POTENSI BAKTERI AKTINOMISET FILOSFER TANAMAN LILIACEAE SEBAGAI AGENS ANTAGONIS CENDAWAN PATOGEN Alternaria solani PADA TOMAT

Abstract

Penyakit tanaman merupakan salah satu faktor biotik penting penyebab kehilangan hasil pada tanaman tomat, termasuk penyakit bercak cokelat yang disebabkan oleh cendawan patogen Alternaria solani. Saat ini petani masih banyak menggunakan pestisida sintetik sebagai pengendalian utama penyakit ini. Penggunaan pestisida yang tidak bijak dapat menimbulkan dampak negatif bagi tanaman, manusia, maupun lingkungan. Pengendalian alternatif yang lebih ramah lingkungan dan berkelanjutan sangat diperlukan seperti memanfaatkan bakteri aktinomiset. Penelitian ini bertujuan menentukan aktinomiset filosfer tanaman Liliaceae yang berpotensi mengendalikan A. solani pada tomat dan mengidentifikasi isolat aktinomiset potensial secara molekuler. Tahapan penelitian meliputi isolasi dan identifikasi cendawan A. solani, perbanyakan isolat aktinomiset, uji antagonisme aktinomiset terhadap A. solani, karakterisasi morfologi dan identifikasi aktinomiset secara molekuler. Sebanyak 22 isolat aktinomiset yang telah berhasil diseleksi berdasarkan uji keamanan hayati selanjutnya diuji kemampuan antagonismenya secara in vitro terhadap A. solani dengan metode dual culture menggunakan rancangan acak lengkap (RAL). Empat isolat aktinomiset dengan tingkat hambatan relatif (THR) paling tinggi diidentifikasi secara molekuler dengan teknik PCR berdasarkan sekuen gen 16S rRNA. Persentase THR aktinomiset terhadap A. solani berkisar antara 17,13%-56,91%. Isolat dengan persentase THR tinggi yaitu BBW12, ACW23, BGW8 dan BGW5. Hasil identifikasi molekuler berdasarkan analisis nukleotida dengan BLAST untuk isolat BGW8 dan BGW5 masing-masing memiliki kemiripan identitas dengan bakteri Tsukamurella tyranosolvens dan Achromobacter sp. sebesar 99,90% dan 98,96%.

Plant disease is one of biotic factors that cause significant yield loss in tomato worldwide, including brown spot caused by pathogenic fungi Alternaria solani. Currently, farmers still rely heavily on synthetic pesticides as the primary method of disease control. However, the improper use of synthetic pesticides can potentially have negative impacts on plants, humans, and the environment. Therefore, alternative control methods that are more environmentally friendly and sustainable are urgently needed, such as the use of actinomycete bacteria. This study aims to determine phyllosphere actinomycetes from Liliaceae plants with the potential to control A. solani on tomatoes and to identify the most potential isolates using molecular methods. The stages of the research included the isolation and identification of A. solani, propagation of actinomycete isolates, antagonism tests of actinomycetes against A. solani, morphological characterization, and molecular identification of actinomycetes. A total of 22 actinomycete isolates that had passed biosafety screening were subsequently tested for their in vitro antagonistic ability against A. solani using the dual culture method in a completely randomized design (CRD). Four isolates with the highest relative inhibition levels (RIL) were identified molecularly using PCR techniques based on 16S rRNA gene sequences. The RIL values of the actinomycete isolates against A. solani ranged from 17.13% to 56.91%. The isolates with high RIL values were BBW12, ACW23, BGW8, and BGW5. Molecular identification of 16S rRNA nucleotide using BLAST analysis showed that isolates BGW8 and BGW5 were closely related to Tsukamurella tyranosolvens and Achromobacter sp., with 99,90% dan 98,96% respectively.