Botany

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Start date: 2010End date: 2019

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    Spatial Variation in Trophic Structure of Dominant Fish Species in Lake Dongting, China during Dry Season
    (Water, 2018) Yu, J.; Guo, L.; Zhang, H.; Xu, J.; Hu, H.; Xue, T; Luo, C.; Yi, C.; Hu, Y.; De Silva, K.; Xie, P.
    Understanding trophic interactions in food webs is crucial to revealing the transfer of substances and energy from primary food sources to consumers in aquatic ecosystems. We hypothesize that the trophic structure of consumers can be significantly affected by primary food sources (pelagic, benthic, and littoral sources) through complex trophic interactions. This study used stable isotope analysis and Bayesian mixing models to estimate the trophic levels of fish consumers and the contributions of primary food sources in the three sub-lakes (Eastern, Southern, and Western Dongting) of Lake Dongting, which have different physical and chemical parameters of water, fish species diversity, and plankton (phytoplankton and zooplankton) density. Results showed the differences in community structures of fish among sub-lakes. Fish trophic levels were significantly higher in Eastern Dongting than those in the two other areas. The contributions of primary food sources to fishes were as follows: the pelagic source was the main basal food source in Eastern Dongting, and littoral and pelagic sources played equally essential roles in Southern Dongting; fishes in Western Dongting relied on more benthic source to growth than those in the two other regions. This study can fill gaps in our knowledge of the influence of the underlying food available on trophic structure of consumers by exploring the role of primary food sources and making the trophic structure of consumers in the aquatic food web highly complicated and diverse through control of the distribution of primary food sources.
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    Substrate characteristics and species diversity of marine angiosperms in a micro-tidal basin estuary on the west coast of Sri Lanka
    (Sri Lanka Journal of Aquatic Sciences, 2010) De Silva, K.; Amarasinghe, M.
    Diversity of marine angiosperm species (seagrasses) at Kadolkele in Meegamuwa (Negombo) estuary was studied with a view to understanding the effect of substrate characteristics on diversity. Seagrass samples were obtained along three line transects, laid perpendicular to the shoreline at 20 m intervals. Shannon-Wiener index was used to determine the species diversity of seagrasses in the study site at Kadolkele that was divided into three strata, demarcated by the distance, i.e. 0-10 m, 10-20 m and 20-30 m from the shoreline. Comparison of Shannon-Wiener index values indicated that the diversity of first stratum close to the shoreline was significantly different from that of the other two among which no significant difference was found to occur. Substrate pH, soil electrical conductivity, organic mater content and particle size distribution were measured from the substrate samples taken from each stratum. No statistically significant difference was observed with pH (3.92-6.82) and particle size distribution among the three strata. Soil electrical conductivity and organic matter content of stratum 3 however, was significantly different (p< 0.05) from the other two strata. Kadolkele seagrass bed consisted of two species and Halodule pinifolia (5822 shoots m-2) dominated over Halophila ovalis (1030 shoots m-2). The area adjacent (0-3 m) to the mangroves at the shoreline was devoid of seagrasses and H. ovalis was absent in stratum 1, indicating that substrate characteristics have a marginal effect on the species richness of the seagrasses. Although species richness was similar in the other two strata, higher (Shannon) evenness (0.231), despite the relatively low abundance in stratum 2, contributes to its higher species diversity. Present study therefore documents the subtle habitat partitioning of co-existing marine angiosperm species in a limited area in Meegamuwa estuary.
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    Potential impact of predicted sea level rise on carbon sink function of mangrove ecosystems with special reference to Negombo estuary, Sri Lanka
    (Global and Planetary Change, 2018) Perera, K.; De Silva, K.; Amarasinghe, M.
    Unique location in the land-sea interface makes mangrove ecosystems most vulnerable to the impacts of predicted sea level rise due to increasing anthropogenic CO2 emissions. Among others, carbon sink function of these tropical ecosystems that contribute to reduce rising atmospheric CO2 and temperature, could potentially be affected most. Present study was undertaken to explore the extent of impact of the predicted sea level rise for the region on total organic carbon (TOC) pools of the mangrove ecosystems in Negombo estuary located on the west coast of Sri Lanka. Extents of the coastal inundations under minimum (0.09 m) and maximum (0.88 m) sea level rise scenarios of IPCC for 2100 and an intermediate level of 0.48 m were determined with GIS tools. Estimated total capacity of organic carbon retention by these mangrove areas was 499.45 Mg C ha− 1 of which 84% (418.98 Mg C ha− 1) sequestered in the mangrove soil and 16% (80.56 Mg C ha− 1) in the vegetation. Total extent of land area potentially affected by inundation under lowest sea level rise scenario was 218.9 ha, while it was 476.2 ha under intermediate rise and 696.0 ha with the predicted maximum sea level rise. Estimated rate of loss of carbon sink function due to inundation by the sea level rise of 0.09 m is 6.30 Mg C ha− 1 y− 1 while the intermediate sea level rise indicated a loss of 9.92 Mg C ha− 1 y− 1 and under maximum sea level rise scenario, this loss further increases up to 11.32 Mg C ha− 1 y− 1. Adaptation of mangrove plants to withstand inundation and landward migration along with escalated photosynthetic rates, augmented by changing rainfall patterns and availability of nutrients may contribute to reduce the rate of loss of carbon sink function of these mangrove ecosystems. Predictions over change in carbon sequestration function of mangroves in Negombo estuary reveals that it is not only affected by oceanographic and hydrological alterations associated with sea level rise but also by anthropogenic processes, therefore the impacts are site specific in terms of distribution and magnitude.
