Skrining Aktinomiset Pelarut Fosfat Asal Rizosfer Dehaasia pugerensis Koord. & Valeton di Kawasan Bandealit

Abstract

Dehaasia pugerensis Koord. & Valeton is a Critically Endangered (CR) plant species endemic to Jember Regency, Indonesia. Its natural habitat is dominated by calcareous soils, which tend to have low phosphorus availability due to calcium binding. This condition may inhibit plant growth, thereby necessitating the role of phosphate-solubilizing microorganisms, including actinomycetes. This study aimed to determine the ability of actinomycetes isolated from the rhizosphere of D. pugerensis to solubilize phosphate and to identify the best isolates based on their macroscopic and microscopic morphological characteristics. A total of 24 actinomycetes isolates from the Sub-Microbiology Collection of the Faculty of Mathematics and Natural Sciences, University of Jember, were used in this study. Phosphate-solubilizing ability was screened on Pikovskaya agar by observing clear zones and calculating the phosphate solubilization index. Isolates with the highest phosphate solubilization indices were subsequently characterized macroscopically on ISP-4 medium and microscopically using Gram staining and the cover slip method to observe spore chains. The results showed that most isolates formed clear zones, indicating phosphate-solubilizing activity. The ten isolates with the highest phosphate solubilization indices were DP30, DP21, DP11, DP17, DP10, DP27, DP4, DP9, DP14, and DP24. Macroscopic characterization revealed considerable variation in colony morphology, including colony shape, margin, elevation, aerial and substrate mycelial color, and pigment production among the selected isolates. Morphological characterization revealed that all isolates exhibited spiral spore chains and long, straight chains of spores. According to Bergey’s Manual of Systematic Bacteriology (9th Edition), these characteristics indicate that the isolates belong to the genus Streptomyces. All isolates were Gram-positive. It can be concluded that actinomycetes from the rhizosphere of D. pugerensis have potential as phosphate solubilizers, with isolate DP30 showing the highest phosphate solubilization index.