Resistance of Black Pepper Seedlings to Phytophthora capsici-Induced Basal Stem Rot Using Arbuscular Mycorrhizal Fungi and Monopotassium Phosphate Fertilizer

Background The disease caused by Phytophthora capsici is a major constraint in black pepper cultivation, with infections beginning as early as the seedling stage. Enhancing seedling resistance is crucial to mitigating losses, especially for replanting on infected land. Objective This study aimed to evaluate the effectiveness of Arbuscular Mycorrhizal Fungi (AMF) and monopotassium phosphate (KP) fertilizer in suppressing foot rot disease in black pepper seedlings. Methods A split-plot randomized complete block design (RCBD) was employed. The main plot comprised two levels of AMF application (with and without), while the subplot consisted of five KP fertilizer doses (0, 1.5 g, 2.5 g, 3.5 g, and 5.0 g per seedling or polybag). Each treatment was replicated three times, with 10 seedlings per replicate. Observed variables included disease severity, disease incidence, disease infection rate, AUDPC, incubation period, and shoot length increment to evaluate seedling resistance to P. capsici. Results The AMF application enhanced black pepper seedling resistance to P. capsici , reducing disease severity and incidence, latent period, and AUDPC value, while promoting shoot growth. The application of KP fertilizer, up to a dose of 5.0 g per polybag on non-mycorrhizal seedlings, effectively induced resistance, as reflected by lower AUDPC values, slower disease progression, and delayed symptom onset. Conclusion The combined use of AMF and KP fertilizer during the seedling stage offers a promising strategy to strengthen black pepper resistance against the disease, while also potentially reducing dependence on chemical inputs.