Effects of different rootstocks on contents of endogenous hormones and polyamines in Cabernet Sauvignon grape seeds

Abstract:【Objective】Xinjiang is the earliest region to grow grape and also a major province for wine grape cultivation and brewing in China. However, Xinjiang's diverse climate, drought, salinity, cold and other ecological conditions restrict the further development of wine grape industry, resulting in a significant reduction in grape yield and quality. The grape grafting can adapt to different soil types and growth environments of biological (like soil pests) and non-biological (such as salinity, moisture or temperature) stresses. Plant hormones and polyamines are compounds, which derive through many important metabolic pathways in plants. Not only can they regulate plant growth and metabolism, but are also be closely related to stress resistance. This study compared the trend of changes in the content of related hormones and polyamines in seeds of Cabernet Sauvignon grapevine grafted on different rootstocks. It can provide a theoretical basis for the research on the effect of scion-rootstock interaction on fruit hormone and polyamine metabolism.【Methods】Five resistant rootstocks (5BB, V. riparia, SO4, 140R and 3309M) were collected all from Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences. The scion was Cabernet Sauvignon 169 (CS), which was planted in the grape test garden in 2014. The rootstock-scion combinations included CS/5BB, CS/ V. riparia, CS/SO4, CS/140R and CS/ 3309M. The experiment started on July 28, 2020 (berry veraison period), until the end of sampling on September 8, 2020 (fruit ripening period). Sampling was completed once every 10 days, totaling for 5 sampling times. Random samples were taken during each sampling and brought back to the laboratory in time. The pulp and seeds were accurately separated and quickly frozen in liquid nitrogen, and 0.5 g of each sample was weighed, which was repeated for 3 times. Then the samples were placed in a refrigerator at -80 °C. Determination of titratable acid and reducing sugar contents in berries and the contents of gibberellins A3(GA3), indole acetic acid (IAA) and abscisic acid (ABA), Putrescine (Put), Spermidine (Spd), and Spermine (Spm) in seeds was made at different periods. Then correlation analysis between berry acid content and seed hormone and polyamine contents was performed.【Results】All the tested grape rootstock types can reduce the titratable acid content in Cabernet Sauvignon grape berries. During berry maturity period, the titratable acid content with each rootstock combination was lower than that with CS by 19.09%- 35.29% . Simultaneously, it was found that the contents of various hormones in seeds during the berry veraison stage with each rootstock combination were generally higher than that during the fruit maturity stage, and the GA3 content in the seed had a trend of M- changing style, the IAA content continued to decline, and the ABA content first decreased and then increased; Spd content continued to decrease, while the Put and Spm contents increased first and then decreased. The difference was that the Put content peak appeared during the berry veraison period, while the Spm content peak appeared during the fruit ripening period. At different stages of fruit development, rootstocks exerted different effects on the contents of related hormones and polyamines in scion seeds. During the berry veraison period, the rootstock increased the number of seeds and significantly reduced the IAA, ABA and Spd contents in the seeds, and increased the Put and Spm contents; at the same time, it decreased the IAA and Spm contents during the berry maturity period, and increased the contents of GA3, ABA, Put, and Spd.【Conclusion】Compared with self-rooted seedlings, rootstock grafting can affect the metabolism level of hormones and polyamines in seeds.