Botany

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Start date: 2000End date: 2009

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    Inhibition of aspergillus flavus link and aflatoxin formation hy essential oils of cinnamomum xeylanicum (L) and cymbopogon nardus rendle
    (Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 2002) Jayaratna, K.H.T.; Pranagama, P.A.; Abeywickrama, K.P.; Nugaliyadde, L.
    The essential oils of Cinnamomum zeylanicum (L.) leaf and Cvmbopoeon nardus Rendle were tested for their fungistatic, fungicidal and qflatoxin suppressing efficacy against an isolate of Aspergillus flavus Link, isolated from rice. The mycelial growth and the aflatoxin formation in SMKY semi synthetic liquid medium in the presence of different concentrations of two test oils were monitored. At concentrations varying from 100 to 500 ppm of the essential oil of C. zeylanicum. the mycelial dry weight decreased from 0.49 to 0.01 g/50 ml. The percentage inhibition of the mycelial growth of A. flavus increased from 50 to 95 when treated with 1000 to 1800 ppm of C. nardus oil. The minimum lethal concentrations (MLCs) for the essential oils of C. zeylanicum leaf and C. nardus were 1000 and 4000 ppm, respectively. Aflutoxins were not present in the medium at or above the concentrations of400 and 600 ppm C zeylanicum leaf and C nardus oils, respectively
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    The effect of spraying essential oils of Cymbopogon nardus, Cymbopogon flexuosus and Ocimum basilicum on postharvest diseases and storage life of Embul banana
    (The Journal of Horticultural Science and Biotechnology, Taylor & Francis., 2003) Anthony, S.; Abeywickrama, K.; Wijeratnam, S.W.
    Embul banana hands were sprayed with emulsions of the essential oils of Ceylon citronella (Cymbopogon nardus) (0.4% v/v) lemon grass Cymbopogon flexuosus (0.16% v/v), or Indian sweet basil (Ocimum basilicum) (0.16% v/v) and stored cool (13.5 ± 1°C) or at ambient temperature (28 ± 1°C) at 94% relative humidity. A benomyl spray (0.1% w/v) was included as a standard fungicide control treatment. The effects of the essential oils on post-harvest diseases, and on organoleptic and cosmetic quality and various properties of the fruit (percentage weight loss, changes in fruit firmness, total soluble solids and titratable acidity) were determined. Treatment with Ocimum basilicum oil controlled crown rot and anthracnose, enabling bananas to be stored for up to 21 d at 13.5 ± 1°C without any detrimental effect on their organoleptic properties; results were comparable with treatment with benomyl. Rapid-ripening induced by ethral after cool storage resulted in better quality bananas. The oil of C. nardus affected the texture and flavour of the fruit and that of C. flexuosus did not give complete control of crown rot. Spraying Embul bananas with emulsions of the essential oil of Ocimum basilicum prior to cool storage can be recommended therefore as a safe, cost-effective method, with commercial potential, for controlling post-harvest diseases and extending storage life.
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    Repellency and toxicity of four essential oils to Sitophilus oryzae L. (Coleoptera: Curculionidae)
    (2004) Paranagama, P.A.; Abeysekera, K.H.T.; Nugaliyadde, L.; Abeywickrama, K.P.
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    Deterrent effects of some Sri Lankan essential oils on oviposition and progeny production of the cowpea bruchid, Callosobruchus maculatus (F.)(Coleoptera; Bruchidae)
    (2003) Paranagama, P.; Adhikari, C.; Abeywickrama, K.P.; Bandara, P.
    Essential oils extracted from five plant materials were tested on oviposition and progeny production of F1 adult of cowpea bruchid, Callosobruchus maculatus on cowpea seeds. All oils tested showed a significant inhibition of oviposition and F1 adult emergence compared to the control during no-choice tests. Cymbopogon citratus and C. nardus showed higher effect on oviposition and F1 adult emergence than the essential oils of Alpinia calcarata, Cinnamomum zeylanicum and Murraya koinigii. In the choice test, the percentage ovipositions in all oils treated samples (except 10 mg of M. koinigii) were significantly lower than that of the control and ethanol treated samples. The percentage eggs deposited decreased with increasing doses of the oils ranging from 10 to 160 mg. The percentage of eggs laid was zero in samples treated with 40 mg of C. nardus or A. calcarata, 80 mg of C. citratus and 160 mg of C. zeylanicum. The essential oils of M. koinigii showed the lowest effect on oviposition when compared to other four essential oils.
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    Cymbopogon citratus (lemongrass) and citral a+ b spray treatments alone or in combination with sodium bicarbonate in controlling crown rot in Embul banana (Musa acuminata AAB)
    (2004) Abeywickrama, K.P.; Kularathna, L.; Sarananda, K.; Abeygunawardena, D.
    The mounting pressure against synthetic fungicidal dips and sprays, restrict their use in controlling crown rot, a major post-harvest disease in banana. Generally regarded as safe (GRAS) compounds have a great potential to be used as alternatives to fungicides. Identification of chemical constituents of Cymbopogon citratus oil revealed the presence of citral as the main component. Cymbopogon citratus and citral with sodium bicarbonate (SBC) was fungicidal against the 3 banana fungal pathogens at 0.10-0.20 % v/v and 0.07-0.08 % v/v respectively. Embul banana sprayed with C. citratus alone or in combination with SBC after induced ripening, indicated a crown rot severity of 25 - 5 0% whereas, citral treatment resulted in a slightly lower disease severity. The physico-chemical parameters tested were not affected by the treatments. Oil/citral, SBC treated bananas and control were ranked good to excellent with respect to odour, flavour, taste and overall acceptability. The low disease severity of crown rot due to spray treatment of citral and SBC highlights the importance in adapting this simple, alternate treatment strategy for quality maintenance.
