Amitabh Singh

Germination Responses of Fungal Spores to Magnetically Restructured Water

The effect of magnetically restructured water was examined on spore germination of some fungi. Restructuring of water was done by exposing the water samples separately to dipoles of a 0.3 T permanent magnet for variable lengths of time. Spore germination of some fungi was observed by mixing the spores in a drop of restructured water samples on separate depression glass slides and incubating the slides for 24 h at 27 ± 2°C. Fungal spores for the present study were obtained from freshly grown cultures of Alternaria alternata, A. carthami, A. mali, A. sesamicola, Aspergillus niger, A. terreus, Fusarium liniand Helminthosporium sativum on potato dextrose Difco powder agar medium. This study reveals that changes in water structure produced by different lengths of exposure by different magnetic poles (of a permanent magnet) differentially inhibit spore germination of various fungi. The varying inhibitory effects of water exposed to different magnetic poles indicates the possible existence of magnetic-pole memor...

Antifungal activity of the mixture of quaternary alkaloids isolated from Argemone mexicana against some phytopathogenic fungi

The anti-fungal activity of a mixture of quaternary alkaloids of Argemone mexicana was observed at different concentrations (1000, 2000, 3000, 4000 and 5000 μl/ml) against 10 fungi, viz., Ustilago cynodontis, Cercospora cajani, Sphaerotheca sp., Cercospora sp., Alternaria solani, Bipolaris sp., Helminthosporium sp., Curvularia sp., Fusarium udum and Alternaria cajani. Spore germination was inhibited at 2000, 3000, 4000, 5000 μg/ml. Analysis of phenolics by high performance liquid chromatography (HPLC) recorded 11 peaks in the alkaloids but only three could be identified, viz., tannic, caffeic and ferulic acids. The significant efficacy of the alkaloid under in vitro conditions may open the possibility of its use by farmers under field conditions for controlling some crop diseases.

The role of phenolic compounds in disease resistance in geranium

The present study was conducted in the hill station of G B Pant University of Agriculture and Technology, Ranichauri, Uttarakhand, which is known for its diversity in medicinal and aromatic plants. The plant geranium, also known as rose or lemon geranium is highly valued for its essential oil which is used in the cosmetic and preferring industries. The plant suffers due to stem and root rot both during summer and winter seasons. In the present study, geranium plants showed maximum stem rot incidence (60.55%) and plant mortality (17.20%) during the winter season, whereas in summer the crops showed maximum root rot and wilt complex incidence (38.33%) with plant mortality up to (12.22%). The average stem rot mortality was comparatively low (16–20%) in summer but increased to 18–26% in winter crop. Several phenolic acids such as as tannic, gallic, caffeic, ferulic and benzoic were detected by using high performance liquid chromatography (HPLC) in variable amounts in these plants. The disease intensity varied from 97.77 to 92.46% from season to season. The significance of the phenolic compounds is discussed in relation to disease prevalence.

Antimicrobial efficacy, disease inhibition and phenolic acid-inducing potential of chloroform fraction of cow urine

High-performance liquid chromatographic (HPLC) analysis of chloroform fraction (CF) of cow urine showed rich pool of phenolic acids. Antifungal and antibacterial bioassays of CF have shown its tremendous efficacy against some fungal plant pathogens as well as human pathogenic bacteria at very low concentrations. The CF also inhibited powdery mildew (Erysiphe cichoracearum) of balsam (Impatiens balsamania) under field conditions during pre- and post-inoculation treatments. HPLC analysis of pre- and post-inoculation-treated plant leaves indicated that CF induced phenolic acid synthesis as compared to control. The results revealed that CF of cow urine has the potential for controlling some important human diseases. The result on balsam powdery mildew is a good signal that CF may also be effective against other plant diseases in the field.

Antifungal activity of two alkaloids of Zephyranthes citrina and their field efficacy against powdery mildew (Erysiphe cichoracearum) of balsam

The anti-fungal activity of two alkaloids isolated from bulbs of Zephyranthes citrina was observed against 10 fungi, viz, Aternaria solani, A. triticina, Curvularia lunata, C. maculuns, Cercospora malvacearum, Erysiphe sp., Fusarium udum, Helminthosporium pisi, H. speciferum and Ustilago cynodontis. Different concentrations (200, 400, 600, 800, 1000 µg/ml of alkaloids (A and B) were used. Spore germination was inhibited at 600, 800, 1000 µg/ml. B alkaloid was used against Erysiphe cichoracearum causing powdery mildew in balsam (Impatiens balsamina) in the field as pre- and post-inoculation treatments at 1000, 1500, 2000 µg/ml doses. The extract was effective in both pre- and post-inoculation treatments. Foliar application of this alkaloid resulted in inducing synthesis of phenolic acid in the leaves of balsam. Maximum phenolics were detected in the leaves treated with 1500 µg/ml in both pre- and post-inoculation treatments. The increase in the production of phenolics in treated leaves of balsam can be correlated with the induction of resistance in treated plants against powdery mildew. The significant efficacy of the alkaloid under field conditions opens the possibility of its use by farmers for also controlling other diseases.

