Browsing by Author "Subhashini, M.H.A.D."
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Item Detection of Fungal Contaminations in Export Coir Consignments(Uva Wellassa University of Sri Lanka, 2018) Weerapura, W.H.T.P.; Subhashini, M.H.A.D.; Chandrasena, G.; De Silva, P.D.P.M.Coir or coconut fibre is a natural hard fibre extracted from the husk of the coconut. Coir is a good source for harboring and growth of fungi due to the high moisture content and the nutrients, it can support the growth of pathogens harmful to men, animals and plants. Export market is looking for coir products with minimum contaminants which is important to control the crop infections and maintain the human health. In the present study attempt was made to identify the fungal species present as contaminants in the export coir consignments which threatens the bio security of importing countries. Fungi in coir samples were isolated by inoculating the PDA plates with direct culture 'method and dilution series method under the aseptic conditions. Nine fungal species were isolated after 72 hours of incubation period. Isolated fungi were sub cultured separately to obtain the pure cultures which is important in the process of identification. Fungal and spore morphology was examined under the inverted compound microscope (Labomed TCM 400) for the identification of fungal species. Mucor sp., Aspergillus sp., Fusarium sp., Colletotrichum sp., Geotrichum sp., Paradoxa sp., Rhizopus sp., Trichoderma sp., and Penicillium sp., were found after the investigation of 8 samples of different coir exporting companies in Sri Lanka. Aspergillus sp. and Mucor sp. were the most abundant fungal species among the companies while Paradoxa sp., Fusarium sp. and Trichoderma sp. were recorded only in samples from 3 companies.Item Investigating the Existence of Candidatus Liberibacter asiaticus in Murraya koenigii(Uva Wellassa University of Sri Lanka, 2020) Athukorala, H.; Subhashini, M.H.A.D.; Alwis, L.M.H.R.; De. Silva, P.D.P.M.In 2015 the European Union banned importing fresh curry leaves from Sri Lanka due to Citrus greening disease reported in Sri Lanka. Citrus greening is the most dangerous disease in citrus cultivation. The disease is caused by the infection of non-culturable bacteria named Candidatus Liberibacter (CLas). This bacterium transferred by a vector named Asian citrus psyllid (Diaphorina citri). Asian citrus psyllid is one of the major pests in Curry leaves. This study was conducted to confirm the existence of Candidatus Liberibacter in Curry leaves by conducting a pathogenicity test to test the ability of CLas to cause the disease. 11 Citrus plants and 11 Curry leaves plants were tested for Candidatus Liberibacter. The presence of CLas in leaf samples were identified by amplification of 1160 bp fragment of 16s rRNA. 10 Curry leaves and 10 Citrus plants were placed inside of a rearing cage in the protected house. One curry leaf and one citrus plant kept outside of the cage but inside the protected house as controls. Approximately, 500 Diaphorina citri insects were collected from several Districts in Sri Lanka and kept in a secondary cage to facilitate the mating process for a week with one feeding plant. Insects were inserted into the main cage. After a month, all plants and some random insect samples were tested for the presence of Candidatus Liberibacter. Initially, all the curry leaves plants and citrus plants give negative results confirming the absence of CLas. After a month, one citrus plant was positive for the presence of CLas and other 9 citrus plants and curry plants produce negative results confirming the absence of CLas. Two random Diaphorina citri samples were checked. One sample was positive and the other one is negative for the presence of CLas. Results indicate that CLas is unable to survive in curry leaves plants, but further studies should be conducted. There is a potential to export fresh curry leaves, due to the absence of CLas in curry leaves. Keywords: Citrus Greening, Candidatus Liberibacter asiaticus, Murraya koenigiiItem Investigating the Presence of Candidatus Liberibacter asiaticus in Murraya koenigii and Citrus spp. from Selected Areas in Sri Lanka(Uva Wellassa University of Sri Lanka, 2019) Wickramasinghe, G.A.; Subhashini, M.H.A.D.; Alwis, L.M.H.R.Citrus Greening (CG) disease is the most detrimental bacterial disease for citrus and it is caused by Candidatus Liberibacter asiaticus (CLas). In Asia, CG is mainly transmitted by Asian Citrus Psyllid (ACP) which is recognized as a major pest in Murraya koenigii (curry leaves). This study was carried out to investigate the presence of CLas in Murraya koenigii and Citrus spp. in selected locations, where fresh curry leaves are harvested for exporting. Leaf samples of curry leaves and Citrus spp. were collected from Anuradhapura, Puttalam and Badulla areas. The presence of CLas was tested in twenty-seven leaf samples of each plant using DNA extraction by modified CTAB method followed by Polymerase Chain reaction (PCR). CLas presence was detected by amplification of 1160 bp fragment of 16s rRNA coding gene of CLas by using OI1 and OA1 as forward primers and OI2c as common reverse primer and by amplification of 703 bp and 669 bp fragments of rplKAJL-rpoBC operon gene of CLas using forward primer A2 and reverse primer J5. None of the curry leaf samples produced any amplicon indicating zero presence of CLas, while Citrus leaf samples produced amplicons in all three areas indicating the presence of CLas. Citrus in Anuradhapura area displayed the lowest percentage (40%) of presence, while the highest percentage (80%) was observed from Badulla area. Citrus in Puttalam area showed 53% of presence. Results indicated that, within three selected areas, CLas is totally absent in curry leaves, while CLas presence is detected in Citrus spp. in same fields. CG is restricted to Citrus spp. in Anuradhapura, Puttalam and Badulla areas and Murraya koenigii (curry leaves) that is host for ACP is free of CLas.