Time filter

Source Type

Sri Jayewardenepura Kotte, Sri Lanka

Freeman S.,Israel Agricultural Research Organization | Protasov A.,Israel Agricultural Research Organization | Sharon M.,Israel Agricultural Research Organization | Mohotti K.,Tea Research Institute of Sri Lanka | And 4 more authors.
Symbiosis | Year: 2012

The ambrosia beetle, Euwallacea aff. fornicata Eichhoff was first recorded in Israel in 2009. The symbiotic fungus Fusarium sp. nov., carried in the mandibular mycangia of the beetle, is responsible for typical wilt and dieback symptoms inflicted on avocado (Persea americana Miller) trees. The beetle-fungus complex has become a serious threat to the future of the avocado industry in Israel and elsewhere. When reared on Petri dishes, inoculated with 7-day-old cultures of the symbiotic Fusarium sp. nov., the beetle successfully completed its lifecycle and developed from egg to fertile adults in approximately 60 days. Galleries that were produced in the PDA medium by the adults, resembled those excavated in host plant xylem under natural host colonization conditions. Euwallacea aff. fornicata from avocado in Israel was not able to survive when fed with F. ambrosium but resulted in approximately 25 % mortality when fed on F. solani; both isolates originated from infected tea. Likewise, the larvae of E. fornicatus from tea in Sri Lanka, were not able to survive or complete their lifecycle when supplied with a feed of the Fusarium sp. nov. isolated from avocado in Israel. Isolates of two other Fusaria, F. mangiferae from mango and F. oxysporum f. sp. melonis from melon, were not able to support development or survival of the beetle larvae from avocado from Israel, using the same Petri dish rearing method. This indicates that the Fusarium sp. nov. isolate from avocado is obligately required for the survival and development of Euwallacea aff. fornicata currently occurring in Israel, affecting this crop and additional hosts. The usefulness of the Petri dish assay to study the interactions between ambrosia beetles and their fungal symbionts is discussed. © 2013 Springer Science+Business Media Dordrecht. Source

Karlsson M.F.,Swedish University of Agricultural Sciences | Birgersson G.,Swedish University of Agricultural Sciences | Witzgall P.,Swedish University of Agricultural Sciences | Lekfeldt J.D.S.,University of Aarhus | And 4 more authors.
Phytochemistry | Year: 2013

Guatemalan potato moth, Tecia solanivora, lay eggs in the soil nearby potato Solanum spp. and larvae feed on the tubers. We investigated the oviposition behaviour of T. solanivora females and the survival of larval offspring on healthy vs. stressed, i.e. light exposed and/or damaged potato tubers. In choice tests, females laid significantly more eggs in response to potato odour of healthy tubers and female oviposition preference correlated with higher larval survival. Survival of larvae was negatively correlated with the tuber content of the steroid glycoalkaloids α-solanine and α-chaconine: healthy potatoes contained lower amounts than stressed tubers, ranging from 25 to 500 μg g-1 and from 30 to 600 μg g-1, respectively. Analysis of volatile compounds emitted by potato tubers revealed that stressed tubers could clearly be distinguished from healthy tubers by the composition of their volatile profiles. Compounds that contributed to this difference were e.g. decanal, nonanal, isopropyl myristate, phenylacetaldehyde, benzothiazole, heptadecane, octadecane, myristicin, E,E-α-farnesene and verbenone. Oviposition assays, when female moths were not in contact with the tubers, clearly demonstrated that volatiles guide the females to lay fewer eggs on stressed tubers that are of inferior quality for the larvae. We propose that volatiles, such as sesquiterpenes and aldehydes, mediate oviposition behaviour and are correlated with biosynthetically related, non-volatile compounds, such as steroidal glycoalkaloids, which influence larval survival. We conclude that the oviposition response and larval survival of T. solanivora on healthy vs. stressed tubers supports the preference performance hypothesis for insect herbivores. © 2012 Elsevier Ltd. All rights reserved. Source

Jeganathan B.,University of Peradeniya | Punyasiri P.A.N.,University of Colombo | Kottawa-Arachchi J.D.,Tea Research Institute of Sri Lanka | Ranatunga M.A.B.,Tea Research Institute of Sri Lanka | And 3 more authors.
International Journal of Food Science | Year: 2016

