Rainy Season Research Articles

Phytochemical variability in essential oils of Juniperus communis var. saxatilis populations grow wild in western Himalaya, India

Needle and berry samples of Juniperus communis L. var. saxatilis Pall. were sampled separately during post rainy season to comparatively investigate the essential oil (EO) yield and phytochemical variability in eight populations grow wild in western Himalaya, India. The EOs obtained from air-dried needle and berry samples separately by hydrodistillation method using Clevenger type apparatus varied in yield with geographic origin of populations, ranged between 2.5-3.4% and 1.8-2.8% (v/w, dried weight basis), respectively. GC-MS analysis of EO profiles resulted in identification of a total ninety-four phytochemicals, representing over 95% of total oil content. Both, needle as well as berry EO samples were dominated by monoterpene hydrocarbons α-pinene (18.52-30.65% and 14.31-27.37%), D-limonene (17.01-28.96% and 15.80-29.70%), β-myrcene (3.74-5.59% and 4.12-14.23%), followed by sesquiterpene hydrocarbons β-elemene (0.86-4.13% and 0.77-3.65%) and germacrene D (0.27-2.57% and 0.20-6.15%), respectively. The oxygenated sesquiterpenes α-cadinol (0.34-5.90% and to 5.63%) and α-bisabolol (to 3.39 and 0.95-6.71%) constituted the third most abundant group of terpenes while oxidized monoterpenes with α-terpineol (0.73-2.17% and 0.10-3.51%) and α-terpinyl acetate (2.10-4.76% and 0.05-3.54%) were the least dominant group. The principal component and hierarchical cluster analysis indicated that selective local environmental forces driving the microhabitat conditions appeared to be linked to high variability in essential oil composition of different common Juniper populations instead of their geographical proximity. The present study revealed that common Juniper essential oils from western Himalaya, India fulfil minimum requirements of European Pharmacopoeia and warrants its further exploitation as a natural resource of commercial significance for dietary and therapeutic applications.

Effect of season on testicular morphometry and sperm production in adult guinea cocks

A study was conducted to investigate the effect of season on testicular morphometric parameters and sperm production in adult Guinea cocks. Five (5) Guinea cocks (GCs) were randomly selected from a group of thirty homogenous adult pearl Guinea cocks during the major rainy, minor rainy season, and dry seasons of the year. The selected GCs were humanely euthanized and used for determining testicular morphometric parameters, sperm reserve, and sperm production. The results of this study showed that the body weight of Guinea cocks (GCs) and testicular morphometric parameters were significantly (P<0.05) higher in the rainy season than in the dry season, while testicular weight and the gonado-somatic index (GSI) were similar. Sperm reserves and daily sperm production were significantly (P<0.05) higher in the rainy season than in the dry season. The study concluded that the season of the year affected the body weight of the Guinea cocks, testicular morphometric parameters, sperm reserve, and sperm production in adult Guinea cocks.

Assessing the ecological patterns of Aedes aegypti in areas with high arboviral risks in the large city of Abidjan, Côte d’Ivoire

Background The city of Abidjan, Côte d’Ivoire has increasingly faced multiple outbreaks of Aedes mosquito-borne arboviral diseases (e.g., dengue (DEN) and yellow fever (YF)) during the recent years, 2017–2023. Thus, we assessed and compared Aedes aegypti larval and adult population dynamics and Stegomyia indices in four urbanized areas with differential arboviral incidences in Abidjan, Côte d’Ivoire. Methods From August 2019 to July 2020, we sampled Aedes mosquito immatures (larvae and pupae), adults and breeding habitats in Anono and Gbagba with high arboviral incidences and Ayakro and Entente with low arboviral incidences in the Abidjan city, using standardized methods. Sampling was conducted in the peridomestic and domestic (indoors and outdoors) premises during short dry season (SDS), short rainy season (SRS), long dry season (LDS) and long rainy season (LRS). The abdomens and ovaries of Ae. aegypti females were examined to determine their blood-meal and parity statuses. Stegomyia indices (container index: CI, house index: HI and Breteau index: BI), blood-meal status and parity rates were compared by study sites and seasons and with the World Health Organization (WHO)-established epidemic thresholds. Results Overall, Aedes and arboviral risk indices were high and similar between the four study areas. In total, 86,796 mosquitoes were identified and dominated by Ae. aegypti species (97.14%, 84,317/86,796). The most productive larval breeding habitats were tires, discarded containers and water storage containers. CI, HI, and BI in Anono (22.4%, 33.5% and 89.5), Ayakro (23.1%, 43.8% and 91.0), Entente (15.9%, 24.8% and 48.5) and Gbagba (23.3%, 43.0% and 102.0) were high in the respective study sites. Stegomyia indices were higher than the WHO-established epidemic thresholds during any seasons for DEN, and LRS and SRS for YF. The numbers of Ae. aegypti-positive breeding sites were higher in the domestic premises (68.0%, 900/1,324) than in the peridomestic premises (32.0%, 424/1,324). In the domestic premises, Ae. aegypti-positive breeding sites (94.6%, 851/4,360) and adult individuals (93.4%, 856/916) were mostly found outdoors of houses. Aedes aegypti adult females were mostly unfed (51.3%, 203/396), followed by blood-fed (22.2%, 88/396), gravid (13.9%, 55/396) and half-gravid (12.6%, 50/396), and had parity rate of 49.7% (197/396) that was comparable between the study sites. Conclusions The city of Abidjan, Côte d’Ivoire is highly infested with Ae. aegypti which showed comparable ecological patterns across study sites and seasons. Thus, the local communities are exposed to high and permanent risks of transmission of DEN and YF viruses that were above the WHO-established epidemic thresholds throughout. The results provide a baseline for future vector studies needed to further characterize the observed patterns of local Ae. aegypti abundances and behaviors, and risks of transmission of these arboviruses. Community-based larval source management of identified productive containers might reduce Ae. aegypti numbers and risks of transmission of Aedes-borne arboviruses in Abidjan, and other sub-Saharan African cities.

