Comprehensive evaluation on resistance of different grape rootstocks to vine dehydration and drought stress during overwintering

Abstract：【Objective】The low temperature and dry air during winter and spring in the arid and semi-arid areas in Northwestern China causes the vine shriveling, which seriously affects the yield and quality of grapes and restricts the development of grape industry in this region. The resistance of grapes can be improved by selecting appropriate rootstocks with high resistance by grafting cultivation. This study aimed to selecting highly resistant grape rootstocks that were suitable for planting in this area by comparing the resistance of vines to shriveling and drought.【Methods】The experiment was carried out in the grape rootstock germplasm resources nursery of Ningxia Yuquanying Farm. 12-year-old grape rootstocks were selected as experimental materials including 3309C, 161- 490, 196- 17, 420mgt, Riparia, 1103P, 110R, SO4, 41bmgt and Rupestris du Lot. Ten kinds of rootstocks were not buried with earth or applied with any cold-proof measure in winter and the shriveling-resistance of rootstocks was evaluated by investigating the bud break rate of the annual and lateral shoots in the spring in the following year. All the rootstocks were not stressed after investigating the bud break rate with normal water and fertilizer management. The rootstocks were treated for 30 days in response to drought stress after full irrigation on August 14, 2017. The degree of drought stress was observed by measuring the predawn leaf water potential. On the 0th , 10th , 20th and 30th day after drought stress treatment, Pn was measured by the photosynthesizer 3051D and the functional leaves in the middle of each variety were collected and frozen in liquid nitrogen. The samples were taken back to the laboratory for determination of MDA, Pro and soluble protein contents and SOD and CAT activity. Comparison of differences in physiological indexesof grape rootstocks under drought stress was performed by different significance tests, the 30th day physiological indexes of drought stress were evaluated by the membership function method. According to the average membership value, the rootstocks were divided into 3 drought- resistance types: 0.00-0.30 referred to low drought-resistance (LDR), 0.31-0.60 to moderate drought-resistance (MDR), and 0.61- 0.80 to high drought-resistance (HDR).【Results】The results showed that there were only 3309C, 161- 490, 196-17, 420mgt and Riparia sprouted in the spring of the following year and the bud break rates of annual vines were 79.85%, 57.35%, 64.02%, 47.93% and 24.8%, respectively, and the bud break rates of the lateral vines were 72.94%, 75%, 61.87%, 52.95% and 50%, respectively. The bud break rate of other rootstocks was 0 and the annual vines were shriveled and dead. Therefore, the order of the resistance of vines to shriveling according to the bud break rates of rootstocks was 3309C ＞161-490 ＞196- 17 ＞420mgt ＞Riparia, 1103P, 110R, SO4, 41bmgt and Rupestris du Lot. After drought stress, the leaf water potential and Pn decreased, MDA and Pro contents, and the activity of SOD and CAT increased. Except for Rupestris du Lot, soluble protein contents in other treatments increased with the enhancement of drought stress. The leaf water potentials of 1103P, 3309C and Riparia were higher than other types and higher water retention capacity was observed at 30th day after drought stress. The Pn of 3309C was the lowest and its photosynthesis was almost unaffected by drought stress, whereas Pn with 41bmgt was the lowest 30th day after drought stress. The contents of MDA with 196-17, 161-490, Riparia and 3309C were lower than the rest types and their degree of the membrane lipid peroxidation was serious after drought stress for 30 days. The Pro content with 196-17 was the highest among the 10 types of rootstocks after drought stress. The SOD activity of 1103P and Riparia and the CAT activity of 196-17 and 1103P were significantly higher than other types and higher contents in 196-17, 161-490 and 420mgt were found whereas the reverse was true with SO4, Rupestris du Lot and 41bmgt at 30th day after drought stress. Correlation analysis of various indexes of rootstocks at 30th day after drought stress showed that the Pn and MDA contentwere significantly negatively correlated (p ＜ 0.05), the contents of MDA and Pro were significantly negatively correlated (p ＜ 0.01), and the activity of SOD and the content of soluble protein were significantly negatively correlated (p ＜ 0.05). However, the content of soluble protein was significantly positively correlated (p ＜ 0.05) with the activity of SOD. According to the method of membership function to comprehensive evaluation on all physiological indicators, the results showed that 3309C, 196-17, 1103P and Riparia were of higher drought resistance, 161-490, 420mgt and 110R of moderate drought resistance, and SO4, 41bmgt, and Rupestris du Lot of low drought resistance. Therefore, the order of the drought-resistance according to the average membership value was 3309C ＞196-17 ＞1103P ＞Riparia ＞161-490 ＞420mgt ＞110R ＞SO4 ＞41bmg ＞Rupestris du Lot.【Conclusion】Rootstocks 196-17, 161-490 and 3309C were more suitable for applying in arid and semi-arid region, in terms to the resistance to vine shriveling- and drought stress, whereas the SO4, Rupestris du Lot and 41bmgt were lower than the other types. When the drought- resistance of 1103P was strong, the resistance to vine shriveling was weak. Therefore, the rootstock resistance to vine shriveling- was related to its resistance to drought stress, but both were not completely consistent. In summary, rootstocks 3309C and 196-17 possessed higher resistance to drought stress and can be used as rootstocks where no mound was required in the arid and semi-arid regions of Northwestern China.