Humid Tropical Regions Research Articles

Exergoeconomic analysis of solar photovoltaic power plants: Case study in differents tropicals zone (Maroua and Douala) in Cameroon

The present work highlights the exergoeconomic analysis of photovoltaic (PV) systems. It consists in carrying out an exergy and economic balance of these systems to evaluate the energy losses at all levels of the production chain. For this purpose, a 11,52 kWp power plant with storage installed at Maroua Airport (tropical dry region) and a 1,25 MWp grid connect plant at Douala Airport (tropical humid region) are considered. The meteorological data and the cells' temperature which highly affect the PV performances are directly measured on site. The estimated useful exergy production of electricity is about 1585.68 kWh/kWp/yr in Maroua PV plant and 1452.75 kWh/yr in Douala PV plant. The losses are respectively evaluated to be 142.76 kWh/kWp/yr in Maroua and 37.6 kWh/kWp/yr in Douala. The performance of each plan is evaluated using the exergy matrix concept. The results obtained give an exergy payback time value of 6.19 years for the Maroua plant, which is higher than the exergy return time of the Douala plant, which is 5.25 years due to losses related to storage system, the cost per kilowatt-hour of useful electrical energy produced is 0.130 UDS for the Maroua plant and 0.002 USD for the Douala plant. The cost of exergy losses per kWp/yr is estimated at 19.163 USD for the Maroua plant, and 0.065 USD for the Douala plant. Thus, the exergy losses are higher for solar PV systems installed in the Sahelian regions of the country, and even higher for systems with storage. Based on this analysis, it appears that the PV plant installed in the dry tropical zone is more efficient, while the one installed in the humid tropical zone has a better production cost. Fortunately, these climatic regions are favorable for the implementation of PV plants.

Ensemble of fuzzy-analytical hierarchy process in landslide susceptibility modeling from a humid tropical region of Western Ghats, Southern India.

The western flanks of the Western Ghats are one of the major landslide hotspots in India. Recent rainfall triggered landslide incidents in this humid tropical region necessitating the accurate and reliable landslide susceptibility mapping (LSM) of selected parts of Western Ghats for hazard mitigation. In this study, a GIS-coupled fuzzy Multi-Criteria Decision Making (MCDM) technique is used to evaluate the landslide-susceptible zones in a highland segment of the Southern Western Ghats. Fuzzy numbers specified the relative weights of nine landslide influencing factors that were established and delineated using the ArcGIS, and the pairwise comparison of these fuzzy numbers in the Analytical hierarchy process (AHP) system resulted in standardized causative factor weights. Thereafter, the normalized weights are assigned to corresponding thematic layers, and finally, a landslide susceptibility map is generated. The model is validated using the area under the curve values (AUC) and F1 scores. The result reveals that about 27% of the study area is classified as highly susceptible zones followed by 24% area in moderately susceptible zone, 33% in low susceptible, and 16% in a very low susceptible area. Also, the study shows that the plateau scarps in the Western Ghats are highly susceptible to the occurrence of landslides. Moreover, the predictive accuracy estimated by the AUC scores (79%) and F1 scores (85%) shows that the LSM map is trustworthy for future hazard mitigation and land use planning in the study area.

Correlation analysis of agricultural drought risk on wet farming crop and meteorological drought index in the tropical-humid region

In the tropical-humid region, wet farming crops (e.g., paddy) are a common agricultural commodity with a high-water requirement. Usually planted in the Asia monsoon region with a high precipitation rate, these crops are divided into the wet cropping season and the dry cropping season. During the dry cropping season, they are particularly vulnerable to agricultural drought caused by the decrease in precipitation. This study used Indonesia as a case study and is aimed at assessing the agricultural drought risk on a wet farming crop during the dry cropping season by examining the correlation between the drought hazard and its risk. For hazard assessment, Standardized Precipitation Index (SPI) was used to assess the agricultural drought, by using the Global Satellite Mapping of Precipitation (GSMaP) which has 0.1° × 0.1° spatial resolution. The result of correlation analysis between the SPI and drought-affected areas on a city scale showed that SPI-3 in August is the most suitable timescale to assess the agricultural drought in Indonesia. The agricultural drought risk assessment was conducted on the grid scale, where the crop yield estimation model was developed with the help of Normalized Difference Vegetation Index (NDVI). Based on the correlation analysis between SPI-3 and the detrended crop yield as drought risk indicators, the higher yield loss was found in the area above the threshold value (r-value ≤ 0.6) indicating that those areas were more vulnerable to drought, while the area below the threshold value has lower crop yield loss even in the area that was hit by the most severe drought, because the existing irrigation system was able to resist the drought’s impact on crop yield loss.

