Journal of Food Legumes 24(3): 165-174, 2011
Pigeonpea, often considered as a drought tolerant crop, has the
distinct advantage of having a large range of variation for
maturity, leading to its adaptation to a wide range of
environments and cropping systems. It encounters a number of
abiotic stresses during its life cycle. The most important are
extremes of moisture and temperature, photoperiod and mineral
related stresses. While waterlogging affects plant growth by
reducing oxygen diffusion rate between soil and atmosphere
and by changing physical and chemical properties of soil,
drought and high temperature mostly influence long duration
pigeonpea, resulting in its forced maturity. Similarly, low
temperature leads to conversion of intracellular water into ice
and consequently shrinking of cells and wilting and death of
plants. Soil salinity affects pigeonpea plants through osmotic
stress and interference with uptake of mineral nutrients.
Aluminium toxicity also reduces nutrient uptake efficiency of
this crop. Though these stresses have a drastic impact on
reducing productivity of pigeonpea, only limited efforts have
been made towards screening and development of pigeonpea
genotypes having tolerance to these abiotic stresses. Further,
even these limited accomplishments are not well-documented.
The present review provides comprehensive information vis-a-
vis the work done on abiotic stress tolerance in pigeonpea.
Key words:Abiotic stresses, Aluminium toxicity, Cajanus cajan,
Drought tolerance, Low temperature, Mineral stress,
Photoperiod, Pigeonpea, Waterlogging
Pigeonpea [Cajanus cajan (L.) Millspaugh] is one of
the major food legume crops of the tropics and sub-tropics. In
India, after chickpea, pigeonpea is the second most important
pulse crop. It is mainly eaten in the form of split pulse as ‘dal’.
Despite its main use as de-hulled split peas, the use of
immature seeds is very common as fresh vegetable in some
parts of India such as Gujarat, Maharashtra and Karnataka.
Besides this, in the tribal areas of various states, the use of
pigeonpea as green vegetable is very common (Saxena et al.
Pigeonpea is grown in a number of countries of Asia,
Eastern and Southern Africa, Latin America and Caribbean
countries. Globally, it is cultivated on 4.92 million ha (mha)
with an annual production of 3.65 million tons (mt) and
productivity of 898 kg/ha (http://www.icrisat.org). India has
the largest acreage under pigeonpea (3.90 mha) with a total
production and productivity of 2.89 mt and 741 kg/ha,
respectively (DAC 2011).
Pigeonpea is considered as a drought tolerant crop with
a large variation for maturity period. As a result, it is widely
adapted to a range of environments and cropping systems.
Broadly, four maturity groups are recognized in pigeonpea:
extra early (90 – 120 days), early (120 – 150 days), medium (150
– 200 days), and late (200 – 300 days). These variations for
maturity have direct relevance on the survival and fitness of
the crop in different agro-ecological niches (Choudhary 2011).
Pigeonpea encounters various abiotic stresses during
its life cycle such as moisture (waterlogging/drought),
temperature, photoperiod and mineral (salinity/acidity) stress.
Among these stresses, moisture stress is common because
pigeonpea is generally grown as a rain-fed crop. In the north-
western and north-eastern parts of India, the stress imposed
by extremes of temperature (too low/ too high) during the
reproductive stage often leads to crop failure. Some areas in
these regions have acidic soils with problems of aluminium
toxicity. In some other areas such as parts of Haryana and
Punjab, the crop suffers from both waterlogging and soil
salinity stresses. Empirical evidences reveal that one abiotic
stress is often linked with several other stresses, making it
difficult to know the exact cause of the crop failure. The
literature pertaining to screening, identification of tolerant
genotypes and their utilization for improving tolerance to such
abiotic stress in pigeonpea is scanty and also not well-
documented as compared to cereals. Therefore, the present
paper aims to review the available information on abiotic
stresses and discusses the ways to improve the tolerance to
these stresses in pigeonpea.
Non-wetland crop species require well-drained soils for
optimal growth and production of yield. Prolonged water
saturation has a significant impact on both biotic and abiotic
attributes of the soils. Drastic reduction in oxygen partial
pressure is the primary plant stress under excessive moisture
condition. Inability of non-wetland crop species (including
pigeonpea) to withstand low oxygen conditions in rhizosphere,
caused by waterlogging or any other factor, results in
substantial yield losses. Roots of most plants are highly
sensitive to anaerobic conditions, which support a unique
Breeding for abiotic stresses in pigeonpea
A.K. CHOUDHARY1, RAFAT SULTANA2, ADITYA PRATAP1, N. NADARAJAN1 and UDAY CHAND JHA1
1Indian Institute of Pulses Research (IIPR), Kanpur – 208 024 (Uttar Pradesh), India; 2International Crops Research
Institute for the Semi-Arid Tropics (ICRISAT), Patancheru – 502 324, Andhra Pradesh, India;
(Received: June 30, 2011; Accepted: August 20, 2011)
166Journal of Food Legumes 24(3), 2011
microbial community compared to aerobic conditions, and this
severely affects the nutrient relation of the soil. Shortly after
the onset of waterlogging conditions (2-3 days), obligate
aerobic bacteria become inactive, and facultative/obligate
anaerobic bacteria become active and dominate the micro-
flora/fauna of inundated soils. Over time, the activity of
anaerobic bacteria causes sharp decline in redox potential,
which causes severe nutrient imbalances. Another important
side effect of excessive moisture is leaching of mineral nutrients
and/or essential intermediate metabolites from the roots into
the volume of water in which they are immersed. Excessive
soil moisture causes major changes in physical and chemical
properties in rhizosphere. Oxygen diffusion rates (ODR) in
flooded soil is about 100 times lower than air (Kennedy et al.
