Plant and Molecular Biology

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Root-foraging behavior ensures the integrated growth of Vallisneria natans in heterogeneous sediments
(Environmental Science and Pollution Research, 2017) Chen, J.; Hu, X.; Cao, T.; Zhang, X.; Xi, Y.; Wen, X.; Su, H.; De Silva, W.; Zhu, T.; Ni, L.; Xie, P.
Abstract The present study was carried out to determine the efficacy of root foraging and the physiological response of Vallisnaria natans grown in heterogeneous sediments. V. natans was cultivated in two homogeneous and two heterogeneous sediments. The results suggested that V. natans grown in heterogeneous sediments presented a significantly higher root proportion in its total biomass, exhibited root foraging, and grew well, as indicated by a total biomass, ramet number, and plant height very close to those of plants grown in nutrient-rich clay sediment. Moreover, the more sensitive physiological response of the roots than the stems or the leaves to sediment nutrients suggested that root foraging occurred, and the approached values between the two heterogeneous sediments and the homogeneous clay sediment indicated that V. natans could satisfy its nutrient requirements via root foraging. The results may be useful in the recovery of macrophytes that remodel part (rather than all) of the substrate and can potentially improve habitats that are unsuitable for plant growth.
High diversity of Ganoderma and Amauroderma (Ganodermataceae, Polyporales) in Hainan Island, China
(Mycosphere, 2018) Hapuarachchi, K.K.; Karunarathna, S.C.; Raspé, O; De Silva, K.H.W.L.; Thawthong, A.; Wu, X.L.; Kakumyan, P.; Hyde, K.D.; Wen, T.C.
Species of Amauroderma and Ganoderma (Ganodermataceae) have been widely used as traditional medicines in Asia over many centuries. The genera are widely researched, owing to their beneficial medicinal properties and chemical constituents with potential nutritional and therapeutic uses. There are, however, taxonomic confusions surrounding the species in these genera, whose circumscription is often unclear. We surveyed species of Amauroderma and Ganoderma in Hainan Island in Southern China. In this paper, we provide data on 15 species found in the W uzhishan and Jiangfengling mountains on the island. One species named Ganoderma ellipsoideum Hapuar., T.C. Wen & K.D. Hyde, sp. nov. is new to science and introduced with evidence from morphology and molecular analysis. The other species collected are described with photographs and compared with similar taxa. We provide a phylogeny for the two genera based on ITS sequence data and the taxonomic status of the species is briefly discussed.
Effectiveness of protected areas in preventing rubber expansion and deforestation in Xishuangbanna, Southwest China
(Land Degradation & Development, 2018) Sarathchandra, C.; Dossa, G.G.; Ranjitkar, N.B.; Chen, H.; Deli, Z.; Ranjitkar, S.; De Silva, K.H.W.L.; Wickramasinghe, S.; Xu, J.; Harrison, R.D.
Protected areas (PAs) are supposedly key refuges for the world's remaining biodiversity. Our study site, Xishuangbanna, harbors a high proportion of China's biodiversity but is threatened by rapid deforestation and expansion of monoculture rubber. We quantified the success of Xishuangbanna's PAs in preventing deforestation.Most previous analyses of PA effectiveness have insufficiently accounted for biases arising from PA location and establishment, because they overlooked the importance of site‐matching in accounting for landscape change.We used matching methods to minimize such biases in comparing land use conversion rates inside and outside‐PAs. By 2010, Xishuangbanna had 3,455.5 km2 (~18%) designated as PAs. However, rubber occupied 22% of its land area and was expanding at a rate of 153.4 km2/year. Between 1988 and 2010, conventional analysis showed a deforestation rate of 9.3 km2/year. However, matching analysis showed a significantly higher rate of deforestation, 10.7 km2/year, which resulted in the deforestation of ~11% of PA's land. We argue that PAs were less effective than had previously been thought. The situation worsened from 2002 to 2010, when the deforestation rate within PAs was actually higher than that of outside PAs, although this difference was not significant. The designated higher levels of protection in ‘core’ zones were also unsuccessful in preventing deforestation. At current rates, within the next 50 years, a further 16% of PAs would be deforested in Xishuangbanna. This could even be an underestimate, as without intervention, drivers of deforestation tend to accelerate. Therefore, reviewing and strengthening current PA management policies is essential.