Relationships between flower-visiting insects and forest cover in cocoa-growing landscapes in Ghana

Abstract Context Increased cocoa cultivation (Theobroma cacao) has led to the conversion of over 6 million hectares of rainforest to cocoa farmlands in West Africa. Globally, pollinator decline has been driven by land use changes. Though land use change through cocoa expansion may affect insect pollinators and, by extension, pollination services, this has rarely been assessed. Objectives Our study examined the relationships between the proportion of natural forest in the landscape (reduced primarily due to cocoa expansion) and flower-visiting insect abundance, and bee abundance, richness, diversity and community composition. The effect of pan trap type (aerial or ground) was also tested. Methods Eighteen sites were selected along a gradient of an increasing proportion of natural forests in the surrounding landscape (from 9 to 100%). Ground and aerial pan traps were deployed in each site to sample flower-visiting insects. Two sampling sessions were conducted; during the rainy season in 2021 and during the dry season in 2022. Results The abundances of Coleoptera, Hymenoptera and Hemiptera increased with increasing proportion of natural forests in the landscape, while Diptera decreased. Natural forest and trap type did not significantly influence bee abundance, species richness, and Shannon diversity. However, bee community composition differed along the forest gradient, indicating that forests and cocoa farms harbour different bee communities. Ground pan traps captured more insects (61% of 19,927 flower-visiting insects) than aerial pan traps, which was driven by the Diptera as the abundances of the other orders were not significantly related to trap type. Conclusions Preserving natural forest in cocoa-growing landscapes is important to sustain the coexistence of diverse flower-visiting insect communities owing to their differential responses to the proportions of natural forests.

Field surveysin rural Tanzania reveal key opportunities for targeted larval source management and species sanitation to control malaria in areas dominated by Anopheles funestus.

Larval source management (LSM) is re-emerging as a critical malaria intervention to address challenges associated with core vector control tools, such as insecticide-treated nets (ITNs), and to accelerate progress towards elimination. Presently, LSM is not widely used in rural settings and is instead more commonly applied in urban and arid settings. A systematic entomological assessment was conducted in rural communities of southeastern Tanzania, where insecticide-treated nets (ITNs) are widely used, to explore opportunities for deploying LSM to improve malaria control. Aquatic habitat surveys were conducted in 2022 and 2023 to understand habitat usage by different mosquito vectors, covering five villages during the rainy season and seven villages during the dry season. Additionally, samples of adult mosquitoes were collected to assess the role of various Anopheles species in malaria transmission in the area, and to explore opportunities for species sanitation using targeted LSM. Adult mosquito surveys showed that in this area, the total entomological inoculation rates (EIR) for indoor collections were 20.1 and 6.5 infectious bites per person per year for outdoors. Anopheles funestus and Anopheles arabiensis were the only Anopheles vectors identified. Anopheles funestus was responsible for over 97.6% of the malaria transmission indoors and 95.4% outdoors. The concurrent larval surveys found that habitats with late instar An. arabiensis and An. funestus comprised only a small subset of 11.2%-16.5% of all water bodies in the rainy season, and 9.7%-15.2% in the dry season. In terms of size, these habitats covered 66.4%-68.2% of the total habitat areas in the wet season, reducing to 33.9%-40.6% in the dry season. From the rainy season to the dry season, the surface area of habitats occupied by An. arabiensis and An. funestus decreased by 92.0% to 97.5%, while the number of habitats occupied by An. arabiensis and An. funestus decreased by 38.0% to 57.3%. Anopheles funestus preferred large, permanent habitats with clear water and vegetation year-round, while An. arabiensis showed contrasting seasonal preferences, favouring sunlit still waters in the rainy season and larger, opaque habitats in the dry season. These findings suggest that An. funestus, which is the dominant malaria vector in the area, mediating over 95% of malaria transmission, preferentially occupies only a small subset of uniquely identifiable aquatic habitats in both wet and dry seasons. This presents an opportunity to expand LSM in rural settings by carefully targeting An. funestus habitats, which might be effective and logistically feasible as a complementary approach alongside existing interventions. Further research should assess the impact of targeted LSM for species sanitation compared to blanket LSM.