1992), and respiration of plant roots, soil micro-flora and fauna
leads to rapid exhaustion of soil oxygen, and thereby causing
anaerobiosis. Oxygen deprivation, either completely (anoxia)
or partially (hypoxia) is detrimental to most species of higher
plants as it disturbs the respiratory cycle of plant by changing
it from aerobic (kreb cycle = 38 ATP) to anaerobic (glycolysis=2
ATP) cycle (Armstrong et al. 1994). However, proximate causes
of plant injury can be oxygen deficit or mineral nutrient
imbalances, a decrease in cytokinins or other hormones
released from the roots, a decrease in available soil nitrogen
and/or nitrogen uptake, an increase in toxic compounds in
soil such as methane, ethylene, ferrous ions or manganese,
an increase in toxic compounds (in the plant) such as ethanol
or ethylene, and an increase in disease causing organisms.
The areas where rainfall is dependent on monsoon are
more prone to waterlogging. Waterlogging occurs when rainfall
or irrigation water is collected on the soil surface for prolonged
periods without infiltrating into the soil. Soil characteristics
that contribute to waterlogging include its physical properties
that allow formation of a crust on the soil surface or a subsoil
pan particularly those of high water holding capacity soils,
such as vertisols and Indo-Gangetic alluvial soils (Reddy and
Virmani 1980). Waterlogging can also occur when the amount
of water added through rainfall or irrigation is more than what
can percolate into the soil within one or two days. This
condition sometimes results in rise of water table, causing
development of salinity/alkalinity as observed in Haryana and
In India, waterlogging is one of the most serious
constraints for crop production and productivity, where about
8.5 mha of arable land is prone to this problem. Out of the total
(3.9 mha) area under pigeonpea, about 1.1 mha is affected by
excess soil moisture, causing an annual loss of 25-30% (Sultana
Pigeonpea is primarily grown between 14º and 30º
latitudes where the mean annual rainfall ranges between 600
and 1500 mm. Waterlogging is a major production constraint
in these regions particularly in deep vertisols. Some of the
important pigeonpea growing areas where severe
waterlogging is encountered are Yavtmal and the adjoining
areas in Maharashtra, Gorakhpur, Faizabad, Varanasi, Jaunpur,
Kanpur, Ghazipur and Fatehpur in Uttar Pradesh, Jabalpur in
Madhya Pradesh, Surat and Navsari in Gujarat and northern
and eastern regions of Bihar.
Fig 1.Pigeonpea genotypes showing chlorosis /nitrogen
deficiency after receiving heavy rainfall continuously
for 10 days at early seedling stage at ICRISAT,
Patancheru during 2009
The risk of crop failure or yield reduction due to
waterlogging is quite high in extra-early and early duration
varieties because they get less time to recover from this stress
as compared to medium and long duration varieties
(Matsunaga et al. 1991). In pigeonpea, a few studies have
shown the relationship between waterlogging and severity of
diseases caused by Phytophthora species (RHS 2010). In
general, waterlogging conditions increased the incidence of
root rot caused by Fusarium cactum. High soil moisture
directly favours Phytophthora species by providing a
continuous water film necessary for zoospore production and
their motility. In addition, high soil water may indirectly favour
infection and colonization of the host tissues by the fungus
by decreasing host vigour and increasing the release of host
exudates that may stimulate germination of dormant propagules
(Duncan et al. 2007).
Waterlogging can affect pigeonpea during germination,
early and late seedling stages as these stages cover peak
monsoon period (Fig. 1). These three critical stages can be
used for screening of tolerant genotypes. Empirical evidences
suggest that waterlogging causes rapid senescence and
drooping of the shoot tips of plants. It reduces plant height
and delays flowering in surviving plants, resulting in reduction
in the number of pods, seeds/pod and seed yield. It has been
observed that seed coat thickness, aerenchymatous cells,
lenticels and adventitious roots also affect tolerance to
waterlogging in pigeonpea. However, these traits need to be
confirmed and re-validated before these can be used as
selection criteria in pigeonpea.
