Among these, abiotic stresses include drought, salinity, water logging, high temperature and chilling frequently limit growth and productivity of chickpea.. Chickpea faces various abioti
Trang 1Abiotic stresses, constraints and improvement strategies in chickpea
UD A Y C JH A1, SU S H I L K CH A T U R V E D I1, AB H I S H E K BO H R A1, PA R T H A S BA S U1, MU H A M M A D S KH A N2 and DE B M A L Y A BA R H3,4
1
Indian Institute of Pulses Research (IIPR), Kanpur, 208024, Uttar Pradesh India;2Centre for Agricultural Biochemistry and
Biotechnology, University of Agriculture, Faisalabad, Pakistan;3Centre for Genomics and Applied Gene Technology, Institute of Integrative Omics and Applied Biotechnology (IIOAB), Nonakuri, Purba Medinipur, West Bengal 721172, India;4Corresponding author, E-mail: dr.barh@gmail.com
With 1 figure and 3 tables
Received June 6, 2013/Accepted November 23, 2013
Communicated by R Varshney
Abstract
Chickpea (Cicer arietinum L.) is cultivated mostly in the arid and
semi-arid regions of the world Climate change will bring new production
sce-narios as the entire growing area in Indo–Pak subcontinent, major
pro-ducing area of chickpea, is expected to undergo ecological change,
warranting strategic planning for crop breeding and husbandry
Conven-tional breeding has produced several high-yielding chickpea genotypes
without exploiting its potential yield owing to a number of constraints
Among these, abiotic stresses include drought, salinity, water logging,
high temperature and chilling frequently limit growth and productivity of
chickpea The genetic complexity of these abiotic stresses and lack of
proper screening techniques and phenotyping techniques and
genotype-by-environment interaction have further jeopardized the breeding
pro-gramme of chickpea Therefore, considering all dispiriting aspects of
abi-otic stresses, the scientists have to understand the knowledge gap
involving the physiological, biochemical and molecular complex network
of abiotic stresses mechanism Above all emerging ‘omics’ approaches
will lead the breeders to mine the ‘treasuring genes’ from wild donors
and tailor a genotype harbouring‘climate resilient’ genes to mitigate the
challenges in chickpea production
Key words: Chickpea breeding — cold stress — drought
tolerance — salinity stress — QTLs
Globally, chickpea (Cicer arietinum L.) is the second most
important legume crop after dry beans (Varshney et al 2013b).
According to FAOSTAT data (2012), chickpea is grown in 54
countries with nearly 90% of its area covered in developing
coun-tries (Gaur et al 2012) Notably, almost 80% of global chickpea
is produced in Southern and South-Eastern Asia and India ranks
first in the world, contributing 68% of the global chickpea
pro-duction accompanied by Australia (60%), Turkey (47%),
Myan-mar (42%) and Ethiopia (35%) (FAOSTAT 2012, Gaur et al.
2012) Worldwide chickpea production is estimated to be
11.30 million tons from 12.14 million ha area with an average
productivity of 931 kg/ha (FAOSTAT 2012) In India, it tops the
list of pulse crops and is cultivated in 8.32 million ha, producing
a total of 7.70 million tons with an average yield of 925.5 kg/ha
(FAOSTAT 2012) From the nutrition perspective, chickpea seed
contains 20–30% crude protein, 40% carbohydrate, and 3–6% oil
(Gil et al 1996) Besides, pulses supplemented diets are also
good source of calcium, magnesium, potassium, phosphorus, iron
and zinc (Ibrikci et al 2003) Chickpea faces various abiotic
stresses during its life cycle such as drought, cold, terminal heat and salinity (Ryan 1997, Millan et al 2006), and it also encoun-ters water logging, acidity and metal toxicity stresses The yield losses due to abiotic stresses may exceed (6.4 million tons) those caused by biotic stresses (4.8 million tons) (Ryan 1997) Substan-tial economic losses of 1.3 billion, 186 million and 354 million
US dollars due to drought/heat, cold and salinity, respectively, have raised tremendous concerns among the chickpea-growing countries (Ryan 1997).
Given the complex genetic architecture and unpredictable occurrence, breeding against abiotic stresses has always been a challenging task Further, drastic climate changes have caused phenotypic plasticity implying changes in phenotype of plant (Nicotra et al 2010), and this phenotypic plasticity permits to adjust their form and function according to the change of resource and habitat (Magyar et al 2007) Tolerance to abiotic stresses exhibits complex quantitative inheritance that is also influenced by a number of genetic and environmental interac-tions As an obvious reason, these strong genotype-by-environ-ment (G 9 E) interactions have also posed impediments in breeding against these stresses An exhaustive search of germ-plasm for appropriate donors to these stresses represents the fore-most step in breeding for stress tolerance Given the context, a detailed list of the genotypes showing tolerance to various abi-otic stresses has been presented in Table 1, which can be used
as potent resistant/tolerant sources for introgressing the quantita-tive trait loci (QTLs) governing stress tolerance to susceptible varieties This review article summarizes the negative impacts and constraints of major abiotic stresses on chickpea yield along with providing a critical appraisal of various conventional breed-ing strategies Additionally, this article also provides an over-view on recent developments of genomic resources and various molecular breeding (MB) approaches including marker-assisted backcrossing (MABC), marker-assisted recurrent selection (MARS), which may act as powerful supplement to conventional breeding particularly in the context of abiotic stresses.
