ABSTRACT
Sesame (Sesamum indicum L.), is an important oilseed crop in the tropics and subtropics, referred as “Queen of Oilseeds” owing to its high cooking quality and medicinal value. Sesame production, particularly in India, has been declining since last decade and ‘Leaf blight’ caused by Alternaria spp. is reported to cause yield loss up to 30-40%. Here, we investigated the fungal toxin produced by Alternaria and its pathogenicity. A total of 164 Alternaria strainswere isolated on potato dextrose agar media from the infected sesame leaves showing circular concentric rings with dark brown spots symptoms. All the isolates were screened for cultural and morphological characters. Colour of the fungus was grey to dark brown, formed smooth, raised, fluffy, and regular to irregular margins. Among 164 isolates, 43 isolates were moderately growing and 121 were fast in growth. The DNA of the isolate was amplified with ITS primers and sequence of BLAST results confirmed seven different species of Alternaria of NCBI database. Further, toxigenic potentiality of the isolates was tested with dilutions of culture filtrate (1:1 to 1:5) on sesame leaves. Among 164 isolates, 23 showed toxigenicity, varied from highly toxigenic to least toxigenic. Pathogenicity of the isolates showed that they were highly virulent to less virulent when tested by the detached leaf method. Based on the toxigenicity, the toxin was partially purified and brown coloured paste was recovered. Chemistry of the toxin was confirmed based on the IR, UV, NMR and mass spectra analyses, and it resembled the structure of alternariol mono methyl ether and altenuene which are mycotoxins in nature. Further, bioassay of toxin was carried out at different concentrations (50 to 2000 ppm) on seeds and seedlings of sesame. Maximum inhibition of seed germination of 81.1% was observed at 2000 ppm and the least was 6.67% at 50 ppm. With the increase in the concentration of toxin, the manifestation of the symptom was conspicuous and quick such as marginal, veinal necrosis, drooping and yellowing with lesion formation. From the present study, it is found that the species of Alternaria are responsible for the cause of blight disease symptoms and the toxicity of toxin produced by the pathogen was very high. The Alternaria toxin could inhibit the growth of the plant as well as seed germination rate.
ABSTRACT
Plants have been extensively investigated for exploring their therapeutic potentials, but there are comparatively scanty reports on drugs derived from animal kingdom, except for hormones. During last decade, the toxins that are used for defense by the animals, have been isolated and found useful tools for physiological and pharmacological studies, besides giving valuable leads to drug development. Toxins with interesting results have been isolated from the venoms of snakes, scorpions, spiders, snails, lizards, frogs and fish. The present review describe about some toxins as drugs and their biological activities. Some fungal, bacterial and marine toxins have also been covered in this article.
ABSTRACT
Three dead dogs were brought to the College of Veterinary Medicine, Kyungpook National University for study. Clinically, all the dogs showed emaciation, anorexia, depression, hemorrhagic vomiting and diarrhea for 7~10 days before death. All the clinical signs were first noted for about one month after feeding the dogs with commercial diets. At necropsy, all 3 dogs had severe renal damage with the same green-yellowish colored nephroliths in the renal pelvis. They also showed systemic hemorrhage and calcification of several organs, which might have been induced by uremia. Microscopically, necrosis, calcification and calculi were detected in the renal tubules, and especially in the proximal convoluted tubules and collecting ducts of the kidney. These findings were supportive of a mycotoxic effect, and especially on their kidneys. However, the precise cause of the toxic effect in these cases of canine renal failure could not be determined.