Monitoring the effects of urbanization and flood hazards on sandy ecosystem services

Urbanization, storms, and floods have compromised the benefits derived from various types of sand dune landscapes, particularly in developing countries located in humid monsoon tropical regions. One pertinent question is which driving forces have had a dominant impact on the contributions of sand dune ecosystems to human well-being. Has the decline in sand dune ecosystem services (ES) been primarily due to urbanization or flooding hazards? This study aims to address these issues by developing a Bayesian Belief Network (BBN) to analyze six different sand dune landscapes worldwide. The study uses various data types, including multi-temporal and -sensor remote sensing (SAR and optical data), expert knowledge, statistics, and GIS to analyze the trends in sand dune ecosystems. A support tool based on probabilistic approaches was developed to assess changes in ES over time due to the effects of urbanization and flooding. The developed BBN has the potential to assess the ES values of sand dunes during both rainy and dry seasons. The study calculated and tested the ES values in detail over six years (from 2016 to 2021) in Quang Nam province, Vietnam. The results showed that urbanization has led to an increase in the total ES values since 2016, while floods only had a minimal impact on dune ES values during the rainy season. The fluctuations of ES values were found to be more significant due to urbanization than floods. The study's approach can be useful in future research on coastal ecosystems.

Sugarcane green harvest management influencing soil phosphorus fractions

Few researchers have evaluated phosphorus (P) fractions in soils from humid tropical regions in which sugarcane (Saccharum spp) is harvested without prior burning. Aiming to evaluate if that practice may promote substantial changes in the availability of soil P, we analyzed the differences in total P, organic P (Po), and extractable inorganic P (Pi) fractions in soil samples collected from an Oxisol. A long-term (14 years) randomized block design was employed with six replicates and two treatments: green-harvest (GH) and burned-harvest (BH) in a sugarcane plantation. Soil samples, with six replicates, were collected at depths of 0–0.05 m, 0.05–0.1 m, 0.1–0.2 m, 0.2–0.3 m, and 0.3–0.4 m from the planting row, 0.25 m perpendicular to the row, and in the inter-row. The total Po fraction had the greatest variation between the GH and BH systems. Total Po concentration was lower in the 0–0.05 m soil layer of the GH system than that of the BH system. Total Po had also accumulated in the 0.2–0.3 m layer, which is where P fertilizer was applied at planting. These differences were observed in the planting row and 0.25 m from the planting row, but not in the inter-row. There was also no relationship between Pi fractions and row position or sampling depth in the two harvest systems. Long-term GH management rather than conventional BH sugarcane promoted greater cycling of Po in the soil, while concentrations of Pi fractions did not differ between harvest systems.

Temporal Transferability of Calibrated Hydrological Model Parameters: A Case Study of Gin Catchment, Sri Lanka

