柑橘不同接穗对枳砧根际土壤理化性质与微生物群落结构的影响OA

Field-grown five-year-old trifoliate orange rootstocks grafted with Newhall navel orange(Citrus sinensis Osbeck cv.Newhall),Nanfeng tangerine(Citrus reticulata Blanco cv.Kinokuni),and Ponk-an(Citrus reticulata Blanco cv.Ponkan)were used to study the effects of different citrus(Citrus L.)scions on the physicochemical properties and the structure of microbial community in rhizospheric soil of trifoliate orange[Poncirus trifoliata(L.)Raf.]rootstocks.Rhizosphere soil samples were collected from the 0-10,10-20,and 20-30 cm soil layers in June,August,and October to determine soil physicochemical proper-ties and enzyme activities.In October,additional rhizosphere soil samples were collected from roots grouped by diameter for 16S rRNA gene amplicon sequencing.The results showed that the rhizosphere soil properties of trifoliate orange rootstock,including pH,alkali-hydrolyzable nitrogen,available phosphorus,available potassium,urease activity,and alkaline phosphatase activity,followed the same descending order across scion treatments:Newhall navel orange>Ponkan>Nanfeng tangerine.Soil organic matter content followed the order:Ponkan>Nanfeng tangerine>Newhall navel orange,whereas soil sucrase activity ranked as Ponkan>Newhall Navel orange>Nanfeng tangerine,and soil acid phosphatase activity as Nan-feng tangerine>Ponkan>Newhall navel orange.Significant differences were observed in the alpha diversity indices of the rhizosphere microbial community among the three graft combinations,with the order Newhall navel orange>Ponkan>Nanfeng tangerine.Within the same scion,alpha diversity across different root or-ders generally decreased in the order:first-order roots>second-order roots>third-order roots.Community composition analysis revealed that Actinobacteria and Proteobacteria were the dominant phyla across all treatments;however,marked differences emerged at the genus level.Specifically,Stenotrophomonas and Amycolatopsis predominated in the Ponkan treatment;Enterobacter and Pantoea in the Nanfeng tangerine treatment;and KD4-96 and Mycobacterium in the Newhall navel orange treatment.Redundancy analysis identified soil pH and available phosphorus as the primary environmental factors driving differences in micro-bial community structure.Collectively,these findings indicate that different citrus scions can modulate the physicochemical properties of trifoliate orange rootstock rhizosphere soil and exert significant influences on microbial diversity and community composition.