The African pepper bark tree, Warburgia ugandensis, accumulates antimicrobial drimane sesquiterpenes in all of its organs. One hypothesis states that plant defense compounds determine endophyte community structure. Another hypothesis suggests that they just facilitate the endophytic lifestyle by exerting a balanced antagonism. To explore this, a representative selection of endophytic bacterial and fungal isolates from this tree species was assayed together with six non-endophytic strains to determine their tolerance and susceptibility to the root and leaf extract fraction containing high and low drimane sesquiterpene amounts respectively. Inhibitory effects were explored by assessing both growth and growth efficiency, the latter of which relates respiratory activity to growth. The susceptibility of the tested strains showed considerable variation and the obtained patterns did not allow a clear distinction between root and leaf endophytes as well as endophytes and non-endophytes. In addition, all strains were also assayed against juglone, an antimicrobial and redox-active aromatic naphthoquinone. A comparison of differential pulse voltammograms and efficacy in variants of the deoxyribose degradation assay revealed that drimane sesquiterpenes possess anti- and pro-oxidant activities that compare to those of juglone. Leaf endophytes showed higher resistance to oxidative stress than root endophytes, quite contrary to the actual exposure. The obtained results support the notion that structural diverse plant defense compounds can contribute to a balanced antagonism against but not to structuring of endophyte communities. Oxidative stress seems to be involved in generating this effect albeit it cannot explain it alone.
Tag: community
Analysis of trade-offs in agricultural systems: current status and way forward
Trade-off analysis has become an increasingly important approach for evaluating system level outcomes of agricultural production and for prioritizing and targeting management interventions in multifunctional agricultural landscapes. We review the state-of-the-art for trade-off analysis, assessing different techniques by exploring a concrete example of trade-offs around the use of crop residues in smallholder farming systems. The techniques for performing trade-off analyses have developed substantially in recent years aided by mathematical advancement, increased computing power, and emerging insights into systems behaviour. Combining different techniques allows the assessment of aspects of system behaviour via various perspectives, thereby generating complementary knowledge. However, this does not solve the fundamental challenge: trade-off analyses without substantial stakeholder engagement often have limited practical utility for informing practical decision-making. We suggest ways to integrate approaches and improve the potential for societal impact of future trade-off analyses.
Assessment of Design and Constraints of Physical Soil and Water Conservation Structures in respect to the standard in the case of Gidabo sub-basin, Ethiopia
In Ethiopia institutional and extensive soil and water conservation (SWC) started in the 1970s. Due to several factors, most SWC works have not fully achieved the intended objectives. The disparity between dimensions of the implemented SWC work and the standard is the main factor. Therefore, this research work aimed to assess the design and constraints of SWC in the Gidabo sub-basin, of the Ethiopian rift valley. Data were generated through field observation, field measurements, household survey, interview, group discussion, and Arc GIS. According to the result, about 47.3% of the physical design of the implemented SWC structures failed to meet the standard dimension. In addition, the SWC lacks the standard supportive activities, such as the cut of the drain, check dam, biological work, and frequent maintenance. FGD and KII showed about 71.3% of the farmers accepted SWC technologies, but they have constraints for SWC. These were small land size, food insecurity, lack of resources, technical skill, field guidance, poor maintenance, as well as young migration. The researchers used the chi-square test for the significant variation of constraints along with different agro ecology. According to the chi-square result, significant association was observed between land size, access to fertilizers, seeds, pesticides, construction materials, technical skill, and maintenance of the structures versus agro ecology. Therefore, the implementation of SWC practices should be focused on the way to avoid/lower the observed mismatch of the structures against the standard. Also the constraints in different agro ecology should be solved through full community participation in order to follow the standard SWC measures for sustainable socio-economic and environmental development.