Potensi bakteri endofit sebagai agens pengendalian hayati terhadap penyakit darah pada tanaman pisang

Abstract

Blood disease of banana caused by blood disease bacterium (BDB) is an important disease of bananas in Indonesia. The available control techniques have not been able to solve the disease problem effectively. Therefore, the development of more effective control method is needed. Endophytic bacteria have potencies as candidates of biological control agents to blood disease, because the bacteria as reported to be associated with plant resistance to pathogens and plant growth promotion. The aim of the studies were to (1) explore, select and identify endophytic bacteria to control blood disease on banana; (2) determine the mechanisms of endophytic bacteria to control blood disease on banana; (3) evaluate endophytic bacterial colonization on banana plant and their effect on the effectiveness to control blood disease; and (4) analyse the effect of application method of endophytic bacteria to their effectiveness to control blood disease on banana. Ninety isolates of endophytic bacteria have been isolated from the root of banana. The average population densities of the bacteria varied between 6.0 x 103 and 4.2 x 105 cfu/g fresh weight of root. Twenty seven among the ninety isolates positively produced inhibition zone toward blood disease bacterium (BDB). However, only four isolates (EAL15, EKK10, EKK20, EKK22) were able to reduce the incidence of blood disease on banana with ranged from 66.67% to 83.33%. Based on the partial sequence of 16S rRNA, four isolates were identified as Serratia liquefaciens (EAL15), Bacillus megaterium (EKK10), Enterobacter cloacae (EKK20) and Pectobacterium cypripedii (EKK22). The mechanisms of endophytic bacteria to control blood disease on banana were induced resistance, based on their activities in increasing peroxidase, polyphenol oxidase and salicylic acid content. The endophytic bacteria EAL15-Rif colonized within roots and stem tissues of young banana trees at four weeks after inoculation. Histological analysis using Scanning Electron Microscopy showed that EAL15-Rif colonise within the root and stem tissues of banana. The colonization period of endophytic bacteria during the eight months suppressed the blood disease incidence on banana ‘Cavendish’ with ranged from 66.67% to 83.33%. Application of endophytic bacterial community K-AL3 and K-RB1 were able to suppress the blood disease incidence on ‘Kepok kuning’ cultivar as much as 75.00% and 83.33%.

Penyakit darah (blood disease) yang disebabkan oleh Blood Disease Bacterium (BDB) merupakan salah satu penyakit penting pada tanaman pisang di Indonesia. Infeksi BDB pada tanaman pisang dapat menyebabkan tanaman mati atau menghasilkan buah yang tidak dapat dikonsumsi. Daging buah pisang yang terinfeksi BDB menjadi berlendir yang mengandung massa bakteri. Bakteri endofit berpotensi untuk dikembangkan sebagai agens pengendalian hayati penyakit darah pada tanaman pisang karena mampu menginduksi ketahanan tanaman terhadap patogen dan menstimulasi pertumbuhan tanaman. Penelitian ini bertujuan untuk : (1) mengeksplorasi, menyeleksi, dan mengidentifikasi isolat bakteri endofit yang berpotensi untuk mengendalikan penyakit darah pada tanaman pisang; (2) menganalisis mekanisme kerja bakteri endofit dalam mengendalikan penyakit darah pada tanaman pisang; (3) mengkaji kemampuan kolonisasi bakteri endofit antagonis di dalam jaringan tanaman pisang dan pengaruh periode kolonisasi bakteri endofit terhadap keefektifan pengendalian penyakit darah; dan (4) menganalisis pengaruh metode aplikasi bakteri endofit terhadap keefektifan pengendalian penyakit darah pada tanaman pisang.