Abstract
The antioxidant mechanism is crucial for resisting oxidative damage induced by drought stress in plants. Different antioxidant mechanisms may contribute to the tolerance of cassava to drought stress, but for a specific genotype, the response is still unknown. The objective of this study was to investigate antioxidant response and physiological changes of four cassava genotypes under water stress conditions, by keeping the soil moisture content as 80% (control), 50% (medium), 20% (severe) of field capacity for a week. Genotypes RS01 and SC124 were keeping higher relative water content (RWC) and relative chlorophyll content (SPAD value) and less affected by oxidative stress than SC205 and GR4 under drought stress. RS01 just showed slight membrane damage and oxidative stress even under severe drought conditions. A principal component analysis showed that cassava plant water status was closely related to the antioxidant mechanism. Antioxidant response in genotypes RS01 and SC124 under drought stress might attribute to the increased accumulation of ascorbate (AsA) and glutathione (GSH) content and higher superoxide dismutase (SOD) and catalase (CAT) activities, which explained by the up-regulation of Mn-SOD and CAT genes. However, Genotypes SC205 and GR4 mainly depended on the accumulation of total phenolics (TP) and increased glutathione reductase (GR) activity, which attribute to the up-regulation of the GR gene. Our findings could provide vital knowledge for refining the tactics of cultivation and molecular breeding with drought avoidance in cassava.
Highlights
Drought stress is commonly induced by rainfall patterns, greenhouse effect and the variations of temperature
When severe drought stress occurred, relative water content (RWC) of GR4 was reduced by 7.31%, compared with 5.10%, 5.67% and 3.12% in SC124, SC205, and RS01 respectively
The SPAD values of SC124 and RS01 shoots increased under medium drought stress while decreased after exposure to severe drought stress
Summary
Drought stress is commonly induced by rainfall patterns, greenhouse effect and the variations of temperature It is an important environmental stress factor that limits plant growth, regulation, and distribution[1,2,3]. During a prolonged drought stress condition, reactive oxygen species (ROS) generate excessively and cause oxidative damage[11]. In order to counteract the production of ROS under such conditions, antioxidant defense mechanisms were formed in the long-term evolvement in plants. The activities of SOD, CAT, and POD in cassava leaves increased to remove superoxide free radicals and control the level of membrane lipid peroxidation during drought stress conditions[14]. The studies on response mechanism under drought stress in cassava were limited to the physiological or molecular method only. The present research was aimed at the elucidation of antioxidant response mechanism under drought in cassava seedlings combining genetic, physiological and molecular approaches
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