Drought Stress
Background constraints and its effects Drought is one of the most important abiotic stresses, which limits production in different parts of the world and has remained the
© 2014 Blackwell Verlag GmbH
Trang 2Table 1: Sources of resistance to various abiotic stresses and their basis of tolerance in chickpea
Abiotic
stress Tolerant sources
Underlying mechanism/physiological and biochemical basis for tolerance References Drought
tolerance
H208, H355, S26, G24, RS10, RS11 and Azerbaijan 583 – Saxena and Singh (1987) ICC4958 Deep rooting, 30% more root volume
and mass than cultivated genotypes
Saxena et al (1993), Krishnamurthy et al (2003) and Kashiwagi
et al (2005, 2006a)
ICC96029 Early flowering Kumar and Rao (1996)
ICCV93032, ICCV94008, ICCV90033 and ICC89204 – Kanouni et al (2002) ICC5680, ICC10448 Small leaf and leaf area Saxena (2003)
RILs from ICC49589 Annegiri Prolific rooting and deep rooting trait Serraj et al (2004a) ILC1799, ILC3832, FLIP98-141, ILC3182, FLIP98-142C,
ILC3101 and ILC588
Escape through earliness Sabaghpour et al (2006) ICC8261 Avoidance through root traits Gaur et al (2008) Beja and Kesseb Lower nodule mortality Labidi et al (2009) ICC4958, ICC8261 Root length density and root dry
weight
Kashiwagi et al (2008) ACC316 and ACC317 Early flowering(escape mechanism) Canci and Toker (2009) ICC13124 Root length, root weight and root
volume
Parmeshwarappa et al (2010)
HC-5 and H02-36 Rooting depth and root biomass Kumar et al (2010a) MCC544, MCC696 and MCC693 Mesophyll resistance and proline
accumulation
Mafekheri et al (2010) ILC482 Higher proline content Mafakheri et al (2011) ICC7571 Harvest index and rate of partitioning
positively associated with (DRI)
Kashiwagi et al (2013) Terminal
Heat
stress
ILC482, Annegiri, ICCV10 Cell membrane stability Srinivasan et al (1996)
ACC316and ACC317 Early flowering Canci and Toker (2009) ICC1205 Pollen germination and tube growth Devasirvatham et al (2010) ICC456, ICC637, ICC1205, ICC3362, ICC3761, ICC4495,
ICC4958, ICC4991, ICC6279, ICC6874, ICC7441, ICC8950,
ICC11944, ICC12155, ICC14402, ICC14778, ICC14815,
ICC15618
Early flowering, seed yield at maturity Krishnamurthy et al (2011)
ICC14346 Early maturing Upadhyaya et al (2011)
ICC1205 and ICC15614 High pod no; filled pods/plant under
heat stress
Devasirvatham et al (2012, 2013) ICC14778 High rate of partitioning, cooler canopy
temp Extract maximum soil water
Kashiwagi et al (2008), Zaman-Allah et al (2011a,b) and Krishnamurthy et al (2013a)
Freezing
tolerance
ILC-794, ILC-1071, ILC1251, ILC1256, ILC1444, ILC1455,
ILC1464, ILC1875, ILC3465, ILC3598, ILC3746, ILC3747
– Singh et al (1989) ILC3791, ILC3857, ILC3861, FLIP-85-81C, FLIP82-85C,
82-313C, 84-112C, FLIP85-4C, FLIP 85-49C, FLIP 81-293C,
FLIP 82-127C and FLIP82-128C
ICCV 88502, ICCV88503 Pod set at cold temperature(tolerance/
resistance)
Srinivasan et al (1998, 1999)
ICCV96029, ICCV96030 Earliness(escape mechanism) Sandhu et al (2002) and
Kumar and Rao (1996)
Sonali and Rupali Pollen selection at low temperature Clarke et al (2004)
Salinity
tolerance
CSG88101, CSG8927 Lower Na+ in root, that is, exclusion
of Na+ Dua and Sharma (1995) Amdoun l Protection of photosynthetic organ
from attack of Na+ by retaining Na+
in root and supply of K+ to shoot
Slemi et al (2001)
FLIP.98-74, FLIP.87-59, FLIP.87-85, and ILC 3279 Physiological Bruggeman et al (2003) SG-11 and DHG-84-11 Physiological Singh et al (2001) and
Singh (2004) CSG8962 and ICCV96836 – Maliro et al (2004)
ICC5003, ICC15610 and ICC1431 Higher yield under salinity Vadez et al (2007)
JG62 Higher yield under salinity, Early
flowering
Vadez et al (2007, 2012b)
Trang 3most recalcitrant when attempted to address through traditional
breeding approaches (Tuberosa and Salvi 2006, Toker et al.
2007a) It is important to note that the water scarcity alone causes
70% of agricultural yield loss across the globe (Boyer 1982).
Moreover, in concern with drought, desiccation has been reported
as the most severe form of drought that leads to loss of
protoplas-mic water (Yordanov et al 2003) Drought imposes negative
effects on plant growth and development by impeding lipid
bio-synthesis and lowering the membrane lipid, which ultimately
results in loss of membrane integrity (Pham-Thi et al 1987,
Monteiro de Paula et al 1990, Gigon et al 2004, Harb et al.
2010) and irreversible cell damage (Vieira da Silva et al 1974).
Further, the water deficit hinders the foremost biological process
of photosynthesis and other metabolic activity of plant (Chaves
1991, Chaves et al 2003, 2009, Pinheiro and Chaves 2011)
Nota-bly, almost 90% of chickpea is grown under rainfed conditions
(Kumar and Abbo 2001) where terminal drought limits its
produc-tivity (Toker et al 2007a) The result of drought relies upon the
water-holding capacity, evapo-transpiration and need of water for
crop plants (Toker et al 2007a) Drought accounts for 40–45%
yield losses in chickpea across the globe (Ahmad et al 2005).
Strategy for drought acclimation
Harnessing genetic variability, genetic basis and breeding for drought
tolerance
To a large extent, success of any crop-improvement programme is
determined by the quantum of exploitable genetic variation that
exits in the crop germplasm Keeping the above in view, a large
number of accessions have been routinely screened for various
traits specifically to incorporate drought tolerance in chickpea For
instance, a preliminary study conducted during 1992 to 1995 at
Tel Hayda (northern Syria) using 4165 lines by establishing the
proper screening and rating scale (1–9), and subsequently, a total
of 19 drought resistant lines were identified (Singh et al 1997) In
a similar manner, 64 chickpea lines were evaluated under rainfed
conditions for drought tolerance showed 53% yield advantage of
the mentioned lines under non-stressed conditions compared with
stress conditions (Toker and Cagirgan 1998) Likewise, a set of 24
genotypes was screened considering five important indices, viz.
drought response index (DRI), stress tolerance index (STI),
toler-ance (TOL), mean productivity (MP) and geometric mean
produc-tivity (GMP), which were recorded under two different moisture
levels at two different sowing times STI and MP were chosen as
the best indices for evaluation of drought resistance (Kanouni
et al 2002), and similarly, Pouresmael et al (2013) reported STI
as an important parameter for drought tolerance in chickpea.
In any crop species, wild species are the natural reservoir of
both biotic and abiotic stress resistance However, during the
process of crop domestication and selection, these natural
reser-voirs of immense genetic variation have gone unnoticed (Zamir
2001) In regard to chickpea, perennial wild Cicer species, viz.
C anatolicum, C microphyllum, C montbretti, C oxydon and
C songaricum, were evaluated for drought tolerance, using a
scale of 1 (highly tolerant) to 5 (highly susceptible) (Toker et al.
2007b) Taken into consideration the drought tolerance index
(DTI), a mini-core collection comprising 211 chickpea
acces-sions was screened for three consecutive years The study
revealed a wide range of variation for days to 50% flowering,
maturity, shoot biomass and seed yield under drought condition,
and the cluster analysis categorized five accessions as highly
tol-erant, 78 as toltol-erant, 74 as moderately toltol-erant, 39 as sensitive
and 20 as highly sensitive (Krishnamurty et al 2010) Similarly
from mini-core collection, 10 accessions were identified showing drought tolerance relying on drought susceptible index (DSI) and drought tolerant efficiency per cent (DTE%), tested during 2006–2007 The genotype ICC13124 performed best among the genotypes used and gave maximum yield under irrigated (1220 kg/ha) and rainfed condition (990 kg/ha)
(Parmeshwarap-pa et al 2010) In another instance, screening of 377 accessions using 1 (free from heat and drought stress) to 9 (susceptible to heat and drought) scale led to identification of two genotypes viz ACC316 and ACC317 possessing resistance to drought and heat accompanying least impact of heat and drought on seed weight and having highest heritability (Canci and Toker 2009).