Potential spreading risk of an invasive snail species (Pomacea canaliculata) in freshwater habitats of Asia
(Current Science, 2019) De Silva, W.; Cao, T.; Wen, Z.; Zhang, X.; Ni, L.
The invasive success of the freshwater snail species (Pomacea canaliculata) continues to wreak havoc around the world. The present study was initiated to analyse spatial trend and associated environmental conditions related to the invasive success of P. canaliculata in Asia. Systematic searches were performed to identify relevant studies through different databases, and appropriate statistical methods like spatial autocorrelation, standard deviational ellipse method and PCA were used to generate new knowledge on this species. The potential invasive range of this species is between 40°N and 40°S lat. The present study reveals that the spatial distribution of P. canaliculata is most significantly correlated with human population density, followed by humidity, temperature and precipitation. Moreover, the grazing rates are dramatically affected by nutrient content of freshwater macrophytes. Spatial autocorrelation analysis result indicates clustered dispersion pattern of this snail, and standard deviational ellipse depicts the invasion trend of P. canaliculata moving from East Asia to potential areas in South and West Asia. We therefore conclude that P. canaliculata is likely to be the ‘next harmful visitor’ to South and West Asian countries.
Phylogenetic Revision of Savoryellaceae and Evidence for Its Ranking as a Subclass
(Front. Cell. Infect. Microbiology, 2019) Dayarathne, M.C.; Maharachchikumbura, S.S.N.; Jones, E.B.G.; Dong, W.; Devadatha, B.; Yang, J.; Ekanayaka, A.H.; De Silva, W.; Sarma, VV.; Al-Sadi, A.M.; Khongphinitbunjong, K; Hyde, K.D.; Zhao, R.L.
Morphology, phylogeny, and molecular clock analyses were carried out on Savoryellaceae in order to understand the placements of taxa in this family. Ascotaiwania and Neoascotaiwania formed a well-supported separate clade in the phylogeny of concatenated partial SSU, LSU, TEF, and RPB2 gene data. These two genera share similar morphological features, especially in their asexual morphs, indicating that they are congeneric. Hence, we synonymize Neoascotaiwania under Ascotaiwania. Ascotaiwania hughesii (and its asexual morph, Helicoon farinosum) and Monotosporella setosa grouped in a clade sister to Pleurotheciales and are excluded from Ascotaiwania which becomes monophyletic. A novel genus Helicoascotaiwania is introduced to accommodate Ascotaiwania hughesii and its asexual morph, Helicoon farinosum. A novel species, Savoryella yunnanensis is introduced from a freshwater habitat in Yunnan Province, China. Comprehensive descriptions and illustrations are provided for selected taxa in this family. In addition, we provide evolutionary divergence estimates for Savoryellomycetidae taxa and major marine based taxa to support our phylogenetic and morphological investigations. The taxonomic placement of these marine-based taxa is briefly discussed. Our results indicate that the most basal group of marine-based taxa are represented within Lulworthiales, which diverged from ancestral Sordariomycetes around 149 Mya (91–209) and Savoryellomycetidae around 213 Mya (198–303).
Pathogenicity of Stem-end Rot Associated Fungi Isolated from Karthakolomban Mango and Their Control by Spray and Fumigation Treatments with Selected Essential OilsPathogenicity of Stem-end Rot Associated Fungi Isolated from Karthakolomban Mango and Their Control by Spray and Fumigation Treatments with Selected Essential Oils
(The Journal of Agricultural Sciences - Sri Lanka, 2020) Kodituwakku, T. D.; Abeywickrama, K.; Karunanayake, K. O. L. C.
