Exploration of endophytic bacteria for inducing plant growth and diseases resistance to vascular streak dieback (Ceratobasidium theobromae) on cacao

Abstract

Indonesia is the third largest cacao production in the world after Ghana and Ivory Coast. The yield loss of cacao is drastically limited by the cacao diseases. Endophytic bacteria has been reported plays important role in inducing plant growth and diseases resistance. The aim of this research is to explore the endophytic bacteria capable to induce plant growth and diseases resistance to vascular streak dieback on cacao. The research step included: (1) isolation of endophytic bacteria from cacao tissues; (2) selection of endophytic bacteria as inducer of plant growth; (3) selection of endophytic bacteria as inducer of cacao plant resistance to Ceratobasidium theobromae; and (4) identification of potential isolates. Isolation of endophytic bacteria from Southeast Sulawesi, West Sumatera, and West Java resulted 288 bacterial isolates, and 40 of them induced strongly cacao seed germination. Further characterization on inducing plant growth characters and production of metabolite compound resulted 15 bacterial isolates for further analysis. Analysis phytoalexin compound produced by cacao seedling treated with endophytic bacteria revealed 10 isolates increases the relative ratio of Cyclohexene, 2-Methoxy-guaiacol, and 2,3-Dihydrobenzofuran, indicated inducing plant resistance to C. theobromae. Molecular identification showed highly similarity to Bacillus cereus, Pseudomonas geniculata, Stenotrophomonas rhizophila, and S. maltophilia, respectively.