To find out the associations of various drought-related traits with DRI, a set of 21 drought-responsive genotypes was tested for two consecutive years and the experimental results demon-strated the positive association of crop growth rate (CGR) with DRI, whereas water-use efficiency (WUE) showed a negative correlation with the DRI (Kashiwagi et al 2013) Moreover, one chickpea landrace (ICC 7571) exhibited a noticeably tolerant reaction against drought across both years Kashiwagi et al.
2013 also reported the significant contribution of rate of parti-tioning or partiparti-tioning coefficient (p) towards grain yield under drought conditions, and this observation was also confirmed in another study conducted on a reference collection of chickpea comprising 280 cultivated accessions (Krishnamurthy et al 2013a) Under terminal drought stress, path analysis performed
in the reference collection of chickpea exhibited the positive associations of carbon isotope discrimination with harvest index (HI) (Krishnamurthy et al 2013b) In addition to germplasm collections, segregating populations derived from possible com-binations of four genotypes viz ICCV 2, A1, ICC 4958 and ICCV 10448 were tested for physiological traits imparting drought tolerance Of the six F2 populations evaluated, highest yield was obtained from progeny sharing ICCV4958 as one of the parent The segregates obtained from A19 ICC 4958, ICCV
2 9 ICC 4958 explained high seed yield, early and high root mass (Mannur et al 2009) Efforts were also carried out to find out the gene actions underlying drought tolerance using joint scaling test in the cross ‘Hashem’ (cultivar) 9 ICCV 96029, and the investigation elucidated the presence of additive 9 dom-inance = [j] gene action for grain yield, biological yield and proline content, whereas duplicate epistasis (additive 9 domi-nance = [j] and dominance 9 dominance = [l] gene action) was observed for number of pods/plant and number of seeds/pod (Farshadfar et al 2008) Two important QTLs (Q3-1 and Q1-1) underlying drought tolerance (given in Table 2) were identified from population ILC 588 9 ILC 3279, and these QTLs were located on LG3 and LG1 (Rehman et al 2011) More recently,
a comprehensive molecular investigation targeting genetic dis-section of drought tolerance was carried out in chickpea (Varsh-ney et al 2013a) Two mapping populations namely ICC
4958 9 ICC 1882 and ICC 283 9 ICC 8261 were chosen for rigorous phenotypic screening using a variety of drought compo-nent traits, which were phenotyped across five different loca-tions in India The phenotypic data along with the genotypic data were subsequently analysed to discover QTLs associated with drought tolerance Importantly, not only main-effect QTLs (45 m-QTLs) but epistatic-QTLs (e-QTLs) were also detected indicating the occurrence of complex genetic interactions con-trolling drought tolerance In total, the 45 m-QTLs explained almost 60% variance, while 973 e-QTLs accounted upto 90% of the phenotypic variance for various component traits (Varshney
et al 2013c).
Trang 4Physiological and biochemical tolerance
The plant acclimatizes under drought conditions through
differ-ent mechanisms like escape, avoidance and tolerance (Levitt
1972, Turner 1986, Loomis and Connor 1992) Drought
resis-tance and its components are almost constantly being redefined
(Blum 2005).
Drought escape through early phenology
Drought escape enables selection of plants completing their life
cycle in short period thus making judicious use of available
moisture condition (Turner and Whan 1995, Siddique et al.
1997) Under terminal drought conditions, early flowering trait
provides advantage of avoiding drought and avoids yield loss in
chickpea (Subbarao et al 1995, Siddique et al 1999, Kumar and
Abbo 2001, Berger 2007) In context of early flowering, a major
recessive gene ‘efl-1’ was reported to be responsible for early
flowering (Kumar and van Rheenen 2000), and this finding
sub-sequently facilitated the development of super early genotype
ICCV 96029 (derived from ICCV 2 9 ICCV 93929 cross)
which flowered within 24 days (Kumar and Rao 1996) at
ICRI-SAT Sabaghpour et al (2006) screened a total of 40 kabuli
genotypes and identified ILC1799, ILC3832, FLIP98-141,
ILC3182, FLIP98-142C, ILC3101 and ILC588 as superior early
genotypes that can escape terminal drought (Table 1) However,
selection of genotypes with shorter vegetative period may result
in yield penalty (Basu and Singh 2003).
Drougth avoidance through root traits
Root system of plant imparts drought tolerance through acquiring
soil moisture by deep penetration of root, adequate root density
and sufficient longitudinal conductance of main roots (Fisher
et al 1982) Chickpea genotypes with high root biomass and
showing marked drought tolerance have been reported (Brown
et al 1989, Saxena et al 1994, Krishnamurthy et al 1996) One
of such drought resistant genotype ICC4958 recorded 30%
higher advantage in root dry matter as compared to ‘Annegiri’
(Saxena et al 1994) Among various root traits, the depth of rooting allows availing the deep soil water in drought conditions (Saxena et al 1993, Krishnamurthy et al 2003 and Kashiwagi
et al 2005) Role of deep and prolific rooting trait affecting drought avoidance and yield was examined using ICC4958 9 ‘Annegiri’ based RIL population consisting of 257 lines However, no significant yield improvement was recorded
in this study (Serraj et al 2004a) In addition, the ‘root length density’ (RLD) and maximum ‘root depth’ (RDp) can benefit in drought resistance without affecting yield as assessed in mini-core collection of chickpea (Kashiwagi et al 2005) Using 12 chickpea genotypes, a positive association of RLD with seed yield was illustrated at 35 days after sowing (DAS) (Kashiwagi
et al 2006a) Notably, genotypes with prolific and deep rooting have been found to be more adapted to drought, but little infor-mation is available on the genetic control of root system Taken the above into account, generation mean analysis (GMA) was conducted to estimate the genetic effects of root and shoot traits using six generations (P1, P2, F1, F2, BC1P1 and BC1P2) based
on two different crosses viz ICC283 9 ICC 8261 and ICC4958 9 ICC1882 The study suggested existence of additive gene action and additive 9 additive gene interactions, which control RLD and root dry weight (RDW) (Kashiwagi et al 2008) In contrast to the destructive method involved in screen-ing of root traits, polyvinyl chloride (PVC) pipes are used mak-ing the samplmak-ing of root traits easier and efficient in chickpea (Upadhyaya et al 2012) In an investigation aiming at detecting significant QTLs, a major QTL was discovered that controlled one-third of the entire variation for root length and root biomass (Chandra et al 2004) Kumar et al (2010a) investigated the root traits for drought tolerance in six genotypes in both irrigated and rainfed conditions and identified two genotypes viz HC-5 and H02-36 showing high dry matter of roots, high root depth, and high root to shoot ratio, and ultimately, the plant yield advantage However, it has also been observed in some recent studies that profuse and deep rooting do not contribute drought
Table 2: Different QTLs identified for various abiotic stresses in Chickpea
Trait Mapping population Markers Identified QTL
Linkage group
Phenotypic variation (%) References Drought
tolerance/
avoidance
ICC49589 Annigeri – One major QTL contributing
root biomass – – Gaur et al (2008) ICC82619 ICC283 and QTLs contributing root traits – – Gaur et al (2008) Drought
tolerance
ILC 5889 ILC 3279 97 SSR
markers
Two QTL for HI – 38 Rehman et al (2011) – Four QTL for flowering – 45 Rehman et al (2011) – Three QTL for maturity
explaining
– 52 Rehman et al (2011) – Three QTL for gs+six QTL
for Tc–Ta – 7–15 Rehman et al (2011) – Two QTL (Q3-1 and Q1-1) LG3 and
LG1
– Rehman et al (2011) Drought
tolerance
ICC49589 Annigeri TAA170,
ICCM0249, STMS11 and GA24
Several QTLs contributing drought tolerance
LG4 – Jaganathan et al (2013)
Salinity
tolerance
ICCV 29 JG 62 216 markers One QTL for seed yield under
salinity on
LG3 19 Vadez et al (2012a) ICCV 29 JG 62 – Many QTL associated with
seed no and 100 seed wt under salinity
LG 6 14.8–49.7 Vadez et al (2012a)
ICCV 29 JG 62 – Many QTL associated with
50% flowering, seed no
shoot dry wt
LG 4 8.8–37.7 Vadez et al (2012a)
gs, Higher stomatal conductance; [Tc–Ta], cooler canopies (canopy temperature minus air temperature); HI, Harvest Index
Trang 5tolerance in terms of improving yield under drought stress,
whereas some moisture preservation traits determine yield
improvement under drought in chickpea (Zaman-Allah et al.
