Vijaya Kumar

Bio: Vijaya Kumar is an academic researcher from University of Peradeniya. The author has contributed to research in topics: Bark & Murraya. The author has an hindex of 17, co-authored 41 publications receiving 927 citations. Previous affiliations of Vijaya Kumar include University of Münster.

The cowpea aphid, Aphis craccivora, host plant odours and pheromones

Abstract: Olfactometer experiments were conducted with apterae and alatae of the cowpea aphid, Aphis craccivora, Koch (Hom.:Aphidoidea). The occurrence of density dependent related pheromones and odour response to their host plant Vigna unguiculata was studied. Apterae responded with positive anemotaxis to air passed over both small groups of apterae and alatae (≤10 individuals) but negatively to air that passed over a bigger group (≥20 individuals). Alatae responded in the same way to groups of apterae but were repelled by alatae independent of the size of the group applied as odour source in the olfactometer, except when exposed to air passing ten alatae feeding on cowpea leaves. This may be due to interaction between aphid pheromones and host plant odour. Both apterae and alatae showed a general attraction to green plants and were also able to distinguish between other host plants and cowpea, which was the original host of the aphid clone used in the experiments. When attacked by aphids, the cowpea plant responded with a temporal increase in attractivity that reached a maximum after 48 h and had disappeared after one week.

Evaluation of the Ethnomedical Claims of Murraya koenigii.

Abstract: Based on sethnomedicine, Murraya koenigii. (L.) Spreng. is used as a stimulant, antidysentery, and for the management of diabetes mellitus. Twelve carbazole alkaloids were isolated from the stem, seed, and leaf of the plant growing in Nigeria and Sri Lanka. The methanol extracts were devoid of hypoglycemic activity, and some isolates decreased insulin secretion when they were subjected to both in vivo. and in vitro. (insulin secretion from INS-1 cells) antidiabetic tests. The cytotoxicity of the leaf and stem methanol extracts determined by the brine shrimp lethality bioassay were LC50 61.5 and 14.5 µg/ml, respectively. These extracts caused CNS depression in albino mice at the dose levels of 25–400 mg/kg. Also, they had an IC50 of 34.0 and 35.0 µg/ml at 24 h, respectively, against trichomonas. These results confirmed the use of the plant as an antidysentery caused by trichomonas but refute the antidiabetic and stimulant ethnomedical claims for the plant. The differences observed in their alkaloid...

Plant extracts as potential mosquito larvicides

Abstract: Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain and adverse effects on environmental quality and non target organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Review article no. 92 a survey of antifungal compounds from higher plants, 1982-1993

Abstract: Index-Flowering plants; antifungal agents; constitutive compounds; phytoalexins; second- ary metabolites. Abstract-Recent work on the characterization of antifungal metabolites in higher plants is reviewed. Interesting new structures are discussed and the distribution of those substances in different plant families is outlined. Distinction is made between constitutive antifungal agents and phytoalexins, which are specifically formed in response to fungal inoculation. The literature survey covers the 12 years since 1982. INTRODUCTION A fungal spore landing on the leaf surface of a plant has to combat a complex series of defensive barriers set up by the plant before it can germinate, grow into the plant tissues and survive. The arsenal of weapons against the fungus includes physical barriers (e.g. a thick cuticle) and chemical ones, i.e. the presence or accumulation of anti- fungal metabolites. These can be preformed in the plant, the so called ‘constitutive antifungal substances’, or they are induced after infection involving de