Arbuscular mycorrhizal fungi in the East African Highland banana cropping systems as related to edapho-climatic conditions and management practices : case study of Rwanda

Root colonization, soil population density and diversity of arbuscular mycorrhizal (AM) fungi were assessed in 188 banana fields in contrasting soil types across five eco-regions in Rwanda (Butare–Gitarama, Gashonga, Bugarama, Kibungo, Ruhengeri). Root colonization was observed in all banana plants, whatever the soil type, field site and farm. The population density was higher on the wetter (1 300–1 500 mm yr?1) volcanic soils (Gashonga 59.8 and Ruhengeri 48.5 propagules 100 g?1 soil, respectively) as compared to the dryer (900–1?200 mm yr?1) soils derived from schist and granite (Butare–Gitarama 2.0, Kibungo 8.5, Bugarama 14.7 propagules 100 g?1 soil). The diversity was highest in Kibungo and lowest in Butare–Gitarama (10 and 2 spore morphotypes, respectively). These results suggested that AM fungi were widespread in banana cropping systems in Rwanda, but that root colonization, population density and diversity varied considerably depending on edapho-climatic conditions (i.e. rainfall, soil texture and P content) and soil management practices (tillage)

Tracing the range shifts of African tree ferns: Insights from the last glacial maximum and beyond

African tropical forests are experiencing rapid decline as a result of several factors, including increasing population pressure, recurrent wildfires, selective logging practices, land use changes, intensified agricultural activities, and other social and economic issues. Using MaxEnt, paleoclimatic data, and future climate scenarios, the present study seeks to explore the presence of tree ferns in tropical and Saharan Africa during the Last Glacial Maximum, African Holocene Humid Period (AHHP; ca. 14,500–5000 years ago) and to project the effects of climate change on the distribution of tree ferns in Africa under two future climatic scenarios, Representation Concentration Pathways (RCP) 4.5 and 8.5. Our study reveals that despite a significant increase in precipitation during the AHHP, precipitation distribution was variable and insufficient to support the five tree fern species examined in this study. While some tree fern species have experienced range shifts over time, we found that most of them have maintained their presence within refuge areas that probably endured the late Pleistocene extinction event. These refugia provided a haven for some tree ferns, allowing them to persist and survive amidst challenging and varying environmental conditions. This highlights tree ferns' remarkable adaptability in changing climate as well as the critical importance of these refugial areas in safeguarding their populations during climatic upheaval. Our study further demonstrates that different species respond to climate change differently, with some experiencing minimal range contractions of 2.0 %, up to more than 57.0 % range expansion in other species. Preserving refugia not only safeguards tree fern populations but also contributes to conserving overall forest biodiversity and ecosystem functioning. This knowledge is crucial for implementing targeted conservation actions that promote sustainable forest management and can mitigate the threats posed by climate change and anthropogenic activities in African closed wet forests

Preliminary investigations reveal that Bacillus thuringiensis δ-endotoxin CryIA(c) incorporated in soil does not affect arbuscular mycorrhiza in Sorghum bicolor (L.) (Moench)

The imminent introduction of transgenic crops into Kenya requires a rigorous assessment of the potential risks involved. This study focused on the possible effect of Bacillus thuringiensisδ-endotoxin [CryIA(c)] on arbuscular mycorrhizal fungi (AMF) associated with sorghum. In green house experiments, sorghum seedlings were inoculated with a mixed culture of AM fungi and grown in black cotton soil that contained increasing concentrations of B. thuringiensis toxin. The plants were sampled after 2, 4, 6 and 12 - week intervals. There was a progressive increase in AMF colonization from the 1st harvest (after 2 weeks) to the 4th harvest (after 12 weeks) in all treatments. Additionally, the total root length, fresh shoot weight and fresh root weight was not influenced significantly by the presence of the Bt toxin. These findings suggest that the presence of the Bt toxin in soil does not affect AM of sorghum. Keywords: Arbuscular mycorrhiza; fungi, Bacillus thuringiensis, endotoxins; CryIA(c), Sorghum bicolor; symbiosis Journal of Tropical Microbiology and Biotechnology Vol. 3(1) 2007: pp. 12-1

Soil fertility management in sub-Saharan Africa

Published online: 04 May 2017Most of the population in sub-Saharan Africa depends on agriculture for livelihood, which is mainly practiced by resource-constrained smallholder farmers. Due to persistent low crop yields, food and nutrition insecurity, farmers have been opening new lands through deforestation or encroachment into marginal lands where possible, seeking for additional yields, which has aggravated soil erosion, land degradation, and eutrophication of water bodies. Adoption of integrated soil fertility management practices in the smallholder farming systems has been affected by several factors including poor access to improved agricultural inputs, poor understanding of the practices and their benefits, and importantly limited financial capacity. Here we review challenges of soil fertility management in the smallholder farming systems of sub-Saharan Africa. Our major findings are: (1) most countries have not been able to meet the fertilizer target of 50 kg nutrients ha−1 by 2015 in the 2006 Abuja Declaration; over 65% of the smallholder farmers have not used fertilizer and 75% of the agricultural soils have been affected by nutrient depletion. (2) Poor agricultural practices have resulted in an average annual nutrient loss of 50 kg ha−1, which represented an equivalent of US$ four billion lost in 2008 and an estimated economic cost of up to 18% of the gross domestic product in addition to eutrophication of water bodies. (3) Value cost ratios of agricultural inputs that are less than three are common, which has limited the profitability of integrated soil fertility management practices. (4) Proliferation of fake agricultural inputs has been reported in over 40–60% of the cases as a consequence of poor enforcement of quality standards. (5) In addition to blanket recommendations, fertilization has focused on nitrogen, phosphorus and potassium, with little emphasis on secondary and micro-nutrients as well as organic amendments or liming materials in acid soils, which has generally resulted in poor crop responses or low yield increments. (6) Effective adoption of integrated soil fertility management would result in at least doubling the current nutrient agronomic use efficiency in the smallholder farming systems and reduction of the actual yield gap averaged to more than 300% for cereal and legume crops. Based on these findings, operationalization of supportive policies to increase adoption of good agronomic practices and investment in research to develop solutions appropriate to smallholder farmers should be recommended