Browsing by Author "Kodituwakku, T. D."

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Antifungal activity of chitosan-plant extract-based coating for crown rot disease in banana (cv. Embul)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Piyumali, W. M. D. T.; Gunaratna, A. G. M. J.; Kodituwakku, T. D.
Proper postharvest handling is essential to reduce postharvest losses and maintain the quality of fresh produce. Banana crown rot, which is caused mainly by Colletotrichum musae and Fusarium poliferatum is one of the most economically significant diseases affecting banana fruits. It impacts both the yield and marketability of bananas. Fungal infection occurs through the cut surface of crown tissues of dehanded banana. Symptom development initiates as a blackening of crown tissues which later advances down the fruit stalks. Fungal control methods often rely on synthetic fungicides and may cause environmental and health concerns due to their toxicity. Thus, this study was planned to develop an eco-friendly alternative to chemical fungicides to control banana crown rot disease. This research investigated the potential of soursop (Annona muricata) pulp extract in combination with chitosan as a natural antifungal coating to inhibit the growth of C. musae and F. poliferatum in banana (cv. Embul). In the initial stages of the study, soursop pulp oil was extracted using a Soxhlet apparatus. The solvent was evaporated using a rotary evaporator and freeze-dried. Fruit coating was prepared using chitosan, glycerol, Tween 80 and soursop pulp. A range of pulp oil concentrations were tested including 2.5%, 5.0%, 7.5% and 10% combined with chitosan (1%). The food poisoning technique was used to test the antifungal activity of the fruit coating using One-way ANOVA and Tukey’s pair-wise comparison tests. Mancozeb was used as positive control and DMSO was used as negative control for antifungal assay. A significant difference in antifungal activity was observed among several concentrations of peel and pulp coating solutions (p < 0.05). For In vivo application C. musae inoculated Embul banana were treated with pulp coating, fungicide and distilled water as control. The impact of the treatments was assessed by measuring the percentage weight loss, fruit firmness, total soluble solids (TSS), titratable acidity (TA) and pH values. Complete inhibition of the pathogen (in vitro) was observed at both pulp and peel extract concentrations of 7.5% and above for both fungal species. The minimum inhibitory concentration (MIC) for C. musae and F. poliferatum was considered to be 7.5%. The minimum lethal concentration (MLC) was 10%, at which no mycelial growth was noted in the growth revival test. In vivo, pulp extract coating showed significant inhibition of C. musae compared to the control. Kruskal – Wallis test showed a statistically significant difference in disease severity among the treatment groups (H = 6.77, p = 0.034) with the coating applied group showing lowest disease severity. Previous research findings revealed that chitosan possesses antifungal activity. The combined antifungal efficacy of chitosan and A. muricata extracts inhibits fungal growth and these findings suggest that the developed fruit coating has the potential to be an effective strategy for mitigating crown rot in bananas caused by C. musae and F. poliferatum.
Dip treatment of Aloe vera gel and Aloe vera in combination with cinnamon essential oils on stem-end rot of mango cv. ‘Karthakolomban’
(2022) Karunarathna, N. S. N.; Abeywickrama, K.; Kodituwakku, T. D.
This study was conducted to investigate the applicability of Aloe vera gel alone and mixed with cinnamon leaf and bark oil in controlling stem-end rot (SER) and extending the shelf life of mango cv. ‘Karthakolomban’. Mangoes were subjected to dip treatments of Aloe vera gel and Aloe vera gel in combination with cinnamon bark oil (2.0 μL/mL) and cinnamon leaf oil (2.0 μL/mL) and their pathological, physicochemical, sensory properties, and percentage shriveling were evaluated after a 10 d storage period at 12-14℃. Dip treatment of Aloe vera gel + cinnamon oils and Aloe vera gel reduced SER by 3.0 - 6.0%. Physicochemical and sensory properties did not show drastic alterations among all treatments and controls. Mangoes subjected to Aloe vera gel + cinnamon oil treatments demonstrated 0% shriveling. Uncoated fruits showed the highest shriveling. The findings highlight that Aloe vera gel may have a better prospect in the preservation and quality maintenance of mango in combination with cinnamon oils.