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    An integrated treatment of basil oil (Ocimum basilicum) and alum with modified atmosphere to control crown rot disease in Embul banana
    (2009) Abeywickrama, K.P.; Wijerathna, C.; Herath, H.; Sarananada, K.H.
    A study was undertaken with the objective of developing environmental friendly integrated treatment strategies for controlling crown rot disease in Embul banana. The fungicidal potential of 1% alum (sodium aluminium sulphate) was observed in vitro. Findings indicate that alum+basil oil (0.16% or 0.20% v/v) treated 80, 85, 90 day mature Embul banana fruits were relatively free from crown rot dis-ease after subjecting to modified atmosphere packaging (MAP) and storage at optimum temperature. Crown rot disease severity of 85-day mature and vacuum packed 1% alum (w/v) washed banana was lower and comparable to carbendazim (bavistin) treatment. After ripening, there was no significant difference in physico-chemical properties (titratable acidity, total soluble solids, pH, fruit firmness) of all treated fruits compared to the control. Sensory properties were slightly affected as compared to un-treated fruits. MAP and vaccum packaging in combination with alum and/ or basil oil spray treatments at 12-140C could extend the storage life of Embul banana upto 32 days which could be recommended for sea shipment.
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    Aflatoxigenic Aspergillus flavus and aflatoxin formation in selected spices during storage
    (2009) Rajasinghe, M.; Abeywickrama, K.P.; Jayasekera, R.
    Proliferation of aflatoxigenic fungi and accumulation of aflatoxins take place during storage of spices at various environmental conditions. The objective of this research was to identify the aflatoxigenic fungal species and their aflatoxin forming potential in selected spices during storage in the laboratory and refrigerator. Dilution series of spice samples namely chilli (Capsicum annum) powder, curry powder, turmeric (Curcurma longa) powder and pepper (Piper nigrum) powder (purchased from two producers) were prepared separately and the frequency of occurrence of aflatoxigenic and other fungi were assessed after plating each on Potato Dextrose Agar and incubating at ambient temperature. Aflatoxin formation of A. flavus was confirmed by growing a pure culture on a SMKY medium and identifying toxins on thin layer chromatographic plates. The presence of aflatoxins in spice samples stored at 30 ± 20C and 40C was also confirmed. Long storage of spices leads to aflatoxin production irrespective of storage temperature hence, it is advisable to consume spices such as chilli powerder, tumeric etc. within a relatively short period to avoid build up of aflatoxins.
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    Effect of the essential oils of Cymbopogon citratus, C. nardus and Cinnamomum zeylanicum on pest incidence and grain quality of rough rice (paddy) stored in an enclosed seed box
    (WFL Publisher, 2003) Paranagama, P.A.; Abeysekera, T.; Nugaliyadde, L.; Abeywickrama, K.P.
    The protective effect of the essential oils of Cymbopogon citratus, C. nardus and Cinnamomum zeylanicum leaf on paddy stored in wooden boxes lined with aluminium foil were evaluated. After 168 days of storage in oil treated boxes Sitotroga cerealella population was significantly lower in oil treated paddy than the control. The 1000 grain weight was higher in all three treatments (21.1 - 22.9 g) compared to the control (19.8 g). Percentage grain damage was lower in C. citratus and C. nardus treated paddy than the control. The percentage seed germination was not significantly different from that of the control in oil treated paddy though, in C. citratus treatment the seed germination was reduced. The milling quality of paddy was not affected by the essential oil treatment however; the flavour and stickiness of cooked rice was enhanced when treated with C. zeylanicum and C. citratus oils.
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    Fungicidal and anti-aflatoxigenic effects of the essential oil of Cymbopogon citratus (DC.) Stapf. (lemongrass) against Aspergillus flavus Link. isolated from stored rice
    (The Society for Applied Microbiology, 2003) Paranagama, P.A.; Abeysekera, K.H.T.; Abeywickrama, K.P.; Nugaliyadde, L.
    Aims: To develop a natural fungicide against aflatoxigenic fungi, to protect stored rice, using the essential oil of lemongrass. Methods and Results: Aspergillus flavus Link. was isolated from stored rice and identified as an aflatoxigenic strain. Lemongrass oil was tested against A. flavus and the test oil was fungistatic and fungicidal against the test pathogen at 0Æ6 and 1Æ0 mg ml)1, respectively. Aflatoxin production was completely inhibited at 0Æ1 mg ml)1. The results obtained from the thin layer chromatographic bioassay and gas chromatography indicated citral a and b as the fungicidal constituents in lemongrass oil. During the fumigant toxicity assay of lemongrass oil, the sporulation and the mycelial growth of the test pathogen were inhibited at the concentrations of 2Æ80 and 3Æ46 mg ml)1, respectively. Conclusion: Lemongrass oil could be used to manage aflatoxin formation and fungal growth of A. flavus in stored rice. Significance and Impact of the Study: Currently, fungicides are not used to control fungal pests or mycotoxin production on stored rice. Rice treated with the essential oil of lemongrass could be used to manage fungal pests as well as the insect pests in stored rice. The essential oil is chemically safe and acceptable to consumers, as synthetic chemical fungicides can cause adverse health effects to consumers.
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    Bioconcentraton of metals in edible aquatic plants from a Sri Lankan freshwater wetland
    (Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Amarasinghe, M.D.; Nirbadha, K.G.S.; Liyanage, J.A.