2011a,b).
Tolerance through osmotic adjustment
Osmotic adjustment (OA) is an important physiological
phenom-enon, which controls the water absorption and cell turgor
pres-sure under drought stress (Cattivelli et al 2008) OA confers
drought tolerance in many crops of commercial importance like
wheat (Blum et al 1999, Morgan 2000), barley (Blum 1989),
sorghum (Morgan 1984) In addition to sustaining turgor
mainte-nance during water stress condition (Ali et al 1999), OA also
plays a significant role during grain formation under drought
stress in wheat (Morgan and Condon 1986) Similarly, several
reports have been published in chickpea providing knowledge
about the association of OA and yield (Morgan et al 1991, Basu
and Singh 2003, Moinuddin and Khanna-Chopra 2004) For
example, Serraj and Sinclair (2002) deduced positive role of OA
in regard to yield through root development towards higher soil
water However, no strong evidence was reported concerning the
direct association of OA with yield of plant under drought stress.
With the progress of water stress, OA enhances progressively
witnessed by measuring plant water potential and relative water
content (RWC) (Lecoeur et al 1992) By subjecting a set of
advanced breeding lines of chickpea to drought stress, variation
in OA was recorded for both Indian and Australian conditions.
No yield advantage was seen under Australian conditions, except
the case of early flowering where OA effect exhibited high yield
advantage (Turner et al 2007) Similarly, Basu et al (2007) also
investigated the genetic difference for OA existing among
differ-ent chickpea genotypes They also suggested that lowering water
potential will reduce the leaf starch content, but soluble sugars
hexoses and sucroses get increased, not due to change in OA,
suggesting reliability of OA for drought tolerance is not
promis-ing in chickpea.
Water-use efficiency (WUE) is described as amount of
bio-mass produced at the cost of per unit transpired water (Bacon
2004) High WUE is another important criterion while dealing
with drought tolerance, and it is calculated by graviometric
method in pot culture based on transpiration and yield
correla-tion (Krishnamurthy et al 2007, Upadhyaya et al 2012).
A robust screening technique known as carbon isotope
discrimi-nation ( D13
C) was used for measuring WUE in chickpea
(Kash-iwagi et al 2006b) At different levels of vapour pressure
deficit under both field and controlled conditions, some
chick-pea genotypes displayed low canopy conductance especially at
vegetative stage under irrigated conditions and exactly opposite
at pod filling stage (Zaman-Allah et al 2011a,b) Based on
nodule mortality symptom, inoculating five lines with
Mesorhiz-obium ciceri UPMCa7 and noticing change in N content and
root to shoot ratio, loss of chlorophyll, and consequently, the
genotypes ‘Beja’ and ‘Kesseb’ were found to be tolerant under
drought conditions (Labidi et al 2009) Similarly, antioxidant
enzyme activities of ascorbate peroxidase and peroxidase in
nodule produced by Mesorhizobium ciceri strains contribute to
drought tolerance in chickpea (Esfahani and Mostajeran 2011).
By imposing drought at three different growth stages viz (i)
vegetative, (ii) anthesis and (iii) both the vegetative and
anthe-sis stage, more accumulation of carbohydrate, catalase (CAT)
and peroxidase (POX) was observed in tolerant genotypes
indi-cating the importance of CAT and POX in drought tolerance
(Mafakheri et al 2011) With the purpose of identifying some new resistant sources to breed for drought tolerance, the toler-ance or susceptibility reactions of 150 Iranian kabuli genotypes were checked under rainfed and irrigated conditions The results obtained were further validated using a pot experiments, and as
a consequence, three genotypes MCC544, MCC696 and MCC693 were declared as tolerant to drought stress (Ganjeali
et al 2011) The above investigation also confirmed the pre-sence of significant negative correlations between yield and days to flowering under drought conditions Moreover, it also provided emphasis on the fact leaf area can be taken as a deci-sive factor, while assessing the drought tolerance due to less transpiration in decreased leaf area While evaluating 14 chick-pea accessions under moisture and non-moisture environment, three genotypes namely Phule G09103, Phule G 2008-74 and Digvijay were found as drought tolerant which may be due to higher value of drought tolerance efficiency, chlorophyll con-tent, proline concon-tent, reduction in drought susceptibility and membrane injury indices (Ulemale et al 2013) Other crucial physiological parameters viz., photochemical efficiency of PII system, RWC, SPAD chlorophyll metre reading, cell membrane integrity and stomatal conductance contributing to drought toler-ance have also been investigated in chickpea (Pouresmael et al 2013).