Cytogenetic and photosynthetic responses of plants after exposure to water from a lake environment.

Plants are sensitive to environmental pollutants and are excellent organisms for genetic and physiological testing. Plant-based test systems are often used to study aquatic, aerial, and terrestrial pollution, especially Allium cepa, but studies with Tradescatia pallida specimens have gained prominence due to their sensitivity and applicability. Among the biomarkers, cytogenetic damage and chlorophyll levels are used in stress studies due to their responses to single or combined factors. The aim of this study was to evaluate cytogenetic and photosynthetic responses in T. pallida, and cytogenetic responses in A. cepa exposed to water from three sampling stations in the Juara lagoon (Municipality of Serra, ES, Brazil), collected in two sampling campaigns. The cytotoxic, genotoxic, and mutagenic potentials were analyzed using the T. pallida root tip mitosis assay and the Allium cepa test. Chloroplast pigment levels were measured in T. pallida leaves after chronic exposure to the lagoon water. The cytogenetic tests showed cytogenetic alterations at two sampling stations in at least one sampling campaign, suggesting the presence of potential pollutants, the effects of which were maximized during the rainy season. The study of photosynthetic metabolism in T. pallida showed a relationship between the levels of chloroplast pigments and the amount of nutrients present in the water.

Source appointment and health risk assessment for atmospheric carbonyls in hot tropical city, Vietnam.

The aim of this study is to assess the spatiotemporal variation, sources, and health impacts of the carbonyl compounds (carbonyls) in Ho Chi Minh City (HCMC), the third-most populous city in Southeast Asia. Sampling was conducted according to the US.EPA Method TO-11A, from 2012 to 2016 in both the dry and the rainy seasons at twelve sites. The result shows that the carbonyl mixing ratios are high when compared to typical cities. Formaldehyde, acetaldehyde, and acetone are the most abundant carbonyls together accounting for 89% of the measured carbonyls. The carbonyl mixing ratio in rainy (46.0 ± 32.2ppb) is about twofold higher than that in dry (23.7 ± 10.3ppb). An inverse distance weighting method was adopted to map the spatial distribution of carbonyls across the city. The result shows that the carbonyl levels tended to be high in the city center. Three carbonyl sources are resolved by the PCA/APCS method: industrial sources and solvent usage (54%), vehicle exhausts (24%), cooking emissions (11%). Both lifetime cancer risk (LCR) and non-cancer hazard index (HIs) were calculated to estimate the health impacts on the community due to inhalation exposure to current carbonyl levels. The LCR values vary from 5.31 × 10-6 to 5.75 × 10-5 for formaldehyde higher than those of 6.61 × 10-7 to 1.36 × 10-5 for acetaldehyde, which mostly exceeded the US.EPA recommendation for five age groups. The hazard quotient values are 12.0 to 68.4 for acrolein, 0.44 to 2.84 for acetaldehyde, 0.55 to 1.85 for formaldehyde, and 0.13 to 0.89 for propionaldehyde.

