Growth and metabolic responses of contrasting chickpea (Cicer arietinum L.) genotypes to chilling stress at reproductive phase

Chilling stress (< 10A degrees C) at reproductive phase of chickpea results in abortion of flowers and pods leading to poor yield. The metabolic causes associated with cold sensitivity of chickpea are not well understood. Hence, in the present study, we evaluated four chickpea genotypes (ICC 16348, ICC 16349, PBG1 and GPF2) having contrasting cold sensitivity for their reproductive growth and metabolism subjected to cold stress (average day temperature: 17.6A degrees C; average night temperature: 4.9A degrees C). Genotypes ICC 16348 and ICC 16349 showed flowering and set pods, while PBG1 and GPF2 failed to do so during the stress conditions indicating the former to be cold tolerant. The stress injury in the leaves such as increase in electrolyte leakage, decrease in chlorophyll content and relative leaf water content was significantly less in ICC 16348 and ICC 16349 genotypes. The analysis of carbohydrates indicated total sugars and starch to be present in greater content in ICC 16348 and ICC 16349 relative to PBG1 and GPF2 genotypes. The enzymes related to carbohydrate metabolism such as beta-amylase, invertase and sucrose synthase showed significantly higher activity in the leaves of ICC 16348 and ICC 16349 compared to the other two genotypes. PBG1 and GPF2 genotypes experienced greater oxidative stress measured as malondialdehyde and hydrogen peroxide. ICCV 16348 and ICC 16349 possessed significantly higher levels of enzymatic (superoxide dismutase, catalase, ascorbate peroxidase) and non-enzymatic antioxidants (proline and ascorbic acid) relative to PBG1 and GPF2. Particularly, proline and ascorbic acid were markedly higher in cold-tolerant genotypes compared to the sensitive ones suggesting their deciding role in governing the cold tolerance.