Abstract
Peanut, an important oilseed crop, frequently encounters drought stress (DS) during its life cycle. In this study, four previously developed mtlD transgenic (T) peanut lines were used for detailed characterization under DS, at the reproductive stage using lysimeter system under controlled greenhouse conditions. In dry-down experiments, T lines maintained better photosynthetic machinery, such as, photosynthesis rate, stomatal conductance, transpiration rate, and SPAD (Soil-Plant Analyses Development) values, and had lower oxidative damage, including lipid membrane peroxidation and hydrogen peroxide and superoxide radical accumulation than WT, when exposed to 24 days of DS. WT plants had a more negative water potential (WP; up to −3.22 MPa) than T lines did (−2.56 to −2.71 MPa) at day 24 of DS treatment. During recovery, T lines recovered easily whereas 67% of WT plants failed to recover. In T lines, the rate of photosynthesis strongly and positively correlated with the transpiration rate (r = 0.92), RWC (r = 0.90), WP (r = 0.86), and total chlorophyll content (r = 0.75), suggesting its strong correlation with water retention-related parameters. Furthermore, yield parameters such as, pod weight and harvest index of T lines were up to 2.19 and 1.38 times more than those of WT plants, respectively. Thus, the significantly better performance of mtlD T peanut lines than of WT plants under DS could be attributed to the accumulation of mannitol, which in turn helped in maintaining the osmoregulation and ROS scavenging activity of mannitol and ultimately conferred water-economizing capacity and higher yield in T lines than in WT plants.
Highlights
Peanut or groundnut (Arachis hypogaea L.), a glycophytic plant, is vulnerable to water deficit stress or drought since it is usually grown under rainfed conditions on sandy soils (Banjara et al, 2011; Bhauso et al, 2014a)
The mtlD gene coding for MTD was used for studying the imposition of drought tolerance in T peanut lines
Among four T lines, significantly higher MTD activity was recorded in MTD1, MTD2, and MTD4, while least activity was recorded in MTD3 at day 24 of drought stress (DS) treatment (Table 1)
Summary
Peanut or groundnut (Arachis hypogaea L.), a glycophytic plant, is vulnerable to water deficit stress or drought since it is usually grown under rainfed conditions on sandy soils (Banjara et al, 2011; Bhauso et al, 2014a). The adverse effect of DS on plants begins with a decrease in the transpiration rate (TR) and stomatal conductance (SC) and leaf water potential (WP), resulting in overall imbalance in water relationships and the photosynthetic rate (Pn) (Farooq et al, 2009; Krasensky and Jonak, 2012; Ashraf and Harris, 2013; Osakabe et al, 2014) These effects are followed by a reduction in the turgor pressure, transpiration, and relative water content (RWC) and often the formation of reactive oxygen species (ROS), resulting in an increase in malondialdehyde (MDA) content and poor yield (Farooq et al, 2009; Akcay et al, 2010; Patel et al, 2016)
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