Terminal Heat Stress
Background constraints and its effects Concerning heat stress, Wahid et al (2007) reported that the rise
in temperature beyond certain optimum level is detrimental to the crop growth causing severe injuries that are collectively termed as ‘heat stress’ Impact of high temperature on plant growth has been reported on various legume crops including dry bean (Prasad et al 2002), groundnut (Prasad et al 2003) and soybean (Baker et al 1989) However, a significant progress has not been achieved in regard to the effect of heat on different morphological and physiological stages of chickpea (Wang et al 2006) Being a cool season crop, chickpea is also susceptible to high temperature (30–35°) for few days at flowering stage and can cause substantial yield loss (Summerfield and Wein 1980, Saxena et al 1988) Summerfield et al (1984) found the nega-tive relationship between the effect of high temperature at repro-ductive phase and yield in chickpea Evolution or more precisely the domestication of chickpea has enforced the selection of vari-ous phenological changes in accordance with the changes of habitats (Berger et al 2011) In the Mediterranean region, chick-pea confronts extremely low temperature in winter (Berger 2007) and tremendously high temperature during the reproductive stage (Iliadis 1990) While in case of Indian subcontinent condition, chickpea encounters day temperature of 5–10°C during vegeta-tive stage and 20 –27°C and even >30°C temperature during reproductive stage (Summerfield et al 1984, 1990, Berger and Turner 2007) Exposure of various chickpea genotypes beyond
35 °C temperature shows no pod setting (Basu et al 2009) The preanthesis and anthesis stages are the stages that are most vul-nerable to high temperature stress (Devasirvatham et al 2013) High temperature hampers photosynthesis by damaging both structural and functional activity of chlorophyll and lowers the chlorophyll content (Xu et al 1995) Temperature beyond 40°C causes disruption in photo system I and II (Baker 1991, Sharkey 2005) and also affects respiration (Kurets and Popov 1988), membrane composition and its stability (Levitt 1969), nitrogen
Trang 6fixation (Black et al 1978) and water relation (McDonald and
Paulsen 1997) High temperature stress exerts pronounced effect
on reproductive phase, which leads to impairment in
pre-anthe-sis, postanthesis and fertilization processes ultimately resulting in
loss of seed weight and yield (Nakano et al 1997, 1998, Prasad
et al 2003, Upadhyaya et al 2011) In chickpea, high
tempera-ture stress also causes reduction in number of flowers, pollen
production, pods/plant and most importantly, the filled pods/
plant (Wang et al 2006, Basu et al 2009, Devasirvatham et al.
2012) The sensitivity of chickpea pollen to high temperature is
more than stigma, and this observation has been confirmed both
in field as well as under controlled conditions using genotypes
like ICC1205/ICC15614 (heat tolerant) and ICC 4567/ICC10685
(sensitive) (Devasirvatham et al 2012, 2013) Heat stress marks
noticeable effects in anther locule number, anther epidermis wall
thickening and pollen sterility (Devasirvatham et al 2013) For
instance, when ICC 5912 was kept at 35/20 °C for 24 h before
anthesis, the genotype became sterile, whereas the other
geno-type ICCV92944 produced fertile pollens (Devasirvatham et al.
2010).
Strategy for heat acclimation
Harnessing genetic variability, genetic basis and breeding for heat
tol-erance
Germplasm variability for heat tolerance is inevitable for
devel-oping a genotype with heat tolerance Dua (2001) documented
two genotypes ICCV 88512 and ICCV 88513 exhibiting heat
tolerance Another chickpea genotype ICCV 92944 was declared
as heat tolerant in field condition (Gaur et al 2010) and
subse-quently released as cultivar in India (JG14) and Myanmar (Yezin
6) (Gaur et al 2012) Furthermore, while screening the reference
collection (280 accessions) at two locations in India (Patancheru
and Kanpur), three genotypes ICC3362, ICC6874 and ICC12155
were shown as heat tolerant based on the criterion ‘heat
toler-ance index’ (HTI) (Krishnamurthy et al 2011) Similarly, a
promising heat-tolerant line ‘ICC14346’ was recovered through
the assessment of 35 different early maturing germplasm lines
(Upadhyaya et al 2011) Likewise, taken the pod setting ability
(under high temperature ≥37°C) into consideration,
Devasirva-tham et al (2012, 2013) registered two chickpea genotypes
ICC1205 and ICC15614 as heat-tolerant lines Notwithstanding
the immense importance of heat tolerance, extensive studies have
not been carried out to discover the inheritance patterns of heat
tolerance in chickpea However, recently Upadhyaya et al.
(2011) suggested that heat tolerance in chickpea is under the
control of multigenes As an alternative to direct selection of the
heat-tolerant genotypes, choice of early flowering and maturity
genotypes can be made, thereby bypassing cumbersome
pheno-typing for heat stress in Mediterranean spring sown and south
Indian sown chickpea (Toker et al 2007a, Berger et al 2011).
While understanding the mechanism of heat tolerance, cell
membrane stability can be chosen as an important index
(Sulli-van 1972), which is evident from various reports available
from different legumes including chickpea (Srinivasan et al.
1996) Other factors like lipid composition and heat shock
pro-tein accumulation in the pollen can also assist in identification
of heat-tolerant genotypes (Blum 1988) Besides, osmoregulator
contents can also provide defiance against heat stress (Evan
and Malmberg 1989, Flores 1991) Importantly, the external
application of abscisic acid (ABA) can protect plant from heat
stress by inducing other osmolytes viz., proline, glycine betaine
and trehalose (Kumar et al 2012) Electrolyte leakage and
fluo-rescence tests can aid in screening for heat stress (Srinivasan
et al 1996) Additionally, as reported in some cereal crops like wheat, high grain filling rate and high grain weight under heat stress condition can also act as crucial selection criteria for heat tolerance (Tyagi et al 2003, Singha et al 2006, Dias and Li-don 2009) Similarly, in case of chickpea, pod filling rate and high 100-seed weight can be important selection parameters for heat tolerance Nevertheless, Fokar et al (1998) suggested some other important standards to assess heat tolerance like stay green character and retention of chlorophyll under heat stress In the current scenario of rising global temperature, screening of pollen viability and pollen-based screening tech-niques under high temperature can be particularly beneficial for elevating the levels of heat tolerance in chickpea genotypes (Devasirvatham et al 2012).
Low Temperature Stress
Background constraints and its effects Cold temperature stress represents a major limiting factor in chickpea production especially in North India, Canada and some parts of Australia Based on the severity of cold, low tempera-ture injury can be classified into two types: (i) chilling injury when temperature remains above freezing point ( >0°C) and (ii) freezing injury at temperature below freezing point (0°C) The chilling and freezing injury cause serious damages to plants, which includes disruption of membrane (Steponkus et al 1993, McKersie and Bowley 1997), hampered pollen formation or pol-len germination Moreover, it adversely affects photosynthesis (Bell 1993), electron transport (Hallgren and Oquest 1990) and enzymes involved in CO2fixation (Sassenrath et al 1990) Due
to chilling temperature, the activities of reactive oxygen species (ROS) increase and thus, aggravate chilling injury (Omran 1980, Hodgson and Raison 1991, Prasad et al 1994) Cold tolerance mechanism involves a series of biochemical and physiological changes that cause increase in ABA (Rikin and Richmond 1976, Ciardi et al 1997, Morgan and Drew 1997), alteration in lipid composition in cell membrane (Graham and Patterson 1982, Mu-rata 1983, Tasaka et al 1990) and also the changes in osmolytes and increase in antioxidants (Fridovich 1986, Halliwell and Gut-teridge 1989) Low temperature stress is becoming more preva-lent in temperate region creating a serious threat to vegetative growth by several means like creating chlorosis, necrosis of leaf tip and curling of whole leaf Similarly, reproductive stage repre-sents the most vulnerable phase within where plenty of damag-ing events may take place, such as, the juvenile buds drop, aborted pods, reduced pollen viability and stigma receptivity, inhibited pollen tube growth and ultimately, deteriorated seed quality and seed yield (Kumar et al 2007, 2010b) The harmful effect of low temperature (below 15°C) is reported from various chickpea-growing areas like Australia (Siddique and Sedgley 1986), Mediterranean region (Singh 1993), India (Savithri et al.
