| Wine regions are mainly located in arid and semi-arid areas in China.The average annual precipitation is low and the annual rainfall distribution is uneven.Drought occurs from time to time.The occurrence of droughts has become more and more serious and frequent with the global climate change,which affects the growth,development and regular physiological metabolism of grapevines,and seriously threatens the development of grape and wine industry.Arbuscular mycorrhizal fungi(AMF)are fungi that exist widely in nature and can be mutually beneficial and symbiotic with plants,which can promote plant growth and nutrient absorption.Studies in a variety of plants have found that arbuscular mycorrhizal fungi can improve the drought resistance of plants,but there are few studies on the effects of AMF on the drought resistance of wine grapes.The inoculation effect of AMF in grapes varies greatly in various studies.It is difficult to predict the inoculation effect of AMF in grapes at present.The inoculation effect of different AMF inoculants on wine grapes was studied in the experiment.In this experiment,various varieties and rootstocks were inoculated with different AMF inoculants.The inoculation effects of different AMF inoculants on grapes were verified by indicators such as colonization rate,grape biomass,nutrient content,and root growth.AMF inoculants which can significantly promote growth and nutrient absorption were screened.Screened inoculant with significant positive effects on wine grape growth were used to study the effect of AMF on the drought resistance of wine grape ’Ecolly’.In this experiment,the effects of AMF on the drought resistance of grapes were studied from the aspects of photosynthesis,osmotic regulation,antioxidant capacity and gene expression related to drought resistance.The main findings are as follows:(1)The five AMF inoculants all formed a symbiotic relationship with wine grape plants,and all of them could promote grape growth and nutrient absorption to varying degrees.Under greenhouse conditions,AMF inoculants 3,4,and 5 significantly increased the nitrogen content of grape leaves,the fine root length density,the biomass of shoots,trunks and roots,and significantly decreased the diameter of fine roots compared with the control.Under field conditions,each AMF inoculant promoted the absorption of mineral elements in’Pinot Noir’ grapes to varying degrees.Each AMF inoculant significantly increased the content of calcium and boron in the leaves of ’Pinot Noir’.AMF inoculants 2 and 5significantly increased nitrogen,phosphorus,calcium,magnesium,boron,zinc,iron,manganese,copper and sodium content in the leaves of ’Pinot Noir’.All AMF inoculants promoted the nitrogen absorption of ’Riesling/SO4’ and ’Riesling/3309C’ to different degrees,and reduced the carbon-nitrogen ratio.(2)The effect of AMF inoculant on grape growth and nutrient absorption varied by rootstocks.Own-rooted ’Cabernet Sauvignon’ and ’Cabernet Sauvignon/3309C’ had different performances under the same inoculum.The biomass of shoots,trunks and roots of own-rooted ’Cabernet Sauvignon’ seedlings was increased by inoculant 5 with the most significant effect by 61.0%,50.5% and 37.3%,respectively,while the biomass of shoots,trunks and roots of ’Cabernet Sauvignon/3309C’ was increased by 163.8%,101.0% and119.4%,respectively.(3)AMF inoculant screened from the previous study was colonized in the roots of grapevine ’Ecolly’ and formed a symbiotic relationship with plants under greenhouse conditions.Under drought stress and well-water conditions,inoculation with AMF inoculum significantly increased the dry biomass of shoots and roots of plants compared with non-AMF inoculation.Under drought stress,AMF significantly increased the water content and chlorophyll content in leaves.AMF improved photosynthesis and photosystem II.Under drought stress,inoculation with AMF significantly increased the photosynthetic rate,stomatal conductance and transpiration rate of leaves,significantly reduced the intercellular CO2 concentration;significantly increased the maximum photochemical efficiency,the potential photosynthetic activity of PSII,actual photochemical quantum yield,and significantly reduced non-photochemical quenching compared with non-inoculation.(4)Under drought stress,the content of sucrose and proline in grape leaves which inoculated with AMF were significantly higher than those in non-inoculated grape leaves.AMF promoted plants to produce more soluble substances,improved osmotic regulation ability,and improved plant drought resistance.Under drought stress,inoculation with AMF significantly decreased the contents of malondialdehyde,hydrogen peroxide and superoxide anion in leaves,and significantly increased SOD,POD enzyme activities and glutathione contents in grape leaves.AMF increased the content of antioxidant substances and the activity of antioxidant enzymes,improved the antioxidant level of plants,and reduced the damage caused by drought stress to plants.(5)Under well-water conditions,inoculation with AMF significantly increased the expression of Vv SIP,Vv PIP1;2,Vv PIP2;2 and Vv TIP2;1 genes in grape leaves compared with non-AMF inoculation.AMF promoted water uptake by inducing the expression of aquaporin-related genes under well-water conditions.The expressions of Vv SIP,Vv PIP1;2were significantly down-regulated,and the expressions of Vv NCED,Vv P5 CS,Vv BG,Vv PIP2,Vv PIP2;2,Vv TIP2;1,Vv TIP4;1 were significantly up-regulated under drought stress compared with well-watered condition.Under drought stress,the expression levels of Vv NCED,Vv P5 CS,Vv BG,Vv PIP1;2,Vv PIP2;2,Vv TIP2;1 and Vv TIP4;1 genes in AMF-inoculated leaves were significantly higher than those in non-AMF inoculated leaves.In summary,under drought stress,AMF,which forms a symbiotic relationship with grapevine,can improve grape photosynthesis and photosystem II,improve plant osmotic regulation and antioxidant capacity,and induce the expression of drought resistance-related genes,which enhances the growth of grape plants.AMF plays an important role in relieving drought stress of grapevine. |
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