| The companion cultivation model can not only improve the yield and quality of plants,but also effectively prevent and control continuous cropping obstacles.In this study,oriental melon alone was used as the control,and the companion cultivation of fennel and oriental melon was treated.4 different companion densities of fennel were set,namely 5(T1),10(T2),15(T3),and 20(T4).Firstly,the differences of plant growth,mineral nutrient absorption,fruit quality and yield caused by different companion densities of fennel were analyzed to select the best companion cultivation density of fennel.Secondly,the microbial characteristics,phenolic metabolites and related enzyme activities of the rhizosphere soil of cucumis melo with thin skin under the optimal cultivation density of fennel were explored in order to provide practical reference and theoretical basis for the cultivation model of melon with thin skin.The main results are as follows:When fennel and oriental melon were cultivated together,fennel and thin peel culture showed significantly higher plant height,stem diameter,root activity,plant total phosphorus content and plant total potassium content than monocrop;T3 treatment increased fructose and sucrose content by 60.6% and 16.5%,respectively;T1 and T4 treatment showed no significant difference.In terms of soluble sugar and glucose,T3 treatment increased by 22.1%and 31.2% respectively,while T1,T2 and T4 treatment showed no significant difference.In terms of single fruit weight and vitamin C content,compared with single cropping,T1,T2 and T3 treatment showed significant increase in single fruit weight.Therefore,when the gradient of fennel is 15,it is more suitable for concomitant cultivation with thin-skinned melon.In terms of soil nutrient content,compared with single cropping treatment,T3 treatment significantly increased the total nitrogen content in soil.In the fruit expansion stage,T3 treatment significantly increased the total nitrogen content in soil by 22.2% compared with CK treatment,and there was no significant difference among other treatments.The total phosphorus content in the soil treated with T3 significantly decreased.In the fruit-setting stage,T3 treatment significantly decreased by 20.0% compared with CK treatment,and there was no significant difference between other treatments.All the four treatments had a decrease effect on the total potassium content of soil,but T3 treatment had the greatest decrease.T2 and T3 treatments significantly reduced the content of available nitrogen,and in the extended period,T2 and T3 treatments significantly decreased by 7.2% and 7.0% compared with single cropping.There was no significant difference between T1 and T4.The available p content inthe soil under T3 treatment was significantly increased.In the fruit expansion stage,T3 treatment significantly increased by 26.4% compared with CK,and there was no significant difference among other treatments.T2 treatment significantly increased the content of available potassium in the soil,but there was no significant difference between other treatments.Therefore,when the gradient of fennel is 15,it is more suitable for concomitant cultivation with thin-skinned melon.of soil,but T3 treatment had the greatest decrease.T2 and T3 treatments significantly reduced the content of available nitrogen,while T1 and T4 treatments showed no significant difference.The available p content in the soil under T3 treatment was significantly increased,while the difference between other treatments was not significant.T2 treatment significantly increased the content of available potassium in the soil,but there was no significant difference between other treatments.Because T3 treatment has a prominent performance in various soil indexes,it is more suitable for concomitant cultivation with melon when fennel gradient is 15.Comparing with single process,association cultivation not only can raise the microorganisms variety and richness in soil,but also improve some bacterial richness,which could improve the richness of some bacteria,such as Bacteroidetes,Actinobacteria,Proteobacteria,etc.The root morphology of fennel and melon changed during the accompanying cultivation,and the mean diameter,surface area,length and volume increased significantly compared with the single treatment.There were significant differences in phenolic substances in the roots of thin-skinned muskmelon under associated cultivation.For example,malondialdehyde content in the roots of muskmelon decreased significantly,while flavonoids content increased significantly.On the 5th day,the flavonoids content in the roots of muskmelon under associated treatment with fennin was significantly increased by 36.2%compared with that under single cultivation.The content of lignin and total phenol increased significantly.The enzyme activity in the root system was also different,for example,the activity of-1,3 glucanase was significantly increased,the activity of polyphenol oxidase was increased,and the activity of phenylalanine ammonia-lyase was increased.On the 15 th day,the activity of PAL in the anise associated treatment was 22.3% higher than that in the single treatment.The activity of peroxidase increased,and the POD enzyme activity in melon root system was significantly higher than that in melon single cropping at 10 days after inoculation.The root morphology changed during the companion cultivation of fennel/melon,with the average diameter,surface area,length and volume increasing significantly.There weresignificant differences in phenol substances in the root system of cucumis melo l.For example,the obvious reduction of malondialdehyde,augment of flavonoid,and raise of total phenolics for melon root.Furthermore,it also can cause the diversity of mould activity,such as enlarging activity of 1-3 glucanase,increasing activity of polyphenol oxidase,rasing activity of phenylalanine ammonia-lyase,and largening activity of peroxidase.To sum up,T3 treatment is significantly different from CK treatment in terms of plant growth and development,fruit quality,and nutrient content in soil.Therefore,the density of15 fennel plants screened out is more conducive to companion cultivation,and through microbial sequencing,it is found that companion cultivation is conducive to improving microbial diversity and richness.After inoculation of muskmelon fusarium wilt bacteria,companion culture is more conducive to increase disease resistance. |
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