Drone-assisted herbicide optimization for energy efficiency, weed control and economics in transplanted rice (Oryza sativa)

The experiment was conducted during summer and rainy (kharif) seasons of 2021 and 2022 at Agricultural Research Station (Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu), Bhavanisagar, Tamil Nadu to evaluate the efficiency, economics and energetics of drone-based herbicide spray (fluid) application in transplanted rice (Oryza sativa L.). During the experiment the application of pre-emergence and post-emergence herbicides was done using drone and knapsack sprayer to assess the weed control efficiency (WCE). Treatments included 3 herbicide combinations, viz. pyrazosulfuron ethyl as pre-emergence (PE); pyrazosulfuron ethyl as pre-emergence (PE) fb bispyribac sodium as PoE; and pyrazosulfuron ethyl as PE fb metsulfuron methyl + chlorimuron ethyl as PoE; and 4 spray fluids applied using drone and knapsack sprayer (25, 37.5, 75 and 500 litre/ha). Weed free and unweeded check plot were used as reference for calculating WCE. Application of pyrazosulfuron ethyl fb bispyribac sodium using knapsack sprayer reduced weed density from 77.74–86.45% and weed dry weight from 89.60–91.40% over unweeded plot. Moreover, it was found on par with drone application of 37.5 litre/ha using herbicides during both the seasons. Interaction effect between herbicides and drone spray fluids was found to be non-significant. Pyrazosulfuron ethyl fb bispyribac sodium application through knapsack sprayer (500 litre/ha) and drone (37.5 litre/ha) produced higher grain yield and straw yield. Higher net return, benefit: cost ratio (2.49 and 2.40), energy-use efficiency (13.44 and 13.40 MJ) and energy productivity (0.414 and 0.416 kg/MJ) were noticed with drone application of pyrazosulfuron ethyl fb bispyribac sodium using 37.5 litre/ha spray fluid in both the seasons. From the experiment, drone application of pyrazosulfuron ethyl fb bispyribac sodium with spray volume of 37.5 litre/ha was found as an effective strategy to manage weeds in transplanted rice and more advantageous in terms of energy-use efficiency and profitability.

Survey and molecular characterization of begomovirus, and assessment of yield losses caused by leaf curl disease of sunflower (Helianthus annuus)

A comprehensive survey was conducted during winter (rabi) and rainy (kharif) seasons of 2019–20 to 2021–22 in the Kurnool, Nandyal, and Prakasam districts of Andhra Pradesh, focusing on the incidence of leaf curl disease in hybrid sunflower (Helianthus annuus L.) crop. The results revealed a high incidence of the disease, ranging from 40–94.5% across most of the surveyed hybrid varieties. Leaf curl-infected samples collected from the surveyed fields were analyzed by PCR using specific primers for the DNA-A component of the virus to confirm the presence of the pathogen. The PCR-amplified fragments were cloned and sequenced. Sequence analysis revealed that the sunflower isolate (Snf-AP) shared 99.2% nucleotide identity with the tomato leaf curl Karnataka virus (ToLCKV), which infects sunflower crops in Karnataka. This indicates a strong geographical and genetic connection between the viral strains affecting sunflowers in Andhra Pradesh and Karnataka. This genetic similarity is significant, as it suggests that the same or closely related viral strains are responsible for sunflower leaf curl disease across broader regions. The disease was found to affect sunflowers at all growth stages, with the highest incidence (42.3%) observed at the star bud stage. Infection at the star bud stage leads to substantial seed yield losses, with reductions of up to 82.8%. This level of damage underscores the economic impact of early infections, as yield losses of this magnitude can severely affect the profitability of sunflower farming. Additionally, a positive correlation was found between the whitefly population, weather parameters, and disease development.

Efficacy of new generation herbicide mixtures in irrigated maize (Zea mays)

The experiment was conducted during rainy (kharif) seasons of 2020 and 2021 at Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu to study the efficacy of new generation herbicide mixtures in irrigated maize (Zea mays L.). The experiment was laid out in a randomized complete block design (RCBD) consisted of 9 treatments including pre-emergence herbicides, new generation post emergence herbicides and other weed management practices [T1, Weedy check; T2, Weed free check; T3, Spraying of atrazine @1 kg/ha as pre-emergence + Hand weeding on 25 DAS (days after sowing); T4, Spraying of atrazine @0.75 kg/ha as pre-emergence + Spraying of topramezone @25.2 g/ha as post-emergence on 25 DAS; T5, Spraying of atrazine @0.75 kg/ha as pre emergence + Tembotrione @120 g/ha on 25 DAS; T6, Spraying of atrazine @1 kg/ha as pre-emergence + Topramezone @25.2 g/ha on 25 DAS; T7, Spraying of atrazine @1 kg/ha as pre-emergence + Tembotrione @120 g/ha on 25 DAS; T8, Spraying of topramezone @25.2 g/ha + atrazine @0.75 kg/ha on 15 DAS; and T9, Spraying of tembotrione @120 g/ha + atrazine @0.75 kg/ ha on 15 DAS], replicated thrice. The results evinced that application of topramezone at 25.2 g/ha + atrazine at 0.75 kg/ha on 15th day after sowing significantly reduced the weed density and dry weight leading to higher weed control efficiency and lower weed index of 62.0% and 3.1%, respectively, during both the years of study. This treatment resulted in higher grain yield (7675 kg/ha), net returns (₹72884/ha) and benefit cost (B:C) ratio (2.33) in irrigated maize.