1980, Srinivasan et al 1998) and even within controlled labora-tory conditions (Srinivasan et al 1999, Clarke et al 2004, Nay-yar et al 2005).
Strategy for low temperature tolerance acclimation
Harnessing genetic variability, genetic basis and breeding for low tem-perature tolerance
Identification of cold tolerant chickpea in Mediterranean region poses the essential prerequisite for enhancing yield during winter sowing, both at freezing (below 1.5 °C) and chilling ( 1.5 to
Trang 715 °C) temperatures, which affects the entire crop development
process starting from germination to maturity (Croser et al.
2003) Phenological stage should be taken under consideration
for assessing the cold tolerance of a genotype from germination
to flowering stage To ascertain the sowing date for freezing
resistance, 29 genotypes were screened at five locations at two
severe winter ( 10°C to 18°C) temperatures, as a result FLIP
81-293C, FLIP 82-127C and FLIP82-128C offered resistance to
low temperatures (Wery 1990) In regard to the number of genes
underlying tolerance, the genetics of cold tolerance was
eluci-dated by Malhotra and Singh (1991) They considered six
differ-ent crosses for applying combining ability and GMA, and
consequently, the presence of additive 9 additive and
domi-nance 9 dominance interactions with duplicate epitasis was
revealed Furthermore, the inheritance analysis also demonstrated
that tolerance to cold is dominant over susceptibility.
Considering pollen as vital component in manipulating the
chilling tolerance, selections for pollen at gametophytic stage
practiced in chickpea and flower colour was chosen as an
effec-tive visible marker during the selection of genotypes (Clarke
et al 2004) Alternatively, mutation breeding has also appeared
as promising way to creating freezing stress tolerant genotypes
in chickpea (Akhar et al 2011) Use of gamma rays as a potent
mutagen to induce mutation was manifested in three chickpea
genotypes at different doses, that is, 60, 100, 140 and 180 Gy of
gamma rays and keeping the shoots at LT50(50% of lethal
tem-perature) The two genotypes MCC741 and MCC495 showed
the highest survival of 80.1% and 64.6% at 180 and 140 Gy
doses, respectively (Akhar et al 2011) With the objective of
developing high yielding and low temperature tolerance in cooler
region, a panel of 40 genotypes with a susceptible check ILC533
was tested considering different phenological and postharvest
trait data for assessing cold tolerance The genotypes showing
high tolerance to cold were FLIP95-255C, FLIP93-260C and
Sel95TH1716 (Kanouni et al 2009) As another notable
obser-vation, morphological traits such as plant height, number of
pri-mary branches and number of leaves were found to be more in
cold tolerant chickpea genotypes in comparison with sensitive
genotypes especially at early stage (30 and 60 DAS) (Chohan
and Raina 2011) Annual wild species of chickpea have the
potential for freezing tolerance as evident from three C
echino-spermum and two C reticulatum annual wild chickpea
geno-types along with 225 cultivated genogeno-types of chickpea in both
field and controlled condition The most promising wild
acces-sions were ILWC81, ILWC106, ILWC139, ILWC181 and
ILWC235, whereas cultivated genotypes exhibiting tolerance
were Sel96TH11404, Sel96TH11439, Sel96TH11488,
Sel98TH11518, x03TH21 and FLIP93-261C (Saeed et al 2010).
Besides lines of C bijugum, ILWC-29/S-10 line of C
pinnatifi-dum and ILWC-35/S-3 line of C echinospermum were reported
as resources of freezing tolerance (Singh et al 1990).
Physiological and biochemical basis of tolerance
As indicated by double bond index (DBI), the external
applica-tion of abscisic acid (ABA) increases fatty acid desaturaapplica-tion in
plasma membrane and results in low cell lysis at low temperature
(Bakht et al 2006) Cold stress can be ameliorated by glycine
betaine application at budding stage, which improves pollen
ger-mination, pollen viability, pollen tube growth, stigma receptivity
and ovule viability On the other hand, application at podding
stage increases seed yield, number of seeds/pod and RWC
(Nay-yar et al 2005) The fundamental changes by which external
ABA confers cold tolerance in chickpea involve retention of chlorophyll, greater pollen viability, pollen germination, flower retention and pod set, increase in seed weight and single seeded pod, and decrease in infertile pod in comparison with cold stressed plants Further, ABA also prevents the oxidative damage through enhancing the activities of antioxidants and proline in plant (Kumar et al 2007) Similarly, Bakht et al (2006), illus-trated application of exogenous ABA aids in acclimation in frost condition It has also been reported that antioxidative enzymes such as catalase, ascorbate peroxidise, glutathione reductase and sucrose synthase can protect seeds and pod walls from the cold stress and thus can help greatly in developing cold tolerant lines
in chickpea (Kaur et al 2009).
Salt Stress
Background constraints and effects Chickpea production is adversely affected due to salinity in arid and semi-arid regions of world (Ryan 1997, Ali et al 2002) Dua (1992) determined the threshold level of electrical conduc-tivity (EC) of 6dS for survival of chickpea under salinity Salt stress (i) reduces water potential (Hayashi and Murata 1998, Munns 2002, Benlloch-Gonzalez et al 2005), (ii) creates imbal-ance in ion (Hassanein 2000) and (iii) causes toxicity Salinity also imposes osmotic stress and ion toxicity (Munns 2005), ion-imbalance and nutrient deficiency (Tejera et al 2006) in plant Millan et al (2006) discussed the effects of soil salinity on anthocyanin pigmentation in foliages of both desi and kabuli types chickpea In addition to inhibiting growth, photosynthesis, energy and lipid metabolism (Ramoliya et al 2004, Parida and Das 2005), salinity also restrains flower and pod formation (Kat-erji et al 2001, Vadez et al 2007, 2012a) Sohrabi et al (2008) analysed the effect of sodium (Na) salinity at different levels (0,
3, 6 and 9dSm-1) in kabuli (‘Hashem’ and ‘Jam’) and desi (‘Kaka’ and ‘Pirooz’) genotypes for growth and yield parameter suggested the plant growth, pod number, flower, seed weight and seed number get reduced due to the effect of salinity More-over, salinity also exerts negative effects on nodulation, nodule size and N2 fixation (Swaraj and Bishnoi 1999, Flowers et al 2010) Interestingly, Samineni et al (2011) declared that both growth stages, that is, vegetative and reproductive are equally sensitive to salinity.
