| Tobacco is one of the main economic crops in my country,and exploring a green and safe tobacco bio-fertilizer is an important measure to promote tobacco production.As a widely used entomogenous fungus,Isaria cateinannulata can be used to control spider mites,Spodoptera litura,diamondback moth and other pests.It is an environmentally friendly microbial agent.Both Beauveria bassiana and I.cateinannulata belong to entomogenous fungi.Recent studies have found that Beauveria bassiana can colonize plants by artificial inoculation and affect their growth.Whether I.cateinannulata has a similar effect is still unclear.Based on the above ideas,this paper selects four strains of I.cateinannulata preserved in the laboratory and uses artificial inoculation to explore the effects of different inoculation treatments on tobacco colonization rate,growth indicators,physiological indicators and rhizosphere microbial diversity,In order to provide theoretical guidance for the use of entomogenous fungi endophytes to improve tobacco yield and quality.High-throughput sequencing technology was used to detect the microbial composition of rhizosphere soil at different periods after tobacco transplantation and its correlation with tobacco growth indicators.The main findings are as follows:1 There are differences in the colonization efficiency of different strains,different inoculation methods and inoculation concentrations in tobacco.The colonization rate of roots was the highest when inoculated with irrigation roots,reaching 75.39%,and the colonization rate in roots and leaves was significantly higher than that of stems,which were 603.92%and 475.92%higher than that of stems,respectively.There was no significant difference in the colonization rate of 1×107/mL and 1×108 mL,which reached 52.17%and 52.31%in stems,respectively.However,from the perspective of cost saving,the concentration of 1×107/mL was chosen.The colonization efficiency of strain X8 in different parts of tobacco was significantly higher than that of the other three strains.2 Different inoculation treatments have different effects on tobacco seedling growth indexes.Tobacco seedlings cultivated by root irrigation have the largest leaf length,leaf width,plant height,stem thickness and stem circumference.This is consistent with the best colonization technique screened out in the colonization rate.3 The effect of colonization of I.cateinannulata on the growth and physiological indexes of tobacco at different stages after transplanting.On the 7th,14th,21st and 28th days after tobacco transplantation,the maximum leaf length,maximum leaf width,plant height,number of leaves,stem thickness and stem circumference of the chain treatment group tobacco were higher than those of the control.In the 4 periods after transplanting,the plant height and maximum leaf width between the two treatment groups reached significant differences.The chain treatment group was 37.13%and 23.72%,37.92%and 1.97%,9.35%higher than the control,respectively.And 7.30%,14.63%and 18.09%,indicating that the inoculation of I.cateinannulata in the seedling stage can effectively improve the growth of tobacco.After colonization,I.cateinannulata can significantly increase the activities of catalase,peroxidase and superoxide dismutase in tobacco at different periods after transplanting.Among them,the effect of POD enzyme is the most obvious,in the four periods respectively.Increased by 98.20%,154.42%,180.65%and 170.38%.At the same time,the inoculation of I.cateinannulata can also reduce the malondialdehyde content of tobacco in various periods.Taken together,the colonization of I.cateinannulata is beneficial to improve the resistance of tobacco to abiotic factors.4 The effect of colonization of I.cateinannulata on tobacco root development and dry matter accumulation.At different periods after transplanting,the root system indexes of the chain treatment group were better than those of the control group,indicating that the inoculation of C.circulans was helpful to the development of tobacco roots.From the total root length,total root projected area,total root surface area and other indicators,the chain treatment group had the most obvious promotion effect on tobacco on the 14th day after transplanting.The treatment group was 43.66%,51.64%and 43.66%higher than the control group.72.61%.The dry weight of the upper and lower parts of tobacco changed in different periods after transplanting.On the 7th day after transplanting,the difference between the dry and fresh weight of the chain treatment group and the control group was not obvious,but on the 14th and 21st days At 28 days and 28 days,the upper dry weight and lower dry weight of the chain treatment group were significantly higher than those of the control group.5 The effect of colonization of I.cateinannulata on tobacco rhizosphere microbial diversity.The rhizosphere microbial community composition of the ring-chain treatment group and the control group tobacco was similar,but the microbial abundance was different.A total of 15 phyla,40 classes,80 orders,168 families,314 genera,510 species,1120 OTUs were detected in 6 groups of samples,and 37 phyla,109 classes,261 orders,434 families,827 genera,1601 were detected.Species,3216 OTU.During the three periods of treatment,the microbial diversity of the control treatment group was higher than that of the loop-chain treatment group,indicating that the growth and reproduction of other microorganisms in the rhizosphere would be inhibited for a period of time after loop-chain inoculation.The similarity between the fungal communities in the loop-chain treatment group was significantly reduced on the 14th day after transplantation,but the changes between the bacterial treatment groups were not obvious.The functional groups with higher abundance in the fungal community include Undefined Saprotroph,Dung Saprotroph-Undefined Saprotroph,Dung Saprotroph and Animal Pathogen.The functional groups with higher abundance in the bacterial community include Amino acid transport and metabolism(8.95%?9.05%),Transcription(7.61?8.04%),Carbohydrate transport and metabolism(7%?7.19%),Energy production and conversion(7.0%?7.16%),etc.In the fungal community of the control group,the maximum leaf width had the greatest correlation with the fungal community.There was a positive correlation between an undefined genus,Trichosporum genus,a taxonomic fungal genus and 6 growth indicators in the Ascomycota.In the ring-chain treatment group,the correlation between stem thickness and fungal community was the largest,and an undefined genus in the order of the sclerotomycetes was positively correlated with 6 growth indicators,and grape ear mold and cephalosporium were positively correlated with 6 indicators.Negative correlation.In the bacterial community of the control group,the correlation between stem thickness and bacterial community was the greatest,and the rhizobia had a positive correlation with the 6 indicators.In the control group,the correlation between the number of leaves and the bacterial community was the largest.Termites,Microbacteria,a genus of bacteria with unknown taxonomic status,and 6 growth indicators are all negatively correlated. |
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