Influence of drip irrigation, crop geometry and mulching on morphological and nutritional traits of okra (Abelmoschus esculentus)

The experiment was conducted during rainy (kharif) seasons of 2019 and 2020 at College of Agriculture, Swami Keshwanand Rajasthan Agricultural University, Bikaner, Rajasthan to study the effect of crop geometry, mulching and different irrigation levels on the morphological and nutritional traits of okra [Abelmoschus esculentus (L.) Moench]. The experiment was conducted in a split plot design (SPD) comprised of 4 irrigation levels in the main plot (40%, 60%, 80% and 100% pan evaporation) and 2 different crop geometry (paired row sowing and normal sowing) and 3 types of mulches (no mulch, plastic mulch and straw mulch) were employed in the subplots and sub-subplots, respectively. Results indicated that 100% potential evapotranspiration (PE), drip irrigation (DI) and paired row sowing at 30 cm × 70 cm significantly increased the number of branches/plant, plant height (cm), length of fruit (cm), diameter of fruit (cm) and chlorophyll content of leaves compared to lower irrigation levels and normal sowing. Additionally, straw mulch positively influenced the above-mentioned parameters in the okra fruits as compared to without mulch. Drip irrigation, paired row sowing, and straw mulching also resulted in a significant increase in net returns per hectare. The study demonstrated that combining paired row sowing with straw mulch and irrigating at 100% potential evapotranspiration (PE) yielded the best growth attributes, highest fruit quality, and maximum net returns for okra.

Induced genetic variability for quantitative and biochemical traits of local landraces of rajmash (Phaseolus vulgaris) of north-western Himalayas

The present study was carried out during rainy (kharif) seasons of 2020 and 2021 at Regional Horticulture Research Station (Sher-e-Kashmir University of Agricultural Sciences and Technology, Jammu, Jammu and Kashmir), Bhaderwah, Doda, Jammu, Jammu and Kashmir to evaluate genetic variability for quantitative and biochemical traits of local landraces of rajmash (Phaseolus vulgaris L.) of north-western Himalayas. Twenty-two induced mutant lines of rajmash generated with gamma rays and ethyl methane sulphonate were screened for quantitative, qualitative and anthracnose reactions under natural and artificial conditions in the field during kharif 2020 (M3) and 2021 (M4). The highly significant differences imply that induced mutant lines for different traits exhibited substantial amount of genetic diversity. Zinc content (55.38) and grain yield/plant (33.24) both had high phenotypic coefficients of variation, while 1000-seed weight (10.14) and protein content had low values (9.83). Zinc content had highest genetic advance, measured as a percentage of the mean, and the highest heritability, followed by grain yield/plant, iron content, number of pods/plant, number of clusters/plant, days to flowering and number of seeds/pod, whereas days to maturity and 1000-seed weight were moderate. The number of pods/plant (0.774), number of seeds/pod (0.556), number of clusters/plant (0.729), length of pod (0.648) and 1000-seed weight (0.620) all exposed a highly significant relationship with grain yield/plant but the days to flowering (-0.636) and days to maturity showed negative correlation (-0.602). It is obvious that the 9 induced mutant lines of Bhaderwah local and Poonch local i.e. R-BL-M3-1, R-BL-M3-9, R-BL-M3-10, R-BL-M3-12, R-BL-M3-13, R-BL-M3-14, R-PL-M3-18, R-PL-M3-20 and R-PL-M3-22 showed the minimum anthracnose disease incidence along with early emergence and superiority in grain yield/plant compared to controls. These mutant lines may be carried forward for the development of mutant genetic stocks and varietal development programmes of rajmash for north-western Himalayan region.

