JournalTOCs

Tropical Agricultural Research
Number of Followers: 2

This is an Open Access Journal

Open Access journal
ISSN (Print) 1016-1422
Published by Sri Lanka Journals Online

[71 journals]

Insecticide Resistance, Resistance Mechanisms, and Phylogeny of Three
Myzus persicae Populations in Cabbage from Three Agroclimatic Zones of Sri
Lanka
- Abstract: The aphid, Myzus persicae is an important sucking pest and a virus vector in many crops. The management of M. persicae is mainly through synthetic pesticides. The development of resistance against common pesticides has resulted in control failures of M. persicae. The objective of this study was to examine the status of pesticide resistance and the genetic structure of M. persicae populations. Samples were collected from cabbage cultivations in the dry (Anuradhapura), wet (Kandy), and intermediate (Badulla) zones of Sri Lanka during 2017-2019. Bioassays were conducted against five insecticides using the leaf dip method. Biochemical assays examined the activity of insecticide detoxifying enzymes and the insensitivity of the organophosphate/carbamate target site, acetylcholinesterases (AChEs) in the Badulla and Kandy populations. A 636 bp mtCOI gene sequence was used to infer the phylogeny. The resistance spectrum of the populations was low to moderate; 17-25% resistance to thiamethoxam, 11-15% to acetamiprid, 20-28 % to carbosulfan, 20-41 % to etofenprox, and 4-9 % to profenofos. Elevated activity of esterases (specific activities 0.91-1.11 μmol/min/mg protein) and glutathione S-transferases (1.27-1.82 μmol/min/mg protein) were observed for increased metabolism of pesticides. Monooxygenase-based detoxification was noticeable in neonicotinoid resistance. Insensitive AChEs contribute to organophosphate and carbamate resistance. Phylogenetic analysis revealed that 2 haplotypes of the studied mtCOI gene sequence are present in the three populations tested, indicating that environmental and biological pressure, including pesticide selection pressure, may be contributing to the emergence of novel genotypes of M. persicae. Published on 2023-04-01 00:00:00
Total Phenolic Content, Antioxidant Activity and in vitro Bioaccessibility
in “Gasnivithi” (Talinum triangulare) and “Keren koku”
(Acrostichum aureum) Available in Sri Lanka
- Abstract: Underutilized wild edible species or neglected crop species are still used at low levels within the local communities, but show a high potential to contribute to the food supply with more health benefits. This study was conducted to assess the nutritional properties of two underutilized wild edible species, namely, Acrostichum aureum and Talinum triangulare available in Sri Lanka. Plant extracts were analyzed for their ascorbic acid content, total phenolic content, antioxidant activities, and mineral contents (Ca, Cu, Zn, and Fe). Bioaccessibility of minerals was also tested through an in vitro digestion model. Ca is the most abundant micronutrient (45.61–102.91 mg/100 g) in both tested species, while the in vitro bioaccessibility assay shows a higher fraction of Ca (47.46%) in A. aureum and Cu (64.68%) in T. triangulare. The highest concentrations of ascorbic acid and total phenolic content were found in T. triangulare (AAC: 165 mg/100 g; TPC: GAE,34.8 mg/100 g). Studied species were found to have significant antioxidant activities as evaluated by two different methods, such as DPPH and ABTS radical scavenging activity. In relation to the tested data, T. triangulare has shown the greatest antioxidant activity in both methods. Hence, consumption of identified underutilized plant species may serve as good sources of antioxidants and minerals in their natural form. Published on 2023-04-01 00:00:00
Comparison of High-Performance Liquid Chromatography (HPLC) Profiles and
Antimicrobial Activity of Different Cinnamomum Species in Sri Lanka