Lack of observed data for model calibration hinders the application of hydrological models in many poorly-gauged catchments, particularly in the humid tropical region. Despite much less attention given, it is vital to assess transferability of calibrated parameters in order to apply hydrological models in such catchments to assist their water resources planning and management activities. Thus, this study investigated temporal transferability of a lumped conceptual hydrological model’s (MIKE 11 NAM) calibrated model parameters for rainfall-runoff simulations in two different time periods beyond its calibration period. Study area was selected as Gin catchment located in the humid tropical region. MIKE 11 NAM model was calibrated for the period 1995-1998 [Nash Sutcliffe coefficient (NSE) = 0.73, percent bias (PBIAS) = 3.9%, ratio of the root mean square error to the standard deviation of measured data (RSR) = 0.52] and validated for the period 1999-2002 (NSE=0.66, PBIAS = 8.7%, RSR = 0.59) for the Gin catchment. The temporal transferability of the calibrated model parameters was tested using two scenarios which formulated based on the temporal lag between the calibration period and the transfer period: scenario A having a 4-year time lag and scenario B having a 8-year time lag. Scenario A which evaluated the model performance using 2003-2006 streamflow data indicated only a marginal loss in the model performance in comparison to the calibration. It showed an overall ‘good’ performance (NSE=0.64, PBIAS = 8.6%, RSR = 0.59) including promising capability to reproduce the peak flows (<10th percentile) with Pearson’s correlation coefficient of 0.6. However, scenario B which evaluated the model performance using 2007-2010 streamflow data indicated ‘unsatisfactory’ model performance (NSE=0.42, PBIAS = 13.6%, RSR = 0.76). Therefore, this study suggests that the calibrated parameters of MIKE 11 NAM model can be temporally transferred within a catchment with a 4-year time lag from the calibration period implying the applicability of this modelling framework for rainfall-runoff simulations especially in the catchments where streamflow data is sparse.

Mechanical Behavior of Hydrated-Lime–Liquid-Stabilizer-Treated Granular Lateritic Soils

Granular lateritic soil is commonly used for road construction in humid tropical and subtropical regions. However, the high plastic clay content and poor particle distribution of some laterite materials make them unsuitable for bases and subbases. Lime treatment is a widely used method for improving problematic lateritic soil, and liquid ionic stabilizers are considered an environmentally friendly solution for reinforcing such soils. However, using only lime or only stabilizers may not be optimal. This study investigated the effect of treating granular lateritic soil with hydrated lime and a new liquid stabilizer, Zhonglu-2A (ZL-2A). A series of indoor tests, including compaction, California bearing ratio, and unconfined compressive strength tests, were conducted to evaluate the effects of hydrated lime content and stabilizer content on the mechanical properties, mineralogical composition, and microstructure of the soil. The results show that an increase in hydrated lime dosage increases the optimal moisture content and decreases the maximum dry density. The CBR of lime-stabilizer-treated laterite was at least 2–3 times higher than that of the only-lime-treated soil. The highest CBR was observed in samples treated with 0.2‰ ZL-2A stabilizer. The sample with 6% lime and 0.2‰ ZL-2A stabilizer exhibited the highest unconfined compressive strength, and a nearly linear increase was observed between the unconfined compressive strength and CBR. Further investigation of the stabilization mechanism using X-ray diffraction mineralogy analysis and scanning electron microscopy revealed that the inorganic substances of the ZL-2A stabilizer and the hydrated lime provided the basic conditions for the reaction and generated cementitious hydrates on the clay particles. The mixture of granular lateritic soil and hydrated lime was wrapped by the ZL-2A stabilizer, forming a complex spatial structure and improving the strength of the soil. To improve the bearing capacity of subgrades in actual subgrade engineering, a combination of a liquid ionic stabilizer and lime should be used to treat laterite.

Developing an intelligent cloud attention network to support global urban green spaces mapping

Urban green spaces (UGS) play an important role in understanding of urban ecosystems, climate, environment, and public health concerns. Satellite derived UGS maps provide an efficient and effective tool for urban studies and contribute to targets and indicators of the sustainable development goals, at the global level, set by the United Nations. However, clouds create a challenging issue in optical satellite image processing, leading to significant uncertainty in UGS mapping. In this study, we propose an automatic UGS mapping method by integrating satellite images with crowdsourced geospatial data while aiming to reduce the uncertainty caused by cloud contamination. The proposed method consists of three parts: (1) auxiliary data pre-processing module; (2) cloud attention intelligent network (CAI-net); and (3) non-cloud scenes classification module. The auxiliary data pre-processing module was used to convert crowdsourcing geospatial data into auxiliary maps. The CAI-net was proposed to retrieve detailed UGS classes within clouds from satellite image patches and auxiliary maps, while non-cloud scenes classification module was used to extract UGS from satellite image patches. The proposed method was applied to generate spatial continuous global UGS map products, considering the uncertainty caused by cloud contamination. The results show the proposed method yielded a high-quality global UGS map with average overall accuracy as high as 92.96% when satellite images had cloud coverage ranging from 0% to 50%. The geospatial AI, specifically CAI-net, can provide more accurate UGS mapping regardless of different geographical and climatic conditions of the study areas, which is especially significant for humid tropical and subtropical regions with frequent clouds and rains.

