Biovar 2 of Ralstonia solanacearum Species Complex Causes Tomato Bacterial Wilt Disease in Tanzania

This research article published by Science Alert, 2020Background and Objective: Bacterial wilt disease (BWD) caused by complex species of Ralstonia solanacearum (RSSC) has been categorized as one of the most significant plant diseases in the world. It is a serious problem of tomato and causes significant economic losses of tomato in Tanzania. The purpose of this study was to determine biovars of RSSC causing tomato BWD in Tanzania. Materials and Methods: Tomato stems showing typical symptoms of BWD were collected from main agro-ecological regions and were characterized by pathological and carbohydrate oxidation tests. The least significance difference (LSD) procedure was used for mean separation (p = 0.05) of disease incidence and severity. Results: A total of 29 out 40 RSSC isolates from infected tomato stems produced typical colonies of RSSC on triphenyl tetrazolium chloride medium out of which 19 (52%) were pathogenic on tomato variety Tanya. Carbohydrate oxidation test showed that most (90%) predominating isolates in main agro-ecological regions belong to biovar 3 while the rest (10%) belong to biovar 2 and prevail in the southern zone of Tanzania. This is the first report of prevalence of biovar 2 of Ralstonia in Tanzania and suggests a recent introduction of biovar 2 in tomato fields in Tanzania. Conclusion: Biovar 2 of RSSC is reported for the first time to cause tomato bacterial wilt disease in Tanzania. This alerts plant health regulators to embark on necessary phytosanitary measures to prevent further spread and/or introduction of the disease considering its quarantine status in different countries

Identification and Management Challenges Associated with Ralstonia solanacearum (Smith), Causal Agent of Bacterial Wilt Disease of Tomato in Sub-Saharan Africa.

This research article published Science Alert, 2017Tomato is the world's most consumed vegetable crop after potato and it is source of vitamins, minerals, fiber, lycopene, β-carotene and income. Despite its significant importance tomato can heavily be attacked by different pathogens including Ralstonia solanacearum that incites bacteria wilt disease. The disease is very devastating causing a considerable yield loss worldwide. The pathogen can survive in plant debris, infected plants and host weeds and spread from one field to another by irrigation or flood water, soil, farm equipment and workers and weeds which usually grow along waterways and it is difficult to manage due to complication in biology, nature of infestation and wide host range. In areas like the Sub-Saharan Africa where there exists a wide diversity of plant species, the pathogen becomes even more difficult to manage. It is on this basis that this review article, clearly discusses challenges for bacterial wilt disease identification and management in tomato farming systems with respect to the diagnosis methods used, pathogen genetic diversity and host range and pathogen survival mechanisms under different environment. The information will empower the responsible personnel involved in tomato production chain to have clear information about the pathogen and management options available against the disease in Sub-Saharan Africa

Novel use of portable gamma sensors to rapidly assess soil status and recovery in degraded East African agro-pastoral land

This Research Article was published by the University of Plymouth Research Outputs , 2024Soil resources in East African agro-pastoral lands are being rapidly depleted by erosion, threatening food, water and livelihood security. Here we explore the utility of innovation in portable gamma sensors to rapidly assess soil health via proxy measurement of soil organic matter (SOM) providing visual information that enables local communities to take action to mitigate land degradation before it reaches a critical tipping point. This study is grounded in the outcomes of an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places. The work has shown that limitations to delivering socially acceptable and environmentally desirable solutions can be addressed by (1) closing fundamental gaps between the evidence bases of different disciplines and indigenous knowledge and (2) addressing, through participatory action, the implementation gap between science-based recommendations, policy makers and practitioners. Key adaptations implemented in the study region include new bylaws to enforce altered grazing regimes, grassland recovery and tree planting. Against this context, we report a first trial of a portable gamma spectrometer to rapidly assess spatial variability in soil health using total and radionuclide-specific gamma emissions from naturally occurring radioisotopes as a proxy for soil organic matter. A Medusa MS-700 portable gamma spectrometer was deployed on foot across a landscape of known variability in soil health status encompassing a spectrum of impact from severely gullied soil/subsoil, heavily grazed surface soil, recovered grazed soil (ca 3 years exclusion of livestock) and conservation agriculture plots. In-situ field results showed a clear gradient in raw total gamma count rate with sample areas in each zone at 1200 ± 100, 980 ± 70, 814 ± 60 and 720 ± 60 counts per second across the above four areas respectively. Correlations between radioisotope-specific gamma spectrometer data and organic matter (range 15 ± 2 to 30 ± 3 g kg-1 from degraded land to conservation agriculture) were evaluated to explore the dominant control on sensor response. Further comparisons are made to major and minor element geochemistry. Feedback from local Maasai community members who participated in the research further underpins the value of the sensor as a qualitative assessment tool e.g. using visual colour coding in the live data feed in the field. Quantitative comparison of sensor and laboratory data will permit development of protocols for airborne (drone) gamma spectrometry that offers community scale evaluation of grazing pressure on soil health to inform livestock future exclusion policy in common land prone to soil erosion