- Abstract: The demand for Ceylon cinnamon (Cinnamomum verum syn. C. zeylanicum ) is consistent due to its superior characteristics. Besides that, Sri Lanka is home to seven other wild species: Cinnamomum capparu-coronde, Cinnamomum citriodorum, Cinnamomum dubium, Cinnamomum litseifolium, Cinnamomum ovalifolium, Cinnamomum rivulorum, and Cinnamomum sinharajaense. Since cinnamon bark contains more than seventy bioactive compounds, it possesses various pharmacological and health benefits, including antimicrobial activity. Even though there is some literature on the antimicrobial activity and chemical composition of C. verum, wild species have not been studied yet. The present study evaluated the antimicrobial activity and biochemical compounds of Cinnamomum species found in Sri Lanka using bark methanol extract and crude. Trans-cinnamaldehyde, cinnamyl alcohol, cinnamyl acetate, coumaric acid, and coumarin were quantified using HPLC techniques. The antimicrobial properties were evaluated by disc diffusion assay against two standard pathogenic strains, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. There were no detectable coumarin or coumaric acid levels in any of the species. The highest trans-cinnamaldehyde content and antimicrobial activity were observed in C. verum, followed by C. sinharajaense and C. capparu-coronde. Further, C. ovalifolium, C. dubium, and C. rivulorum did not show positive inhibition zones against the two pathogenic strains and detectable levels of trans-cinnamaldehyde. Moreover, the results showed a strong positive correlation between antimicrobial activity and trans-cinnamaldehyde content. The results suggest that the antibacterial activity of C. sinharajaense and C. capparu-coronde should be tested against a broader range of pathogenic strains and could be useful in future breeding programs. Published on 2023-04-01 00:00:00
Rainfall and Streamflow Trends in the Upper Maduru Oya Sub-watershed in
Sri Lanka: A Comparative Study Using Different Statistical Methods
- Abstract: Analysis of historical data on rainfall and streamflow provides useful information for water resources management in a river basin. The objective of this study was to assess the variations and trend analysis of rainfall and streamflow data in the upper Maduru Oya sub watershed in Sri Lanka during a 30 year period (1989 October to 2019 September) using daily rainfall data from two gauging locations (Padiyathalawa and Bibile) and daily average streamflow data from one gauging location (Padiyathalawa). Descriptive statistics were used to assess the variations. The Mann Kendal Trend Test (MK test) and Innovative Trend Analysis method (ITA) were used to analyze the trend, and Sen’s Slope Estimator was used to assess the magnitude of the trend. Based on the MK test, most of the rainfall trends obtained are in an increasing direction, and streamflow trends are in a decreasing direction. Rainfall trends found in Padiyathalawa are not statistically significant. Annual, First Inter Monsoon, March, and May time scales of rainfall showed significant upward trends at Bibile (p<0.1) while streamflow in January, April, and September showed significant negative trends (p<0.1) at Padiyathalawa. The results displayed by all three tests were in very good agreement for rainfall. ITA results showed similar trend types of 77%, 95% and 41% at Padiyathalawa and Bibile rainfall and streamflow, respectively. A significant positive (ρ<0.01) strong and lower correlation between the trend value of the ITA and the Z value of the MK test were found for rainfall and streamflow, respectively. Changes in rainfall are not sufficient to explain the observed trends in streamflow. Therefore, future research should be directed at the causal aspects of streamflow change in this watershed. Published on 2023-04-01 00:00:00
Livelihood Resilience of Smallholder Dairy Farmers Against External
Shocks: A Case Study in the Northern Dry Zone of Sri Lanka
- Abstract: Improving dairy farmers’ livelihood resilience helps them sustain farming and reap higher economic returns. This study was conducted in the Jaffna District, part of the dry zone of Sri Lanka. Households’ livelihood resilience to environmental challenges and shocks was determined through the Structural Equation Model (SEM). The SEM path diagram was developed based on the Resilience Model developed by FAO, which uses resilience as a latent variable and is a function of six components that are not directly measured from the data set. The SEM analysis revealed that the latent variable ‘livelihood resilience’ correlates positively and significantly with the five components. Further, the study found that the independent variables, such as dietary diversity index (P> z =0.081), the quality score of health services (P> z =0.052), frequency of assistance (P> z =0.000), quality evaluation of assistance (P> z =0.000), land owned (P> z =0.086), educational level (P> z =0.017), and the number of household members who lost their jobs (P> z =0.010), significantly influenced the livelihood resilience of the dairy farmers. The findings of this study will help develop a policy framework that could support gaining sustainability in milk production through fostering the livelihood resilience of the dairy farmers in the Northern Dry Zone of Sri Lanka. Published on 2023-04-01 00:00:00