Strategy for salinity acclimation Like other breeding programmes, breeding for salt tolerance relies on assessment of allelic variation for salt tolerance in the germplasm accompanied by transferring the beneficial allele(s)/ gene(s)/QTLs to the other genetic background to create modern high-yielding cultivars.
Harnessing genetic variability, genetic basis and breeding for salinity tolerance
Genetic variation in chickpea genotypes for yield under saline stress was evaluated by several researchers (Sharma et al 1982, Saxena 1984, Flowers et al 2010) Assessment of 160 genotypes
of chickpea using 50 mMNaCl or 25 mM Na2So4salt facilitated identification of the salt tolerant cultivar ‘L550’ and showed that the presence of Na in the shoots checked the normal growth of plant under salinity stress (Lauter and Munns 1986) In another instance, the tolerance of two chickpea genotypes ICCC32 and 1CCL86446 against chloride ion Cl- salinity was demonstrated
Trang 8choosing various yield parameters (Dua 1992) The same way,
effects of salinity were tested at germination and seedling stages
in a set of 30 chickpea genotypes The genotypes C10, C14,
C16, C17, C19 and C29 had tolerance for medium salinity
(6 dS/m) Notably, the two genotypes C28 and C29 retained
their tolerance at all salt levels (Al-Mutawa 2003) Likewise,
imposing salinity of 0.5, 2, 4, 6 dS/m in six genotypes resulted
in comparatively higher production of dry matter by the
geno-types FLIP97-74, FLIP87-59 and ILC3279 (Bruggeman et al.
2003) Of 252 accessions, 211 mini-core collections of chickpea
were examined for salt tolerance, and kabuli types exhibited
tol-erance to salinity, whereas desi types had susceptibility to salt
tolerance (Serraj et al 2004b) Extensive genetic variability for
salinity was observed in 200 accessions of chickpea including
19 wild relatives (Maliro et al., 2004) In a similar manner, large
degree of variation was also evident in 263 accessions of
chick-pea mini-core collection, and a positive relationship (r2= 0.5)
was found between seed yields obtained under salinity and
non-salinity conditions The report also suggested that the desi types
are more tolerant than kabuli types (Vadez et al 2007) A QTL
analysis conducted on population ICCV 2 9 JG 62 revealed
occurrence of significant QTLs for seed yield under saline
condi-tion and these QTLs were mapped on linkage group 6 (Vadez
et al 2012b) An exhaustive testing for salt tolerance was
per-formed on a sample consisting of landraces and wild relatives
from 28 different countries using three different sampling
strate-gies based on scoring of necrosis score and shoot biomass
reduc-tion (Maliro et al 2008) Considerable genetic variareduc-tion for
salinity tolerance was noticed among 55 chickpea genotypes that
were tested at variable salinity levels, and it was concluded that
high pod and seed number bearing genotype which gathers low
concentration of salt will provide better tolerance under salinity
stress in chickpea (Turner et al 2013) While practicing
selec-tion, emphasis should be placed in the direction of constitutive
(higher number of flowers) and adaptive traits (higher number of
seeds) for salinity tolerance in chickpea (Vadez et al 2012a).
Physiological and biochemical basis of tolerance
Several physiological parameters such as stomatal conductance,
evapo-transpiration and leaf area, and essentially, yield can be
chosen as factors for determining the tolerance against salinity
(Katerji et al 2003) Another important physiological parameters
viz., early maturity, higher predawn water potential, maintenance
of high osmotic adjustment and retention of high number of
stems per plant can provide tolerance to salinity (Katerji et al.
2005) The negative effect of salinity on plant growth was
inves-tigated by Singla and Garg (2005), using two desi (CSG8962
and DCP92-3) and two kabuli (CSG9651 and BG267) tested
under different salinity levels of 0, 4, 6 and 8/dSm resulting
reduction in dry matter of root and shoot and ultimately lowering
in productivity CSG9651 performed high tolerance to salinity.
Ion exclusion is a fundamental mechanism through which plants
can tolerate salt concentrations (Munnes and James 2003,
Gart-hwaite et al 2005), which was elucidated in chickpea by
reten-tion of Na+ in root and supply of K+
to shoot in Amdoun 1 (tolerant) and Chetoui (sensitive) (Slemi et al 2001).
Water Logging Stress
Excess moisture and water logging predispose plants to disease
attacks and insect pests that finally affect the yield and quality
of grains Given the context, at flowering stage, water logging
causes mortality in chickpea ranging from 10% (line 946-512) to 65% (cv ‘Amethyst’) (Singh and Singh 2011) The mortality of plants increased with water logging just before and after flower-ing of plant confirmflower-ing 13% mortality of plants under water log-ging for 6 days before flowering The mortality rates were recorded as 65% and 100% with water logging one day after flowering and 7.5 days after flowering, respectively (Cowie
et al 1995) Similarly, a set of 100 accessions was grown in excess of water for 50 days, and based on experimental results,
it was noticed that 19 genotypes did not show any germination, five genotypes survived upto <20 days Outstandingly, the prog-eny derived from the cross DZ10-4 9 JG9-2-3-88 had tolerance and survived for 45–60 days (Bejiga and Anbessa 1995) Fur-ther, the effects of water logging at various physiological stages were monitored by keeping the plants in waterlogged condition showed survival of plant decreases in water logging condition with increase in physiological stage (Cowie et al 1996) The effect of water logging on root growth, plant biomass and seed yield was examined in two chickpea cultivars, ‘Almaz’ and ‘Ru-pali’ witnessing 54% and 44% yield reduction, respectively
(Pal-ta et al 2010).