Demonstration of Local Honeybee Flora “Mentesie” (<i>Becium grandflorum</i>) Propagation Techniques in Wag - Himra Zone, Ethiopia

The demonstration of local honeybee flora "Mentesie" (<i>Becium grandiflorum</i>) propagation techniques was carried out over two rainy seasons in the Gazgibla district, Debreweyla watershed closure area of the Northeastern Amhara region. The shrub has numerous benefits for the community, including honey production, fuel use, and soil and water conservation. However, it has been gradually declining. To preserve these valuable shrubs, various propagation techniques were tested. The objectives of the experiment were to demonstrate the propagation techniques of <i>Becium grandiflorum</i> to beekeepers and to generate wider demand for its plantation among beekeepers and extension workers. The experiment compared two selected propagation techniques with local farmers’ traditional planting practices, under the guidance of forestry researchers. The treatments included seeds and cuttings. Seeds were collected from mature fruits, and cuttings were taken early in the morning from natural, mature, young, and healthy mother plants at a height of 40 cm during 2020/21. These materials were packed in perforated polyethylene bags. The average mean of flower numbers, branch numbers, and canopy cover for the enhanced propagation techniques (seedlings with pots) were 4107, 21.81, and 92.5, respectively. These values were higher than those for the comparative propagation technique, which had flower numbers of 2462, branch numbers of 19.4, and a canopy cover of 92.5. There were significant differences (p<0.05) among the propagation techniques in terms of canopy cover, height, number of flowers, and branches per plant. Farmers recognized the higher flower biomass, canopy cover, and potential for greater plant height of the enhanced techniques, which are beneficial for bee forage and soil and water conservation. Therefore, planting seedlings using pots were found to be the best method for the wider production of <i>B. grandiflorum</i> in its natural growing areas.

Assessment Of The Existing And Proposed Dike System Along The Cabulig River In Lower Jasaan, Misamis Oriental, Philippines

Abstract. The issue of flooding in the town of Jasaan in Misamis Oriental province poses a threat to 42% of the population. This is more worrisome during the rainy season, especially in the months of October and December were typhoons are at their strongest and passes in proximity to Mindanao island. Residents have reported significant damage to their properties due to flooding, and typhoons like Super Typhoon Odette in December 2021 have worsened the situation when it brought rain while the dike system was dilapedated. The dike systems in the area have been damaged by these natural disasters, and the lack of repair has made the situation worse. Flood hazard mitigation measures have since been implemented. With the frequent occurrence of flooding in the Cabulig River, a validated model is needed to investigate the behavior of the river during strong and significant rainfall events while taking into consideration the current state of the existing dike systems by coupling the modelling systems HEC-HMS and HEC-RAS. Data from the USGS, DOST-PAGASA, DPWH, and Landsat 8 have been used in this study. The results of the Flood Inundation Analysis showed that most of the flooded areas in Barangay Lower Jasaan and Bobontugan are urban areas which exacerbates during heavy rain events. The results of the simulations of the researchers' proposed dike structures shows that it should be extended towards the upstream direction and a minimum dike height of 2.5m is needed with no discontinuities. A 2.5m high dike on the Bobontugan side should also be placed.

Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization.

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico. Our study investigated changes in the composition and concentration of DOM and evaluated carbon dioxide (CO2)production rates (C-CO2) through laboratory experiments. We compared three sites representing the middle and lower river basins, including their transitional zones, during the rainy and dry seasons. After incubation (120 h at 25°C), the DOM decreased between 25% and 89% of C content. Notably, the initial high proportion of C in DOM in samples from the middle-forested zone and the transition led to elevated C-CO2 rates (>10 mg l-1 day-1), in contrast to the lower initial C proportion and subsequent C-CO2 rates (<7 mg l-1 day-1) in the lower river basin. We also found that dissolved organic carbon uptake and NO3- and NH4+ production were higher during the dry season than in the rainy season. The low water flow in the river during the dry season accentuated the differences in elemental composition and microbial processing of DOM among the sites, while the high water flow of the rainy season homogenized these factors. Our findings indicate that microbial metabolism operates with reduced efficiency in C-rich environments like forests, particularly when faced with high C/N and C/P ratios in DOM. This study highlights the influence of the tropical hydrological regime (rainy and dry seasons) and the longitudinal changes in the river basin (middle and lower) topography and land cover on microbial metabolism by constraining DOM characteristics, emphasizing the crucial role of elemental ratios in river DOM processing.

The Taxonomic and Functional Diversity of Leaf-Litter Dwelling Ants in the Tropical Dry Forest of the Colombian Caribbean

There have been few advances in understanding the organization and dynamics of ants in tropical dry forests. The latter are a seriously threatened ecosystem, and ants are important indicators of diversity, disturbance, and restoration in forest ecosystems. Using diversity data and morphofunctional traits, we evaluated the spatial and temporal variation of taxonomic and functional ant groups; in addition, we explored the variation in functional traits and diversity among communities. Ants were sampled during the dry and rainy seasons using mini-Winkler bags. A total of 9 subfamilies, 57 genera, and 146 species were collected. Ant species composition and richness varied both spatially (75 to 119 species) and temporally (121 and 127 species). The fragments from N2 and N3 showed higher diversity than those from N1. The dissimilarity among all areas was moderate (50–60%), mainly attributable to species turnover processes (77%). Twenty functional groups were identified. The N3 fragments had the highest functional diversity, with lower resistance to species loss, while the N1 and N2 fragments reduced functional diversity and increased similarity among species. Our results highlight the importance of integrating a functional analysis with the taxonomic assessment of ants as an important contribution to understanding the organization and dynamics of this community of insects that inhabit the tropical dry forest.

