| Blueberry(Vaccinium spp.) as a shallow-rooted plant,has poor ability to absorb soil moisture and nutrients.In arid or semi-arid areas,intermittent drought has become one of the adversities that plants often face,causing stems and leaves.Issues such as wilting and reduced fruit yield.Dark septal endophytes(DSE)are the more common symbiotic fungi in the soil,and Ericoid mycorrhizal fungi(ERMF)are typical species of rhododendrons that form symbiosis.In order to explore whether the mixed inoculation of Ericoid mycorrhizal fungi and Dark septal endophytes in the blueberry rhizosphere has a synergistic effect on the growth and stress resistance of plants,and whether the effects are in a linear relationship.In this study,5 dark septate endophytes(DSE)and 5 Ericoid mycorrhizal fungi(ERMF)were isolated,purified and identified from blueberry roots in different regions of Guizhou Province,and PEG-6000 was used to simulate drought stress.Two strains with strong drought resistance were selected as the tested strains.Taking Vaccinium australe "O’Neall" blueberry as the research object,we discussed single inoculation of DSE,Ericoid mycorrhizal fungi and 1:1mixed inoculation of two bacteria.Effects of(D1N1),1:2 mixed inoculation(D1N2),2:1mixed inoculation(D2N1)and non-inoculated CK treatment on the growth status of blueberries,plant nutrients,soil enzyme activities and soil nutrients.Potted plant water control experiment was conducted on each inoculated blueberry,and 4 water gradients were set for normal water(T1),mild drought(T2),moderate drought(T3)and severe drought(T4)to explore the water physiology of blueberries after inoculation.Physiological response of cell membrane permeability,antioxidant enzyme activity and osmotic adjustment substances to drought stress.The main findings are as follows:(1)The results of using PEG-6000 to simulate drought stress show that D79(Cladosporium cladosporioides)and D65(Phialocephala fortinii)of DSE have the best drought resistance,and Ericoid mycorrhizal fungi N12(Oidiodendron citrinum)and N07(Acephala sp.)are more resistant to drought.The plate confrontation test was carried out on the four fungi in pairs,and it was found that the growth inhibition rate of each hyphae between D79 and N12 was the smallest,and the symbiotic culture could be carried out.D79 and N12 have strong ability to dissolve phosphorus and potassium and produce indole acetic acid(IAA).(2)Both D79 and N12 single inoculation and mixed inoculation D2N1 can promote the growth of blueberries,and the growth-promoting effect of mixed inoculation is better than that of single inoculation.Compared with CK,the blueberry seedling height,ground diameter,dry weight of the above-ground part,dry weight of the underground part,total biomass and root vitality were increased by 45.61%,82.35%,120%,109.09%,119.23% and 190.35%respectively;And 190.35%。 However,there was no significant difference in the tap root length among the treatments.(3)Single inoculation and mixed inoculation improved the absorption capacity of blueberries to nutrient mineral elements to varying degrees.The total phosphorus and total potassium content of seedlings treated with mixed inoculation was significantly higher than that of single inoculation,and there was no significant difference in total nitrogen.All treatments can increase the enzyme activity of blueberry rhizosphere soil and accelerate the release of nitrogen,phosphorus and potassium in the soil.Among them,D2N1 treatment had the largest soil urease activity,and D1N2 soil had the largest acid phosphatase activity.Correlation analysis shows that there is a significant or very significant positive relationship between blueberry growth status and soil nutrients,soil enzyme activities,and the ability of the strain to dissolve phosphorus and potassium to produce IAA.(4)Different drought stresses have different effects on the physiological indexes of blueberries.With the aggravation of drought stress,the SOD enzyme activity of leaves increased first and then decreased with the aggravation of drought stress,while the electrical conductivity and MDA content of leaves gradually increased.The chlorophyll content,relative leaf water content and leaf water potential showed a continuous decreasing trend.The content of proline,soluble protein and soluble sugar all increased in varying degrees with the increase of drought stress.The overall drought resistance effect of mixed inoculation of blueberry seedlings was better than that of single inoculation.Through the drought resistance analysis of membership function,it is concluded that N treatment and all mixed inoculations have the highest comprehensive membership value under moderate drought stress,and the symbiont formed by mixed inoculation can survive well under moderate drought and have strong stress resistance.D1N2>D1N1>N.In summary,according to the growth status of blueberry plants,rhizosphere soil enzyme activity and soil nutrient changes after inoculation,D2N1 treatment has the best growth-promoting effect on plants,followed by D1N2 and D1N1,indicating that mixed inoculation has better growth-promoting effects Single inoculation and CK treatment.From the physiological response of the mycorrhizal seedlings formed by each treatment to different drought stresses,D1N2 and D1N1 treatments can significantly enhance the drought resistance of blueberries.The mixed inoculation of D79(C cladosporioides)and N12(O citrinum)at a ratio of 1:2 has the best effect on improving blueberry growth and drought resistance. |
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