The chickpea yield (Cicer arietinum L.) is reduced by cold stress in autumn and spring cultivation. In this experiment, biochemical and molecular responses in the nodules of two chickpea genotypes, cold tolerant (Sel96th11439) and cold sensitive (ILC533), incubated with Mesorhizobium ciceri during cold stress treatment (4˚C) were studied in a factorial experiment completely randomized design with three replications. Comparing to control conditions, the rate of cellular damage index (hydrogen peroxide) in tolerant and sensitive genotypes nodules showed significant decrease (by 53%) and increase (by 32%) on the sixth day of cold stress, respectively. Under cold stress, in the tolerant genotype nodules, increased expression of CaADC, CaODC, CaSPDS and CaSAMDC genes resulted in induction of biosynthesis pathway and accumulation of PAs. Results showed that CaADC had a more efficient role in activation of this biochemical pathway compared to CaODC gene. The highest increase in relative expression of studied genes was observed on the sixth day of cold stress, which corresponded to a decrease in cell damage index (H₂O₂) and an improvement in the degree of tolerance to cold stress. These results indicated that in chickpea nodules, physiological-molecular mechanisms determine the degree of tolerance to cold stress. In general, the use of efficient rhizobium strains can be useful in developing breeding approaches aimed at improving tolerance to cold stress due to the symbiosis of chickpea-rhizobium.

Keywords: Gene Expression, Hydrogen Peroxide, Polyamines, Cold stress, Chickpea

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