Flavonol glycosides in tea leaves have been quantified as aglycones, quercetin, myricetin, and kaempferol. Occurrence of the said compounds was reported in fruits and vegetable for a long time in association with the antioxidant potential. However, data on flavonols in tea were scanty and, hence, this study aims to envisage the flavonol content in a representative pool of accessions present in the Sri Lankan tea germplasm. Significant amounts of myricetin, quercetin, and kaempferol have been detected in the beverage type tea accessions of the Sri Lankan tea germplasm. This study also revealed that tea is a good source of flavonol glycosides. The Camellia sinensis var. sinensis showed higher content of myricetin, quercetin, and total flavonols than var. assamica and ssp. lasiocalyx. Therefore flavonols and their glycosides can potentially be used in chemotaxonomic studies of tea germplasm. The nonbeverage type cultivars, especially Camellia rosaflora and Camellia japonica Red along with the exotic accessions resembling China type, could be useful in future germplasm studies because they are rich sources of flavonols, namely, quercetin and kaempferol, which are potent antioxidants. The flavonol profiles can be effectively used in choosing parents in tea breeding programmes to generate progenies with a wide range of flavonol glycosides. © 2016 Brasathe Jeganathan et al. Source

Punyasiri P.A.N.,University of Colombo | Jeganathan B.,University of Peradeniya | Kottawa-Arachchi J.D.,Tea Research Institute of Sri Lanka | Ranatunga M.A.B.,Tea Research Institute of Sri Lanka | And 3 more authors.
Journal of Analytical Methods in Chemistry | Year: 2015

Chemical analysis of the Sri Lankan tea (Camellia sinensis, L.) germplasm would immensely contribute to the success of the tea breeding programme. However, the polyphenols, particularly catechins (flavan-3-ols), are readily prone to oxidation in the conventional method of sample preparation. Therefore, optimization of the present sample preparation methodology for the profiling of metabolites is much important. Two sample preparation methodologies were compared, fresh leaves (as in the conventional procedures) and freeze-dried leaves (a new procedure), for quantification of major metabolites by employing two cultivars, one is known to be high quality black tea and the other low quality black tea. The amounts of major metabolites such as catechins, caffeine, gallic acid, and theobromine, recorded in the new sampling procedure via freeze-dried leaves, were significantly higher than those recorded in the conventional sample preparation procedure. Additionally new method required less amount of leaf sample for analysis of major metabolites and facilitates storage of samples until analysis. The freeze-dried method would be useful for high throughput analysis of large number of samples in shorter period without chemical deterioration starting from the point of harvest until usage. Hence, this method is more suitable for metabolite profiling of tea as well as other phenol rich plants. © 2015 P. A. Nimal Punyasiri et al. Source

Perera G.A.A.R.,Tea Research Institute of Sri Lanka | Amarakoon A.M.T.,Tea Research Institute of Sri Lanka | Amarakoon A.M.T.,University of Kelaniya | Illeperuma D.C.K.,University of Peradeniya | Muthukumarana P.K.P.,Tea Research Institute of Sri Lanka
LWT - Food Science and Technology | Year: 2015

Effects of dhool (particles resulting from rolling of green leaf) fermented for varying durations, black tea and the rejected fraction in black tea manufacture which is known as 'broken mixed fannings' (BMF) as raw materials on the physicochemical and organoleptic properties of instant black tea were studied. Total polyphenols and theaflavins contents of instant black teas prepared by using fermented dhools (38.4-40.1 g/100g and 1.05-3.10 g/100 g respectively) were significantly higher than those of instant black teas prepared by using black tea (35.2g/100g and 0.37g/100g) and BMF (33.5 g/100 g and 0.28 g/100 g). Further, trolox equivalent (TE) antioxidant activities of instant black teas prepared by using fermented dhools (542 - 564 TE mg/g) were significantly higher than those of instant black teas prepared by using black tea (488 TE mg/g) and BMF (341 TE mg/g). Type of raw material did not affect significantly on the yield and fluoride and aluminium contents of instant black tea. Chemical composition, organoleptic properties, antioxidant activity and physical properties of instant black tea can be improved by using dhool fermented to 2-21/2h as raw material. © 2015 Elsevier Ltd. Source

Discover hidden collaborations