Choudhary et al.: Breeding for abiotic stresses in pigeonpea 167
Preliminary screening of pigeonpea cultivars and
genotypes for waterlogging tolerance has been done at
ICRISAT (Patancheru, Hyderabad), IIPR (Kanpur) and Institute
of Agricultural Sciences (BHU, Varanasi). Some tolerant
cultivars and advance breeding lines have been identified
Perera et al. (2001) studied the genetics of different
morphological traits. The results showed that the additive
and dominant gene effects control the expression of most of
the important traits. It was also observed that crosses between
the tolerant and sensitive lines showed more genetic variation
than those among tolerant lines, suggesting potential for
genetic improvement for these traits. Sarode et al. (2007)
worked out genetics and identified the gene for waterlogging
tolerance in pigeonpea. They studied segregation pattern in
two crosses derived from tolerant parent ‘ICPL 84023’ and
sensitive parents ‘DA 11’ and ‘MA 98 PTH 1’. Their study
revealed that waterlogging tolerance is a dominant trait and is
governed by a single gene. Therefore, it can easily be
transferred by backcrossing to leading varieties, which are
sensitive to waterlogging. However, it could be possible that
parents might be differing at a single locus. Therefore, they
suggested making more efforts involving a large number of
tolerant and sensitive parents to understand the genetic
control of waterlogging tolerance. This may be helpful in
breeding waterlogging tolerant varieties, so that the crop
efficiency can be increased and the true potential of pigeonpea
as pulse crop can be fully exploited.
There is need to standardize screening techniques
against excessive soil moisture in pigeonpea. This calls for
large-scale utilization of pigeonpea germplasm for re-validation
of screening techniques (strategic research). Identification of
gene(s) conferring waterlogging tolerance (basic research)
and its incorporation into the cultivars (applied research) to
have viable outcome (anticipatory research) merit special
attention. Besides, adaptation mechanisms to waterlogging
tolerance also need to be explored.
B. Drought Stress
Pigeonpea is grown in kharif season as a rainfed crop.
It is considered as a drought tolerant legume on account of its
deep root system. Among the four maturity groups, extra-
early and early types complete their life cycle just after
recession of the monsoon season. However, their reproductive
phase more often encounters terminal drought. The situation
becomes even worse for medium and long-duration pigeonpea
as their flowering and pod-filling stages coincide acute soil
moisture deficit in absence of any supplementary irrigation.
Likoswe and Lawn (2008) studied species differences
in drought response of three grain legumes, namely soybean,
cowpea and pigeonpea to assess how water deficit affects
water use, growth and survival of plants in pure stand and in
competition. In pure stand, pigeonpea appeared to be slow,
tolerant and slow for the rate of plant available water (PAW)
depletion, no. of nodes and node growth and senescence of
the lower leaves, respectively. Cowpea and pigeonpea
extracted almost all PAW and died after an average of 18 days
and 14 days, respectively following maximum PAW depletion.
In contrast, soybean died before 90% of PAW was depleted
and so in pure stand used less water. There were otherwise
only minor differences between the species combinations in
the timing and maximum level of PAW depletion. The ability
of cowpea and pigeonpea to maintain leaf water status above
lethal levels for longer was achieved through different means.
Pigeonpea appeared to rely primarily on dehydration
tolerance and maintained high tissue water status for longer.
Significant level of osmotic adjustment (OA) was identified in
pigeonpea, which benefited leaf survival. Pigeonpea invested
significantly more total dry matter (TDM) in roots than either
cowpea or soybean. Cowpea survived longest in pure stand
whereas pigeonpea and soybean survived shortest in pure
stand, suggesting that the dehydration avoidance response
of cowpea was more effective in competition with like plants
whereas the dehydration tolerance strategies of pigeonpea
and soybean were least effective when competing against
like plants. On the average, TDM/plant ranked in the order of
cowpea > soybean > pigeonpea, largely reflecting initial
differences in plant size when water was withheld. However,
there was an inverse relation between TDM of a species and
that of its competitor, so that in effect, water not used by a
given plant to produce TDM was used by its competitor.
A large spectrum of genotype duration (from long to
early and extra-early duration) and matching genotype
duration with likely period of soil water availability is the first
strategy used against terminal drought stress (Serraj et al.
2003). Drought resistant genotypes can avoid moisture stress
through faster root growth. Onim (1983) observed the
differences in root depth at 31 days between resistant and
susceptible genotypes. The difference was up to 18 cm and
deep rooting was positively correlated with seed yield/plant.
The effect of moisture stress imposed at pre-flowering
stage has been associated with greatest reductions in nodule
nitrogenase activity (70-90%), followed by the rate of
photosynthesis (50-71%), and root and nodule respiration
(31-45%). Large seeded cultivars have been observed more
sensitive than small seeded ones. Among small seeded
cultivars, those with indeterminate growth habit have been
found more drought resistant than those with alternative type
(determinate growth habit). Values for relative water content
(RWC) and water retention in leaves were also higher in
cultivars with indeterminate growth (Kuhad et al. 1989). Kimani
et al. (1994) noted genetic variation for vegetative
development, leaf water potential, RWC, photosynthesis, and
stomatal conductance during two cycles of water stress and
recovery. They suggested to use water status parameters
(especially RWC) as indicators of drought tolerance while
breeding for drought resistance in pigeonpea.