Assessment of Virtual Water of Irrigated Agriculture, Imports, Exports and
Water Footprint for Sri Lanka
- Abstract: Irrigated agriculture is the highest water user in Sri Lanka. Therefore, when there is an increasing demand of other sectors such as drinking, industries, environment etc., it is required to reallocate water from the irrigated agriculture sector to meet this increased demand. However, this needs to be done while ensuring the food security of the nation using the virtual water concept, which is defined as the embedded water in a product. Therefore, this study is conducted with the objective of assessing the, i) virtual water of agricultural production, ii)virtual water of food imports and exports, iii) virtualwater trade and iv) water footprint of the nation. The dataon crop water requirements, extent cultivated, imported,and exported agricultural products were collected fromsecondary sources and the analysis was made accordingto the globally accepted methodology. The annual virtualwater value of domestic production is found to be 8.13Gm3 of which paddy contributes 54.7%. The averagevirtual water value of paddy in Maha season is less thanthat in the Yala season whilst the virtual water value ofpaddy in minor schemes are higher than that in the majorschemes in both seasons implying that more water isrequired to produce 1kg of paddy in minor schemes. Thenet import of Virtual water is 3.8 Gm3 per year. The waterfootprint of Sri Lanka is 12.0 Gm3 per year with a percapita water footprint of 535.22 m3 per year. The waterrequired for domestic production is about 15.8% of thesurface runoff of the country indicating the possibility ofmeeting the food demand with the available waterresources. Published on 2023-04-01 00:00:00
Comparative Assessment of Soil Chemical Characteristics in Two Contrasting
Vegetable Cultivation Systems of Sri Lanka
- Abstract: Vegetable cultivating systems in Sri Lanka are characterized by intensive and highly commercialized with very high agricultural inputs. Diagnosing soil fertility levels is essential to supply plant nutrients in a complete and balanced manner minimizing environmental pollution. The objective of this study was to assess soil chemical properties in two intensive vegetable cultivating systems in central highlands of Sri Lanka. Study was conducted in two contrasting vegetable cultivating systems: vegetable-potato-vegetable in Nuwara Eliya (NE) and vegetable-paddy-vegetable in Marassana (M). Soil samples were analyzed for pH, pH-buffer capacity (pHBC), electrical conductivity (EC), cation exchange capacity (CEC), total carbon (TC), total nitrogen (TN), available nutrients such as Phosphorus (P), Potassium (K), Magnesium (Mg), Sulphur (S), Copper (Cu) and Zink (Zn) and optimum values were compared. Among measured properties pHBC, EC, TC%, TN%, from nutrients P, K, Mg, S, and Zn were significantly high (P
Development and Validation of a Model to Simulate Phenology, Canopy Growth
and Yield of Maize, Mungbean and Tomato under Tropical Farming Systems
- Abstract: A significant portion of crop production in the tropics occurs at subsistence level with high vulnerability to climate change. Process-based crop simulation models are effective tools to predict environmental impacts, including climate change effects, and make management decisions on crop production. The principal objective of this work was to develop crop-specific simulation models to predict phenology, canopy growth, and yield performance of maize, mungbean, and tomato crops grown in the tropics, with special relevance to locally adapted inbred germplasm. The developed models consisted of sub-models to simulate canopy growth, radiation interception and conversion, and dry matter partitioning. All sub-models were parameterized by detailed measurements of leaf growth, dry matter accumulation, and partitioning