Bioprospecting of Essential Oil Nanoemulsion-Tolerant PGPR from Chili Rhizosphere as a Multifunctional Agent Against Colletotrichum scovillei

Abstract

Plant Growth-Promoting Rhizobacteria (PGPR) offer a sustainable alternative to chemical fertilizers and pesticides in chili (Capsicum annuum L.) cultivation. This study aimed to explore and isolate potential PGPR from the chili rhizosphere in West Java Province using a novel selection method. Isolation was performed on Nutrient Agar (NA) medium supplemented with 2% biopesticide nanoemulsion, resulting in 80 successfully obtained isolates. Characterization results showed that 50 isolates were Gram-positive, 43 isolates exhibited positive hemolysis activity, and 43 isolates showed negative hypersensitivity reactions, indicating their potential safety for plant application. Bioassay screening identified 7 isolates (A2, A11, A12, B5.3, B5.5, B5.13, and C2.5) with strong antagonistic activity and 2 isolates (AT11, C5.2) capable of phosphate solubilization. Furthermore, enzymatic assays demonstrated significant functional diversity: 7 isolates produced chitinase, 9 produced amylase, and 14 produced protease. Specifically, several isolates exhibited multiple enzymatic and growth-promoting properties simultaneously. These findings suggest that indigenous PGPR from West Java, particularly those surviving on nanoemulsion-supplemented media, possess significant potential as biofertilizers and biocontrol agents to enhance chili productivity