168Journal of Food Legumes 24(3), 2011
In short-duration pigeonpea, the maintenance of both
leaf area index (LAI) and fractional canopy light interception
appears to indicate genotypic drought tolerance. Some
possible characteristics that may improve drought resistance
of short-duration pigeonpea include the ability to maintain
TDM, low flowering synchronization, small pod size with a
few seeds/pod and large 100-seed weight (Lopez et al. 1996,
OA is considered as an important physiological
mechanism of drought adaptation in many crop plants. In a
group of 26 early-duration pigeonpea genotypes, Subbarao
et al. (2000) observed a significant correlation of mean leaf
osmotic potential with the mean OA under water stress
condition at 60-92 days after sowing. Mean leaf osmotic
potential accounted for 72% of the genotypic variation in
OA. Significant genotypic variation was observed for the
initiation, duration, and degree of OA. Genotypic differences
in grain yield under drought was best explained using stepwise
multiple regression to account for differences in OA at 72, 82,
and 92 days after sowing (r2 = 0.41**; n= 78). The degree of
OA at 72 and 82 days after sowing (DAS) contributed
positively to the grain yield, whereas OA at 92 DAS contributed
negatively to this relationship. In another study, Flower and
Ludlow (1987) screened 22 pigeonpea accessions for variation
in osmotic adjustment and dehydration tolerance of leaves.
However, no difference in osmotic adjustment was found under
field condition, but moderate variation (0.7-1.3 MPa) was found
among twenty-two accessions grown under controlled
conditions. In addition, moderate variation in dehydration
tolerance was found among the accessions; lethal leaf water
potentials ranged from -6.8 to -8.2 MPa, although the level of
tolerance was high compared with other grain legumes. In
view of the general genetic diversity of the accessions, they
concluded that the probability of finding greater variation in
these traits is small. Moreover, because pigeonpea has high
OA and high dehydration tolerance compared to other crops,
they suggested that high priority should not be given to
attempting improvement of drought resistance by increasing
the magnitude of these two traits in pigeonpea.
Screening of pigeonpea varieties for high reproductive
fitness under actual water deficit condition may be a realistic
approach. Reddy (2001) screened ‘LRG 30’, ‘ICPL 85063’, and
‘ICPL 332’ as the most suitable varieties out of the ten cultivars
evaluated under rainfed condition. He concluded that higher
yield of these cultivars (1980 kg/ha, 1800 kg/ha, 1787 kg/ha,
respectively) under moisture deficit might be due to their high
RWC, pods/plant and harvest index.
Jaleel et al. (2008) studied involvement of Paclabutrazol
(PBZ) and ABA on drought induced osmoregulation in
pigeonpea. They used two watering treatments (100 and 60%
field capacity) to understand the effects of water deficit with
and without PBZ and ABA on biochemical constituents,
proline and antioxidant metabolisms of pigeonpea plants.
There was a significant enhancement in the proline content
and ã-glutamyl kinase and reduction in proline oxidase
activities under water deficit stress. Drought stress caused
an increase in the free amino acid and glycine betaine (GB)
content. PBZ and ABA acted as stress ameliorating agents by
further enhancing these parameters in water stressed
pigeonpea plants. The stress mitigating effect was significant
in the case of PBZ treated plants compared to ABA treated
According to Kumar et al. (2011), a progressive water
stress causes significant physiological and biochemical
changes in pigeonpea. RWC parameter could be used to select
high-yielding genotypes that maintain cell turgor under water
deficit environment. Enhanced proline accumulation during
stress indicated that proline plays a cardinal role as an osmo-
regulatory solute in plants. The increased activities of
antioxidant enzymes including superoxide dismutase (SOD)
and peroxidase (POD) indicated that an effective antioxidant
defense mechanism protects pigeonpea from destructive
In conclusion, physiological parameters such as
dehydration tolerance, RWC and OA appear to be important
in pigeonpea for combating moisture deficit condition.
However, conclusive evidences that these parameters also
confer reproductive advantages to the surviving genotypes
are scanty. Agronomic traits such as pods/plant, seeds/pod,
seed size and seed yield/plant under actual water deficit
condition should be given much importance while breeding
for drought resistance in pigeonpea.
C. Temperature Stress
In north India, pigeonpea experiences low temperature
stress during winter months (December–January). The stress
adversely affects growth, survival and reproductive capacity
of plants if the minimum temperature falls below 5°C. At
freezing temperature, intracellular water gets converted into
ice, which in turn causes shrinkage of cells inside the plant,
resulting in wilting and death of plants. According to Wery et
al. (1993), the intracellular ice in the plants causes cell
dehydration and cell membrane destruction due to freeze-thaw
cycle leading to death of the plants under cold conditions.
Genetic variation for germinability and root-length under
low temperature (14°C) has been noticed (Kumar et al. 1991).
It has been established that greater root: shoot ratio (>1.0)
may be used as a selection criterion for cold tolerance at the
seedling stage (Kumar et al. 1991, 1995). In a field study in
China, Yong et al. (2002) reported enormous variation in plant
mortality and plant survival under cold stress condition (- 3°C
to - 0.3°C). Conclusive evidence for the presence of genetic
variability vis-à-vis cold tolerance was provided by Sandhu
et al. (2007). They screened for cold tolerance in a set of 480
pigeonpea lines at PAU, Ludhiana. During the first fortnight
of January, minimum temperature more often touches 0°C,
Choudhary et al.: Breeding for abiotic stresses in pigeonpea169
which was good enough to assess cold reaction. As many as
32 genotypes were rated cold tolerant as the plants retained
their normal morphology with intact floral buds. They
suggested for utilizing these genotypes to enhance cold
tolerance of sensitive varieties and study the genetics of cold
Upadhyaya et al. (2007) reported the results of an
evaluation trial of pigeonpea germplasm accessions collected
from low (<500 m), medium (501–1000 m), high (1001–1500 m)
and very high elevation zones (>1500 m) of Kenya at ICRISAT,
Patancheru, India. They observed that accessions from the
very high elevation zone (>1500 m) were late flowering with a
large number of tertiary branches, large seeds and a high
shelling percentage and could be a source for cold tolerance
and breeding of vegetable types. Results indicated that the
elevation of collection sites is important in determining
variation patterns of pigeonpea in Kenya.
