Abstract
Drought tolerance is governed by constitutive and acquired traits. Combining them has relevance for sustaining crop productivity under drought. Mild levels of stress induce specific mechanisms that protect metabolism when stress becomes severe. Here, we report a comparative assessment of “acquired drought tolerance (ADT)” traits in two rice cultivars, IR64 (drought susceptible) and Apo (tolerant), and a drought-tolerant wheat cultivar, Weebill. Young seedlings were exposed to progressive concentrations of methyl viologen (MV), a stress inducer, before transferring to a severe concentration. “Induced” seedlings showed higher tolerance and recovery growth than seedlings exposed directly to severe stress. A novel phenomic platform with an automated irrigation system was used for precisely imposing soil moisture stress to capture ADT traits during the vegetative stage. Gradual progression of drought was achieved through a software-controlled automated irrigation facility. This facility allowed the maintenance of the same level of soil moisture irrespective of differences in transpiration, and hence, this platform provided the most appropriate method to assess ADT traits. Total biomass decreased more in IR64 than in Apo. The wheat cultivar showed lower levels of damage and higher recovery growth even compared to Apo. Expression of ROS-scavenging enzymes and drought-responsive genes was significantly higher in Apo than in IR64, but differences were only marginal between Apo and Weebill. The wheat cultivar showed significantly higher stomatal conductance, carbon gain, and biomass than the rice cultivars, under drought. These differences in ADT traits between cultivars as well as between species can be utilised for improving drought tolerance in crop plants.
Highlights
Rice (Oryza sativa L.), being a semiaquatic species, is generally cultivated under puddle conditions
A significant reduction in growth was observed in MVtreated seedlings of the rice cultivars, with a strong reduction in root length, especially in the susceptible cv
The wheat cultivar, Weebill, on the other hand showed better tolerance with sustained shoot and root growth compared to the tolerant rice cv
Summary
Rice (Oryza sativa L.), being a semiaquatic species, is generally cultivated under puddle conditions. With the impending climate change combined with domestic and industrial demands for fresh water, cultivation of rice in the conventional puddle system is fast becoming less feasible [1]. This necessitates development of suitable water-saving agronomic practices to save water. Practices such as semiirrigated aerobic cultivation are known to save more than half of the water used and avoid the destruction of soil structure while puddling [2]. A concomitant yield loss by more than 40% when grown under the aerobic system has been observed [3, 4]. We should attempt to enhance the genetic potential that can produce more biomass and yield with reduced water requirement
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