Response of Cigar Tobacco (Nicotiana tabacum L.) Varieties to Low Potassium Stress and Dissecting Biochemical Determinants of Low Potassium Tolerance Mechanism

Potassium content is an important standard for measuring tobacco quality. However, research on the mechanism of low potassium tolerance in cigar tobacco (Nicotiana tabacum L.), which differs from regular tobacco, did not draw researchers’ attention. This study evaluated the tolerance to low potassium of 23 cigar varieties by investigating 20 phenotypic and physiological indicators. Utilizing principal component analysis, membership function analysis, and cluster analysis, the research comprehensively identifies the tolerance of cigar tobacco varieties to low potassium. The results indicate that the tolerance to low potassium of cigar tobacco is complex and varies among different traits and varieties. The current study identified six crucial indicators for measuring tolerance to low potassium in cigar tobacco leaves, including plant height, maximum leaf area, leaf surface area, total root absorption area, and active root absorption area. Based on the comprehensive evaluation value D of the low potassium tolerance coefficient for these six indicators, the study classified the 23 cigar varieties into four categories: one low potassium-sensitive variety, five low potassium-low tolerance varieties, eleven low potassium-relative tolerant varieties, and six low potassium-tolerant varieties. These research outcomes significantly contribute to the elucidation of tolerance to low potassium in cigar tobacco, facilitating the evaluation, screening, and cultivation of cigar tobacco varieties resilient to low potassium conditions. Additionally, this study lays the foundation for exploring scientific issues such as how plants can effectively utilize potassium, the mechanism of potassium ions in plants, the improvement and development of cigar quality, the enhancement of potassium utilization efficiency, and conservation of limited potassium resources to ensure long-term potassium availability.