| The dry root of Astragalus mongolica is a traditional medicinal material with high economic and medicinal value,but Astragalus planting and production are suppresss by the low germination rate of seeds.Although seed microbiome can promote seed germination and plant growth,little is known about their diversity,assembly process and functional changes of microbial communities during the germination of Astragalus seeds.Amplicon sequencing technology was used in this study to explore the community diversity and assembly process of microbiome related to germination of Astragalus seeds,and to elucidate the seed microbial communities in different ecological niches(endophytes and spermosphere),germination and ungermination,and at different time.The differences in soil microbial function between germinated and ungerminated seeds were analyzed by metagenome sequencing technology,and microbes that promote seeds germination and growth-related functions were isolated and verified using inoculation test.The performance of germination and plant growth,and finally obtain excellent production strains with application potential.The following are the main findings:(1)Based on amplicon sequencing analysis,the results showed that the communitiesα-diversity in endophytic was lower than spermosphere.The α-diversity of endophytic bacterial community in germinated seeds was higher than in ungerminated seeds,and there was no significant difference in spermosphere microbial community between germinated and ungerminated seeds.Within germination period,the α-diversity of bacteria in the seeds increased,while the α-diversity of bacteria and fungi in the seeds decreased.The results of microbial community composition analysis showed that the microbial community composition was significantly different in different niches,germinated and ungerminated,and at different time,and the potential pathogenic fungus Fusarium was enriched in the ungerminated seeds endophytic and spermosphere.(2)Through the construction of co-occurrence network,we found that the microbial network in endophytic was simpler than spermosphere.Compared with ungerminated spermosphere soil,the microbial co-occurrence network of germinated spermosphere was more complex.Through neutral model and null model analysis,we found that homogeneous selection can shape the assembly process of bacterial community in germinated seeds,and ecological drift has a greater impact on the assembly of fungal community in ungerminated seeds.In addition,the homogeneous selection of the seed bacterial community increased with time,and the fungal community increased with time,and the ecological drift increased.(3)Through metagenomic data analysis and functional prediction,we found that microbiome in germinated seeds was specifically enriched in functional genes related to metabolism,and functional genes related to secondary metabolites and antibiotics were enriched in ungerminated seeds.The microbial functional diversity of germinated spermosphere soil was lower than non-germinated.Spermosphere soil microbiome from germinated seeds were enriched with functional genes related to cellulose degradation,transporters and bacterial drug resistance,while ungerminated were enriched with ABC transporters,MFS transporters and other transport-related functional genes.In addition,the trophic patterns of fungal communities associated with germinated and ungerminated seeds were different.The fungi associated with germinated seeds were dominated by symbiotic and saprophytic fungi,while the pathogenic fungus Fusarium was dominated by ungerminated seeds.(4)Based on the analysis of amplicon and metagenomic data,the differential microbiotas and functions of germinated and ungerminated seeds and spermosphere soil were obtained.It was confirmed by experiments that the germination of Astragalus seeds was affected by the seed coat cellulose,the hormone IAA and the seed pathogen Fusarium.The isolated strains significantly promoted the germination of Astragalus seeds,and the ability of these functional strains was significantly correlated with the indicators for promoting the germination of Astragalus seeds.The strains distributed in Bacillus and Trichoderma had the highest germination-promoting ability of astragalus seeds in the plate media.It was further found that Paenibacillus sp.and Trichoderma sp.and their combination could significantly promote the seeds germination and plant growth of Astragalus in the soil.In conclusion,this study revealed the differences in microbial diversity,assembly process,co-occurrence pattern and function related to the seed germination of Astragalus mongolica through amplicon and metagenomic sequencing,and explored the potential microbial taxa and functional guilds that may affect the germination of Astragalus mongolica seeds.In addition,the strains with the ability to promote seed germination were isolated using the culture method,and the effects of Paenibacillus sp.and Trichoderma sp.in promoting the seed germination and plant growth of Astragalus mongolica were verified.This study provides theoretical guidance as well as strains using microbial resources to promote the germination of Astragalus seeds and improve plant traits. |
