| The main producing areas of wine grapes in China are mainly arid and semi-arid climates,especially in the northwestern region,with drought and little rain,and severe soil water deficit,which affects the growth of wine grapes.Therefore,it is of great significance to study the drought resistance characteristics of grape for alleviating drought stress.Many studies have shown that growth-promoting bacteria with 1-aminocyclopropane-1-carboxylic acid(ACC)deaminase activity can effectively promote plant growth under drought stress and can significantly alleviate the effects of drought stress on plants.However,isolating growth-promoting bacteria with ACC deaminase activity from grape and studying their resistance to stress have not been reported.In this study,the growth-promoting bacteria with high activity of ACC deaminase were isolated from leaves,rhizosphere soil and roots of Cabernet Sauvignon(Vitis vinifera L.)in Qingtongxia,Ningxia and Yangling,Shaanxi.The isolated strains were identified by morphology and 16 S r DNA.Two different species strains with no environmental harm were selected and made into bacterial agents T1(with high activity of ACC deaminase),T2(with low activity of ACC deaminase)and T3(mixed with T1 and T2 strains),which were injected into the rhizosphere of annual cabernet sauvignon plants for the two-factor pot drought stress test.After the stress,the basic growth indexes,photosynthetic physiological indexes and drought resistance physiological indexes of the plants were measured.The main results were shown as follows:1.A total of 26 growth-promoting bacteria with ACC deaminase activity were isolated from leaves,rhizosphere soil and roots.The ACC deaminase activity of the isolated strains were between 0.01 and 10.9 μmol α-KA/(mg Pr·h),and the IAA concentration was between2.54 and 15.64 mg/L.All the 26 strains had nitrogen fixation ability.19 strains had the phosphorus solubilizing properties.2.The isolated strains with high ACC deaminase activity and other growth-promoting properties were identified by morphology and 16 S r DNA.Finally,seven isolated strains were confirmed belonging to Pseudomonas fluorescens,Pseudomonas corrugata,Pseudomonas frederiksbergensis,Enterobacter soli and Achromobacter xylosoxidans.3.Inoculation of high activity ACC deaminase-promoting bacteria T1,T2 and T3 can effectively promote the growth of grape plants.Inoculation of the bacterias increased the plant height and diameter,and there was no significant difference in the growth promoting effects of the single bacteria and the mixed bacteria.Inoculation of mixed bacteria T3 significantly increased the relative water content of leaves under mid-degree drought stress.4.Both inoculated single bacteria and mixed bacteria could increase Pn,Gs,Ci and WUE under drought stress,and reduce Tr.Inoculation of single bacteria T2 and mixed bacteria T3 can significantly increase chlorophyll content under different drought stress.5.Inoculation of bacteria significantly improved the drought resistance of grape plant.Inoculation with single strain T1 significantly increased root activity,total root length,total root surface area and proline content,and significantly reduced relative conductivity content under mid-degree stress;significantly increased total root surface area,total root volume,soluble sugar and ABA content under severe stress,and significantly reduced malondialdehyde content.The inoculated single strain T2 significantly increased the root activity and soluble sugar content under mid-degree stress,which was 14.81% and 17.91%higher than that of the non-bacterial control group.The total root length,proline content and ABA content were significantly increased under severe stress.The inoculated mixed T3 significantly increased the total root surface area and proline content under moderate stress;the proline content was significantly increased under severe stress(60.16 μg/g),which was84.98% higher than that of the non-bacterial control group.The inoculated single bacteria T1 and T2 could significantly increase the activity of SOD enzyme under the drought stress degree.The inoculated mixed T3 significantly increased the activity of superoxide dismutase(SOD)enzyme only under mid-degree stress,and the increase range was 23%～78.93% compared with the non-inoculation control group.The inoculation of three microbial agents could effectively increase the activity of peroxidase(POD)enzyme under various drought stress levels.The inoculation of T2 microbial agents was the highest in severe stress,which was 1.1 times higher than that in the control group.Inoculation of single strain T1 significantly increased Catalase(CAT)enzyme activity under mid-degree stress,which was 40.44% higher than that of the non-inoculation control group.In general,the inoculation of single bacteria T1,T2 and mixed bacteria T3 under the conditions of this experiment have a good growth promoting effect.The inoculated single bacteria T1,T2,T3 were effective to alleviate the stress of grape seedlings under mid-degree and severe drought stress,severe stress,mid-degree stress.Bacterias with ACC deaminase activity can effectively alleviate the drought stress of grape plant,and bacterias with high ACC deaminase activity can better alleviate the drought stress. |
