Potassium Nutrient Status-mediated Leaf Growth of Oilseed Rape(Brassica napus)and Its Effect on Phyllosphere Microorganism
To investigate the effect of potassium(K)nutrition on leaf growth and phyllosphere microbial community in oilseed rape(Brassica napus),a field experiment with three K fertilizer application rates(0,30,and 180 kg K2O·hm-2),referred to as K0(deficient K),K30(insufficient K),and K180(sufficient K),was conducted.Typical leaves were selected to measure the phenotypic parameters during the seedling stage.The composition of the phyllosphere microbial com-munity was determined using high-throughput sequencing of the 16S RNA gene.The main findings revealed K fertilization significantly affected leaf K content.Compared to the K0 treatment,the K content increased by 66.7％and 158.3％for the K30 and K180 treatment,respectively.Significant differences in the structure and components of oilseed rape leaves were observed under different K nutritional conditions.Leaf K content exhibited a significant positive correlation with leaf area,and content of soluble sugar,sucrose,fructose,and starch,while it showed a significant negative correlation with leaf stomatal density.K fertilization had a remarkable impact on the diversity of phyllosphere microbial community.K fertilization led to a significant increase in the diversity index,while no significant difference was observed between the K30 and K180 treatments.However,the K30 treatment displayed greater dispersion in terms of community β-diversity compared to the K180 treatment.K deficiency increased the relative abundance of Proteobacteria,resulting in an obvious enrichment of Xanthomonadaceae.The application of K fertilizer simplified the bacterial co-occurrence network but in-creased the interaction between high-abundance species and other species.A comprehensive analysis of leaf phenotypic parameters and phyllosphere bacterial communities revealed that leaf sugar components(soluble sugar,sucrose,fruc-tose,and starch),dry matter weight,and leaf area were the key factors influencing the phyllosphere bacterial communities and dominant species.In conclusion,K fertilizer application influenced the material compositions of oilseed rape leaves and regulated the microbial community structure.The establishment of"homeostasis"within phyllosphere microbial communities by maintaining sufficient leaf K nutrition status might serve as a potential pathway for enhancing crop bio-logical stress resistance.
K nutritionoilseed rape(Brassica napus)phyllosphere microorganismstomatal densitysucrose
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