KOMUNITAS BAKTERI ENDOFITIK KULTIVAR PISANG KLUTHUK DAN AMBON SERTA POTENSI PEMANFAATANNYA

TRIASTUTI RAHAYU, Ir. Donny Widianto, Ph.D.; Dr. Yekti Asih Purwestri, S.Si., M.Si.; Prof. Ir. Siti Subandiyah, Ph. D.;

2022 | Disertasi | DOKTOR BIOTEKNOLOGI

Ketahanan kultivar pisang terhadap cekaman biotik dan abiotik diduga terkait dengan mikroorganisme endofitiknya. Penelitian ini bertujuan untuk mengungkap keberadaan komunitas bakteri (bakterioma) endofitik tanaman pisang kultivar Kluthuk (tahan) dan Ambon (rentan), keterkaitannya dengan lingkungan tempat tumbuh, dan potensinya sebagai plant growth promoting bacteria (PGPB) pada pisang. Anakan pisang dicuplik dari lapangan pada tanah loamy sand (LM) dan silt loam (SL) termasuk tanah rizosfernya. Sebelum dianalisis, akar, bonggol, dan tangkai daun terlebih dahulu disterilisasi permukaannya. Pendekatan tangayut biakan menggunakan platform illumina sequencing untuk menganalisis komunitas bakteri endofitik dan komunitas bakteri endofitik inti, sedangkan pendekatan gayut biakan dilakukan dengan mengisolasi, melihat keragaman, mengidentifikasi, dan mengkarakterisasi kemampuannya sebagai PGPB. Isolat terseleksi diujicobakan ke planlet pisang Cavendish dan diamati respon pertumbuhannya. Analisis tangayut biakan menunjukkan dominansi Proteobacteria pada Kluthuk (42,97-83,85%) dan Ambon (34,24-51,55%). Indeks keragaman pada bonggol Kluthuk di tanah LM dan SL masing-masing adalah 2,85 dan 2,74, sedangkan pada bonggol Ambon 2,39 dan 2,51, walaupun keragaman beta pada semua sampel tanah tidak berbeda nyata. Empat puluh genera terdeteksi sebagai komunitas bakteri endofitik inti pada Kluthuk dengan kelimpahan tertinggi Bacillus (9,67-13,48%) dan Pseudomonas (2,03-16,49%), sedangkan pada Ambon terdeteksi 34 genera dengan kelimpahan relatif tertinggi pada Bacillus (4,27-10,30%) dan Brevibacillus (0,80-14,39%). Analisis gayut biakan menunjukkan bahwa populasi bakteri endofitik di kedua kultivar pisang memiliki pola yang sama yaitu di akar berkisar antara 5,9.102 -2,3.104 CFU/g jaringan, di tangkai daun 0,5.101 - 1,9.103 CFU/g jaringan, dan di bonggol 0,1.101 - 1,9.101 CFU/g jaringan. Keragaman bakteri endofitik di bonggol berkisar antara 0-1,68, pada akar 1,80-2,69, dan tangkai daun 0,69-2,55 dengan dominansi filum Proteobacteria sebanyak 74,39 dan 78,95% masing-masing pada Kluthuk dan Ambon. Pantoea, Microbacterium, Acinetobacter, Enterobacter, Bacillus, dan Pseudomonas terdeteksi memiliki banyak karakter sebagai PGPB. Dari uji in planta, diperoleh 3 isolat yang mampu mendukung pertumbuhan pisang Cavendish yaitu Acinetobacter oryzae strain B23 (T) (K3), Klebsiella grimontii strain SB73 (K28), dan Variovorax guangxiensis strain GXGD002 (K111). Hasil uji kolonisasi, ketiga isolat tersebut tidak atau belum terkonfirmasi. Dapat disimpulkan bahwa cv. Kluthuk dan Ambon memiliki komunitas bakteri endofitik dan komunitas bakteri endofitik inti yang berbeda, tetapi komunitas bakteri tanah rizosfer kedua kultivar memiliki banyak kemiripan. Perbedaan tersebut mungkin berkorelasi dengan ketahanan tanaman pisang terhadap cekaman lingkungan. Isolat bakteri endofitik asal kultivar pisang tahan menunjukkan dukungannya terhadap pertumbuhan tanaman pisang rentan walaupun belum terbukti perannya secara endogen. Selanjutnya, masih perlu dikaji tentang peran isolat tersebut untuk meningkatkan ketahanan tanaman pisang, merekrut, melindungi, atau menstimulasi plant growth promoting rhizobacteria (PGPR) lain.