The carbon sink of secondary and degraded humid tropical forests.

The globally important carbon sink of intact, old-growth tropical humid forests is declining because of climate change, deforestation and degradation from fire and logging1-3. Recovering tropical secondary and degraded forests now cover about 10% of the tropical forest area4, but how much carbon they accumulate remains uncertain. Here we quantify the aboveground carbon (AGC) sink of recovering forests across three main continuous tropical humid regions: the Amazon, Borneo and Central Africa5,6. On the basis of satellite data products4,7, our analysis encompasses the heterogeneous spatial and temporal patterns of growth in degraded and secondary forests, influenced by key environmental and anthropogenic drivers. In the first 20 years of recovery, regrowth rates in Borneo were up to 45% and 58% higher than in Central Africa and the Amazon, respectively. This is due to variables such as temperature, water deficit and disturbance regimes. We find that regrowing degraded and secondary forests accumulated 107 Tg C year-1 (90-130 Tg C year-1) between 1984 and 2018, counterbalancing 26% (21-34%) of carbon emissions from humid tropical forest loss during the same period. Protecting old-growth forests is therefore a priority. Furthermore, we estimate that conserving recovering degraded and secondary forests can have a feasible future carbon sink potential of 53 Tg C year-1 (44-62 Tg C year-1) across the main tropical regions studied.

Seed traits and tropical arboreal species conservation: a case study of a highly diverse tropical humid forest region in Southern Costa Rica

Tropical areas are vital for conserving endangered tree species. However, barriers to the propagation and storage of plant material still limit preservation outcomes. Seed traits are essential in conservation but have rarely been applied in the tropics. In this work, we compile information about the germination and seed desiccation tolerance behaviour of 953 arboreal species from the Osa Peninsula, Costa Rica. We analysed how those traits are related to the growing strata, seed size, and dispersal mode and how they can be used to improve conservation initiatives based on the species distribution, abundance, extinction risk, and ex situ cultivation. Over a third of the species are probably recalcitrant but this number increase to almost half among the endangered and endemic ones. Most species have seeds dispersed by animals, but wind dispersal is usually orthodox and dominant in secondary forests. All species with tiny seeds and most understorey ones with small seeds are orthodox. Approximately half of the species have dormant seeds, while nearly one-third of nondormant species have cohorts with extended germination. Almost half of the species are conserved ex situ; however, several endangered, endemics could be expected to be considered exceptional. Seed traits could target orthodox species for seed banking in tropical forests, including the potential of secondary forests and a subset of oligarch species. For the recalcitrant ones, approaches based on the risk of extinction, distribution, abundance, and ex situ status allow for prioritizing collection and conservation strategies. Under this approach, we develop a list with priority species.

Spatiotemporal changes in Hourly Wet Bulb Globe temperature in Peninsular Malaysia

Global warming causes a temperature rise and alteration of other meteorological variables that directly or indirectly affect human comfort. The wet bulb globe temperature (WBGT) incorporates the effects of multiple meteorological variables to provide a reliable measure of human thermal stress. Despite the large significance of WBGT on public health, studies related to characterization and trends assessment of WBGT are limited in the tropical humid region like Peninsular Malaysia due to the unavailability of all meteorological variables required for such analysis. This study employed reanalysis meteorological data of ERA5 to assess the characteristics and changes in hourly, daily, monthly, seasonal and annual outdoor WBGT over peninsular Malaysia for the period 1959–2021 using the Liljegren method. The WBGT values were classified into five categories to assess the human thermal stress levels defined by the United States Department of the Army (USDA). The mean daily WBGT in PM varies from 21.5 °C in the central south elevated region to 30.5 °C in the western coastal region. It always reaches a heat-related illness risk level (31.20 °C) in the afternoon during monsoon and extreme stress conditions during inter-monsoonal periods. The trend analysis revealed an increase in WBGT for all the time scales. The higher increase in the mean and maximum WBGT was estimated in the coastal and south regions, nearly by 0.10 to 0.25 °C/decade. The increase in mean nighttime WBGT was 0.24 °C/decade, while in mean daytime WBGT was 0.11 °C/decade. The increase in WBGT caused a gradual expansion of areas experiencing daily WBGT exceeding a high-risk level for 5 h (11 AM to 3 PM). The information and maps generated in this study can be used for mitigation planning of heat-related stress risk in PM, where temperature extremes have grown rapidly in recent years.