First report of Curvularia chiangmaiensis causing leaf spot in elephant grass in Brazil.

Elephant grass, Cenchrus purpureus, exhibits high efficiency in sequesting atmospheric CO2 during photosynthesis, leading to significant biomass production. As a C4 plant, it holds immense potential for alternative biodiesel production and serves as fresh feed for cattle (Negawo et al. 2018). Field observations in commercial pastures planted with elephant grass, located in the Brazilian cerrado, revealed necrotic leaf spots with a brownish center and a yellowish halo, reaching a severity of 30 to 50% between 2022 and 2023 in Palmas (10°24'08"S 48°21'45" W) and Gurupi (11°46'21"S 49°02'08" W), municipalities located in the state of Tocantins, Brazil. In both years, the field incidence of the disease on young and mature leaves approached 100% during the rainy season. Affected leaves were collected, packed in a thermal box, and taken to the phytopathology laboratory. The 198 leaves were sanitised in 1% hypochlorite for 30 seconds and washed thrice in sterile water. Upon sanitisation, leaf tissues were cut and cultured on potato dextrose agar (PDA) medium and incubated in a controlled chamber (BOD) at 28°C with a 12-hour photoperiod. Colonies exhibited a greyish colour with whitish edges, and the top plate was brownish, growing to a diameter of 5 cm over seven days. The colonies obtained from monosporic cultures formed curved conidia, predominantly with three septa, of a brownish colour, with lengths ranging from (7 µm to 14 µm and widths from 5 µm to 7 µm. (N=-50, Fig 1) (Yasanthika et al. 2023). The UFTCC01 isolate's DNA was extracted using the extraction kit (PROMEGA ®), amplified for genes (ITS, Gapdh and Tefα1), sequenced (OR345316.1, OR344427.1 and OR344428.1) and compared in BLASTn at Gen Bank deposited sequences. Phylogenetic analysis using the parsimony method in MEGA X identified the isolate as Curvularia chiangmaiensis, showing 99.5% identity with reference sequences (MN215651.1, MN264085.1, and MN263942.1). Concatenated region comparison revealed 94% similarity to sequences (OP564987.1 and MF490814.1) in the phylogenetic tree, confirming the species. The pathogenicity test used 60 seedlings of 50-day-old elephant grass, 30 of which were inoculated with a spore suspension (3.0 × 106 spores/mL) and 30 with sterile water. The solutions were sprayed twice. Only plants inoculated with the spore suspension exhibited symptoms akin to those observed in the field. Then, the fungus was reisolated from the lesions and Koch's postulates were confirmed twice.Previous studies have documented the C. chiangmaiensis pathogenicity in other grasses, such as maise in Thailand (Marin et al. 2017). Our studies constitute the first report of C. chiangmaiensis causing leaf spots on elephant grass in the Brazil.

Effect of Methods of Establishment and Zinc Management on Growth and Yield of Rice (Oryza sativa L.)

The field experiment was conducted at Shradhay Bhagwati Singh Agriculture Research Farm (Hajipur), Chandra Bhanu Gupta Krishi Snatkottar Mahavidyalaya, B.K.T., Lucknow (Uttar Pradesh) during Kharif (rainy) season in 2023-24. The treatment consisted of three methods of establishment (M1 – Direct seeding in lines after pre-irrigation, M2 -Broadcast of sprouted seed on puddled soil , M3 – System of Rice intensification (SRI) of (25 x 25cm) 12 days old seedling.) and five Zinc management practices (Zn0- Without zinc (control), Zn1- Zinc Sulphate ZnSo4@20kg ha-1 (Basal), Zn2- Foliar spray of Zn@0.5% at tillering and panicle initiation stage, Zn3- Seedling dipping in 2% ZnSO4+ 2 Foliar of Zn@0.5% at tillering and Panicle stage, Zn4- Seedling dipping in 2 % ZnSO4 solution+ Foliar spray of Zn@0.2% at tillering and panicle initiation stage) were tested in split-plot design with 3 replications. The Experimental site was silty loam having medium organic carbon (0.70%) and available nitrogen (270 kg ha-1), phosphorous (27 kg ha-1) and Potassium (262 kg ha1). All the growth parameters, yield attributes, yield, Zinc content and uptake of Zn into grains and straw, were increased significantly with SRI method (M3) followed by direct seeding in Lines after pre-irrigation (M2). Amongst zinc management, all the growth parameters and yield attributes of rice were maximum under Seedling dipping in 2% ZnSO4+ 2 Foliar of Zn@0.5% at tillering and panicle initiation stage, followed by Seedling dipping in 2 % ZnSO4 solution+ Foliar spray of Zn@0.2% at tillering and panicle initiation stage the maximum gross income of Rs 158938.18 ha-1 was accrued with (SRI method + T4) treatment combination. However, a combination of SRI method along with T3 treatment accrued the maximum net profit of Rs 107981.21 ha-1 and benefit: cost ratio of 2.08 which was followed by a combination of SRI method along with T4 with net income of Rs 107234.99 ha-1 and benefit cost ratio of 2.07.