Impact of Molecular Breeding and Genomics and Its Hope in Abiotic Stress Breeding in Chickpea
Owing to its quantitative inheritance, drought tolerance remains
a complex attribute, which is controlled not only by major-effect QTLs but also by plenty of such QTLs experiencing smaller effects on the phenotype (Varshney et al 2013a) Additionally, the other phenomena like G 9 E and epistatic interactions also hamper the progress of trait improvement using traditional breeding techniques (Varshney et al 2013b) Therefore, to strengthen the chickpea breeding, several genomic tools and technologies have been developed recently that have apparently enabled the detailed dissection of the complex traits (Varshney
et al 2013a) A holistic approach enabling the implementation
of the genomic tools and technologies, and the judicious exploi-tation of available genetic recourses for improvement of abiotic stress has been illustrated in Fig 1 Among various MB schemes, marker assisted backcrossing (MABC) is the simplest method routinely used for defect elimination (Hospital 2003, Varshney and Dubey 2009, Gupta et al 2010) Technically, it resembles conventional backcrossing, and here, gene/QTLs are transferred from donor parent to elite cultivars with the help of marker-based foreground and background selections thereby eliminating the chances for receiving the undesirable linkage drags (Hospital and Charcosset 1997, Frisch et al 1999) MABC is the method of choice to incorporate QTLs that control sizeable variation for the trait of interest Recently, MABC tech-nique was undertaken at ICRISAT to transfer drought tolerance from ICC 4958 to JG 11 and from ICC 8261 to two kabuli chickpea cultivars ‘KAK 2’ and ‘Chefe’ (Gaur et al 2012) With the similar objective of introgressing drought tolerance, extensive use of MABC was demonstrated successfully in trans-ferring a genomic region that harbours several QTLs related to root and drought traits (described as QTL-hot spot) from ICC
4958 to a popular high-yielding cultivar ‘JG11’ (Varshney et al 2013a) Besides MABC, other potential MB approaches like MARS have also been propounded, which are able to tap the genetic variation that is accounted to smaller effects QTLs (Varshney et al 2013c) Nevertheless, in contrast to MABC which exploits pre-estimated QTL effects, MARS scheme
Trang 9involves the construction of an ad hoc marker index, and this is
further accompanied by marker index-based selections of
desir-able genotypes and intercrossing of the selected individuals in
advanced generations (Stamp 1994, Ethington et al 2007,
Ri-baut and Ragot 2007, Bernardo 2008, RiRi-baut et al 2010, Gupta
et al 2010, Tester and Langridge 2010, Chamarthi et al 2011,
Gaur et al 2012) Experimental as well as simulation results
have confirmed that the magnitude of genetic gains achievable
through MARS scheme is more than the phenotypic selection
(PS) and MABC (Bernardo and Charcosset 2006, Eathington
et al 2007, Ribaut and Ragot 2007, Gupta et al 2010) By its
virtue, MARS is efficient in extracting several minor-QTLs
scat-tered throughout the genome (Ribaut and Ragot 2007, Varshney
et al 2013b) Given the context, MARS was attempted recently
in chickpea for transferring QTLs related to complex traits in
chickpea (Gaur et al 2012) QTLs attributing yield-related traits
under salinity (Vadez et al 2012b) and drought (Rehman et al 2011) have been mapped recently (Table 2) Similar to MARS, advanced backcross QTL (AB-QTL) is another MB scheme that does not need predefined gene-trait associations (Tanksley and Nelson 1996) Given its ability to capture the tremendous genetic variation existing among wild relatives, AB-QTL scheme has also been implemented in chickpea at ICRISAT (Gaur et al 2012, Varshney et al 2013d) Apart from MABC and MARS, another MB method has been invented, in which genotypes are selected on the basis of genome-wide marker information, and the method is known as genomic selection (GS) or genome-wide selection (GWS) (Meuwissen et al 2001, Bernardo 2010, Varshney et al 2013d) Instead of detecting sig-nificant QTLs, the DNA marker data and phenotyping scores in
GS are used to calculate genomic estimated breeding value (GEBV), and GEBV is later used to select worthy individuals
Fig 1: Deploying genomic tools and technologies in regular breeding for enhancement of abiotic stress tolerance
Table 3: Genomic resources for various abiotic stresses in chickpea
Trait ESTs/Transcript developed Technique used References Drought tolerance 2800 ESTs Subtractive Suppressive hybridization (SSH) Jayashree et al (2005) Drought tolerance 17 493 unique transcripts SuperSAGE Molina et al (2008) Drought tolerance 20 162 ESTs cDNA libraries Varshney et al (2009)
Chattopadhyay (2010) Drought tolerance 4815 differentially expressed unigenes DNA microarray Wang et al (2012) Drought tolerance 3062 unigenes SSH Deokar et al (2011) Drought tolerance 1278 genes regulated under drought 454/Roche GS FLX Titanium platform Jain et al (2013) Salinity tolerance 21 401 unique transcript Next Generation Sequencing and super SAGE Molina et al (2011) Salinity tolerance 1163 genes regulated under salinity 454/Roche GS FLX Titanium platform Jain et al (2013) Drought, Cold and
high salinity
tolerance
215 and 30 genes, consensually differentially expressed (DE) for susceptible and tolerant genotypes for drought, cold and salinity
cDNA microarray approach Mantri et al (2007)
Cold tolerance 4800 transcript derived fragments TDFs cDNA AFLP Dinari et al (2013)
Trang 10(Meuwissen et al 2001) Therefore, it can be postulated that
growing approaches such as MARS, GS and genome wise
asso-ciation (GWA) studies (Syvanen 2005, Myles et al 2009,
Rafal-ski 2010) would be more relevant than the family-based genetic
linkage mapping because the former methods require
phenotyp-ing only once while testphenotyp-ing variable alleles for their association
with tolerance to abiotic stresses thereby minimizing the time
and painstaking work that is otherwise consumed in identifying
and further pinpointing the gene/QTLs responsible for these
stresses It is important to emphasize that genomics-based
approaches have led to the identification of QTLs and their
cloning for subsequent use in breeding programmes (Salvi and
Tuberosa 2007) The various MB approaches deployed in
differ-ent crops to tackle abiotic stresses and their subsequdiffer-ent impacts
are discussed elaborately in various articles (Tuberosa and Salvi
2006, Vij and Tyagi 2007, Cattivelli et al 2008, Ashraf 2010,
Varshney et al 2011, Mir et al 2012, Ashraf and Foolad 2013).
In chickpea also, tremendous progress in genomics tools and
technologies has leveraged the genomic resources particularly
for abiotic stresses (Table 3).
Summary and Outlook
The global climate is changing drastically, and the unpredictable
changes in rainfall and an increase in temperature are causing
severe drought conditions Further, high evapo-transpiration and
scarcity of water have led to the depletion of the groundwater,
hence creating problems of salinity All considered, these factors
have put a strong barrier to the progress of development of stress
tolerant cultivars Notably, due to the severe pressure of global
climate change and ever increasing demand for food production,
implementation of high-throughput and cost-effective techniques
is required, which would invariably support the traditional
breed-ing schemes Therefore, immediate attention needs to be placed
towards (i) large scale exploration and characterization of the
available germplasm for abiotic stresses tolerance, (ii) easy
access to the high-throughput and robust screening techniques,
(iii) standardization of selection criteria for various adaptive/
physiological traits, (iv) utilization of genome-wide DNA marker
systems and sequencing techniques to discover the beneficial
alleles, (v) multilocation and multiyear testing under both
con-trolled and stressed conditions and (vi) finally, pyramiding of
several component traits conditioning resistance against various
abiotic constraints In summary, the growing ‘omics’ approaches,
availability of community-oriented genetic and genomic
resources for chickpea will enable the breeders to better correlate
the huge genotypic data with the extensive phenotypic
informa-tion to derive the valid conclusions Therefore, it is expected that
the MB methods coupled with the recently available phenotyping
platforms will allow chickpea breeder to genetically manipulate
the abiotic stress and exploit the full potential of the crop to
combat against the food security and malnutrition-related
chal-lenges and arranging the protein-rich quality food for over seven
billion people across the globe.
Financial Disclosure
No financial assistance was received for this work.
Conflict of Interests
All authors declare no conflict of interest.
Author Contribution
UCJ conceived the idea and wrote the manuscript, SKC pro-vided input on breeding point of view, AB developed the Fig 1 and edited the manuscript, PSB provided input on physiological aspects, MSK provided input on genomics point of view, and
DB provided input for overall improvement of the entire article.
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