The resistance of banana cultivars to biotic and abiotic stresses is reported to be related to their endophytic microorganisms. This study aimed to reveal the presence of endophytic bacteriome of banana cultivars Kluthuk (resistant) and Ambon (susceptible), its relationship to the environment in which it grows, and its potential as plant growth promoting bacteria (PGPB) on bananas. Suckers and rhizospheric soils were sampled from banana grown in loamy sand (LM) and silt loam (SL) soils. The independent culture approach uses the illumina sequencing platform to analyze endophytic bacteriome and core endophytic bacteriome, while the dependent culture approach was carried out by isolating, analyzing isolates diversity, identifying, and characterizing its ability as PGPB. The selected isolates were tested on Cavendish banana plantlets and their growth response was observed. Independent culture analysis showed the dominance of Proteobacteria in Kluthuk (42.97-83.85%) and Ambon (34.24-51.55%). The diversity index of the Kluthuk corm in LM and SL soils were 2.85 and 2.74, respectively, while in the Ambon corm was 2.39 and 2.51, although the beta diversity in all soil samples was not significantly different. Forty genera were detected as core endophytic bacterial community in Kluthuk with the highest abundance of Bacillus (9.67-13.48%) and Pseudomonas (2.03-16.49%), while in Ambon 34 genera were detected with the highest relative abundance of Bacillus (4.27-10.30%) and Brevibacillus (0.80-14.39%). Culture dependent analysis showed that the endophytic bacterial population in both banana cultivars had the same pattern, namely in the roots ranging from 5.9 x 102 � 2.3 x 104 CFU/g tissue, in the petiole 0.5 x 101 � 1.9 x 103 CFU/g tissue, and in the corm 0.1 x 101 - 1.9 x 101 CFU/g of tissue. The diversity of endophytic bacteria in the corm of Kluthuk and Ambon ranged from 0 - 1.68, in the root 1.80-2.69, and the petiole 0.69-2.55 with the dominance of the phylum Proteobacteria as much as 74.39 and 78.95%, respectively. Pantoea, Microbacterium, Acinetobacter, Enterobacter, Bacillus, and Pseudomonas were detected to have many characters as PGPB. From the in planta test, it was obtained 3 isolates that were able to support the growth of Cavendish banana, namely Acinetobacter oryzae strain B23 (T) (K3), Klebsiella grimontii strain SB73 (K28), and Variovorax guangxiensis strain GXGD002 (K111). The results of the colonization test, the three isolates were not or have not been confirmed. It can be concluded that cultivars Kluthuk and Ambon have different endophytic bacteriome as well as theirs core endophytic bacteriome, however, the rhizosphere soil bacteriomes of both cultivars have many similarities. Those differences might correlate with the resistant character to environmental stresses. Isolated endophytic bacteria from resistant banana cultivars showed their support for the growth of susceptible banana plants, although their role has not been proven endogenously. Furthermore, the role of these isolates in improving banana plant resistance, recruiting, protecting, or stimulating other plant growth promoting rhizobacteria (PGPR) still needs to be studied more deeply.

Kata Kunci : bakteri endofitik, komunitas bakteri endofitik inti, pisang Ambon, pisang Kluthuk, plant growth promoting bacteria (PGPB)