Fifteen million farmers in India engaged in Maize cultivation. India would require 45 MMT of Maize by 2022. But, only 15% of cultivated area of maize is under irrigation and water shortage has been a challenge for sustainability of maize production. Water deficit stress (WDS) during pre-flowering and grain filling stages massively affects the plant performance due to imprecise traits function. Thus, the effect of WDS on non-drought tolerant (NDT) and drought tolerant (DT) maize lines were investigated. WDS increased the flowering days, days to maturity, anthesis silk interval, decreased the leaf number, abnormal expression of secondary stress responsive traits, loss of normal root architecture which overall lead to a reduction in GY/ha. WDS at flowering and grain filling stage leads to significant yield penalty especially in NDT lines than DT lines. The yield penalty was ranged from 34.28 to 66.15% in NDT and 38.48 to 55.95% in DT lines due to WDS. Using multiple statistics, traits which improve WDS tolerance in maize were identified viz; number of leaves, number of stomata on lower surface of leaf, leaf angle at ear forming node internodal length between 3 rd and 4 th leaf from top, flag leaf length, flag leaf width, ear per plants, leaf senescence, pollen stainability, root fresh weight and root length. These traits would help in trait specific breeding in maize for WDS tolerance.
Plant defensins are mainly known for their antifungal activity. However, limited information is available regarding their function in abiotic stresses. In this study, a defensin gene, Ca-AFP, from Cicer arietinum, commonly known as chickpea, was cloned and transformed in Arabidopsis thaliana for its functional characterization under simulated water-deficit conditions. Under simulated water-deficit conditions (mannitol and polyethylene glycol-6000 induced), the transgenic A. thaliana plants had higher accumulation of the Ca-AFP transcript compared to that under non-stress condition and showed higher germination rate, root length, and biomass than the wild-type (WT) plants. To get further insights into the role of Ca-AFP in conferring tolerance to water-deficit stress, we determined various physiological parameters and found significant reduction in the transpiration rate and stomatal conductance whereas the net photosynthesis and water use efficiency was increased in the transgenic plants compared to that in the WT plants under water deficit conditions. The transgenic plants showed enhanced superoxide dismutase, ascorbate peroxidase, and catalase activities, had higher proline, chlorophyll, and relative water content, and exhibited reduced ion leakage and malondialdehyde content under water-deficit conditions. Overall, our results indicate that overexpression of Ca-AFP could be an efficient approach for conferring tolerance to water-deficit stress in plants.
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