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    Screening Anti-Bacterial Activity of Endoi.Ichenic Fungi Collected From Negombo Lagoon Sri Lanka
    (Proceedmgs of the Postgraduate Institute of Science Research Congress. Sri Lanka, 2019) Weerasinghe, W.R.H.; Attanayake, R.N.; Weerakoon, G.; Paranagama, P.A.
    From the ancient past, natural products have been in use to fulfill a variety of human needs, from sustenance to pharmaceutical necessities. With the discovery of Endolichenic fungi (ELF) as a novel source prominent bioactiOt1es in recent years. a new trend has been created to explore more about these fascinating organisms, which live inside the lichen thallus asymptomatically. ELF isolated from the lichens collected from mangrove plants In Negombo lagoon's Kadol kale area (Lititude: 701 Longitude: were identitied using molecular techniques and were subjected to anti-bacterual assay. Ethyl acetate crude extracts of 18 identified endolichenic fungal strains were obtained and their anti-bacterial activities were tested against aerobic bactertal species Escherichia coli, Bacillus subtilis and Staphvlococcus aureus. The assay was carried out using agar well diffusion method using HI of the extracts (5 mg/ml) with Azithromycin as the positive control. The inhibition zone diameters (in cm) against E. coli were 1.2 for Phanerothaete chnsosporium. 1.2 for Xvlaria feejecnsis, ().9 for Gelasinospora seminuda, 0.9 for Chaetomium globosum and 1.5 for Curvularia lunata while Azithromycin as the positive control showed a diameter of 2.1. The inhibition zone diameters against B. subtilis were 1.0 for Cochliobolus sp., 1.0 for P. chnsosporium, 1.8 for X. feeyeensls, 1.7 for G. seminuda, 1 2 for C. globosum, 1.5 for Hvpoxvlon lividipigmentum, 2.0 for (Pennicillium sp), 2.2 for C. lunata, 0.9 for Lasiodiplodia theobromae and 2.4 for positive control. The inhibition zone diameters against S. aureus were 1.1 for P. chrvsosporium, 22 for X'. feejeensis, 1.0 for G. seminuda, 1.0 for Chaetomium globosum, 2.0 for (Pennicillium sp). 1.8 for Curvularia lunata and 2.2 for positive control. Out of the 18 fungal strains, 9 showed significant activity against the tested bacterial species while Endomelanconiopsis endophvtica, Neofusicoccum parvum. Ncofusicoccum occulatum. Hvpoxvlon anthochroum. Cvtospora xvlocarpi, Cerrena sp., Schi:ophvllum commune, Daldinia eschscholt:i, Nodulisporium sp. fungal strains did not show any inhibition. Further studies will be conducted to isolate compounds responsible for these inhibitions.
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    Characterization of Agrobacteriu/ll strains from agricultural soils of Bandarawela, Sri Lanka
    (First National Symposium of Sri Lanka Association for Mycology and Plant Pathology (SLAMPP), 2019) Somarathna, G.M.T.K.; Somachandra, K.P.; Jayalath, W.G.H.; Attanayake, R.N.