Purpose: Stem-end rot (SER) is a major disease of mango that causes serious postharvest losses. Application of fungicides is environmentally unsound and is being practiced currently in its control. This study was conducted to develop essential oil treatment systems as eco-friendly strategies to control SER of Karthakolomban mango and to determine the pathogenicity of several SER associated fungi. Research Method: Pathogenicity of four fungal isolates in SER was assessed by inoculating them on Karthakolomban mango fruits. Karthakolomban mango fruits were subjected to spray and fumigation treatments using four essential oils and their pathological, physicochemical and sensory properties were evaluated after a 8-day storage at 12 – 14 ºC. Findings: Lasiodiplodia theobromae, Pestalotiopsis sp., Phomopsis sp. and Xylaria feejeensis were the major SER pathogens of mango. X. feejeensis was identifi ed as a SER pathogen for the fi rst time in Sri Lanka. Spray and fumigation treatments conducted using basil, clove, cinnamon leaf and cinnamon bark oils eff ectively controlled SER of Karthakolomban mango stored at 12 – 14 ºC for 8 days. Mango sprayed with 1.6 μL/mL cinnamon bark oil has displayed no SER after induced ripening. None of the treatments caused drastic alterations in physicochemical and sensory properties of mango. Research Limitations: Storage period of mango was restricted to 8 days due to the initiation of natural ripening which was the major limitation to achieving a further enhanced shelf life. Originality/value: The treatment strategies developed by this research could be commercialized as biosafe SER control strategies in reducing postharvest losses of mango in the local and international trade.
Potential of Trichoderma harzianum and Trichoderma virens in controlling Meloidogyne incognita on Basella alba
(International Conference on Applied and Pure Sciences, 2020 Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Rajakaruna, R. M. N. P.; Kannangara, B. T. S. D. P.
Meloidogyne incognita, the root knot nematodes are a widely spread group of plant pathogens that affect a variety of economically important plants. Even though chemical nematicides are used to control the nematodes at present, these nematicides pose a huge threat to the environment. Taking this fact into account usage of nematophagous fungi has gained popularity as a more ecofriendly approach to control nematodes. Trichoderma spp. has a great ability to control nematodes by using trapping mechanisms and by secreting nematicidal metabolites. The present study focuses on the potential of using Trichoderma harzianum and T. virens in controlling Meloidogyne incognita. Three weeks old healthy nematode free Basella alba L. (Indian spinach) seedlings were subjected to five different treatments; Soil, Soil+ Nematodes, Soil + Nematodes + Nematicides, Soil + Nematodes + T. harzianum and Soil + Nematodes + T. virens. Six replicate samples were considered for each treatment. The plants were maintained in a homogenous environment. Some below ground direct growth parameters including number of galls, length, fresh weight and the dry weight of the tap root were measured at one month intervals up to three months. As Meloidogyne incognita develop disease symptoms mainly in the root system of Basella alba plants the above ground indirect systems were not considered in the present study. The data collected were analyzed using MINITAB version 18 statistical software. At the end of the second sampling time, the plants grown on soil treated with nematodes alone had a significantly higher number of galls (72 ± 6.97) compared to those treated with nematodes + T. harzianum (7 ± 0.516) ,nematodes + T. virens (8 ± 0.211) and nematodes and nematicides (32 ± 6.98 ) . However a significant difference was not observed in the length of the tap root. This may be because length of the tap root is not directly affected by the Meloidogyne incognita infection. At the end of the third sampling time, the fresh weight (14.42 g ± 1.29) and the dry weight (10.67 g ± 0.29) of the roots of plants infected with nematodes, were significantly higher than the fresh weight(3.83 g ± 0.55 ) and dry weight(2.34 g ± 0.51) of the roots of plants grown in soil. This study clearly indicates that both T. harzianum and T. virens have a great potential to be used as biocontrol agents of the root knot nematode Meloidogyne incognita in Basella alba L. This present study can be further improved by investigating the mechanisms employed by Trichoderma harzianum and Trichoderma virens in controlling Meloidogyne incognita.
