Effects Of Intercropping On Selenium Enrichment Characteristics Of Grape And Solanum Nigrum Var.humile

Vitis vinifera is one of the four major fruit trees in the world,with its delicious and juicy fruit that is loved by consumers around the world.With the continuous expansion of the grape industry,people’s demand for high-quality grapes is increasing,and they are also paying more attention to the selenium nutrition of grapes.Intercropping is one of the important planting methods in traditional Chinese agriculture,which not only improves the yield and quality of crops,but also promotes the uptake and utilization of soil mineral nutrients by crops.Our preliminary research team found that intercropping grapes with Solanum nigrum var.humile can significantly promote selenium enrichment in grapes.However,the mechanism of S.nigrum var.humile’s action on grape selenium enrichment is still unclear.Therefore,in this study,grape and S.nigrum var.humile were intercropped to further study the effect of intercropping on selenium uptake and transport,and differential genes and differential metabolites were screened through transcriptome sequencing and metabolomic analysis.The mechanism of intercropping on selenium accumulation in grape and S.nigrum var.humile was analyzed.The research results can provide a reference for the production of selenium rich grapes.The main research findings are as follows:(1)In 5 mg/kg selenium soil,intercropping increased the total selenium content in the roots and shoots of grape and S.nigrum var.humile.The total selenium content in the roots and shoots of grape increased by 18.45% and 43.13% compared to monoculture,respectively.In terms of subcellular distribution of selenium,intercropping increased the selenium content in the cell walls of grape roots and leaves,which increased by 49.86% and 30.70% compared to monoculture,respectively.Intercropping also increased the selenium content in the cell walls and soluble components of the roots of S.nigrum var.humiles,which increased by28.60% and 35.01% compared to monoculture,respectively.From the perspective of chemical forms of selenium,most of the selenium in the roots and shoots of grape and S.nigrum var.humile mainly exists as selenium-oxalic acid complex(HCl extracted selenium).Intercropping increased the content of HCl extracted selenium in the roots and shoots of grape and S.nigrum var.humile.Among them,the HCl extracted selenium in the shoots of grape and S.nigrum var.humile increased by 58.96% and 48.77% compared to monoculture,respectively.(2)The transcriptome sequencing study showed that the original sequencing data of the four expression libraries of grape monoculture,grape intercropping,S.nigrum var.humile monocropping and S.nigrum var.humile intercropping were screened,and the Clean Data of each sample exceeded 1.9 million,the GC% content of each sample exceeded 42%,and the Q30 base percentage was 93.34% or more.537 differential genes were identified between monoculture and intercropping treatments in grape.Compared with monoculture,intercropping significantly increased the expression of sulfate transporter 3.1 and cysteine synthase in grape leaves,and decreased the expression of multiple ATP-binding cassette transporter.653 differential genes were identified between monoculture and intercropping treatments in S.nigrum var.humile,mainly enriched in pathways such as linoleic acid metabolism,β-alanine metabolism,plant MAPK signaling pathway,and limonene and pinene degradation.(3)Metabolomic analysis showed that a total of 2934 metabolites were screened from grapes and S.nigrum var.humile.413 differential metabolites were identified in grape monoculture and intercropping treatments,which were mainly enriched in glycolysis/gluconeogenesis,pentose phosphate pathway and β-alanine metabolism.780 differential metabolites were identified between monoculture and intercropping treatments in S.nigrum var.humile,mainly enriched in pathways such as flavonoid and flavonol biosynthesis,phenylpropanoid biosynthesis,and arginine and proline metabolism.(4)In 0.5 mg/kg selenium soil,the intercropping of grape grafted seedlings and S.nigrum var.humile increased the total selenium content in their roots and shoots,with the total selenium content in the shoots of grape grafted seedlings increasing by 50.00%compared to monoculture.The intercropping of grape fruiting trees with S.nigrum var.humile improved the external quality(transverse diameter,longitudinal diameter,single fruit weight)and internal quality(soluble solids,vitamin C)of grape berry,while also increasing the total selenium content of the grape berry,an increase of 40.00% compared to monoculture.In summary,intercropping promoted selenium enrichment in grapes and S.nigrum var.humile.As for grapes,intercropping mainly promotes the transport of selenide to chloroplasts and the synthesis of organic selenium by increasing the expression of sulfate transporter 3.1 and cysteine synthase in grape leaves,thus promoting selenium enrichment in grapes.The pathways of linoleic acid metabolism,β-alanine metabolism,MAPK signaling pathway in plants,and degradation of limonene and pinene are involved in the process of promoting selenium enrichment in S.nigrum var.humile through intercropping.