Chickpea and temperature stress: An overview - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 82

environments for stress response has increased our
knowledge of plant responses to stress in chickpea, and
this information has been used in crop improvement.
Physiological response (e.g. canopy temperature) and
male (pollen) and female (ovary) reproductive function
under stress have been investigated to determine their
suitability as stress screening techniques (Clarke &
Siddique, 2004; Ibrahim, 2011). Sources of tolerance to
temperature stress identified using these methods can
be used to develop genetic populations to increase our
understanding of inheritance. These populations can be
used to map quantitative trait loci (QTL) and the result-
ing linked markers used for marker-assisted selection
(MAS). This chapter explores plant responses to high
and low temperatures and the implications for stress
tolerance breeding in chickpea.

Field screening for cold tolerance during the late veg-
etative stage where plants were exposed to −7.4°C for 3
weeks was effective in identifying cold-tolerant geno-
types (Malhotra & Singh, 1991). These authors scored
materials on a scale of 1 to 9 and concluded that the
method was effective in identifying tolerant, moderately
tolerant and sensitive genotypes. This method was
used to screen cultivated and wild chickpea in the
Mediterranean region (Toker, 2005).
Cold temperature generally encourages prolonged
vegetative growth in chickpea. Temperature is the main
determinant for flower initiation in most environments,
although some authors have linked flower initiation in
chickpea to a photothermal response (Roberts et al.,
1985). In northern NSW, Australia, flower initiation can
commence at ≤15°C, although the occurrence of flower
abortion will likely be high (Jenkins & Brill, 2011).
The minimum temperature for germination is 10-15°C
(Ellis et al., 1986). At high temperatures, greater than
42.5°C, germination decreases significantly (Ibrahim,
2011) and above 45°C no germination is observed due to
lack of embryo growth (Singh & Dhaliwal, 1972).
Similarly, high temperature affects photosynthesis, tran-
spiration rate and plant growth (Singh & Dhaliwal, 1972)
and the length of vegetative period is generally reduced.
In other words, phenology can be modified under high
temperature (Summerfield et al., 1984). At high temper-
atures (>35°C), the vegetative period was reduced by 10
to 15 days compared with optimum temperature (28°C)
at Kanpur, India (ICRISAT, 2011). High temperature
therefore accelerates flowering and reduces the overall
crop growth period.
High temperatures can cause cellular abnormalities
such as oxidative stress, and denaturation of proteins
and enzymes. Oxidative injury occurs as lipid peroxida-
tion, and hydrogen peroxide content tends to increase
in heat-sensitive genotypes at day and night tempera-
tures of over 40/30°C compared with heat-tolerant
genotypes (Kumar et al., 2012a). ABA remains high at
40/35°C but was observed to decline at 45/40°C (Kumar
et al., 2012b). A membrane injury test based on electro-
lyte leakage from leaves was shown by Ibrahim (2011)
to be an effective measure of high temperature sensi-
tivity in chickpea, with sensitive types displaying high
degrees of membrane injury. Therefore, heat stress
injury can be measured using a combination of oxidative
stress assessments, ABA level and membrane injury in
chickpea.

5.2 Impacts on productivity

5.2.1 temperature stresses during
the vegetative period
Cold temperature (<15°C) at emergence reduces crop
establishment and results in plants with low vigour. In
some sensitive genotypes, cold temperature causes
whole plant necrosis and plant death. During chickpea
germination, cold temperature also increases suscep-
tibility to soil-borne pathogens thus retarding plant
growth and reducing dry matter production (Wery et al.,
1994). A plant survival score can be used as an index to
describe genotype tolerance to low temperature under
field conditions. Chickpea genotypes (Sel 95Th1716
and Sel 96Th11439) were identified as cold tolerant
based on plant survival scores in northwestern Iran
(Heidarvand et al., 2011). Genotypic differences in
chickpea establishment were identified in Australia, and
the cold-tolerant cultivars CPI 562896, Semsen and
Sombrero showed improved establishment under low
temperatures (Wery et al., 1994).
Cold temperatures decrease membrane stability,
modify proteins and lipids, and cause changes in respi-
ration and photosynthesis (Croser et al., 2003). Abscisic
acid (ABA) content was observed to increase in seed-
lings at temperatures of 1-7°C compared with the
control (23°C) (Nayyar et al., 2005a). The sugar and pro-
line contents also increased under cold stress in the
same study. These observations suggest that manipula-
tion of ABA could improve cold tolerance in chickpea.