Effect of Trichoderma virens on vegetative and reproductive growth of Capsicum annuum cv. MI2 (green chilli)
(International Conference on Applied and Pure Sciences, 2020 Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Sakalasooriya, S. M. C. P.; Kannangara, B. T. S. D. P.; Jayasekara, L. R.
Plant Growth Promoting Fungi (PGPF) facilitate a favorable interaction with plants in the rhizosphere through several biological processes. PGPF play a significant role in phytostimulation, phytoremediation and biofertilization. The use of PGPF as a biofertilizer has steadily increased in sustainable agriculture to reduce the use of chemical fertilizers. The objective of the present study is to investigate the effect of Trichoderma virens on vegetative and reproductive growth of Capsicum annuum cv. MI2 (green chilli). The trials were conducted in a greenhouse in the botanical garden, University of Kelaniya. Six weeks-old seedlings of C. annuum cv. MI2 were transplanted in solarized potting medium prepared by mixing topsoil and compost (3:1), filled into grow bags. Four treatments (103, 105, 107 conidia/ mL) including control (treated with Urea, Triple superphostphate and Muriate of Potash) were carried out along with five replications. Potting medium was inoculated with the conidial suspensions at the time of transplanting, followed by four inoculations until the time of uprooting. At the completion of 10 weeks after transplanting, the plants were uprooted, measured and represented as a percentage increment compared to the control; for the vegetative (shoot height, number of leaves, leaf area, average leaf length, girth of tap root, total leaf chlorophyll, fresh and dry weights of shoot and root mass) and reproductive parameters (number of buds, flowers and pods) of C. annuum cv. MI2. The plants treated with 107 conidia of T. virens per mL showed a significant increase in growth parameters of shoot height (18.55%), leaf number (79.78%), fresh weight of shoot (122.4%), fresh weight of root (14.17 %) and a significant increase in reproductive parameters of, number of buds (18.18%), and number of pods (143.75%) compared to the control was observed. Moreover, the plants treated with 105 conidia of T. virens per mL showed a significant enhancement in the growth parameters, leaf area (17.63%), total chlorophyll content (8.87%) and dry weight of root (54.16%) compared to the control. Present study clearly indicated that C. annuum cv. MI2 show better vegetative, as well as reproductive growth performance, when treated with conidial suspensions of T. virens. Therefore, T. virens can be suggested as a potential biofertilizer for C. annuum cv. MI2.
Fungi vs. Fungi in Biocontrol: An Overview of Fungal Antagonists Applied Against Fungal Plant Pathogens
(Front. Cell. Infect. Microbiology, 2020) Thambugala, K.M.; Daranagama, D.A.; Phillips, A.J.L.; Kannangara, S.D.; Promputtha, I.
Plant pathogens cause severe losses or damage to crops worldwide and thereby significantly reduce the quality and quantity of agricultural commodities. World tendencies are shifting towards reducing the usage of chemically synthesized pesticides, while various biocontrol methods, strategies and approaches are being used in plant disease management. Fungal antagonists play a significant role in controlling plant pathogens and diseases and they are used as Biocontrol Agents (BCAs) throughout the world. This review provides a comprehensive list of fungal BCAs used against fungal plant pathogens according to modern taxonomic concepts, and clarifies their phylogenetic relationships because thewrong names are frequently used in the literature of biocontrol. Details of approximately 300 fungal antagonists belonging to 13 classes and 113 genera are listed together with the target pathogens and corresponding plant diseases. Trichoderma is identified as the genus with greatest potential comprising 25 biocontrol agents that have been used against a number of plant fungal diseases. In addition to Trichoderma, nine genera are recognized as significant comprising five or more known antagonistic species, namely, Alternaria, Aspergillus, Candida, Fusarium, Penicillium, Pichia, Pythium, Talaromyces, and Verticillium. A phylogenetic analysis based on partial sequences of the 28S nrRNA gene (LSU) of fungal antagonists was performed to establish their phylogenetic relationships.