Informing versus generating a discussion: Comparing two approaches to encouraging mitigation of soil erosion among Maasai pastoralists

Soil erosion is a critical problem for pastoralist societies that rely on healthy grazing land for their livelihoods. Previous research suggests that unsustainable land management practice is one of the factors exacerbating soil erosion, and that willingness to adjust this practice is closely linked to community land protection norms. The present research explores approaches to building stronger community norms and intentions linked to mitigating soil erosion among Maasai pastoralists in Northern Tanzania. In particular, we compare two impact approaches based on the information deficit model (exposure to scientific information) and the social identity framework (a group-based discussion). The results demonstrate that the information deficit approach results in stronger perceived land protection norms and, indirectly, stronger intentions, as compared to the discussion-based approach. We discuss contextual features that should be taken into account when interpreting these findings and suggest these may be key for impact approach choices

Determining tributary sources of increased sedimentation in East-African Rift Lakes.

This research article published by Elsevier B.V., 2020Temporal and spatial sediment dynamics in an East-African Rift Lake (Lake Manyara, Tanzania), and its river inputs, have been evaluated via a combination of sediment tracing and radioactive dating. Changes in sedimentation rates were assessed using radioactive dating of sediment cores in combination with geochemical profile analysis of allogenic and autogenic elements. Geochemical fingerprinting of riverine and lake sediment was integrated within a Bayesian mixing model framework, including spatial factors, to establish which tributary sources were the main contributors to recent lake sedimentation. The novel application of Bayesian source attribution on sediment cores and subsequent integration with sedimentation data permitted the coupling of changes in the rate of lake sedimentation with variations in sediment delivery from the tributaries. These complimentary evidence bases demonstrated that Lake Manyara has experienced an overall upward trajectory in sedimentation rates over the last 120 years with distinct maxima between 0.80 and 0.85 g cm yr in the 1960s and between 0.84 and 1.81 g cm yr in 2010. Increased sedimentation rates are largely a result of a complex interaction between increased upstream sediment delivery following changes in land cover and natural rainfall fluctuations. Modelling results identified two specific tributaries as responsible for elevated sedimentation rates, contributing 58% and 38% of the recently deposited lake sediment. However, the effects of sedimentation were shown to be spatially distinct given the domination of different tributaries in various areas of Lake Manyara. The application of source-tracing techniques constrained sedimentation problems in Lake Manyara to specific tributary sources and established a link between upstream land degradation and downstream ecosystem health. This novel application provides a solid foundation for targeted land and water management strategies to safeguard water security and environmental health in Lake Manyara and has potential application to fill knowledge gaps on sediment dynamics in other East-African Rift Lakes

Hunter-gatherer environments at the Late Pleistocene sites of Mwanganda's Village and Bruce, northern Malawi

Mwanganda's Village (MGD) and Bruce (BRU) are two open-air site complexes in northern Malawi with deposits dating to between 15 and 58 thousand years ago (ka) and containing Middle Stone Age (MSA) lithic assemblages. The sites have been known since 1966 and 1965, respectively, but lacked chronometric and site formation data necessary for their interpretation. The area hosts a rich stone artifact record, eroding from and found within alluvial fan deposits exhibiting poor preservation of organic materials. Although this generally limits opportunities for site-based environmental reconstructions, MGD and BRU are located at the distal margins of the alluvial fan, where lacustrine lagoonal deposits were overprinted by a calcrete paleosol. This has created locally improved organic preservation and allowed us to obtain ecological data from pollen, phytoliths, and pedogenic carbonates, producing a regional- to site-scale environmental context for periods of site use and abandonment. Here, we integrate the ecological data into a detailed site formation history, based on field observations and micromorphology, supplemented by cathodoluminescence microscopy and μ-XRF. By comparing local, on-site environmental proxies with more regional indicators, we can better evaluate how MSA hunter-gatherers made decisions about the use of resources across the landscape. Our data indicate that while tree cover similar to modern miombo woodland and evergreen gallery forest prevailed at most times, MSA hunter-gatherers chose more locally open environments for activities that resulted in a lithic artifact record at multiple locations between 51 and 15 ka.publishedVersio