Effect of termite mounds on soil microbial communities and microbial processes: Implications for soil carbon and nitrogen cycling

Fungus-feeding termites are considered to be ecosystem engineers because of their ability to construct massive and complex mounds with different soil physicochemical and biological properties in tropical ecosystems. However, the impact of the termite nesting process on soil microbial communities and microbial functions related to nutrient cycling is poorly understood. In this study, we investigated termite-induced changes in soil microbial communities and their nutrient cycling functions within termite mounds (i.e. live mounds and abandoned mounds) in the humid tropical region of Southwest China. We found that the live mounds harbour intermediate microbial community richness (i.e. PLFAs, fungi, bacteria, G+, and G- bacteria) between surrounding topsoils and deep soils, with the ratio of fungi to bacteria (F:B) in mounds being significantly higher than in surrounding soils. However, the microbial communities gradually transformed to resemble the surrounding soils after the mounds were abandoned because of natural weathering and plant invasion. A relatively more uniform distribution of microbial communities was found within live mounds than in abandoned mounds and surrounding soils, suggesting that termites shaped the environment within the mounds, leading to the homogenisation of microbial communities. In addition, the termite-induced changes of soil physicochemical properties (e.g. water content, pH, organic matter, total N and P) were closely linked to microbial communities. We also observed a reduction in microbial processes associated with nutrient cycling, including microbial respiration, and extracellular enzymatic activities, in mounds relative to the surrounding topsoils. These findings have important implications for exploring microbial communities within termite mounds, which is critical to understand the potential role of termites in regulating soil carbon and nitrogen cycling in tropical ecosystems.

Mulching improves strawberry fruit growth and yield by regulating soil temperature and soil moisture in humid tropical India

Production and quality of strawberry (Fragaria × ananassa, Duch.) fruits are significantly reduced in conventional farming methods in humid tropical India. Little information exists on the effect of mulching and its mechanisms regulating environmental factors, physiological processes as well as biochemical constituents to improve its yield and quality. Here, the effects of different coloured plastic mulches (black, transparent, and red) and organic mulches (paddy straw, banana leaves and weeds) were tested on the yield and quality of strawberries. Black plastic mulches had a large impact on fruit weight, size, and phytochemical content. The mean fruit yield with black plastic mulching was 68% greater than the control. Black polythene mulching adjusted environmental factors and physiological processes to boost productivity and quality of strawberry fruits and hence could be recommended in humid tropical regions.

Rinite granulomatosa por Neoconidiobolus lamprauges em uma mula

ABSTRACT: Conidiobolomycosis has a wide distribution, predominantly in humid tropical regions, affecting several species with significant mortality rates. The genus Conidiobolus is now divided into four genera: Capillidium, Conidiobolus, Microconidiobolus, and Neoconidiobolus. There are no confirmed reports of infection by these fungi in Equidae in Brazil. We present a rhinofacial rhinitis caused by Neoconidiobolus lamprauges in a mule from Rio de Janeiro, Brazil. The mule presented bilateral semi-occlusion of the nostrils, difficulty breathing, and weight loss. The histological examination of the nostril biopsied mass revealed multifocal necrotizing areas with nonstained images of fungal hyphae in the Splendore-Hoeppli reaction and surrounded by macrophages, eosinophils, neutrophils, and multinucleated giant cells. The Grocott methenamine silver staining revealed thin-walled, rarely septated, irregular branching hyphae, with a varying diameter of 12 μm (± 3.63 μm), and terminal ballooning dilations. The determining etiology of this rhinitis was based on the hyphae staining by immunohistochemistry and by amplifying the DNA fragment of N. lamprauges by polymerase chain reaction. Conidiobolomycosis should be included in the differential diagnosis of the causes of rhinitis in equids, mainly in tropical regions.