In vitro antifungal effi cacy of selected essential oils in controlling fungi associated with the stem-end rot disease of mango (cv. Karutha Colomban) fruits and characterisation of antifungal components
(Journal of the National Science Foundation of Sri Lanka,, 2020) Kodituwakku, T.; Ekanayake, G.; Abeywickrama, K; Jayakody, R.
Karutha Colomban is one of the most delightful mango varieties popular among Sri Lankan consumers. A signifi cant postharvest loss of mango takes place every season due to diseases including stem-end rot (SER), which is caused by a group of endophytic fungal pathogens. In this research, in vitro antifungal effi cacy of diff erent concentrations of essential oils of basil, clove, and cinnamon were evaluated for their ability to control SER causing fungal pathogens of mango (cv. Karutha Colomban) as bio-safe alternatives to conventional fungicides, by conducting liquid and disc volatilisation bioassays. Major bioactive compounds of the selected essential oils were identifi ed by gas chromatography-mass spectroscopy (GC-MS). Basil and cinnamon bark oils (0.20 – 0.30 μL/mL) in liquid bioassay showed high effi cacy against Lasiodiplodia theobromae, while basil and cinnamon leaf oils (0.40 – 0.60 μL/mL) successfully inhibited Pestalotiopsis sp. Cinnamon bark oil (0.60 μL/mL) was identifi ed as the most eff ective oil against Phomopsis sp. According to disc volatilisation bioassay, vapour of cinnamon oils (0.20 – 0.40 μL/mL) was the most eff ective in controlling L. theobromae. Pestalotiopsis sp. was effi ciently controlled by clove and cinnamon bark oil (0.20 – 0.60 μL/mL) vapour. In vapour phase, clove and cinnamon oils (0.40 μL/mL) were the most eff ective against Phomopsis sp. According to GC-MS characterisation, methyl chavicol was the most abundant antifungal component in basil oil while it was (E)-cinnamaldehyde in cinnamon bark oil. Moreover, eugenol displayed the highest abundance in clove and cinnamon leaf oils. Based on in vitro studies, it could be concluded that cinnamon bark oil in liquid and vapour phases demonstrated a higher antifungal effi cacy among the tested essential oils in controlling fungal pathogens causing SER of mango.
Fungi vs. Fungi in Biocontrol: An Overview of Fungal Antagonists Applied Against Fungal Plant Pathogens
(Frontiers in Cellular and Infection Microbiology, 2020) Thambugala, K. M.; Daranagama, D. A.; Phillips, A. J. L.; Kannangara, S. D.; Promputtha, I.
Plant pathogens cause severe losses or damage to crops worldwide and thereby significantly reduce the quality and quantity of agricultural commodities. World tendencies are shifting towards reducing the usage of chemically synthesized pesticides, while various biocontrol methods, strategies and approaches are being used in plant disease management. Fungal antagonists play a significant role in controlling plant pathogens and diseases and they are used as Biocontrol Agents (BCAs) throughout the world. This review provides a comprehensive list of fungal BCAs used against fungal plant pathogens according to modern taxonomic concepts, and clarifies their phylogenetic relationships because thewrong names are frequently used in the literature of biocontrol. Details of approximately 300 fungal antagonists belonging to 13 classes and 113 genera are listed together with the target pathogens and corresponding plant diseases. Trichoderma is identified as the genus with greatest potential comprising 25 biocontrol agents that have been used against a number of plant fungal diseases. In addition to Trichoderma, nine genera are recognized as significant comprising five or more known antagonistic species, namely, Alternaria, Aspergillus, Candida, Fusarium, Penicillium, Pichia, Pythium, Talaromyces, and Verticillium. A phylogenetic analysis based on partial sequences of the 28S nrRNA gene (LSU) of fungal antagonists was performed to establish their phylogenetic relationships.