Reports concerning effects of low temperature stress
on the reproductive parts are only a few and also not well-
documented. Singh et al. (1997) studied effects of low
temperature on floral buds and flower drop in the pigeonpea
germplasm. They identified seven highly tolerant genotypes
(including ‘Bahar’, a leading variety of long-duration
pigeonpea in northeastern plain zone of India) on the basis of
low bud and flower drop. They observed that long-duration
cultivars are well-adapted to cold situations because of their
inherent genetic mechanism to cope up with very low
temperature during reproductive stages. However, in both the
years (1992-93 and 1993-94) during which observations were
recorded, mean temperature did not fall below 14°C. Therefore,
it does not seem convincing whether the variation in bud and
flower drop was a consequence of low temperature stress.
Choudhary (2007) recorded data on buds/plant and flowers/
plant in two-temperature environments under field condition
(mean temperature: 16.4°C and 11.4°C). Low temperature stress
(11.4°C) appeared to reduce the number of buds and flowers
in each genotype. ‘IPA 7-2’ (a selection from a local land race
‘Kudrat-3’) was identified as the most tolerant on the basis of
least reduction and better mean performance for the number
of buds and flowers under low temperature condition.
However, the other genotype ‘Bahar’ also appeared at par
with the ‘IPA 7-2’. On the basis of rank correlation (0.943**),
it was suggested that either of the two traits could be used as
a selection criterion for tolerance to low temperature.
The research conducted at the IIPR, Kanpur (Annual
Report 2008-09) revealed that low temperature primarily affects
development and growth of flower buds. In some sensitive
genotypes such as ‘IPA 209’ and ‘IPA 06-1’, filaments of
stamens fail to enlarge at low temperature and thus affect
opening of flowers. Pollen dehiscence does not occur too,
although pollens are fully fertile. As a consequence,
unfertilized flowers wither and fall down, resulting in no pod
formation in these genotypes under low temperature. Detailed
analyses of F1, F2 and backcross populations derived from
crosses between sensitive parents (‘IPA 209’ and ‘IPA 06-1’)
and tolerant parent (‘Bahar’) revealed that low temperature
tolerance in pigeonpea is a monogenic dominant trait (Annual
Report 2008-09), which could be easily transferred to high-
yielding pigeonpea cultivars (such as ‘NA 1’) that are sensitive
to low temperature.
In a similar study in another set of materials, Singh and
Singh (2010) also substantiated the previous finding that pod
setting in pigeonpea under low temperature is a dominant
trait and is governed by a single gene. The lower limits of
average minimum and maximum temperature during both the
years (2003-04 and 2004-05) at the pod setting stage in the
tolerant (such as ‘MAL 19’) parents, its crosses (such as ‘NA
1’ × ‘MAL 19’) with the sensitive (such as ‘NA 1’) parents and
their segregating generations (F2 and backcross generations)
were 9°C and 22.1°C (mean temperature: 15.55°C), respectively.
However, there are certain genotypes like ‘IPA 209’ and ‘IPA
06-1’ and ‘Bahar’ and ‘IPA 7-2’, whose degree of sensitivity
and tolerance to low temperature are even greater than ‘NA 1’
and ‘MAL 9’, respectively.
All the above results related to the effects of low
temperature stress on the reproductive traits of pigeonpea
were carried out under field (uncontrolled temperature)
conditions. Nonetheless, these studies threw at least some
light on the number and nature of gene(s) that governs low
temperature tolerance in pigeonpea. Screening of a large
number of pigeonpea genotypes for low temperature tolerance
under controlled temperature condition is still needed to
confirm those findings and generate precise genetic
Pigeonpea is known to be thermo- and photosensitive
crop. It is grown in the areas where day length varies from 11
to 14 h and large differences in temperature are experienced,
largely due to variations in altitude and latitude. Field studies
have been conducted in pigeonpea with different maturity
durations (extra-early, early, medium and long durations) in
Kenya to determine the effect of photoperiod and temperature
on flowering. It has been found that the extra-short duration
genotype ‘ICPL 90011’ was the least responsive to variation
in photoperiod, while the two long-duration genotypes
‘ICEAP 00040’ and ‘T 7’ were the most sensitive to photoperiod
variation with flowering rate reduced by 0.001 d-1 per hour
increase in day length (Silim et al. 2007). Carberry et al. (2001)
found that flowering in short-duration pigeonpea cultivars
was delayed by up to 100 days when day length in the
photoperiod-inductive phase exceeded a critical value.
