Carbon metabolism and antioxidant responses of two blueberry cultivars to waterlogging recovery

Abstract Flooding stress is a significant factor that restricts the development of the blueberry industry and the recovery process following waterlogging plays a critical role in blueberries' waterlogging response. In the experiment, there were two blueberry cultivars of ‘Duke’ and ‘Reka’. After 7 days of waterlogging treatment (the relative soil water content was 90–100%) the relative soil water content was then restored to 50–60% after the waterlogging treatment. Changes in photosynthetic parameters, superoxide dismutase, catalase, peroxidase sucrose synthase, sucrose phosphate synthase, invertases, amylase activities and malondialdehyde (MDA), soluble sugar contents of blueberries were determined during the recovery period after waterlogging. The results showed that after waterlogging, the MDA content in ‘Duke’ leaves was 22% higher than that in the control. While there were no significant differences in the MDA content of ‘Reka’. During the waterlogging recovery period, the antioxidant enzyme activities in leaves of two blueberry cultivars were increased. The photosynthetic rate and soluble sugar content of the two cultivars of blueberries decreased significantly after waterlogging. On second day of recovery, α-amylase activity in ‘Reka’ leaves was 23% lower than that of the control, while the α-amylase activity in ‘Duke’ leaves was increased by 41% . Under waterlogging stress, ‘Duke’ relies on starch degradation to increase the levels of glucose, fructose and sucrose, whereas ‘Reka’ is less affected in terms of soluble sugar content and accumulates more starch as a reserve. Compared with ‘Duke’, the photosynthesis and MDA contents of ‘Reka’ leaves recovered faster after waterlogging and showed stronger waterlogging tolerance. Significance of the study What is already known on this subject? Previous studies on various plants have shown that waterlogging stress leads to root hypoxia and gas exchange disorders, which impair photosynthesis and respiration, causing a carbon source crisis that inhibits plant growth. However, a plant’s adaptability to adverse environments depends not only on its tolerance during the stress but also on its recovery ability after the stress is removed. Blueberries generally have poor waterlogging tolerance; therefore, studying the recovery mechanisms of blueberries after waterlogging is of great significance for selecting waterlogging-tolerant cultivars and improving blueberry waterlogging tolerance. What are the new findings? After prolonged waterlogging stress, blueberry sugar metabolism shows a certain adaptability to the stress. Upon relief of the waterlogging stress, oxidative stress occurs in blueberries. Accelerating the elimination of oxidative stress can speed up the recovery of blueberries after waterlogging. Reka exhibits stronger waterlogging tolerance. Waterlogging-tolerant cultivars exhibit stronger adaptability to waterlogging stress and a greater capacity to eliminate oxidative stress. During the post-waterlogging recovery period, tolerant cultivars accumulate more stored substances such as starch, enhancing their ability to cope with subsequent stresses. What are the expected impacts on horticulture? Assessing waterlogging stress intensity in blueberries can be effectively conducted by monitoring parameters such as photosynthetic rate, malondialdehyde content and starch content. To enhance blueberry waterlogging tolerance, future research can further explore ways to accelerate the elimination of oxidative stress in blueberries and investigate their molecular response mechanisms to waterlogging.