PROS SEM NAS MASY BIODIV INDON Volume 4, Nomor 2, Desember 2018 ISSN: 2407-8050 Halaman: 178-183 DOI: 10.13057/psnmbi/m040214 Eksplorasi dan identifikasi morfologi koloni isolat rhizo-bakteri pelarut kalium dari rhizosfer tanaman jagung yang berpotensi sebagai pupuk hayati pelarut kalium Exploration and identification of potassium solubilizing rhizo-bacteria isolate colony morphology from corn plant rhizosphere that potentially as a potassium solubilizing biofertilizer DIYAN HERDIYANTORO 1, , TUALAR SIMARMATA 1 , MIEKE ROCHIMI SETIAWATI 1 , NENNY NURLAENY 1 , BENNY JOY 1 , JAJANG SAUMAN HAMDANI 2 , IIN HANDAYANI 3 1 Departemen Ilmu Tanah, Fakultas Pertanian, Universitas Padjadjaran. Jl. Raya Bandung-Sumedang Km. 21 45363, Jawa Barat, Indonesia. Tel./fax. +62-22-7796316,  email: d.herdiyantoro@unpad.ac.id 2 Departemen Agronomi, Fakultas Pertanian, Universitas Padjadjaran. Jl. Raya Bandung-Sumedang KM. 21 45363, Jawa Barat, Indonesia. 3 Departemen Agronomi, Murray State University. Kentucky, United States of America Manuskrip diterima: 23 Juni 2018. Revisi disetujui: 20 Juli 2018. Abstrak. Herdiyantoro D , Simarmata T, Setiawati MR, Nurlaeny N, Joy B, Hamdani JS, Handayani I. 2018. Eksplorasi dan identifikasi morfologi koloni isolat rhizo-bakteri pelarut kalium dari rhizosfer tanaman jagung yang berpotensi sebagai pupuk hayati pelarut kalium. Pros Sem Nas Masy Biodiv Indon 4: 178-183. Ketersediaan unsur kalium (K) dalam tanah bagi tanaman sangat rendah karena sebagian besar (98%) unsur K berada dalam bentuk mineral silikat primer seperti K-feldspar atau terfiksasi dalam mineral silikat sekunder seperti liat tipe 2:1. Rhizo-bakteri pelarut kalium (RBPK) dapat memfasilitasi peningkatan ketersediaan unsur K bagi tanaman. Tujuan penelitian ini adalah mengisolasi dan mengidentifikasi secara morfologi koloni isolat-isolat RBPK dari rhizosfer tanaman jagung yang berpotensi sebagai pupuk hayati (biofertilizer) yang dapat memfasilitasi ketersediaan unsur K bagi tanaman. Penelitian dilakukan dengan metode eksploratif melalui pengambilan sampel tanah rhizosfer tanaman jagung yang dibudidayakan di sekitar Kebun Percobaan Fakultas Pertanian, Universitas Padjadjaran, Jatinangor (J1, J2, J3, J4 dan J5). Pengenceran berseri menggunakan larutan garam fisiologis dilakukan hingga 10 -5 untuk mendapatkan sumber isolat bakteri kemudian diinokulasikan ke dalam cawan petri yang berisi media agar Aleksandrov (K-feldspar sebagai sumber K) mulai dari 10 -3 hingga 10 -5 sebanyak 0,25 mL dan 0,50 mL secara duplo. Koloni bakteri yang tumbuh pada media agar Aleksandrov dan menghasilkan zona bening merupakan koloni isolat RBPK. Hasil penelitian menunjukkan: (i) Proporsi koloni isolat RBPK yang didapatkan dari titik sampling J1, J2, J3, J4 dan J5 masing-masing sejumlah 33% (8% warna bening, 25% warna putih), 100% (92% warna bening, 8% warna putih), 33% (8% warna bening, 25% warna putih), 33% (8% warna bening, 25% warna putih) dan 8% (8% warna putih); (ii) Ciri morfologi utama dari koloni isolat RBPK yaitu: (a) koloni berwarna bening (bentuk: bundar, tepian: licin, elevasi: cembung, ukuran: kecil hingga besar, dan menghasilkan zona bening) dan (b) koloni berwarna putih (bentuk: bundar dengan tepian menyebar, tepian: seperti wol, elevasi: timbul, ukuran: kecil, dan menghasilkan zona bening); dan (iii) Koloni isolat RBPK-DHJ2 mendominasi perolehan koloni isolat RBPK dengan ciri morfologi utama koloni berwarna bening. Kata kunci: Koloni berwarna bening, koloni berwarna putih, media agar Aleksandrov, rhizo-bakteri pelarut kalium, rhizosfer jagung Abstract. Herdiyantoro D, Simarmata T, Setiawati MR, Nurlaeny N, Joy B, Hamdani JS, Handayani I. 2018. Exploration and identification of potassium solubilizing rhizo-bacteria isolate colony morphology from corn plant rhizosphere that potentially as a potassium solubilizing biofertilizer. Pros Sem Nas Masy Biodiv Indon 4: 178-183. The availability of potassium (K) in soil for plants is very low since most (98%) of K elements are in the form of primary silicate minerals such as K-feldspar or fixed in secondary silicate minerals such as 2:1 type clay. Potassium solubilizing rhizo-bacteria (KSRB) can facilitate increased availability of K elements for plants. The purpose of this research was to isolate and identify morphologically the colonies of KSRB isolates from the corn plant rhizosphere as a potential biofertilizer that could facilitate the availability of plant K elements. The research was carried out by explorative method through sampling of soil rhizosphere of corn cultivated around Experimental Garden of Faculty of Agriculture, Padjadjaran University, Jatinangor (J1, J2, J3, J4 and J5). Serial dilutions using physiological saline solution were carried out to 10 -5 to obtain the source of bacterial isolates and then inoculated into a petri dish containing Aleksandrov solid medium (K-feldspar as sole K source) ranging from 10 -3 to 10 -5 by 0,25 mL and 0,50 mL in duplicate. Colonies of bacteria that grow on Aleksandrov solid medium and produce clear zones were KSRB isolate colonies. The research results showed: (i) The proportion of KSRB isolate colonies obtained from sampling point J1, J2, J3, J4 and J5 were 33% (8% clear, 25% white), 100% (92% clear, 8% white), 33% (8% clear, 25% white), 33% (8% clear, 25% white) and 8% (8% white); (ii) The main morphological features of KSRB isolate colonies were: (a) clear colored colonies (shape: rounded, edge: slippery, elevation: convex, size: small to large, and produce clear zone) and (b) white colored colonies (shape: rounded with spread edges, edge: like wool, elevation: arise, size: small, and produce clear zone); and (iii) Colonies of KSRB- DHJ2 isolates dominated the acquisition of KSRB isolate colonies with the main morphological characteristic of clear colored colonies. Keywords: Aleksandrov solid medium, clear colored colonies, corn rhizosphere, potassium solubilizing rhizo-bacteria, white colored colonies