Comparative Study of Perforated Sack Bag, Palm Basket, Plastic Can and Wooden Net Cage as Storage Structures for Okra

Okra (Abelmoschus esculentus L. Moench) is a vegetable crop that easily loses its nutritional quality if stored under poor environment and structure respectively after harvest. Okra is a good source of vitamins A, B and C. It also has good contents of protein, minerals and iodine. The aim of this research is to assess and compare the performance of perforated sack bag, basket, perforated plastic can and wooden net cage as storage structures for okra under tropical humid environmental condition. The four storage structures were analyzed to determine their effectiveness as storage structures for okra handling and preservation. Perforated sack bag and palm basket were purchased, while perforated plastic can and wooden net cage were constructed. The experiment was carried out in the laboratory of ABE department, MOUAU, Nigeria. The use of perforated sack bag (13 days) and wooden net cage (12 days) showed higher resistance to rottenness than palm basket and perforated plastic can (11 days) by one day difference. The weight loss of okra crops in perforated plastic can (46.02%) was lower than other structures. The results showed that perforated sack bag and wooden net cage are preferred for retaining the quality of okra crop for average of 12 days under humid tropical region.

Phosphorus extractants for soils in the humid tropical region of Brazil

Phosphorus extractants for soils in the humid tropical region of Brazil

Late Pleistocene paleoenvironment at a Middle Stone Age archaeological site in Equatorial Guinea: a paleopedological approach

Key evidence of human occupation in Africa during the Middle Palaeolithic (Middle Stone Age [MSA]) is available from the south and east of the continent, where semi-arid climate prevails. Rare evidence of MSA human occupation in the humid tropical region was recently reported from Equatorial Guinea. To identify if paleolithic human occupation occurred in the tropical forest, the stratigraphy of the recently discovered archaeological site “Mabewele I” was analyzed using a paleopedological approach. The properties evaluated along a vertical profile are: granulometry, magnetic susceptibility (K), free iron extractable with sodium dithionite (Fed), total organic carbon (TOC), chemical composition by X-ray fluorescence (XRF), X-ray diffraction mineralogy (XRD), ternary plot of the three main oxides (SiO2-Al2O3-Fe2O3), phytoliths and micromorphology. The predominant fraction is sand, with a significant clay content (> 30 %). The K and the Fed presented low values, as well as the TOC. XRF showed few variations along the sequence and XRD showed that the clays are mainly kaolinites, with a very low component of vermiculites. The phytoliths correspond to tropical vegetation with few changes in the vegetal composition between the deep and superficial zones. A charcoal from the lower part of the profile was dated between 12.57-12.24 ka cal BP, while the main artifact horizon was located at the bottom. The analytical results appear contradictory: on the one hand, there is evidence of intense chemical weathering under a humid tropical climate, but the clay cutans in the pores are very scarce and incipient and the iron nodules are mostly anorthic. This indicates that the sequence is composed of pedosediments associated with a high environmental dynamism, with short periods of erosion-sedimentation-pedogenesis. The results allow us to propose that humans inhabited the tropical forest during the MSA and that erosion-sedimentation processes could be related to anthropization processes.

Herbage and animal responses on continuously stocked ‘Ipyporã’ and ‘Mulato II’ brachiariagrasses

