. echinospermum
.The
secondary gene pool consists of
C. bijugum
,
C.
pinnatifidum
, and
C. judaicum
, while the remain-
Ascochyta Blight (AB)
Breeding cultivars with durable resistance to AB
is a challenging task because of the continu-
ous evolution of the pathogen and the appear-
ance of new virulent pathotypes (Atik et al.
2011; Imtiaz et al. 2011). This makes resis-
tance short-lived and consequently limits the
effectiveness of resistant cultivars. Accordingly
continuous efforts are required to identify new
sources of resistance for deployment in chick-
pea breeding programs. One of the approaches
that breeders are adopting is to find and pyra-
mid different genes into the same cultivar to
improve its resistance level and durability. Con-
siderable progress has been made in identify-
ing resistant germplasm and breeding for resis-
tance to AB (Malhotra et al. 2010; Pande et al.
2011a). Climatic conditions at ICARDA are very
conducive for AB development, and each year
an area of approximately 6 ha is planted with
20,000 to 25,000 lines, under artificial epiphy-
totic field conditions, in order to select resistant
lines, mostly in the Kabuli background. Reddy
and Singh (1984) reported 11 Kabuli and 6
Desi genotypes resistant to AB. However, among
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