Survey and conventional management methods of bacterial wilt disease in open fields and greenhouses in Tanzania

Research Article published by Springer International PublishingA study was conducted from January to February 2018 to determine bacterial wilt disease (BWD) incidence and severity in open-field and greenhouse environments in twelve tomato growing districts in Tanzania. About 220 farmers were interviewed to assess their knowledge on BWD by using a semi structured questionnaire. Results indicated significant (p 80% of 220 respondents) of farmers could not identify sources of BWD in environment and do not adhere to sanitation measures recommended for greenhouse tomato production. 90% of the interviewed famers ventured into greenhouse tomato production by imitating from neighbors without technical guidance. To manage BWD, majority (70%) of farmers use chemicals which they reported as ineffective, 13% use botanical, 10% do crop rotation which was reported to be not practical because of land scarcity and long time that Ralstonia solanacearum can survive. Rest (7%) of farmers do not use any BWD management measure. There was no report of either use of disease resistant cultivars or biological control as a strategy for BWD management in the study area. There is therefore need to develop techniques for farmers to manage the BWD by exploring promising options such as use of effective botanical extracts

Building Resilient Crop Production Systems for Drought-Prone Areas—A Case for Bambara Groundnut (Vigna subterranea L. Verdc) and Groundnut (Arachis hypogaea L.)

Drought is a major crop production constraint worldwide. Some legume crops are known for their ability to resist water deficit stress. This study evaluated the responses of bambara groundnut (Vigna subterranea (L.) Verdc) and groundnut (Arachis hypogaea (L.) to soil water deficit stress. The experiment was set as a split-plot randomized complete block design. Three bambara groundnut landraces: viz DodR, NALBAM 4 and S19-3, and one groundnut variety, MNANJE, were assigned to subplots with three water regimes assigned to main plots (regime one: irrigated throughout the growing period, regime two: water deficit stress was imposed at the start of flowering to the end of first flush flowering, regime three: water was withheld during the pod development). Water deficit stress increased proline content by 123% in stressed plots. The highest (174%) and lowest (89%) proline increases were evident in the genotypes MNANJE and NALBAM 4, respectively. Water deficit decreased stomatal conductance, transpiration rate and photosynthetic rate, with MNANJE and S19-3 showing the smallest percentage decrease in most of the traits. This suggests that the two genotypes are drought resistant. The variations observed among landraces could be exploited to breed resilient varieties for cultivation in drought-prone areas, ultimately improving food security

Building Resilient Crop Production Systems for Drought-Prone Areas—A Case for Bambara Groundnut (<i>Vigna subterranea</i> L. Verdc) and Groundnut (<i>Arachis hypogaea</i> L.)

Drought is a major crop production constraint worldwide. Some legume crops are known for their ability to resist water deficit stress. This study evaluated the responses of bambara groundnut (Vigna subterranea (L.) Verdc) and groundnut (Arachis hypogaea (L.) to soil water deficit stress. The experiment was set as a split-plot randomized complete block design. Three bambara groundnut landraces: viz DodR, NALBAM 4 and S19-3, and one groundnut variety, MNANJE, were assigned to subplots with three water regimes assigned to main plots (regime one: irrigated throughout the growing period, regime two: water deficit stress was imposed at the start of flowering to the end of first flush flowering, regime three: water was withheld during the pod development). Water deficit stress increased proline content by 123% in stressed plots. The highest (174%) and lowest (89%) proline increases were evident in the genotypes MNANJE and NALBAM 4, respectively. Water deficit decreased stomatal conductance, transpiration rate and photosynthetic rate, with MNANJE and S19-3 showing the smallest percentage decrease in most of the traits. This suggests that the two genotypes are drought resistant. The variations observed among landraces could be exploited to breed resilient varieties for cultivation in drought-prone areas, ultimately improving food security

Informing versus generating a discussion: Comparing two approaches to encouraging mitigation of soil erosion among Maasai pastoralists

Soil erosion is a critical problem for pastoralist societies that rely on healthy grazing land for their livelihoods. Previous research suggests that unsustainable land management practice is one of the factors exacerbating soil erosion, and that willingness to adjust this practice is closely linked to community land protection norms. The present research explores approaches to building stronger community norms and intentions linked to mitigating soil erosion among Maasai pastoralists in Northern Tanzania. In particular, we compare two impact approaches based on the information deficit model (exposure to scientific information) and the social identity framework (a group-based discussion). The results demonstrate that the information deficit approach results in stronger perceived land protection norms and, indirectly, stronger intentions, as compared to the discussion-based approach. We discuss contextual features that should be taken into account when interpreting these findings and suggest these may be key for impact approach choices