为探究钾营养介导下的油菜(Brassica napus)叶片生长对叶际微生物群落的影响, 利用田间试验, 设置0、30和180 kg K₂O∙hm^-2 3个钾肥用量, 分别定义为K0 (钾缺乏)、K30 (钾不足)和K180 (钾充足) 3个钾营养水平。在苗期, 分别选取典型叶片测定其表型参数, 并利用16S-RNA基因高通量测序测定油菜叶际微生物群落组成。结果表明, 不同钾肥用量显著影响油菜叶片的钾含量, 与K0相比, K30和K180处理钾含量分别提高66.7%和158.3%。不同钾营养状况下, 油菜叶片结构和组分存在明显差异, 叶片钾含量与叶面积及叶片可溶性糖、蔗糖、果糖和淀粉的含量呈显著正相关, 而与叶片气孔密度呈显著负相关。钾肥施用显著影响油菜叶际微生物的多样性, 与K0处理相比, 施钾处理叶际微生物群落多样性指数显著升高, 而K30和K180处理间无明显差异, 但在群落的β多样性中, K30处理表现出更大的离散性。缺钾增加了油菜叶际变形菌门(Proteobacteria)的相对丰度, 使得黄单胞菌科(Xanthomonadaceae)细菌显著富集。施用钾肥后细菌共现网络变简单, 但促进了高丰度物种与其它物种的相互作用。通过联合分析油菜叶表型性状与叶际细菌群落, 发现叶片糖组分(可溶性糖、蔗糖、果糖和淀粉)、干物质重以及叶面积是影响叶际细菌群落以及优势物种的关键因素。综上表明, 施钾影响油菜叶片的物质组成, 调控油菜叶际微生物群落结构, 充足的钾营造的叶片微生物组“稳态”可能是钾营养增强作物生物胁迫抗性的潜在途径。

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 community 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 increased 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, fructose, 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 biological stress resistance.