Medium- and long-duration cultivars delayed flowering by
over 150 days in response to photoperiod. A pioneer
experiment was conducted by Hugh et al. (1985) to determine
how the rate of development from sowing to flower bud
170Journal of Food Legumes 24(3), 2011
initiation (FBI) and sowing to flowering was affected by
temperature and day length in pigeonpea cultivars with
different maturity periods. They found that both temperature
and day length had substantial effects over the range 16–
32°C and 10–14 h, respectively and the rate of crop growth
from sowing to flower bud initiation varied among cultivars.
The effect of day length on the rate of crop growth was the
greatest between sowing and flower bud initiation, with the
greatest sensitivity between 12 and 14 h. For the range of
conditions considered, temperature had at least as great an
influence as day length on the rates of development from
sowing to FBI and from sowing to flowering.
E. Soil Salinity Stress
Soil salinity can be a major constraint to pigeonpea in
regions where it is predominantly grown (Subbarao et al. 1991).
Salt accumulation in soil surfaces, known as soil salinity, could
lead to the impairment of plant growth and development and
is manifested mostly under irrigated and dryland agriculture.
Excess salts in the soil affects plants through osmotic stress,
accumulation to toxic levels within the cells, and through the
interference with the uptake of mineral nutrients (Chikelu et
al. 2007). Higher sodicity (NaCl / Na2SO4) adversely affects
the rate of photosynthate translocation from the source leaf
to other plant parts including pods (Deshpandey and
Nimbalkar 1982). It has been shown that higher concentrations
of NaCl (15 m mhoes/cm2) reduces plant height, leaf area, leaf
area index (LAI), crop growth rate, net assimilation rate, total
dry matter (TDM) production and seed yield and increases
leaf thickness of pigeonpea (Joshi and Nimbalkar 1983). Salinity
delays days to 50% flowering by 1-2 week and prolongs the
peak period of flower production, and reduces number and
weight of the pods and seeds (Promila and Kumar 1982).
There are reports related to field screening of pigeonpea
for tolerance to soil salinity. Genetic variation for tolerance to
salinity (with respect to survival) has been observed among
cultivated genotypes and wild species especially Cajanus
scarabaeoides (Rao et al. 1981). Some leading cultivars such
as ‘C 11’ (Chauhan 1987), ‘UPAS 120’ (Promila and Kumar
1982), and the like have been identified as salinity tolerant.
Subbarao et al. (1991) studied comparative salinity
tolerance among pigeonpea genotypes and their wild relatives.
Among the cultivated genotypes, ‘ICPL 227’ and ‘Hy3C’ were
observed as the most tolerant and the most sensitive
genotypes, respectively. However, the extent of variation in
salinity response among cultivated genotypes appeared too
limited to warrant genetic enhancement of salinity tolerance.
Among the wild relatives of pigeonpea, several species
including C. scarabaeoides, C. albicans and C. platycarpus
showed a wide range of variation in their salinity tolerance.
The results suggested that using wild relatives for genetic
improvement might increase salinity tolerance of pigeonpea.
According to Subbarao et al. (1990), the transfer of salinity
tolerance from C. albicans to C. cajan would be feasible as
the high level of salinity tolerance in this wild species is
expressed as a dominant genetic trait. They further clarified
that certain physiological attributes that confer salinity
tolerance in this wild species include Na and Cl retention in
the roots and limited translocation to the shoots, high K
selectivity and maintenance of transpiration rate under saline
In another experiment, Ashraf (1994) assessed salt
tolerance of three pigeonpea accessions, namely Local arhar,
‘ICPL 151’ and ‘ICPL 85014’ at the germination, seedling and
adult stages. There was no positive correlation between
tolerance at the early growth stages and at the adult stage
since no clear difference in salt tolerance of the three
accessions was observed at the germination and the seedling
stages, whereas accessions differed considerably at the adult
stage. Although increasing salt concentrations adversely
affected the growth of all three accessions, ‘ICPL 151’ was
superior to the other two accessions in fresh and dry biomass,
yield and yield components when tested at the adult stage.
The tolerant accession ‘ICPL 151’ accumulated significantly
lower Na+and Cl? in shoots. By contrast, the accession had
higher shoot and root K+, K/Na ratio, K vs. Na selectivity,
soluble sugars, free amino acids and proline compared to the
other two accessions.
Differential tolerance to salinity vis-à-vis pigeonpea
maturity groups has been observed (Dua and Sharma 1996).
Late maturing genotypes showed better tolerance than early
maturing ones. No correlation was found between the
tolerance at germination and later stages. However, percentage
survival showed some association with seed yield under
salinity. Low and high accumulation of Na and K, respectively
in the roots and other plant parts (main stem, branches and
leaves) perhaps helped salinity tolerance in pigeonpea.
