Transcriptomic responses of a simplified soil microcosm to a plant pathogen and its biocontrol agent reveal a complex reaction to harsh habitat

AbstractThe environmental bacterium Pseudomonas mosselii produces antagonistic secondary metabolites with inhibitory effects on multiple plant pathogens, including Ralstonia solanacearum, the causal agent of bacterial wilt. In this study, an engineered P. mosselii strain was generated to express R. solanacearum ripAA, which determines incompatible interactions with tobacco plants. The ripAA gene together with its native promoter was integrated into the P. mosselii chromosome. The resulting strain showed no difference in antimicrobial activity against R. solanacearum. Promoter-LacZ fusion and RT-PCR experiments demonstrated that the ripAA gene was transcribed in culture media. Compared with that of the wild type, the engineered strain reduced the disease index by 9.1% for bacterial wilt on tobacco plants. A transcriptome analysis was performed to identify differentially expressed genes in tobacco plants, and the results revealed that ethylene-and jasmonate-dependent defense signaling pathways were induced. These data demonstrated that the engineered P. mosselii expressing ripAA enables improved biological control against tobacco bacterial wilt by the activation of host defense responses.ImportanceNowadays, the use of biocontrol agents is more and more popular in agriculture, but they cannot replaced of chemical agents mostly, due to the poorer control effect. So the study about how to improve the efficacy of biocontrol agents become necessary and urgent. We increase the efficacy against plant pathogen through introducing an avirulence gene from plant pathogen into the biocontrol agent based on “gene to gene” hypothesis. The new engineered strain can improve the systemic resistance and elicit primary immune response of plants. Our research not only provides a new strategy for genetic modification of biocontrol agent, a number of avirulence gene from pathogen or plant can be tested to be expressed in different biocontrol agents to antagonize plant disease, but also help the study of interaction between phythopathogenic avirulence gene and host.

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Penapisan dan potensi bakteri endofit asal tanaman Arecaceae sebagai agens pengendali hayati cendawan Pestalotiopsis sp. penyebab penyakit bercak daun pada kelapa kopyor (Cocos nucifera) [Selection and potency of endophytic bacteria from Arecaceae as biocontrol agents of Pestalotiopsis sp. causing leaf spot diseae on kopyor coconut (Cocos nucifera)]

E-Journal Menara Perkebunan ◽

10.22302/iribb.jur.mp.v85i1.235 ◽

2017 ◽

Vol 85 (1) ◽

Author(s):

Deden ERIS ◽

Abdul MUNIF ◽

Bonny PW SOEKARNO ◽

Agus PURWANTARA

Keyword(s):

Plant Pathogen ◽

Oil Palm ◽

Leaf Spot ◽

Endophytic Bacteria ◽

Biocontrol Agent ◽

Cocos Nucifera ◽

Recessive Gene ◽

Biocontrol Agents ◽

Leaf Spot Disease ◽

Bactris Gasipaes

Kopyor is a recessive-gene-trait coconut that has a delicious taste and high prices. One of several major problems of kopyor coconut cultivation is leaf spot disease. Endophytic bacteria originated from Arecaceae can be used as a biocontrol agents to control the disease in a sustainable way. The objective of the research was to select endophytic bacteria isolated from Arecaceae roots and leaves such as Pejibaye (Bactris gasipaes), Oil Palm (Elaeis guinensis), Kopyor Coconut (Cocos nucifera), Sugar Palm (Arenga pinnata) and Nibung (Oncosperma filamentosa) as biocontrol agent of Pestalotiopsis sp. Fourty isolates of endophyte bacteria are not pathogen to plant or animal and human. There are seven best selected endophytic isolates that can inhibit Pestalotiopsis sp. Some of them have the ability to dissolve phosphate, produce IAA, chitinase, and fix nitrogen. Those isolates are EAKSS 502, EAKSS 507, EAKSS 509, EAKSS 510, EAAPN 237, EAONN 545 and EAKPN 201. EAKPN 201 is the best candidate as biocontrol agent againts Pestalotiopsis sp. with 64,4% inhibition of Pestalotiopsis sp. on antagonist test. [Keywords: Palmae, plant pathogen, antagonist agents, antibiotict test]AbstrakKopyor adalah kelapa dengan sifat gen resesif yang memiliki rasa lezat dan harga yang tinggi. Salah satu masalah utama dalam pembudidayaan kelapa kopyor adalah penyakit bercak daun. Bakteri endofitik yang berasal dari tanaman Arecaceae dapat digunakan sebagai agens pengendali hayati dalam mengendalikan penyakit secara berkelanjutan. Penelitian ini bertujuan untuk menseleksi bakteri endofit yang berasal dari akar dan daun tanaman Arecaceae seperti Pejibaye (Bactris gasipaes), Kelapa Sawit (Elaeis guinensis), Kopyor Coconut (Cocos nucifera), Aren (Arenga pinnata) dan Nibung (Oncosperma filamentosa) yang berfungsi sebagai agen biokontrol Pestalotiopsis sp. Empat puluh isolat bakteri endofit non patogen terhadap tumbuhan atau hewan dan manusia berhasil diperoleh. Tujuh isolat bakteri endofit memiliki daya penghambatan terbaik terhadap cendawan Pestalotiopsis sp. Beberapa isolat memiliki kemampuan dalam melarutkan fosfat, memproduksi IAA, kitinase dan mengikat nitrogen. Ketujuh isolat tersebut yaitu isolat EAKSS 502, EAKSS 507, EAKSS 509, EAKSS 510, EAAPN 237, EAONN 545 dan EAKPN 201 EAKPN 201 adalah kandidat terbaik sebagai agen biokontrol untuk Pestalotiopsis sp. dengan penghambatan sebesar 64,4% pada uji antagonis.[Kata kunci: Palem-paleman, patogen tanaman, antagonis, uji antibiosis]

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