    Agrobacterium is a Gram negative, rod shaped, aerobic and motile soil inhabiting bacterium of the family Rhizobiaceae. It is well known as the causative agent of crown gall disease of many plant species around the world. However, not all the Agrobacterium strains are pathcvenic and can cause galls. Only the virulent strains cause crown gall disease on number of plant species and are found only in contaminated soils. These virulent strains of A. tumefaciens harbor Ti plasmids with transfer DNA (T-DNA) region and virulence (vir) genes that are responsible for the pathogenicity. virD2 gene codes for virD2 protein and the endonuclease domain of the virD2 protein cleaves T-DNA border sequences. The ipt gene is the T-DNA borne cytokinin synthesis gene. Therefore, the presence of virD2 gene and ipt gene are useful in identifying pathogenic strains of Agrobacterium. The major objective of this research was to determine whether agricultural soils of Bandarawela were contaminated with virulence strains of A. tumefaciens. Soil samples were collected and bacteria were isolated using soil dilution method, and cultured on Yeast Mannitol Acar supplemented with Congo red and on Yeast Extract Peptone Affar. Five pure cultures of putatively Agrobacterium were further characterized using morphological and biochemical tests including Gram staining, catalase test, citrate utilization test, sugar fermentation test and 3-ketolactose test. These testes were often used for the species level identification of A. tumefaciens. Out of five isolates four were rod shaped with rounded ends and were either single or in pairs. However, the other isolate was in chains and Iono rod shaped. Interestingly, all the isolates were positive for all the biochemical tests. However, these tests do not help differentiating the virulence strains. Molecular characterization of all the soil isolates were carried out using universal 16s rRNA primers and Agrobacterium specific primers targeting virD2 and ipt genes. PCR amplification with virD2 primers successfully amplified the targeted band of 224 bp in all five isolates while ipt produced the expected fragment of about 427 bp in three of the isolates. virD2 cene sequences of selected soil isolates were 100-99% similar to the tumefaciens of the GenBank accession CP032925 and CP032929 reported from Taiwan. According to morphological, biochemical, and molecular Characterization using virD2 and ipt genes it was confirmed that the soil in the inspected field of Bandarawela is contaminated with pathogenic strains of A. tumefaciens. Therefore, farmers should maintain awareness when cultivating susceptible plant varieties in these fields.
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    Sclerotinia sclerotiorum populations: clonal or recombining?
    (Tropical Plant Pathology (2019) 44:23–31., 2019) Attanayake, R.N.; Xu, L.; Chen, W.
    Sclerotinia sclerotiorum, a homothallic plant pathogen, undergoes sexual reproduction via haploid selfing (equivalent to clonal reproduction), and produces long-lasting surviving vegetative structures called sclerotia, enhancing clonal persistence and spread. Thus it is not surprising to detect clones of the species. Whether outcrossing can occur in the homothallic S. sclerotiorum remains unanswered. Early studies showed that S. sclerotiorum has a clonal population structure, consistent with its life history traits. However, recent studies using polymorphic and co-dominant molecular markers showed frequent genetic recombination, suggesting outcrossing. This review focuses on recent developments in population genetics studies related to detecting recombination, random association of alleles and dynamic mating type (MAT) alleles in Sclerotinia. Despite frequent reports of random association of alleles, the mechanisms for outcrossing in a homothallic species remain elusive. Recent intriguing findings are: the MAT genes in Sclerotinia are subject to inversion or deletion in every meiotic generation, the MAT gene deletion is related to ascospore dimorphism and mating type switching in S. trifoliorum, and ascospore dimorphism was also observed in S. sclerotiorum. Determining the nature of the dimorphic ascospores and their prevalence in relation to environmental cues could significantly advance our understanding how S. sclerotiorum populations behave in nature
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    Nutritional quality of Cavendish banana (Musa acuminata, AAA) as affected by basil oil and determination of basil oil residues by GC-MS
    (Journal of Science of the University of Kelaniya Volume:10, 2019) Siriwardana, H.; Abeywickrama, K.; Kannangara, S.; Jayawardena., B.
    The effectiveness of basil oil on the nutritional properties of Cavendish banana and chemical composition of basil oil and oil residue levels of treated banana fruits were evaluated in this study. Cavendish banana hands were treated with 1% alum (w/v), 1% alum (w/v) + 0.4% Ocimum basilicum (basil) oil, distilled water (control) and packaged in Low Density Polyethylene (LDPE) bags and stored at a cold room at 12-14ºC. After two weeks of cold storage banana were induced ripened and nutritional contents of treated Cavendish banana were determined. Gas Chromatography - Mass Spectrometry (GC-MS) was instrumental in identifying the chemical constituents of basil oil as well as residues in basil oil treated Cavendish banana peel after two weeks of storage at 12-14ºC.1 Nutritional properties of basil oil treated Cavendish banana showed no adverse changes compared to control. Methyl chavicol (estragole) was the most abundant component (74.44%) of basil oil followed by linalool (15.01%). GC-MS data revealed that negligible amount of residues of basil oil retained in treated Cavendish banana after 14 days. Basil oil treatment and subsequent modified atmosphere packaging of Cavendish banana is recommended as an ecofriendly strategy for air freight or long distance transport over land.
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    Postharvest application of defence elicitors to manage anthracnose in mango Fruit
    (Journal of Science of the University of Kelaniya Volume:10, 2019) Karunanayake, K.O.L.C.