Evaluation of in vitro bio-controlling efficacy of Trichoderma virens against plant pathogenic fungi; Fusarium oxysporum, Colletotrichum gloeosporioides and Lasiodiplodia theobromae
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Dissanayak, D. T. I.; Kodituwakku, T. D.; Kannangara, B. T. S. D. P.
Fungi are one of the major causative agents of plant diseases. They damage plants by causing cell death or by causing plant stresses. Chemical fungicides which are commonly used to control fungal pathogens reported to cause a negative impact on human health and environment, despite their high efficiency in controlling the pathogens. Therefore, the use of bio-controlling methods has been recognized as a sustainable, healthy and eco-friendly alternative. Among the available bio-control agents, Trichoderma species have emerged as very promising fungal bio-control agents against fungal pathogens of plants. They are capable of inhibiting pathogenic fungi utilizing an array of mechanisms involving mycoparasitism, antibiosis, rhizosphere competition, enzyme production, and induction of plant defense mechanisms. The present study was aimed on studying the capability of Trichoderma virens (KP985643.1) in controlling three plant pathogenic fungi (Fusarium oxysporum, Colletotrichum gloeosporioides, and Lasiodiplodia theobromae – obtained from the Department Culture Collection) under in vitro conditions. The biological controlling ability of T. virens against the test pathogens was evaluated using the dual culture method and through the microscopic observations of hyphal interactions in slide cultures. Selected test pathogens were tested against T. virens by exposing them to the volatile and non-volatile compounds produced by T. virens. Percentage inhibition of each pathogen was determined after a 6-day incubation period. Results of the dual culture test showed that F. oxysporum and L. theobromae have been significantly controlled (i.e. 60.90% and 80.28% respectively) by T. virens after 6 days. C. gloeosporioides was moderately controlled (i.e. 44.58%) when compared to other pathogens. Volatile components produced by T. virens moderately inhibited the growth of C. gloeosporioides (i.e. 46.98%). In contrast, volatile components of T. virens were not successful in controlling F. oxysporum and L. theobromae. Non-volatile components produced by T. virens significantly controlled the growth of L. theobromae (i.e. 61.05%) when compared to F. oxysporum, which reported only a moderate inhibition (i.e. 41.45%). Unanticipatedly, growth of C. gloeosporioides was not observed in control plates even after repeated attempts, probably due to the loss of the viability of the original C. gloeosporioides culture after a prolonged storage period. The slide culture technique clearly showed the efficiency of T. virens in controlling L. theobromae (but not the other pathogens) by the means of producing coiling structures. Based on these results, it can be concluded that T. virens has the potential of controlling the selected test pathogens by producing volatile and non-volatile components under in vitro conditions. Moreover, T. virens is capable of controlling L. theobromae using hyphal interactions. However, further research is needed to determine other mechanisms adopted by T. virens against the selected pathogens and to investigate its bio-controling ability against a wide range of other fungal pathogens.
Isolation and identification of litter decomposing fungi in Nagacholai Forest Reserve, Mullaitivu, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Bopitiya, B. D. S. S.; Dewangani, H. G. N.; Perera, H. W. K.; Premachandra, J. A. H. P.; Senevirathna, M. A. T. M.; Kalpani, N. N.; Kodituwakku, T. D.; Kannangara, S.
