Introduction
The effect of salinity stress on the quantity and quality of crop production highlights the importance of
managing and reducing the damage caused by this stress factor in agriculture. Increasing soil salinity and
decreasing fertility of arable lands is one of the major problems in saline areas. Cultivation of salt-tolerant crops
which can increase soil fertility could be effective in the sustainable production of these lands. Studying
photosynthesis and its related factors could provide appropriate physiological views in understanding plant
behavior against salinity stress. The present study was conducted to assess the salinity tolerance of chickpea
genotypes for cultivation in saline areas.
Materials and Methods
To evaluate the effects of salinity stress on photosynthetic criteria and yield of chickpeas, an experiment was
conducted in 2018 at the research farm of the faculty of agriculture, Ferdowsi University of Mashhad, Mashhad,
Iran. The experiment was arranged as a split plot based on a randomized complete block design with three
replications. Experimental factors consisted of salinity levels (0.5 and 8 dS.m
-1
) as the main plot and chickpea
genotype (17 kabuli-type genotypes) as the subplot. Seeds were provided from the Mashhad chickpea collection
of the Center for Plant Sciences, Ferdowsi University of Mashhad, Mashhad, Iran. Seeds were planted on March
11th and complementary irrigation was done in three growth stages of pre-flowering, flowering, and pod-filling.
Sodium chloride was used to prepare saline solutions and the irrigation water rate was measured by water meter.
Photosynthetic criteria including photosynthesis rate, evapotranspiration, stomatal conductance, and resistance
and concentration of photosynthetic pigments were measured in the 50% flowering stage.
Results and Discussion
Results indicated that the lowest and highest reduction in the concentration of chlorophyll a was found in
MCC65 (6%) and MCC83 (3.3 times increase), respectively. Increasing salinity level increased the concentration
of chlorophyll b in MCC65 and MCC139, the ratio of chlorophyll a/b in MCC92, MCC139, and MCC776,
carotenoids concentration in MCC77, MCC92, MCC313, and MCC679 and total pigments in MCCMCC77,
MCC92, MCC298, and MCC679. Increasing salinity levels led to higher evapotranspiration in 14 genotypes
except for MCC65, MCC95, and MCC298 in which 37, 54, and 63% decrease of this parameter was observed.
Increasing salinity level increased photosynthesis rate in 7 genotypes of MCC12, MCC65, MCC72, MCC92,
MCC95, MCC679 and MCC776 among which MCC95 and MCC679 showed the highest percentage increase
(61 and 53%, respectively). The highest increase in sub-stomatal CO2 (51, 49, and 40 ppm) with increasing
salinity levels, was found in MCC485, MCC776, and MCC313, respectively. An increase of 28 and 8% in
stomatal conductance was found in MCC65 and MCC95. Stomatal resistance was only reduced in MCC77,
MCC420, and MCC29. Higher salinity levels also led to 3.4 times, 67, 14, and 13% increase in instantaneous
water use efficiency in MCC95, MCC65, MCC92, and MCC298, respectively. Biomass and seed yield declined.142, 148, 167, and 166 g.m-2 respectively in saline conditions. There was a negative significant correlation
between seed yield and evapotranspiration (r=-0.43**), and stomatal resistance (r=-0.38**), and a significant
positive correlation between seed yield and biomass (r=0.61**) and photosynthesis (r=0.24**) and stomatal
conductance (0.36**).
Conclusion
In general, the results of this experiment indicated the diversity among chickpea genotypes for salinity
tolerance caused by saline irrigation water. Studying some photosynthetic criteria in 17 kabuli-type chickpea
genotypes under salinity stress showed high diversity in physiological responses of chickpeas to salinity stress
which could be used in the selection and breeding of salt-tolerant cultivars. MCC65, MCC77, MCC92, and
MCC95 were superior in most studied criteria in saline conditions and even performed, unlike the declining
trend of the other genotypes. It seems that these genotypes could produce reasonable seed yield in salinity levels
up to 8dS.m