Evaluation of cold resistance of one-yearshoots from‘Cabernet Sauvignon’ grape vine grafted on different rootstocks

Abstract:【Objective】The unique climatic conditions such as abundant sunshine and great temperaturedifference between day and night contribute to the excellent quality of wine grapes in Xinjiang, whichis the largest grape producing area in China.‘Cabernet Sauvignon’, as an excellent wine grape variety,accounts for 70%-80% of the cultivated area of wine grapes in Xinjiang. However, affected by continentalmonsoon climate, grapes are prone to freezing injury, resulting in a significant reduction in grapeyield and quality. In order to avoid or alleviate freezing injury of winter grapes, cold-resistant rootstockshave been applied to wine grapes. This study was conducted to comprehensively evaluate the cold resistanceof the shoots of‘Cabernet Sauvignon’grape grafted on different rootstocks, to screen out the excellentrootstocks that can improve the cold resistance of‘Cabernet Sauvignon’grape. The study providesa reference for cold-resistant cultivation of‘Cabernet Sauvignon’grape and rootstock applicationin Xinjiang. 【Methods】Five resistant rootstocks (5BB, SO4, kangzhen3, 5C and 140R) tested in this ex- periment were introduced from Zhengzhou Fruit Research Institute, Chinese Academy of AgriculturalSciences, and the scion was‘Cabernet Sauvignon’(CS). The rootstock- scion combinations includedCS/5BB, CS/SO4, CS/kangzhen3, CS/5C and CS/140R. The self- rooted 'Cabernet Sauvignon' plants(CS) were used as the control. The experimental rootstocks were planted in 2014 and hardwood graftingwas carried out in 2015. On November 10, 2018, winter pruning was carried out and shoots from the 6scion- rootstock combinations or self- rooted plants grown under the same conditions were selectedand stored in sand. The shoots were exposed to artificial low temperatures of -12 ℃,-15 ℃,-18 ℃,- 21 ℃ ,- 24 ℃ , and - 27 ℃ . Physiological and biochemical indicators, such as relative conductivity(REC), malondialdehyde (MDA), free proline, soluble sugars, soluble proteins, bud germination rate,activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD), and other physiologicalindicators were analyzed. Shoots stored at 4 ℃ were used as the control. Semi-lethal temperature(LT50) was obtained from the regressed logistic equation of relative electrical conductivity vs temperature.The data were subject to principal component analysis for comprehensive evaluation of cold tolerance.【Results】With the decrease in temperature, the relative electrical conductivity, malondialdehydecontent, soluble protein content and CAT activity of all the varieties showed an increasing trend, but theincrease range was different. The sprouting rate of shoots decreased gradually with the decrease in temperaturein the range from 4 ℃ to -27 ℃. The sprouting rate of CS/5BB was reached 5% at -27 ℃,which was significantly higher than those of the other grafted plants. The sprouting rate of self-rootedCS plants was the lowest, being 0% at -27 ℃. The contents of free proline, soluble sugars and the activityof POD increased first and then decreased during temperature drop from 4 ℃ to -27 ℃. The contentof free proline reached a maximum at -24 ℃, while the SOD activity showed a“rise-decline-rise-decline”trend. The semi-lethal temperatures of CS/5BB, CS/SO4, CS/kangzhen3, CS/5C, CS/140R andCS were -20.09 ℃, -19.37 ℃, -16.94 ℃, -16.31 ℃, -14.74 ℃, and -13.43 ℃, respectively. The principalcomponent analysis indicated that MDA content, free proline content, soluble protein content,POD activity, germination rate, soluble sugar content and CAT activity were important indexes for evaluatingthe cold resistance of grapes.【Conclusion】The cold tolerance of‘Cabernet Sauvignon’plantsgrafted on the six rootstocks from high to low was CS/5BB> CS/SO4> CS/5C> CS/140R> CS/kangzhen3>CS.