Characterization of Arbuscular Mycorrhizal Fungus communities on Enset (Ensete ventricosum) in Southern Ethiopia and their Potential for Sustainable Intensification of Enset Production

Eradicating hunger, ensuring food security and ending poverty for a growing world population in a changing climate are a prominent part of the Sustainable Development Goals (SDG's). Sustainable intensification in existing agriculture and exploitation of under-utilized crops is needed to achieve those goals. One such an under-utilized crop is enset (Ensete ventricosum) which is native to Ethiopia. Enset is tolerant to recurrent droughts and has a high yield potential. Research on enset agronomy and farm management practices is limited, and there is almost no information on soil microbial symbionts, which can play a vital role in the sustainability of smallholder farming systems. One of these microbial symbionts are Arbuscular Mycorrhizal Fungi (AMF) which co-evolved with a majority of terrestrial plants. The AMF symbiosis is a win-win scenario in which host plants provide carbon compounds to the fungus and in return, AMF provide several benefits to the host plants such as increased water and nutrient uptake and even protection against some pests. Therefore, it is crucial to know farm management practices which affect AMF communities and to evaluate the performance of selected AMF inoculants. To this end, we performed two observational and two experimental studies. The first observational study compared AMF diversity and community composition in wild and cultivated enset, taking into account farm and wild enset site variability. Our results show a difference in AMF communities between cultivated and wild enset roots. AMF diversity is lower in cultivated enset compared to wild enset. Analyses further confirm AMF diversity and richness in wild enset roots being sensitive to increasing levels of available P in the soil. Moreover, soil pH and available P were selected as soil chemical properties changing AMF community composition. The second observational study investigated the intensity of cattle manure application on AMF diversity and community composition. Both intensively and less manured parts of the enset farms contained primarily species belonging to the Glomeraceae family, which accounted for 67% of the total operational taxonomic records. Intensive manuring enhanced soil nutrient availability and soil organic carbon but results in lower AMF richness and diversity, and a change in AMF community composition. Moreover, organic carbon and total N explained a larger part of the variation in AMF community composition compared to available P. In the experimental studies, the performance of indigenous and commercial AMF inoculants on enset growth and P uptake were evaluated. In the first pot experiment, we tested whether commercial and indigenous AMF inoculants can influence the growth of enset differently in soils differing in texture. We used commercial inoculants from three different genera, i.e. Funnelliformis mosseae (BEG12), Rhizophagus clarus (BEG 142), and Gigaspora margarita (BEG34) and a wild inoculant, and examined root colonization, enset growth and leaf P contents of enset plants in two different soil materials, collected from two locations in the Ethiopian Rift Valley, i.e. Dorze and Gircha. Results show that most growth parameters did not significantly differ between AMF inoculated and uninoculated plants in both soils. However, wild AMF and BEG142 inoculations significantly increased fresh shoot weight by 40% compared with uninoculated plants in Dorze soil. Moreover, wild AMF and BEG142 inoculated plants were found to be efficient in supplying P compared with BEG34 in Dorze soil. In both soils, wild AMF inoculated enset plants exhibited the highest mycorrhizal dependence (%MD), reaching a maximum of 50%. Sandier texture in Gircha soil favoured BEG34 root colonization over clayey soil in Dorze soil. AMF inoculation influences also soil available P and interaction effects exist between AMF inoculant and soil type with regard to soil organic carbon. Overall, wild AMF was better than other AMF inoculants in promoting enset plant growth and P uptake. Hence, for enset inoculation, wild AMF inoculum can be considered in future research. In the second pot experiment, we investigated whether different cow manure levels (0, 5, and 15%) in the potting soil and two sources of AMF inoculum (wild AMF and commercial BEG142) influence AMF root colonization, enset growth and leaf P contents. Results show that increasing manure levels improve soil chemical properties, but AMF inoculations had less effect on these properties. In general, increasing manure levels increased consistently enset growth, but either wild or BEG142 inoculation did not prompt enset growth within the 7-month timescale of our experiment. However, at 0% manure with low percent root colonization, wild AMF inoculum provided a positive mycorrhizal effectiveness.

Publication year:2022

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