Risk factors for endemic chronic kidney disease of unknown etiology in Sri Lanka: Retrospect of water security in the dry zone
(Science of the Total Environment, 2021) Hettithanthri, O.; Sandanayake, S.; Magana-Arachchi, D.; Wanigatunge, R.; Rajapaksha, A. U.; Zeng, X.; Shi, Q.; Guo, H.; Vithanage, M.
The prevalence of chronic kidney disease of unknown etiology (CKDu) is receiving considerable attention due to the serious threat to human health throughout the world. However, the roles of geo-socio-environmental factors in the prevalence of the CKDu endemic areas are still unknown. Sri Lanka is one of the countries most seriously affected by CKDu, where 10 out of 25 districts have been identified as the areas with the high prevalence of CKDu (10–20%). This review summarizes the geographical distribution of CKDu and its probable geochemical, behavioral, sociological, and environmental risk factors based on research related to hydrogeochemical influences on CKDu in Sri Lanka. More than 98% of CKDu patients have consumed groundwater as their primary water source in daily life, indicating the interactions of geogenic contaminants (such as F−, total dissolved solids, Hofmeister ions) in groundwater is responsible for the disease. Apart from the hydrogeochemical factors, mycotoxins, cyanotoxins, use of some herbal medicines, dehydration, and exposure to agrochemicals were alleged as risk factors. Sociological factors, including poverty, living habits and anthropogenic activities, may also provoke the emergence of CKDu. Therefore, the interaction of geo-socio environmental risk factors should be sociologically and scientifically considered to prevent the prevalence of CKDu. Future in-depth studies are required to reveal the individual role of each of the postulated etiological factors, possibly using machine learning and advanced statistics.
Revealing the endophytic mycoflora in tea (Camellia sinensis) leaves in Sri Lanka: the first comprehensive study
(Phytotaxa, 2021) Thambugala, Kasun; Daranagama, Sinushani; Kannangara, Sagarika; Kodituwakku, Shenuka
Endophytic fungi are a diverse group of microorganisms that live asymptomatically in healthy tissues of host and they have been reported from all kinds of plant tissues such as leaves, stems, roots, flowers, and fruits. In this study, fungal endophytes associated with tea leaves (Camellia sinensis) were collected from Kandy, Kegalle, and Nuwara Eliya districts in Sri Lanka and were isolated, characterized, and identified. A total of twenty endophytic fungal isolates belonging to five genera were recovered and ITS-rDNA sequence data were used to identify them. All isolated endophytic fungal strains belong to the phylum Ascomycota and the majority of these isolates were identified as Colletotrichum species. Phyllosticta capitalensis was the most commonly found fungal endophyte in tea leaves and was recorded in all three districts where the samples were collected. This is the very first investigation on fungal endophytes associated with C. sinensis in Sri Lanka based on molecular sequence data. In addition, a comprehensive account of known endophytic fungi reported worldwide on Camellia sinensis is provided.
Variation in dichogamy and myophily in two dioecious Bridelia species (Phyllanthaceae)
(Australian Journal of Botany, 2021) Dias, M.A.; Ratnayake, R.M.C.
Duodichogamy and multi-cycle dichogamy are rare forms of temporal separation of staminate and pistillate reproductive functions in angiosperms. We studied the floral phenology, breeding system and pollination of Bridelia retusa (L.) A.Juss. and Bridelia moonii Thwaites, with a particular focus on the alternation of sexual phases to determine variation in their dichogamy. Three dichogamy patterns were identified in B. retusa, including one-cycle dichogamy (staminate → pistillate or pistillate → staminate), duodichogamy (staminate → pistillate → staminate), multi-cycle dichogamy (repeated flowering cycles alternating between staminate and pistillate) and pure staminates. Except for multi-cycle dichogamy, the other dichogamy patterns were prevalent in B. moonii. This study speculated floral mimicry system in Bridelia associated with blowflies.
Potential Use of Mangroves for Coastal Protection: A Case Study from Sri Lanka
(Journal of the Indian Society of Coastal Agricultural Research, 2021) Amarasingha, M.D.; De Silva, W.
