Analysis Of Composition Changes Of Rhizosphere Bacterial Community In Two Ploidy Plants Of Agropyron Gaertn.

There are a large number of beneficial flora in the rhizosphere of plants,which promote the growth of plants and the absorption of nutrients,helping to improve the stress resistance of plants.Rhizosphere microorganisms are often used in agricultural applications to produce microbial fertilizer,promoting crop yield and reducing the use of fertilizers.They can also inhibit the growth of pathogens and reduce the use of pesticides.However,rhizosphere microorganisms do not exist and carry out function independently.They are driven by host plants,environmental conditions and soil factors.Agropyron is a perennial group of the Triticeae in Poaceae,which is an excellent forage with high feed economic value.Most excellent genes such as stress resistance and high photosynthetic efficiency make the species of the genus an important genetic resource for wheat genetic improvement.At the same time,because of its strong resistance and adaptability,it also plays an important role in the fields of wind prevention and sand fixation,soil and water conservation and other ecological restoration.There are three ploidy levels of Agropyron: diploid,tetraploid and hexaploid.Diploids are scattered,tetraploids are common and widely distributed in Eurasia,and hexaploids are only found in parts of the Iranian plateau.In the long-term evolution process,the ploidy variation of Agropyron significantly affect the morphological changes of the aboveground part,while the rhizosphere flora of the underground part may co-evolve with the plant,potentially forming the enrichment changes of the rhizosphere flora of Agropyron with different ploidy.A few studies have shown that there are differences in the rhizosphere microbial community composition of different ploidy plants of the same species,but there are few reports on how the enrichment of rhizosphere microbial community changes dynamically and how the enrichment differences occur between autopolyploid and diploid donor plants.In order to understand the enrichment differences and dynamics of microorganisms in the rhizosphere of different ploidy plants of Agropyron and explore potential beneficial microorganisms,the autotetraploid A.cristatum.and its diploid donor Agropyron pectiniforme Roem et Schult.were sampled,and high-throughput 16 S r DNA sequencing technology combined with bioinformatics analysis methods were used.The differences of bacterial community composition in the rhizosphere of two ploidy Agropyron plants at different growth stages and their correlation with soil hysicochemical properties and plant agronomic traits were estimated.The main results obtained are as follows:(1)There are significant differences in soil pH and available potassium content between A.pectiniforme and A.cristatum groups at seedling stage;there were significant differences in available phosphorus between A.pectiniforme and A.cristatum at the early tillering stage;there was no significant difference in physical and chemical factors between the groups at the late tillering stage.The plant height and leaf length of A.cristatum was significantly higher than that of A.pectiniforme at seedling stage;there was no significant difference in agronomic traits between A.pectiniforme and A.cristatum at the early tillering stage;the plant height,leaf length,leaf width,tiller number and leaf number of A.pectiniforme were significantly higher than those of A.cristatum at the late tillering stage.(2)At the phylum level,the dominant bacteria in the rhizosphere of Agropyron are Proteobacteria,Acidobacteria and Bacteroidetes.At the genus level,the bacterial groups with significant differences in relative abundance between A.pectiniforme and A.cristatum mainly occurred in the low abundance groups.The analysis of bacterial alpha diversity showed that the ploidy difference of Agropyron had no significant effect on the species richness,evenness and phylogenetic diversity of rhizosphere bacteria.Beta diversity analysis showed that the differences of bacterial community composition in the rhizosphere of Agropyron at different ploidy levels were mainly reflected in the late tillering stage.The network analysis showed that the co-occurrence network of A.pectiniforme and A.cristatum rhizosphere flora was determined by plant ploidy and growth stage.Compared with A.cristatum rhizosphere flora,A.pectiniforme rhizosphere flora has more complex network structure.(3)The formation of dominant rhizosphere flora of A.pectiniforme and A.cristatum changed dynamically with the change of growth stage.Alpha diversity analysis showed that the phylogenetic diversity of A.pectiniforme rhizosphere bacteria changed significantly with time;the species richness,evenness and phylogenetic diversity of bacteria in the rhizosphere of A.cristatum did not change significantly with time.Beta diversity analysis showed that the bacterial composition in the rhizosphere of A.pectiniforme and A.cristatum changed significantly with the growth stage.(4)The dominant bacteria were significantly correlated with soil physicochemical properties and plant agronomic traits.Alpha diversity was significantly correlated with available potassium,alkali hydrolyzable nitrogen and soil water content,but not significantly correlated with agronomic traits.Bacterial community composition was affected by available phosphorus,soil water content and available potassium.