on locally adapted varieties of the three crops over two cropping seasons. The same crop varieties were established in a multi-locational field experiment spanning a sufficiently wide temperature gradient over four cropping seasons for model validation. Models were validated by comparing model predictions of phenological development and yield against field observations and additional secondary data from the literature. Overall, simulated phenological development (R2>0.5, RMSE<5 days for all three crops) and yield (R2>0.5, RMSE<68, 48 and 476 g/m2 for maize, mungbean, and tomato, respectively) of the three crops were in agreement with the observed data under a wide range of environmental conditions. These modelling approaches can be successfully applied to open-pollinated (maize) and inbred varieties (mungbean and tomato) growing under the farmer fields in tropical South Asia. Published on 2023-01-01 00:00:00
Development of Liquid Culture System for Rapid Multiplication of
Gyrinops walla
- Abstract: Agarwood is an expensive resinous compound, produced by Gyrinops walla as defence response to external damages. The tissue culture technique is the best alternative for both rapid multiplication and product synthesis. This study demonstrated an efficient method of rapid multiplication using liquid cultures for G. walla. MS medium supplemented with 1.0 mg/L BAP and 0.1 mg/L IBA, 100 mg/L Myoinositol and 30.0 g/L of sucrose, and 3.0 g/L Phytagel (Sigma-Aldrich) was used as the control (T0). The effect of shoot growth on liquid culture on the same medium was investigated without inert support (T1) and kept on a shaker, with the support of filter paper bridges (T2), rigid support (T3), wet foam (T4), and a double layer of liquid and semi-solid medium (T5). At the end of the sixth week, growth rates and cell doubling times were calculated. Results showed significant differences between treatments at α=0.05 probability level (P< 0.0001). All liquid cultures except T3 stimulate the biomass. T1 had the highest growth rate (0.38 g/week) and the shortest cell doubling time (1.82 weeks) of G. walla (11-13 shoots from one shoot), but it also had hyperhydricity, which was overcome by combining liquid cultures with a flexible matrix or using a double-layer system. The nature of the matrix was found to be a vital factor in achieving the desired benefits of the liquid cultures. The use of a matrix is unnecessary if T5 is used to achieve the desired results. Published on 2023-01-01 00:00:00
Evaluation and Characterization of Saccharum Germplasm for Sugarcane
Breeding in Sri Lanka
- Abstract: Genetically-variable sugarcane progenies are generated through the crossing of parents. The commercial varieties with high cane and sugar yields, moderate fibre content, pest and disease resistance, and high adaptability to growing conditions are selected from these progenies. This study was conducted to identify parents with high combining ability of most of these characteristics into the progenies for efficient variety selection in sugarcane breeding. In this regard, 508 accessions from the Saccharum germplasm were assessed for their commercial attributes. Data on cane and sugar yield components were collected from each accession. Phenotypic correlations were estimated for each pair of characteristics. Principal component analysis was performed, and subsequently, cluster analysis was done based on the first three principal components. Phenotypic relationships revealed that the plot yield of an accession is mainly determined by the number of stalks and stalk length, suggesting that accessions with a higher number of stalks and longer stalk lengths can be taken as promising parents for breeding for cane yield. The strong positive relationships of brix to other components of sugar content proved that the parents with high sugar can be classified by hand brix. The selected PCs clustered the accessions into four groups. Group 1 comprises the parental core collection for generating progenies with moderate cane yield, high sugar yield, and moderate fibre content, whilst accessions in group 3 can be used for breeding energy cane. The accessions SLC 91 46 and S 2003-US-247 were identified as the most promising parents in the simultaneous improvement of cane and sugar yields with moderate fibre content. Published on 2023-01-01 00:00:00