Essential oil of seeds of Trachyspermum ammi (Linn.) Sprauge and its pure constituent thymol showed promising results when evaluated for larvicidal, oviposition-deterrent, vapor toxicity, and repellent activity against malarial vector, Anopheles stephensi. Thymol was 1.6-fold more toxic than the oil toward fourth-instar larvae of A. stephensi with LD(50) values of 48.88 and 80.77 microg/ml, respectively. Egg laying by female adults of A. stephensi was much significantly reduced when exposed to vapors of thymol compared to the oil of T. ammi seeds, and similar effects were recorded for subsequent egg hatching and larval survival. Vapor toxicity assay showed LC(50) value of 79.5 mg/mat for thymol against adults of A. stephensi, whereas the crude oil exhibited the LC(50) value of 185.4 mg/mat. Thymol provided complete repellency toward A. stephensi adults at the dose of 25.0 mg/mat after 1 h duration, whereas same degree of repellency was obtained by the oil at the dose of 55.0 mg/mat, indicating its double-fold activity than the oil.
Artemisia annua (Asteraceae) is well known for its antimalarial activities due to presence of the compound artemisinin. We isolated a methoxy coumarin from the stem part of A. annua and confirmed its identity as scopoletin through mass spectral data. The structure was established from 1H‐nuclear magnetic resonance (NMR), 13C‐NMR. The compound scopoletin was evaluated for its feeding deterrence and growth inhibitory potential against a noxious lepidopteran insect, Spilartctia obliqua Walker. Scopoletin gave FD50 (feeding deterrence of 50%) value of 96.7 μg/g diet when mixed into artificial diet. S. obliqua larvae (12‐day‐old) exposed to the highest concentration (250 μg/g diet) of scopoletin showed 77.1% feeding‐deterrence. In a growth inhibitory assay, scopoletin provided 116.9% growth inhibition at the highest dose of 250 μg/g diet with a GI50 (growth inhibition of 50%) value of 20.9 μg/g diet. Statistical analysis showed a concentration‐dependent dose response relationship toward both feeding deterrent and growth inhibitory activities. Artemisinin is found mainly in the leaves of A. annua and not in the stems, which are typically discarded as waste. Therefore identification of scopoletin in stems of A. annua may be important as a source of this material for pest control.
Background: Soybean is an important oilseed crop. Charcoal rot caused by soil borne polyphagous fungus Macrophomina phaseolina in soybean causes about 80 percent yield loss. Methods: Callus and cell suspension cultures derived from immature and mature embryonic axis and cotyledons explants from disease susceptible soybean cultivars (cv JS335 and JS95-60) were treated with purified toxic culture filtrate generated by the fungus Macrophomina phaseolina fortified with MS culture medium. A continuous method of four cycles of selection was executed on toxic medium while during discontinuous method, a silence was given after the second and third cycle of selection using non-toxic medium. Result: The discontinuous method appeared to be superior as it permitted the calli to recover their regeneration capability. Continuous exposure to toxic culture filtrate resulted up to about 65-75 percent mortality. A total of four lines of JS335 and nine of JS95-60 were found resistant amongst an array of putative resistant/tolerant lines during S1 generation.
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