Efforts towards improvement of salinity tolerance
through plant biotechnology have also been done. Several
gene transfer approaches have been shown to improve the
stress tolerance of the crop plants. The transferred genes
include those encoding enzymes required for the biosynthesis
of various osmoprotectants, or those encoding enzymes for
modifying membrane lipids, LEA proteins and detoxification
enzyme. Stress-inducible transcription factors have been
demonstrated to have great potential (Sharma and Lavanya
Srivastava et al. (2006) found that a NaCl treatment of
1.01 g/kg alfisol was suitable to salinity screening in
pigeonpea. Using that treatment, they found large variations
in the salinity susceptibility index (SSI) and the percent relative
reduction (RR %) in both cultivated and wild accessions. The
amount of Na accumulation in shoot showed that more
tolerant materials accumulated less Na in the shoot except the
wild species, which followed a different pattern compared to
cultivars. Overall, they found that C. acutifolius, C.cajanifolius
Choudhary et al.: Breeding for abiotic stresses in pigeonpea171
and C.lineata were mostly sensitive, whereas C. platycarpus,
C. scarabaeoides and C. sericeus provided good sources of
tolerance. It was interesting to notice that C. scarabaeoides
also provided a large range of sensitive materials. It was
expected that accessions originating from putative saline areas
would provide higher levels of tolerance, but the minicore
collection of pigeonpea provided a larger range of variation in
the salinity response. It was noted that tolerant accessions
may be obtained either from the minicore collections or from
the set of accessions from putatively salinity affected areas.
Besides, there was a large number of tolerant accessions
originating from Bangladesh. Further work is going on to
confirm these data to assess yield response to salinity and to
develop intra-or inter-specific populations for the mapping of
Karajol and Naik (2011) assessed salinity tolerance
among ten varieties of pigeonpea during germination at 0,
100, 125, 150, 175, 200 and 250 mM NaCl concentrations.
Germination percentage was not much affected by salinity;
however, it delayed germination at 250 mM in all accessions
to varying degrees. The varieties with white seeds such as
‘WRP 1’, ‘GS 1’ and ‘TS 3’ appeared salinity tolerant compared
to red or black seeded varieties like ‘Black tur’, ‘Asha’ and
‘Bennur Local’ accessions, which were rated highly sensitive
to salt stress based on their germination rate and final
germination percentage. However, they opined that final
evaluation and selection for high-yielding tolerant genotypes
in pigeonpea would require field evaluation in the salt affected
soils. The superior performance of white seeded varieties over
other varieties may be an interesting observation that needs
further confirmation. If revalidated, it will form the basis for
further improvements in the salinity tolerance of pigeonpea
F. Aluminium Toxicity
To meet the growing demand of pigeonpea, it is
imperative to expand its cultivation on wider scale in non-
traditional areas such as hilly tracts of north eastern states.
There are other states like Bihar, Jharkhand and Chhattishgarh
where increasing trend in pigeonpea cultivation has been
observed in recent years. However, these states have
considerable acreage under acidic soils with the serious
problem of aluminium (Al) toxicity (Choudhary and Singh
Most of the grain legumes including chickpea (Singh
and Chaturvedi 2007), pigeonpea (Singh and Choudhary 2009,
Choudhary et al. 2011), pea (Singh and Choudhary 2010) and
alfalfa (Campbell et al. 1988) are sensitive to aluminium.
Considerable variation for tolerance to aluminium toxicity in
plant species and genotypes within species has been reported
(Kinraide et al. 1985, Singh and Choudhary 2009). The work
on screening for tolerance to Al toxicity in pigeonpea is only
a few and also not well-documented.
The four techniques, which are commonly used for
screening of Al toxicity in pigeonpea, are sand and hydroponic
assays, hematoxylin staining and root re-growth assay (Singh
and Choudhary 2009). These four techniques have
unconditional advantages over field screening because
reliable ranking of tolerance in the field screening is difficult
due to the large temporal and spatial variation in acidic soils
(Choudhary et al. 2011). Moreover, screening at field level is
very expensive and time consuming when a large number of
genotypes are under evaluation (Garcia et al. 1979). Besides,
the results obtained with solution culture screening method
correlate positively with those obtained using field screening
(Urrea-Gomez et al. 1996), indicating reliability and
dependability of laboratory screening methods.
Singh and Choudhary (2009) screened 32 genotypes of
pigeonpea for tolerance to aluminum toxicity. No distinct and
visible symptoms of aluminum toxicity were observed in the
shoot of pigeonpea genotypes. However, restriction of root
growth was observed. Shorter roots with absence of normal
branching pattern were observed at higher levels of aluminum
Table 1. Some pigeonpea genotypes/ cultivars tolerant to abiotic stresses
Waterlogging ICPL 84023 (early), Asha
Cultivars/genotypes Tolerance mechanism
Lenticels development, more
root biomass and adventitious
High RWC, pods/plant and HI Reddy (2001)
Sarode et al. (2007) Moisture
Drought LRG 30, ICPL 85063, ICPL 332
IPA 7-2, Bahar, and MAL 19
Ability to flower and pod
setting under low
Reduced translocation of Na
and Cl from root to shoot
Choudhary (2007), Singh et al.
(1997), Singh and Singh (2010)
Salinity C11, ICPL 227, WRP1, GS1 and
UPAS 120 and ICPL 151 (early)
Chauhan (1987), Promila and Kumar
(1982), Subbarao et al. (1991),
Ashraf (1994) and Karajol and Naik
Choudhary et al. (2011)
IPA 7-10 and T 7 (late), 67 B and
GT 101E (early)
172Journal of Food Legumes 24(3), 2011
(30 and 50 µg/ml Al) compared to the control treatment (0 µg/
The results of all the four methods (hydroponic and
sand assays, hematoxylin staining and root re-growth methods)
were almost similar, indicating that any one of these methods
could be used to screen for aluminium tolerance in pigeonpea.
