Diversity Analysis Of Endophytic Fungi Of Maize In The Yellow River Delta And Their Resistance Against Spodoptera Frugiperda（Smith）

Endophytic fungi coexist with plants mutually,promoting their growth and enhancing their resistance,which have great application potential.Spodoptera frugiperda is an invasive pest,which seriously threatens China’s maize production,but there are no sustainable control measures so far.The Yellow River Delta is the youngest Delta in the world,it contains the broadest and most perfect wetland ecosystem and is rich in endophyte resources.In this study,endophytic fungi were isolated from maize leaves in the Yellow River Delta,strains against Spodoptera frugiperda were screened,and their insect resistance mechanism was studied.185 strains were isolated and purified from maize leaves in the Yellow River Delta,and their total DNA was obtained by a simple method,then molecular biology technology was used to identify them,which is belonging to 43 species.The biodiversity characteristics of the above strains were analyzed.Two resistant strains Alternaria destruens and Fusarium pernambucanum to Spodoptera frugiperda were screened which were named A1 and F1 respectively.We artificially inoculated the above two strains into maize,measured their effects on the growth of maize and the growth and development of Spodoptera frugiperda after interacting with maize,and analyzed the correlation between the growth and development of Spodoptera frugiperda and maize defense signal factors JA and SA.The main results are as follows:（1）A rapid extraction method of plant endophytic fungi DNA suitable for PCR was obtained and the template for simple PCR amplification was perfectly prepared throuth optimizing the alkali lysis method.Using 0.5 mol/L Na OH solution combined with 3mm grinding beads,high-throughput tissue grinder instrument and high-temperature treatment.In order to verify the adaptability of this method,The total DNA of 773 strains was rapidly extracted and the PCR amplification of ITS1/ITS4 primers was carried out,711 strains were successfully identified,which belong to 68 genera and 199 species.（2）Healthy maize leaves were collected from 12 counties in Binzhou and Dongying cities of the Yellow River Delta.185 strains were obtained by tissue block separation and tip mycelium purification,and identified as belonging to 43 species.The colonization rate of endophytic fungi in most cities is very high,reaching more than 90%.The dominant species and genera vary from place to place,mainly including Alternaria,Fusarium,Colletotrichum and others.The community composition of endophytic fungi in maize leaves in different regions is different.The areas with the most strains isolated are Guangrao County and Hekou District,with 31 strains belonging to 10 species and genera and 29 strains and 15 species and genera respectively,and others with 7-21 strains belonging to 5-8 species and genera except Bincheng District with only one species.The analysis of cluster,diversity index and similarity coefficient showed that endophytic fungi had rich diversity and specific distribution characteristics.（3）The length of rhizome and leaf increased significantly by 28% compared with the control,which promoted the growth of maize and increased the plant biomass,through the artificial inoculation of the two fungi strains A1 and F1.Feeding on the maize leaves inoculated with endophytic fungi,the mortality of the newly hatched larvae was as high as 30%,and the phenomena of food refusal and deformity occurred.At the same time,the feeding amount,weight gain,and the oviposition were significantly reduced.The results showed that after the interaction of endophytic fungi and maize,plant resistance was induced,and the contents of JA and SA related to insect resistance increased,resulting in the reduction of food utilization,weight loss,abnormal insect state and decreased spawning,indicating that endophytic fungi have application potential in pest control.This study clarified that maize endophytic fungi in the Yellow River Delta have rich biodiversity and regional specificity,and two screened strains promoted maize growth and insect resistance,which provides a new idea for sustainable pest management.