    The use of defense elicitors; which are agents that stimulate or trigger disease resistance responses in plants have proved to be attractive alternatives to hazardous chemical fungicides in recent years. The present study investigated the possibility of using Salicylic acid and Bion® as postharvest elicitors on mango fruit. Three local mango cultivars were used in the study, ‘Karuthacolomban’, ‘Rata’ and ‘Willard’. Salicylic acid was applied as a postharvest spray at concentrations, 100, 500 or 1000 mg/L and Bion® (Acibenzolar-s-methyl, 500 WG, SYNGENTA) at 25, 50, 100 and 200 mg/L. Disease development following artificial inoculation (10 5 conidia / ml suspension) was assessed. Both elicitors were effective (P<0.05) in controlling postharvest anthracnose. The most effective concentration of SA was 500 mg/L for ‘Rata’, 100 mg/ L for ‘Willard’ and both 100 and 500 mg/L for ‘Karuthacolomban’. In Bion® the most effective concentration was 50 ppm for ‘Rata’ and ‘Willard’ and 25 ppm for ‘Karuthacolomban’. In SA treated fruits the percentage reduction in anthracnose ranged from 40- 77 % while values ranged from 67 – 99% for Bion® treated fruits. Results indicate that both SA and Bion® can be used to control postharvest mango fruit loss due to anthracnose.
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    Nutritional quality of Cavendish banana (Musa acuminata, AAA) as affected by basil oil and determination of basil oil residues by GC-MS.
    (Journal of Science 2019, Department of Botany, University of Kelaniya, Sri Lanka, 2019) Siriwardana, H.; Abeywickrama, K.; Kannangara, S.; Jayawardena, B.
    The effectiveness of basil oil on the nutritional properties of Cavendish banana and chemical composition of basil oil and oil residue levels of treated banana fruits were evaluated in this study. Cavendish banana hands were treated with 1% alum (w/v), 1% alum (w/v) + 0.4% Ocimum basilicum (basil) oil, distilled water (control) and packaged in Low Density Polyethylene (LDPE) bags and stored at a cold room at 12-14ºC. After two weeks of cold storage banana were induced ripened and nutritional contents of treated Cavendish banana were determined. Gas Chromatography - Mass Spectrometry (GC-MS) was instrumental in identifying the chemical constituents of basil oil as well as residues in basil oil treated Cavendish banana peel after two weeks of storage at 12-14ºC.1 Nutritional properties of basil oil treated Cavendish banana showed no adverse changes compared to control. Methyl chavicol (estragole) was the most abundant component (74.44%) of basil oil followed by linalool (15.01%). GC-MS data revealed that negligible amount of residues of basil oil retained in treated Cavendish banana after 14 days. Basil oil treatment and subsequent modified atmosphere packaging of Cavendish banana is recommended as an ecofriendly strategy for air freight or long distance transport over land.
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    Morphological Characterization and Molecular Identification of Stem-end Rot Associated Fungal Species Isolated from ‘Karutha Colomban’ Mango Fruits in Sri Lanka
    (The Journal of Agricultural Sciences - Sri Lanka, 2019) Ekanayake, G.; Abeywickrama, K.; Daranagama, A.; Kannangara, S.
    Purpose: Stem-End Rot (SER) is one of the most frequently found mango postharvest diseases in many countries including Sri Lanka. Availability of a significantly detailed study on morphological and molecular characterization of the SER associated fungal species is comparatively low. The present study has been carried out considering the above fact. Research Method: SER disease associated fungi were isolated and identification was carried out using morphological characteristics. Identification was confirmed by phylogenetic analysis of newly generated ITS sequencing data using Maximum Likelihood (ML) with RAxML software (Ver.8.2.10). Findings: From the morphological studies it was observed that the fungal isolates SER1, SER2, SER3 and SER6 produced conidia on Potato Dextrose Agar. Both morphological and molecular results revealed that the isolates of SER1, SER4, SER5, and SER6 which were isolated from diseased Karutha Colomban mango fruits with SER (in Sri Lanka) belong to Lasiodiplodia sp., Nodulisporium sp., Xylaria feejeensis and Pestalotiopsis sp. respectively. Both SER2 and SER3 were confirmed as Phomopsis sp. During the present study two new fungal species (Xylaria spp. and Nodulisporium spp.) were also identified for the first time from SER of Karutha Colomban mango fruits. Research Limitations: The pathogenicity of these isolates will be tested in near future, since the study was mainly focused on the isolation and identification of the SER associated fungal species. Originality/ Value: Results of the present study will be very valuable for stakeholders in Agricultural sector, before designing control strategies at post-harvest level in order to minimize the loss and extend the storage life of mango.