Karakterisasi Fisiologis Rizobakteri Secara In Vitro Terhadap Penyakit Busuk Buah Kakao (Phytophthora palmivora L.)

Abstrak. Salah satu perkebunan di Indonesia menghasilkan kakao (Theobroma cacao L.), yang memberikan kontribusi signifikan terhadap perekonomian dan cadangan devisa Indonesia. Masih terdapat tantangan dalam pengembangan kakao di seluruh Indonesia, termasuk Provinsi Aceh, antara lain adanya penyakit dan hama yang berkontribusi terhadap rendahnya produktivitas kakao. Penelitian ini bertujuan adalah untuk mendapatkan isolat rizobakteri yang mampu berperan sebagai kandidat agen biokontrol dalam menghambat pertumbuhan koloni patogen P. palmivora secara in vitro. Disamping itu penelitian ini bertujuan untuk mengetahui apakah jenis rizobakteri indigenous dapat berperan sebagai kandidat agen pemacu pertumbuhan tanaman dengan isolat patogen P. palmivora. Penelitian ini dilaksanakan di Laboratorium Ilmu dan Teknologi Benih Fakultas Pertanian, Universitas Syiah Kuala, Darussalam Banda Aceh. Pelaksanaan penelitian ini dimulai pada bulan Oktober 2020 sampai Mei 2021. Rancangan Acak Lengkap (RAL) non-faktorial digunakan dalam penelitian ini. Faktor yang diteliti yaitu jenis isolat rizobakteri indigenous sebanyak 8 jenis isolat. Pengamatan yang dilakukan mencakup daya hambat pertumbuhan koloni patogen, laju penghambatan, aktivitas enzim protease, kemampuan melarut fosfat, produksi IAA, produksi HCN, dan produksi senyawa siderofor. Hasil penelitian menunjukkan bahwa kemampuan isolat rizobakteri indigenous GM 8/1 dan GM 7/10 merupakan dua isolat yang memiliki daya hambat sangat tinggi. Sedangkan laju penghambatan relatif lebih tinggi diperoleh dari isolat GM 8/3. Sementara aktivitas enzim protease tertinggi terdapat pada isolat GM 5/6 dan isolat GM 7/10. Kemampuan melarut fosfat tertinggi diperoleh pada isolat rizobakteri GM 7/10. Isolat rizobakteri yang menghasilkan senyawa IAA lebih tinggi pada isolat GM 8/1, GM 8/3 dan GM 8/11. Produksi senyawa HCN diperoleh pada 3 isolat rizobakteri yaitu GM 5/6, GM 7/10 dan GM 8/8. Semua isolat mampu memproduksi senyawa siderofor.Kata kunci : Kakao, Fisiologis Rizobakteri, In VitroPhysiological Characterization of Rhizobacteria In Vitro Against Cocoa Fruit Rot Disease (Phytophthora Palmivora L.)Abstract. Cocoa (Theobroma cacao L.) is one of the plantation commodities in Indonesia which has an important role for the national economy to increase the country’s foreign exchange. Cocoa development broadly, including in Aceh Province, still faces obstacles, namely the presence of pests and diseases that cause low cocoa productivity in Indonesia. The aim of this study was to obtain rhizobacteria isolates capable of acting as candidates for biocontrol agents in inhibiting the growth of P. palmivora pathogenic colonies in vitro. In addition, this study aims to determine whether indigenous rhizobacteria can act as candidates for plant growth promoting agents with pathogenic isolates of P. palmivora. This research was conducted at the Laboratory of Seed Science and Technology, Faculty of Agriculture, Syiah Kuala University, Darussalam, Banda Aceh. The implementation of this study began in October 2020 until May 2021. This study used a non-factorial completely randomized design (CRD) method.  The factors studied were 8 types of indigenous rhizobacteria isolates. The observations made included the inhibition of the growth of pathogenic colonies, the rate of inhibition, the activity of the protease enzyme, the ability to dissolve phosphate, the production of IAA, the production of HCN, and the production of siderophores. The results showed that the ability of the rhizobacteria isolates indigenous GM 8/1 and GM 7/10 were two isolates that had very high inhibitory power. While the relatively higher inhibition rate was obtained from GM 8/3 isolates.  Meanwhile the highest protease enzyme activity was found in GM 5/6 isolate and GM 7/10 isolate. The highest phosphate solubilizing ability was found in GM 7/10 rhizobacteria isolate. Isolated rhizobacteria that produced IAA compounds were higher in GM 8/1, GM 8/3 and GM 8/11 isolates. The production of HCN compounds was obtained in 3 isolates of rhizobacteria, namely GM 5/6. GM 7/10 and GM 8/8.Keywords: Cacao, Physiological Rhizobacteria, In Vitro