Mainstreaming coastal biodiversity certainly brings nature-based solutions for the conservation of offshore and onshore resources. Being an island, the long-term shoreline change of Sri Lanka is particularly important for management of the island’s coastal resources. This study was carried out at the southwestern and southern coasts of Sri Lanka to investigate the protective capacity of mangroves against coastal erosion, and coastal inundation hazards due to the climate associated sea-level rise. Structural diversity of mangrove stands was assessed in terms of alpha-diversity, plant species richness, basal area, tree height, density, and structural complexity index. Analysis of aerial photographs and the ASTER Global Digital Elevation Model was used to identify shoreline changes along the southwestern and the southern coasts of Sri Lanka. Results revealed that by and large, the southwestern coast is highly vulnerable to coastal erosion and inundation hazards whereas the southern coast manifests a tendency to retreat. The average annual rate of shoreline change however varies within the two coastal areas, as there were accreting as well as eroding segments on both southern and southwestern coasts, nevertheless, all retreating beach segments were the sites of improper maritime developments. Segments with lower rates of shoreline erosion and coastal inundation hazards were found to be located close to the mangrove and other coastal vegetation with varying structural complexity and diversity. Reforestation and restoration of vegetation in coastal lagoons and estuarine habitats are evidently effective strategies not only to protect the low-lying coastal hinterlands but also to preserve coastal biodiversity.
Can Anaerobic Soil Disinfestation (ASD) be a Game Changer in Tropical Agriculture?
(Pathogens, 2021) Priyashantha, A.K.H.; Attanayake, R.N.
Anaerobic soil disinfection (ASD) has been identified as an alternative soil-borne pathogen control strategy to chemical fumigation. ASD involves the application of an easily liable carbon source followed by irrigation to field capacity and maintenance of an anaerobic condition for a certain period. A literature search undertaken on ASD found that more than 50 comprehensive research projects have been conducted since its first discovery in 2000. Most of these studies were conducted in the USA and in the Netherlands. Though the exact mechanism of ASD in pathogen control is unknown, promising results have been reported against a wide range of pathogens such as fungi, nematodes, protists, and oomycetes. However, it is interesting to note that, except for a few studies, ASD research in the developing world and in the tropical countries has lagged behind. Nevertheless, with soil quality depletion, reduction in arable lands, and exponential population growth, a drastic change to the current agricultural practices should be adapted since yield gain has reached a plateau for major staple crops. Under such circumstances, we identified the gaps and the potentials of ASD in tropical agricultural systems and proposed promising biodegradable materials.
Anammox bacteria in treating ammonium rich wastewater: Recent perspective and appraisal
(Bioresource Technology, 2021) Weralupitiya, C.; Wanigatunge, R.; Joseph, S.; Athapattu, B. C.; Lee, T. H.; Kumar Biswas, J.; Ginige, M. P.; Shiung Lam, S.; Senthil Kumar, P.; Vithanage, M.
The discovery of anammox process has provided eco-friendly and low-cost means of treating ammonia rich wastewater with remarkable efficiency. Furthermore, recent studies have shown that the possibility of operating the anammox process under low temperatures and high organic matter contents broadening the application of the anammox process. However, short doubling time and extensive levels of sensitivity towards nutrients and environmental alterations such as salinity and temperature are the limitations in practical applications of the anammox process. This review article provides the recent yet comprehensive viewpoint on anammox bacteria and the key perspectives in applying them as an efficient strategy for wastewater treatment.
Physiological disorders of selected Citrus fruit species in Sri Lanka and their effect on fruit quality
(JOURNAL OF HORTICULTURE AND POSTHARVEST RESEARCH, 2021) Jayasekara, A.; Abeywickrama, K.; Daranagama, A.; Kodituwakku, T.