These methods almost consistently discriminated between
tolerant (‘IPA 7-10’, ‘T 7’ and ‘67 B’) and sensitive (‘Pusa 9’,
‘Bahar’ and ‘Pusa 2002-2’) genotypes of pigeonpea at 30 or 50
µg/ml Al concentration (Choudhary et al. 2011). However, 30
ppm (µg/ml) was suggested as the optimum Al concentration
to discriminate between tolerant and sensitive genotypes. The
tolerant genotypes had greater root and shoot length, more
root and shoot dry matter. These four parameters in both sand
and hydroponic assays were highly correlated among
themselves, indicating that any of them could be used
(Choudhary et al. 2011). The intensity of hematoxylin stain
for tolerant genotypes was scored as only partial compared
to complete stain of sensitive genotypes. Root re-growth of
all genotypes decreased significantly with an increase in
aluminum concentration in nutrient solution. It virtually ceased
in ‘Bahar’, ‘Pusa 2002-2’and ‘Pusa 9’ at higher Al
concentrations (30 or 50 µg/ml Al) due to irreversible damage
caused to the root tips. Tolerant genotypes, namely ‘IPA 7-
10’, ‘T 7’, ‘GT 101’ and ‘67 B’ had larger mean root re-growth
(> 1.5 cm) than that of sensitive genotypes (0.25 cm) at 30 µg/
ml Al concentration (Choudhary and Singh 2011).
Tolerant and sensitive genotypes were further assessed
for phosphorus, potassium, calcium and magnesium contents
in their root and shoot. Tolerant genotypes (‘IPA 7-10’, ‘T 7’,
‘GT 101’ and ‘67 B’) accumulated significantly high amounts
of these nutrients (> 1.5 times) compared to the sensitive ones
in both root and shoot. Better performance of tolerant
genotypes could be ascribed to better nutrient uptake
efficiency and distribution within the plants (Choudhary and
Aluminium concentration in the roots of both tolerant
and sensitive genotypes was greater than that for the shoots.
Root aluminium contents were significantly lower for the
tolerant genotypes (‘IPA 7-10’, ‘T 7’) than for the sensitive
genotypes (‘Bahar’ and ‘Pusa 9’) at both 20 and 50 ppm Al
concentrations. This indicated that aluminium tolerance in
these accessions of pigeonpea stemmed from aluminium
exclusion from the root (Choudhary et al. 2011). In addition,
shoot aluminium content was also considerably lower for the
tolerant genotypes than for the sensitive genotypes. This
could be ascribed to reduced translocation of aluminium from
root to shoot in the tolerant genotypes. However, any sign of
internal detoxification could not be detected.
Tolerant genotypes such as ‘IPA 7-10’, ‘T 7’, ‘GT 101’
and ‘67 B’ may be used in future breeding programme to
develop aluminium tolerant pigeonpea cultivars. However,
further study involving land races and wild accessions
(especially from Cajanus scarabaeoides and C. platycarpus)
of pigeonpea for tolerance to aluminium toxicity under field
condition (natural acid soil) is still required. This may generate
comprehensive data for even higher degree of Al tolerance
vis-à-vis reproductive parameters such as yield. This will also
corroborate whether tolerance to Al toxicity in pigeonpea
imparts only survival advantage or also confers increased
reproductive fitness on the tolerant genotypes (Choudhary
and Singh 2011).
G. Conclusions and Future Prospects
Available literature suggests that only limited efforts
have been made to improve the abiotic stress tolerance in
pigeonpea. Since the crop is largely cultivated in Indian sub-
continent, greater efforts, of course, are expected from Indian
scientists. Flow of funds should also come from Indian/ Asian
governments. The current challenge in pigeonpea cultivation
is to reduce the gap between potential and realised yield and
to minimise yield differences among major pigeonpea growing
zones in which above-mentioned abiotic stresses are prevalent.
Efforts are required towards holistic management of these
abiotic stresses through the development of resistant/tolerant
cultivars with consistent performance across the
environments. In this direction, a deeper understanding of
the physiological and genetic bases of variation for tolerance
to these stresses needs greater attention. As environment
and G×E interaction accounts for more than 95% of the total
variation in pigeonpea, more efforts are required towards the
development of high-yielding stable cultivars. The narrow
genetic base is a serious impediment to breeding progress in
pigeonpea (Yang et al. 2006, also see Kumar et al. 2011 for
details). As wild relatives are a rich reservoir of genes for
resistance to biotic and abiotic stresses (Sharma et al. 2003),
introgression of these genes is an option to genetically
mitigate the effects of such stresses. Further, the exploitation
of genomic tools in conjunction with conventional breeding
programmes can also be helpful. In the past few years, a large
number of genomic tools has been developed in pigeonpea
for resistance to various stresses (Kumar et al. 2011). Further,
intensive efforts through in vitro techniques are underway
towards identifying complex abiotic stress traits, alien gene
introgression aided by embryo rescue and rapid fixation of
stress tolerant recombinants through doubled haploid
breeding (Pratap et al. 2010). These techniques in combination
with more efficient screening methods deserve special
attention in the days ahead to make pigeonpea cultivation a
promising, remunerative and viable option for pulse growing
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