AbstractNew hybrid grass cultivars may enhance animal performance in forage‐livestock systems if they possess traits that address edaphoclimatic challenges and pest susceptibility. The objective was to assess herbage accumulation, plant‐part composition, nutritive value, and animal performance of ‘Ipyporã’ [Brachiaria ruziziensis Germ. & Evrard × B. brizantha (Hochst. ex A. Rich.) Stapf] and ‘Mulato II’ (B. ruziziensis × B. brizantha × B. decumbens Stapf) hybrids in the Brazilian Amazon biome. From May 2016 to May 2018, pastures were maintained under continuous stocking with variable stocking rates to maintain canopy height at 30‐cm. Herbage accumulation (HA) was greater in Mulato II (17,370 kg dry matter [DM] ha−1 year−1) than Ipyporã pastures (14,930 kg DM ha−1 year−1) across the years. In Year 1, Mulato II had greater stocking rate (1685 vs. 1215 kg body weight [BW] ha−1) and greater gain ha−1 (1130 vs. 850 kg) than Ipyporã. However, in Year 2, both cultivars had similar plant and animal responses. The Year 1 ADG was similar among cultivars or seasons but in Year 2, rainy seasons had 21 and 77% greater ADG than dry seasons for Mulato II and Ipyporã, respectively. Both cultivars can contribute to the diversification of pasture‐based livestock systems in humid tropical regions. Mulato II presented superior performance when soil moisture and fertility were not limiting (i.e., Year 1). However, both cultivars provide similar plant and animal responses in Year 2, offering viable alternatives for the diversification of pasture‐based livestock systems in the Amazon Biome.

In Vitro Evaluation of the Development of Fusarium in Vanilla Accessions

Vanilla is an economically important crop for low-lying humid tropical regions. World demand for natural vanilla is increasing, but cultivated plants face serious phytosanitary problems. The disease known as Fusarium wilt is mainly related to the fungus Fusarium oxysporum f. sp. vanillae, and for its management, the pathogen–host relationship must be understood. Four in vitro multiplied vanilla accessions were evaluated: two Vanilla planifolia from Colombia and Mexico, one from V. odorata, and one (1) F1 hybrid (V. rivasii × V. trigonocarpa). In addition, three isolates of Fusarium from different symptomatic plants present in small-scale agroforestry systems: (1Fov) F. oxysporum f. sp. vanillae from leaf, (2Fov) F. oxysporum f. sp. vanillae from root and (3Fs) F. solani also from root. Plants with two months of growth were inoculated in vitro by immersion of roots, and the development of Fusarium wilt was recorded for 15 days, using a severity scale to describe symptoms and to calculate the area under the disease progress curve (AUDPC). No statistical differences were found when analyzing the interaction between Fusarium isolates and vanilla accessions. However, when independently analyzing the design factor Fusarium isolates, there were significant differences; the 1Fov isolate of F. oxysporum f. sp. vanillae induced the highest symptoms as well as death in some plants of all accessions, while F. solani was considered a secondary pathogen. There were no statistical differences for the vanilla accessions factor, but the values of AUDPC and symptoms observed suggest a slight resistance in all the accessions. Therefore, it is suggested to explore the vanilla gene pool to generate multiplication material with resistance genes and to contribute with genetic improvement to successfully integrate the management of Fusarium wilt in commercial systems.

Adaptation of the White Fulani cattle to the tropical environment

This review summarizes the available information on the adaptation and the performance of White Fulani cattle in tropical environments. White Fulani cattle is an indigenous breed of cattle widely distributed in the humid tropical regions of Africa and plays significant roles in meat and milk production, as well as draught purposes. Poor management and the harsh environmental conditions in the tropics encumber the optimal productive and reproductive performance of the breed, having about 4.75 years age at first calving, 57% calving rate, 18 months calving interval and 3 to 4 calves are born in a reproductive lifetime. The cattle breed adapts to these climatic patterns via physiological, morphological, behavioral, genetic, and metabolic responses. Different physiological mechanisms and morphological features such as their white coat color, hair coat thickness, and lengthy rump appear to play an important adaptive role. The distinct genetic traits (including the possession of seven genetic variants of HSP 90 gene) of the breed afford them some levels of thermotolerance and high resistivity to some endemic diseases (such as trypanosomiasis, liver fluke, brucellosis and foot and mouth disease) in the tropics constitute inherent characteristics that should be explored in detail using molecular assisted approaches. The productive performance of the breed under different systems is discussed. A better understanding of the adaptive characteristics of White Fulani cattle could provide crucial information on the best management approach/techniques that should be adopted to improve the performance, productivity, and sustainability of this cattle breed. Therefore, this review aims to compile the various production, reproduction and adaptation traits of the breed and presents vital information underlying their thriving and survivability in tropical environments.