Botany
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Item 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.Item Foliage preservatives for vase life extension of two dieffenbachia species(2010) Thambugala, S.; Abeywickrama, K.P.; Karunarathna, S.Cut foliage of Dieffenbachia maculata and Dieffenbachia amoena were subjected to continuous treatment with several foliage preservatives and export simulation. The preservatives used were 1.75% of sodium hypochlorite, 5% vinegar and VimTM dish washing detergent. Tap water without any added chemicals was used as the control. The highest vase life of 45.1 days was observed in D. maculata cut foliage when subjected to continuous treatment with tap water. Cut foliage of D. maculata subjected to continuous treatment with 0.016% (v/v) dish washing detergent (Vim™) solution and 0.016% (v/v) sodium hypochlorite (NaOCl) and subjected to export simulation for two days at 12-140 C and 85-90% relative humidity (RH), had relatively longer vase life of 38.9 days and 37 days respectively. Cut foliage of D. amoena had the longest vase life of 21 days when subjected to 0.016% NaOCl treatment and export simulation. NaOCl which is considered as a biocide and mild vinegar solution which is acidic inhibited the bacterial growth in vase solutions increasing the vase life of cut foliage. A Bacillus sp. and a Staphylococcus sp. were associated with vase solutions of D. maculata and D. amoena cut foliage. Treatment with NaOCl and VimTM satisfactorily extended the vase life of cut foliage of D. amoena and D. maculata respectively and could be recommended as preservatives for use during export.Item Effect of Chemical Pretreatments on the Quality of Minimally Processed Pineapple Stored in Polystyrene Packages(2012) Ediriweera, S.; Abeywickrama, K.P.; Latifah, M.Minimally processed pineapple (Ananas comosus L.) cv. Mauritius stored at cold temperature for seven days were evaluated for physicochemical, sensory and microbiological qualities. Pineapple pieces were treated with 1% sodium chloride, 1% calcium chloride, a combination of 1% sodium chloride and calcium chloride, 1% ascorbic acid, 1% citric acid, 0.1% chitosan and distilled water (control) and packed in polystyrene packages before storage. Pretreatments did not significantly affect the physicochemical properties studied. Many sensory attributes in minimally processed pineapple decreased after seven days of storage. However, sodium chloride (1%) and a combination of 1% sodium chloride and calcium chloride pretreatments resulted in maintaining a better flavour in pineapple after a seven day storage period than the rest of the treatments. Microbial counts for all treatments and the control were within safe-to-consume limits while Salmonella was not detected in any sample.Item Wheat crown rot pathogens Fusarium graminearum and F. pseudograminearum lack specialization(2010) Chakraborty, S.; Obanor, F.; Westecott, R.; Abeywickrama, K.P.This article reports a lack of pathogenic specialization among Australian Fusarium graminearum and F. pseudograminearum causing crown rot (CR) of wheat using analysis of variance (ANOVA), principal component and biplot analysis, Kendall’s coefficient of concordance (W), and κ statistics. Overall, F. pseudograminearum was more aggressive than F. graminearum, supporting earlier delineation of the crowninfecting group as a new species. Although significant wheat line– pathogen isolate interaction in ANOVA suggested putative specialization when seedlings of 60 wheat lines were inoculated with 4 pathogen isolates or 26 wheat lines were inoculated with 10 isolates, significant W and κ showed agreement in rank order of wheat lines, indicating a lack of specialization. The first principal component representing nondifferential aggressiveness explained a large part (up to 65%) of the variation in CR severity. The differential components were small and more pronounced in seedlings than in adult plants. By maximizing variance on the first two principal components, biplots were useful for highlighting the association between isolates and wheat lines. A key finding of this work is that a range of analytical tools are needed to explore pathogenic specialization, and a statistically significant interaction in an ANOVA cannot be taken as conclusive evidence of specialization. With no highly resistant wheat cultivars, Fusarium isolates mostly differ in aggressiveness; however, specialization may appear as more resistant cultivars become widespread.Item Quality of minimally processed modified atmosphere sorted bell pepper, as affected by pre treatments(2015) Ediriweera, S.; Abeywickrama, K.P.; Latifah, M.; Othaman, F.; Hussin, R.; Tham, S.Minimally processed bell pepper strips stored at 8-100C for seven days were evaluated for variation in color, in package gases, firmness, physicochemical sensory and microbiological quality. Bell pepper strips were treated with sodium chloride, calcium chloride, sodium chloride+calcium chloride or distilled water (control) and packed in polystyrene packages before storage. Pretreatments did not drastically affect the physicochemical properties (titratable acidity (TA), total soluble solids (TSS) and pH) when compared to the control. A slight discoloration of bell pepper was evident, indicated by decreasing L*, a* and b* values. Variations in firmness were observed. Fair-ly high level of CO2 accumulation was evident inside packages where O2 concentration displayed a declining trend. Sensory attributes generally declined with time but were within acceptable limits. Microbial counts were within safe-to-consume limits for all samples within the storage period. All pretreatments tested had no drastic effect on sensory properties and maintained low microbial counts, however 1% sodium chloride pretreatment was more successful in retaining higher sensory properties and maintaining lower microbial counts by the end of stor-age period than the other pretreatments.Item Isolation and identification of fungi from mushroom composts and evaluation their biological activity(1999) Wickremasinghe, R.; Abeywickrama, K.P.; Abeythunga, D.T.U.Item Root growth promotion of Ficus species during air-layering(2010) Gamlath, M.; Abeywickrama, K.P.; Wickramarachchi, S.Three chitosan concentrations (1%, 3%, 5% w/v) were tested for their root growth promotion properties in air-layering of three popular ornamental Ficus species namely Ficus triangularis, Ficus microcarpa and Ficus benjamina. Subsequently, these treatment responses were compared with a rooting hormone (naphthalic acetic acid) and an organic root promoting extract (Root Most) available in the local market. Tap water was used as the control. Air-layered plants were further subjected to export simulation for 14 days at 12-14 0C and 90% relative humidity (RH) with the aim of lengthening the storage period. 3% (w/v) chitosan treatment concentration was shown to promote the root growth significantly. 3% (w/v) chitosan treatment resulted in the highest mean root length of (15.3 cm) in F. triangularis compared to the 10.3 cm of tap water control. Similarly, highest mean root length of 38.8 cm was recorded for F. microcarpa for 3% (w/v) chitosan treated layers compared to 14.8 cm of tap water treated layers. Further, the highest mean root density of 3.17 was recorded for 3% (w/v) chitosan treated layers of F. triangularis. A cost effective packaging system was developed during this research which could be utilized in cold storage of air-layers during air or sea freight.Item Fumigant action of selected essential oils against banana fruit pathogens(2010) Abeywickrama, K.P.; Anthony, S.; Watawala, R.Item Disease control strategies for extending storage life of papaya (Carica papaya), cultivars ‘Red Lady’ and ‘Rathna’(2012) Abeywickrama, K.P.; Wijerathna, C.; Rajapaksha, N.; Sarananda, K.; Kannangara, S.Anthracnose (Colletotrichum gloeosporioides), stem-end rot (Lasiodiplodia theobromae) and Phomopsis rot (Phomopsis caricae-papayae) are major post-harvest diseases in papaya resulting in relatively high postharvest losses, up to 45%, in Sri Lanka. The current consumer preference is for tropical fruits free of synthetic pesticides. The objectives of the present investigation were to identify major post-harvest pathogens in papaya fruits, test in vitro fungitoxic effect of basil oil (Ocimum basillicum) and alum (sodium aluminium sulphate) on major fungal pathogens of papaya fruit and develop a relatively safe, disease control strategy. Alum (1% w/v) and basil oil (0.12– 0.16% v/v) in a liquid bioassay, indicated fungistatic and fungicidal efficacy on C. gloeosporioides, L. theobromae and P. caricae-papayae isolated from „Red Lady‟ and „Rathna‟ cultivars of papaya. In vivo investigation of fruits of both papaya cultivars harvested from fruit plantations in Sri Lanka („Red Lady‟–Yatawarawatta plantation, Kurunegala, „Rathna‟ – CIC plantation, Kekirawa and the Agricultural farm, Polonnaruwa) at 25% maturity level indicated that papaya washed in 1% (w/v) alum and subsequently sprayed with an emulsion solution of 0.16% (v/v) basil oil and enclosed in styrofoam sleeves could be stored for 14 days at 12–14 oC. The visual quality rating (VQR) was high (11–13), shriveling and „green islands‟ were low on fruits with zero disease severity where results were statistically similar to 500 mg/L Bavistin treatment. Physicochemical properties assessed were unaffected by the treatments and were comparable to the controls washed only in water. The organoleptic properties were slightly low in fruits subjected to cold temperature compared to fruits subjected to ambient temperature. No residues of basil oil could be detected on fruit peel by gas chromatography at the end of the experimental period of 14 days. The treatment strategy developed could be adopted for sea shipment or temperature-regulated supermarket storage of papaya fruits where storage life could be lengthened up to 14 days.Item 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.