Purpose: This study was conducted to identify the physiological disorders and their symptoms of selected Citrus fruit species (C. sinensis, C. limon and C. crenatifolia). Furthermore, it was aimed to determine whether physicochemical and sensory properties were affected by physiological disorders. Research method: Citrus fruits with physiological disorders were observed separately for visible changes and characters were recorded and photographed. Moreover, Citrus fruits with physiological disorders were analyzed for physicochemical and sensory properties. Findings: Many physiological disorders were recorded from three Citrus fruit species including chilling injury, sun burn, stem-end rind breakdown, oleocellosis, rind disorder, puff and crease, granulation, wind injury, peteca, fruit splitting and fruit cracking. Based on the overall result of sensory analysis, it can be concluded that most of the physiological disorders in studied Citrus species appear on the peel but not adversely affect the edible internal portion of the fruits. Physicochemical properties of C. limon are not adversely affected by physiological disorders whereas C. sinensis and C. crenatifolia are affected by physiological disorders. Limitations: Availability of selected Citrus fruit species throughout the year is limited due to their seasonality. Originality/Value: This study provides novel information about the physiological disorders of some Citrus species in Sri Lanka and other parts of Asia and a future potential exists in controlling these disorders to provide healthy and quality fruits to the market.
Response of mangrove plant species to a saline gradient: Implications for ecological restoration
(Acta Botanica Brasilica, 2021) De Silva, W.; Amarasinghe, M.
Mangroves are salt tolerant plants that occur in tropical and sub-tropical sheltered coasts. Saltwater intrusions into terrestrial landscapes often occur due to either anthropogenic reasons or natural calamities such as tsunamis. We investigated the potential of using mangrove species for rehabilitation of high saline environments by revealing the capacities of species to remove salt from sediment. We established the salt retention capacity of common mangrove species in Sri Lanka i.e., Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, and Avicennia marina through exsitu and in-situ measurements of NaCl content in plant tissue and soil samples, by titrating with 0.01 N AgNO3. The results revealed A. marina to be the most efficient in retaining salt within plant tissues while C. tagal is superior to R. mucronata but inferior to A. marina in performing this function. These findings were further confirmed by measuring salt uptake rates of hydroponically grown seedlings of the same species. Although R. mucronata is the most popular species used for restoration, A. marina appears the most suitable mangrove species not only for coastal mangrove restoration but also for rehabilitating salinity affected landscapes.
In vitro and in vivo Application of Eco-friendly Treatments to Control Postharvest Stem-end Rot of Naturally Infected Avocado (cv. Pollock)
(The Journal of Agricultural Sciences - Sri Lanka, 2021) Nilmini, R.K.; Kodituwakku, T.D.; Abeywickrama, K.; Kuruppu, M.
Purpose: Stem-end rot (SER) is an endophytic fungal infection of avocado causing significant postharvest losses, affecting its marketability. This study was conducted to identify effective concentrations of selected eco-friendly essential oils and chemicals to control SER pathogens by conducting in vitro bioassays and to develop treatments to control SER in naturally infected avocado (cv. Pollock) using less hazardous alternatives to synthetic fungicides. Research Method: In vitro disc volatilization and poison food bioassays were conducted to identify inhibitory concentrations of some essential oils and chemicals against SER pathogens. Avocado fruits were subjected to eco-friendly fumigation and dip treatments and their pathological, physicochemical and sensory properties were assessed after 7 days of storage at 15 °C. Findings: Disc volatilization bioassay revealed that 5 µL/plate clove oil was most effective against Lasiodiplodia theobromae, Diaporthe nelumbonis and Fusarium oxysporum. According to Poisoned food bioassay, 5% (w/v) sodium bicarbonate and 0.07% (v/v) acetic acid were highly effective against the test pathogens. SER incidence of avocado fruits has been successfully delayed for 7 days after subjecting to fumigation treatment with clove oil and dip treatments with sodium bicarbonate and acetic acid, followed by storage at 15 °C. None of the treatments adversely affected physicochemical and sensory properties of avocado. Originality/Value: Treatments could be further improved by conducting a medium-scale in vivo trial to obtain good quality avocado with higher consumer acceptance.