Browsing by Author "Yemisirach Mulugeta"

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    Culturable Endophytes of Enset (Ensete Ventricosum): Diversity, Plant Growth Promotion, and Bacterial Wilt Disease Control Potentials
    (Addis Ababa University, 2015-02-05) Yemisirach Mulugeta; Amare Gessesse; Appollinaire Djikeng
    Enset (Ensete ventricosum (Welw) Cheesman) is a perennial root crop used as a staple and co-staple food in Ethiopia. Enset cultivation is one of the sustainable agricultural systems in the country and offers significant ecological benefits by reducing soil erosion, resistance to different diseases and pests and relative tolerance to drought. Although enset agriculture is a good example of sustainable agriculture, the crop is largely affected by bacterial wilt disease caused by Xanthomonas campestris pv. musacerum. Because the pathogen resides in the vascular tissue of host plant, chemical based control strategies cannot be employed to control the disease. Studies showed that endophytes, symbiotic microorganisms (both bacteria and fungi) that live inside healthy plants have properties of biological control against different plant diseases. Having these properties endophytes might be one component of integrated disease management programs on enset. This study was initiated with the aim of investigating the diversity of culturable endophytic bacteria and fungi from enset and assesses the presence of phytobeneficial properties and their roles in protecting the plant against enset wilt disease. Endophytic bacteria and fungi were isolated from surface sterilized samples of leaf, stem and root of healthy enset plants. A total of 446 bacterial and 105 fungal endophytes were identified indicating the presence of high diversity of bacterial and fungal endophytes associated with enset. The bacterial endophytes were grouped to four phyla and 53 genera. Proteobacteria were the most frequently isolated phylum from all the plant parts followed by gram positive Actinobacteria, Firmicutes, and non-proteobacteria gram negative Bacteroidetes. The fungal isolates were grouped in to two phyla and 42 species. Ascomycota was more detected phylum compared to Zygomycota. The in vitro investigation of plant growth promotion (PGP) characteristics of 105 bacterial and 44 fungal isolates showed that majority of the isolates were positive to one or more plant growth promoting characteristics. IAA production is a more common property among enset endopytes. Moreover, there were isolates that produce siderophore and able to grow on nitrogen free medium. Phosphate solublisation was detected in bacterial isolates but none of the tested fungal endophytes show phosphate solublization. The potential of enset endophytes to control bacterial wilt of enset was also assessed in vitro and in vivo. In the in vitro test bacterial and fungal endophytic isolates belonging to different genera showed marked inhibition of the growth of Xanthomonas campestris pv. musacerum with the highest observed for bacterial isolates belonging to the genera Pseudomonas, Bacillus, and Rhizobium. And from the fungal endophytes two isolates identified as Mycosphaerella coacervata and Plectosphaerella cucumerina inhibited the growth of the pathogen. Plants treated with a mixed culture of bacteria showed a mean disease severity of 30.7% as compared to a disease severity of 47.4% for the control plants. In the endophytic metabolite analysis for potential antimicrobial compounds, hundreds of VOC and NVDOC were identified. The compounds produced include phenols, lactone, cyanide, pyrazine and dimethyl disulfide. Some of the compounds were reported to have antimicrobial activity against different fungal and bacterial pathogens in previous studies. Moreover, other unknown compounds were also detected In conclusion, this study showed high occurrence, diversity, plant growth promoting characteristics and the biocontrol potential of enset endophytes. Furthermore, the results also indicated enset endophytes as a potential alternative increase crop productivity.