A Study on the Water Management Knowledge of Traditional Villages from the Perspective of Stormwater Resilience—A Case Study of Changqi Ancient Village in Guangdong, China

With the advancement of resilience concepts, enhancing resilience capacity has become an effective approach to addressing rainwater and flooding issues. Most rural planning and construction efforts adopt urban planning models from economically developed regions, often leading to surface hardening, which subsequently causes drainage difficulties and severe surface water accumulation during the rainy season. In contrast, traditional Lingnan villages, exemplified by Guangdong’s Changqi Ancient Village, continue to function normally in flood-prone areas, suggesting that their water management knowledge merits investigation. Previous research on rainwater management in traditional Chinese villages has predominantly been qualitative, lacking scientific data support. This study employs an eco-social resilience perspective, combining field surveys and interviews with villagers, and utilizes the SWMM (Storm Water Management Model) software to conduct both qualitative and quantitative analyses of Changqi Ancient Village. The findings reveal the following: (1) The SWMM effectively quantifies rainwater and flood management in traditional villages. (2) From an ecological resilience perspective, the village’s geographical location is crucial. The topography, along with a rainwater regulation system comprising rivers, ponds, ditches, and permeable pavements, significantly influences the village’s drainage performance. (3) From a social resilience perspective, community participation is vital to the long-term stable development of traditional villages. This includes post-disaster collective fundraising by villagers for the restoration of rainwater and flood management facilities, the formulation of village regulations, and the construction and restoration of spiritual sites. (4) From an eco-social resilience perspective, the eco-social resilience system exhibits adaptive cyclical characteristics, where the geographical environment and the local economy significantly shape the ecological spatial patterns of Changqi, while positive interaction between nature and human society ensures the system’s dynamic equilibrium.

Analysis of Paddy Field Changes (1989–2021) Using Landsat Images and Flooding-Assisted MLC in an Urbanizing Tropical Watershed, Vientiane, Lao PDR

Paddy fields are essential for food security and sustaining global dietary needs, yet urban expansion often encroaches on agricultural lands. Analyzing paddy fields and land use/land cover changes over time using satellite images provides critical insights for sustainable food production and balanced urban growth. However, mapping the paddy fields in tropical monsoon areas presents challenges due to persistent weather interference, monsoon-submerged fields, and a lack of training data. To address these challenges, this study proposed a flooding-assisted maximum likelihood classification (F-MLC) method. This approach utilizes accurate training datasets from intersecting flooded paddy field maps from the rainy and dry seasons, combined with the Automated Water Extraction Index (AWEI) to distinguish natural water bodies. The F-MLC method offers a robust solution for accurately mapping paddy fields and land use changes in challenging tropical monsoon climates. The classified images for 1989, 2000, 2013, and 2021 were produced and categorized into the following five major classes: urban areas, vegetation, paddy fields, water bodies, and other lands. The paddy field class derived for each year was validated using samples from various sources, contributing to the overall accuracies ranging from 83.6% to 90.4%, with a Kappa coefficient of between 0.80 and 0.88. The study highlights a significant decrease in paddy fields, while urban areas rapidly increased, replacing 23% of paddy fields between 1989 and 2021 in the watershed. This study demonstrates the potential of the F-MLC method for analyzing paddy fields and other land use changes over time in the tropical watershed. These findings underscore the urgent need for robust policy measures to protect paddy fields by clearly defining urban expansion boundaries, prioritizing paddy field preservation, and integrating these green spaces into urban development plans. Such measures are vital for ensuring a sustainable local food supply, promoting balanced urban growth, and maintaining ecological balance within the watershed.