Strategies Of The Wild And Cultivated Soybeans In Rhizosphere Microbiome And Resistance Molecular Mechanisms To Fusarium Oxysporum

Soybean is one of the oldest crops in the world and was cultivated from the wild soybean(Glycine soja Sieb.& Zucc.(L.)),with the wild soybean may be more resistant to drought,salt and diseases.Rhizosphere,the interface between plant roots and soil,is a dynamic,complex and interconnected ecosystem of living organisms in soil,which may stimulated the immunity,improve the nutrient requisition or regulate the growth and productivity of the plants.Firstly,by sequencing the V3-V4 region of the bacterial 16 S r RNA gene amplicons,the current study assessed the bacterial community assemblage in rhizosphere and bulks soils of wild and cultivated soybeans grown in the suspensions of three important soil types in China,including black,red and soda-salinealkali soils.The results showed that alpha-diversity of the bacterial community in the rhizosphere was significantly higher than that of the bulk soils suggesting that bulk soil lacks plant nurturing effect under the current study conditions.Black and red soils were enriched with nitrifying and nitrogen-fixing bacteria but the soda-saline-alkali soil suspensions had more denitrifying bacteria.We also observed a high abundance of Bradyrhizobium and Pseudomonas,enriched cellulolytic bacteria,as well as a highly connected molecular ecological network in the wild soybean rhizosphere soil.Taken all,the current study suggest that wild soybeans may have evolved to recruit beneficial microbes in its rhizosphere that can promote nutrients requisition,biostasis and diseaseresistance,therefore ecologically more resilient than cultivated soybeans.Secondly,we pertained to the molecular and physiochemical comparison between the cultivated and wild soybeans in response to the pathogenic Fusarium oxysporum Schltdl..In this study,we first used comparative phenotypic and paraffin section analyses to indicate that wild soybean is indeed more resistant to F.oxysporum than cultivated soybean.Genome-wide RNA-sequencing approach was then used to elucidate the genetic mechanisms underlying the differential physiological and biochemical responses of the cultivated soybean,and its relative,to F.oxysporum.A greater number of genes related to cell wall synthesis and hormone metabolism were significantly altered in wild soybean than in cultivated soybean under F.oxysporum infection.Accordingly,a higher accumulation of lignins was observed in wild soybean than cultivated soybean under F.oxysporum infection.Collectively,these results indicated that secondary metabolites and plant hormones may play a vital role in differentiating the response between cultivated and wild soybeans against the pathogen.These important findings may provide future direction to breeding programs to improve resistance to F.oxysporum in the elite soybean cultivars by taking advantage of the genetic resources within wild soybean germplasm.Thirdly,we assessed the rhizomicrobiome and root transcriptome sequencing of wild and cultivated soybean during the invasion of F.oxysporum.Results indicated F.oxysporum infection enriched Bradyrhizobium spp.and Glomus spp.and induced the expression of more MAPKs in wild soybean than in cultivated soybean.MAPK gene expression was positively correlated with Pseudomonadaceae but negatively correlated with Sphingomonadaceae and Glomeraceae in both cultivated and wild soybean.Specifically,correlation profiles revealed that Pseudomonadaceae was especially correlated with the induced expression of Gm MAKKK13-2(Glyma.14G195300)and Gm MAPK3-2(Glyma.12G073000)in wild and cultivated soybean during F.oxysporum invasion.Main fungal group Glomeraceae was positively correlated with Gm MAPKKK14-1(Glyma.18G060900)and negatively correlated with Gm Raf6-4(Glyma.02G215300)in the wild soybean in response to pathogen infection;while there were positive correlations between Hypocreaceae and Gm MAPK3-2(Glyma.12G073000)and between Glomeraceae and Gm Raf49-3(Glyma.06G055300)in the wild soybean response,these correlations were strongly negative in the response of cultivated soybean to F.oxysporum.Taken together,MAPKs correlated with different rhizomicrobiomes indicating the host plant modulated by the host self-immune systems in response to F.oxysporum.