Physiological and biochemical mechanism of the effect of exogenous trehalose on cold resistance in Cabernet Sauvignon seedlings

Abstract:【Objective】Grapes (Vitis L.) are one of the most commercially significant fruit crops in the world, but they have low cold tolerance and are often damaged by late frost, which has a significant impact on their production and economic value. In recent years, trehalose, a non- reducing disaccharide, has been reported to improve the cold resistance in numerous crops; however, the physiological mechanism underlying its ability to mitigate the negative effects of low temperature stress on the growth and development of grape seedlings remains unclear. In order to overcome the problem of late frost damage in wine grapes, the present study used foliar spraying of different concentrations of trehalose to examine the physiological effects of trehalose on seedlings of Cabernet Sauvignon under an artificially simulated late spring cold spell. This research intends to provide reference for the use of trehalose in wine grapes to alleviate the damage from late frost damage.【Methods】The tested material was Cabernet Sauvignon seedlings, and the leaves were sprayed with different doses of trehalose (10, 15, and 30 mmol·L^-1 ) overthree consecutive days, with water spraying serving as the control. The treated seedlings were then placed in a low-temperature incubator to simulate a cold spell that occurs in the late spring, where temperatures were programmed to decrease from 16 ℃ to (-3±0.5) ℃ at a rate of 1 ℃· h^-1 and maintained at (-3±0.5) ℃ for 4 h. The leaves were collected at temperatures of 16 ℃, 4 ℃ and 0 ℃, and at -3 ℃ for 0 h and 4 h. The samples were flash-frozen in liquid nitrogen and kept at -80 ℃ in a freezer. During the period of cold stress treatment, trehalose treatment caused phenotypic alterations were recorded. In addition, several physiological indices related to cold stress response, such as antioxidant enzyme activity, cell membrane integrity, and sugar (glucose, fructose, and sucrose) contents were compared between the trehalose-treated groups and the control under the simulated“late spring cold spell”conditions. In addition, variations in endogenous hormones (ABA, IAA, GA3, and tZR) were examined.【Results】Foliar spraying of trehalose promoted the growth of Cabernet Sauvignon seedlings under artificially simulated late spring cold spell, promoted photosynthesis, induced an increase in the activities of antioxidant enzymes (e.g. CAT and POD); maintained the level of cellular osmoregulation, increased the levels of endogenous hormones (e.g. tZR, GA3 and ABA); and regulated the level of soluble sugars, thereby mitigating the damage caused by low temperature. There was a concentration effect, and foliar spraying with a 15 mmol·L^-1 trehalose solution produced the greatest results. Unlike the control, seedlings treated with 15 mmol·L^{- 1} trehalose did not exhibit plant wilt or any leaf spots caused by freezing, and their survival rate rose by 60.52% compared with the control. 15 mmol·L^{- 1} trehalose treatment also reduced the production of reactive oxygen species (ROS), and the contents of hydrogen peroxide (H2O2) and superoxide anion (O2 ^.-) were decreased by 23.82% and 6.21%, respectively. In addition, CAT and POD activities increased by 221.73% and 54.53% , respectively, while there was no significant difference in SOD activity. Moreover, the contents of ABA, GA3 and tZR increased by 701.21% , 127.66% and 80.03%, respectively, and the content of IAA was not detected in the control group, whereas in the treated group was 0.94 ng · g^{- 1} . Concurrently, the contents of glucose, fructose and sucrose increased by 11.20%, 12.56% and 68.53%, respectively.【Conclusion】Under simulated late spring cold spell, foliar spray of 15 mmol·L^-1 trehalose significantly increased survival rate, chlorophyll content, antioxidant enzyme activity, sucrose contents and IAA and ABA contents, but decreased MDA and ROS contents. Therefore, the effect of trehalose on the cold tolerance of grape seedlings may be related to the diminished effect of low temperature stress on the growth and development of Cabernet Sauvignon seedlings.