Glycine betaine mitigates cold stress damage in Chickpea

Abstract

Chickpea (Cicer arietinum L.) is sensitive to chilling temperatures (<10 °C), especially in its reproductive phase. Consequently it suffers from floral abortion, poor pod set and reduced seed size, leading to substantial yield loss. The underlying mechanisms are yet to be elucidated, which are imperative to understand how to induce cold tolerance in this crop. Glycine betaine, a cryoprotectant, has been associated with induction of cold tolerance. In the present study, chickpea plants previously growing under the warm conditions of a glasshouse (28/12 °C as average maximum and minimum temperature, respectively) were subjected to the chilling stress of the field (12-14/3-5 °C) at the (i) bud or (ii) pod-filling stages. Prior to exposure to stress, 1 mM glycine betaine was applied exogenously for 3 consecutive days. In glycine betaine-treated plants, chilling injury (assessed as electrolyte leakage) was reduced by 63% while cellular respiration increased by 69%. Application of glycine betaine at the bud stage resulted in improvement in flower functioning in terms of pollen germination (in vitro and in vivo), pollen viability, pollen tube growth, stigma receptivity and ovule viability. As a result, the floral retention, pod set and pod retention were increased by 47, 38 and 23%, respectively, over control. Treatment with glycine betaine at the pod-filling stage caused 30, 37, 46% and 9% enhancement in seed yield/plant, number of seeds/100 pods, single-seeded pods/plant and individual seed weight, respectively, while number of double-seeded pods was not affected significantly. Cold tolerance induced by glycine betaine appeared to be related to elevation of relative leaf water content, chlorophyll and sucrose, and decrease in abscisic acid as well as active oxygen species (malondialdehyde and hydrogen peroxide).