Nagacholai Forest Reserve, which was disturbed by local terrorism before 2009, is located in Mullaitivu District in the Northern Province of Sri Lanka. It is a tropical dry zone forest, administrated by the Department of Forest Conservation, Sri Lanka. Litter-fall and subsequent nutrient release from decomposing litter are crucial processes that regulate the nutrient availability and the nutrient cycling in soil, as well as the plant growth in forest ecosystems. Litter decomposition rates of forest ecosystems are governed by both biotic and abiotic factors. Therefore, the present study was conducted to study soil characteristics such as pH and electrical conductivity and to isolate and identify the litter decomposing fungi of the Nagacholai forest. Soil and litter were collected randomly by placing 0.5 m X 0.5 m size quadrats on the forest floor. The pH and electrical conductivity of each soil sample were determined by following standard methods. Litter decomposing fungi were isolated from leaf discs (1 mm X 1 mm) obtained from the collected litter following washing and plating method using sterilized distilled water. Pure cultures of isolated fungi were maintained at 28 °C in PDA and morphologically identified using identification keys. The low moisture content in the soil was reflected by brown colour, sandy-podzolic soil. The high proportion of less decomposed, dense litter layer reflected the low decomposition rate due to decelerated soil microbial activity and low water availability. Soil pH was within the range of 6.34 – 6.80 and electrical conductivity at 30 °C varied between 1.23 – 1.57 mS cm-1. Five different fungal species were isolated in high frequencies (50%>) from leaf litter, while four of them were identified up to the genus level based on their vegetative and reproductive morphology (i.e. Mucor sp., Aspergillus sp., Candida sp. and Pestalotiopsis sp.). The remaining unidentified species produced white colour colonies and branched, hyaline, septate hyphae without showing any sexual reproductive structure. Mucor, Aspergillus and Pestalotiopsis are some of the common fungal decomposers found in most of the forests of different climatic zones. However, Candida is a filamentous yeast, which is not frequently reported as a decomposer in terrestrial ecosystems, but found to be a member of the normal soil microflora in forests as secondary sugar fungi. Therefore, Mucor, Aspergillus and Pestalotiopsis could be identified as the most prominent genera of litter decomposing fungi in the Nagacholai forest. Nevertheless, this preliminary study needs to be elaborated further to confirm their identity up to species level using molecular techniques
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.
The spray of essential oils with passive modified atmosphere packaging to control stem-end rot of mango 'Karutha Golomban'
(lnternational Society for Horticultural Science, lll Asian Horticuttural Gongress 'AHC2020, 2020) Kodituwakku, T. D.; Abeywickrama, K.,; Karunanayake, K. O. L. C.
'Karutha Cotomban' mango is more prone to stem-end rot (SER) disease that causes substantial postharvest losses in quality as well as quantity. The objective of this study was to use aqueous emulsions of basil (1.6 pL/mL), clove (2.0 pL/mL), cinnamon leaf (2.0 pL/mL) and cinnamon bark (1.6 pL/mL) oils as sprays with passive modified atmosphere packaging (MAP) in low density polyethylene (LDPE) bags qs_ a bio-s_afe strategy to control SER of 'Karutha Colomban' mango stored at 12 - 14 "C and 85 - g0% of retative humidity. Distilled water and 0.1% (w/v) carbendazim treatments were used as negative and positive controls respectively. ln-package respiratory gases were measured during storage for B days. Pathological, physicochemical, sensory evaluation and feel color of mango were assessed after transferring to ripening at the end of the storage period. All essential oil treatments combined with passive MAP have significantly reduced SER severity of mango to 0.3 ' 1.1% when compared to the negative controlwithout adversely affecting the physicochemical, sensory properties anl peel color. Mango fruits treated with basil, clove and cinnamon leaf oils obtained a slighily higher preference by the sensory panelthan other treatments. ln-package 02 concentration was at 3.8 - 5.8%, while CO2 was at 4.3 - 5.0% at the end of the B-day storage period. Respiratory gas levels attained a steady state equilibrium which resulied'in extending the shelf life by reducing the metabolism of both commodity and associated microorganisrns. Further, current treatments can be commercialized as eco-friendly treatment strategies to be used during transportation and storage of mango in local trade within one week and for exportation via air cargo that takes approximately 2 - 3 daYs.