Phenolic Acid Content of Some Apple Cultivars with Varying Degrees of Resistance to Apple Scab

Apple scab caused by Venturia inaequalis (Cke.) Wint. is the most important fungal disease of apple, which occurs every year in severe epidemic form under favorable environmental conditions wherever apple is cultivated. This study considered Garhwal and six districts (Pithoragarh, Nainital, Uttarkashi, Dehradun, Chamoli, and Tehri) of Kumaun in 2004–2008. The incidence and severity of scab was widespread. The statistical analysis, which includes regression analysis, coefficient of determinations R2 = 0.983, and fitting of curves were considered. It was found that disease was most severe in leaves and fruit in both places ranging between 0.5–76% on foliage and 5–42% on fruits and intensity ranged between 0.01 to 0.30% in leaves and fruits during 2004 to 2008. The relationship between incidence and severity is linear and curvilinear up to 25%. The phenolic acid content in apple cultivars is considered as a parameter for resistance. The disease incidence was more in 2007 than in 2004.

Antifungal efficacy of some ethyl acetate extract fractions of Cyperus rotundus rhizomes against spore germination of some fungi

Plant products play an important role as safe and ecofriendly method in controlling various plant diseases. Ethyl acetate fractions of Cyperus rotundus rhizomes have been found highly effective against some species of Alternaria (A. alternata, A. brassicola, A. solani, Alternaria chearanthi), Colletotrichum (C. musae, Colletotrichum sp.), Curvularia (C. lunata, C. maculans, C. pallescens, C. pennisetti), Helminthosporium (H. pennissetti, H. spiciferum, H. echinoclova and Heterosporium colocasiae) in vitro. A. brassisicola was highly sensitive to all the fractions at all the concentrations. Fractions 4–7 inhibited complete spore germination at 2000 and 3000 μg/ml as compared to control. However, 100% spore germination inhibition was found in Colletotrichum species in all the fractions at 2000 and 3000 μg/ml but at lower concentrations 50–60% spore germination and 90% reduction of germ tube elongation were observed. Curvularia species was highly sensitive to all concentrations of all the fractions as 50–100% spore germination inhibition was recorded at 500 μg/ml dose. Some species of Helminthosporium were sensitive at 3000 μg/ml in some fractions but other test fractions showed least efficacy. Fractions 4–7 were 100% inhibitory for H. colocasiae. Germ tube elongation was also affected by 60–90%. The germ tube branching and their elongation were affected in almost all species at 30 to 95%. The high efficacy of ethyl acetate fractions of rhizomes of C. rotundus against some fungi indicates that they can be very well tried under field conditions against some important plant diseases as an ecofriendly method of plant disease control.

Phenolic acid changes in mycelia of Sclerotium rolfsii as influenced by neem (Azadirachta indica) cake and Zephyarenthes citrina bulb.

High performance liquid chromatographic (HPLC) analysis of mycelia of Sclerotium rolfsii grown on neem cake, and Zephyarenthes citrina bulb incorporated media was carried out. Several phenoloic acids, e.g., gallic, tannic, caffeic, cinnamic, chlorogenic and O-coumeric acids, were found in considerable amounts in treated mycelial mat as compared to the control. The amount of phenloic acids increased with increased concentration of both the materials in mycelia of 7 and 14 day-old cultures. Due to anti-oxidant and several other properties of phenolic acids, the senescence of the fungus has been prolonged which may be one probable reason of sustaining the virulence of the pathogen.

Antibiotic potential of plant growth promoting rhizobacteria (PGPR) against Sclerotium rolfsii

High performance liquid chromatographic (HPLC) analysis of culture filtrates of plant growth promoting rhizobacteria (PGPR) and medium of inhibitory zone of interaction of Sclerotium rolfsii with PGPR, viz. Pseudomonas aeruginosa, Pseudomonas fluorescens 4, Pseudomonas fluorescens 4 (new) and Pseudomonas sp. varied from sample to sample. In all the culture filtrates of PGPRs, P. aeruginosa had nine phenolic acids in which ferulic acid (14.52 μg/ml) was maximum followed by other phenolic acids. However, the culture filtrates of P. fluorescens 4 had six phenolic acids with maximum ferulic acid (20.54 μg/ml) followed by indole acetic acid (IAA), caffeic, salicylic, o-coumeric acid and cinnamic acids. However, P. fluorescens 4 culture filtrate had seven phenolic acids in which salicylic acid was maximum (18.03 μg) followed by IAA, caffeic, vanillic, ferulic, o-coumeric and cinnamic acids. Pseudomonas sp. also showed eight phenolic acids where caffeic acid (2.75 μg) was maximum followed by trace amounts of ferulic, salicylic, IAA, vanillic, cinnamic, o-coumeric and tannic acids. The analysis of antibiosis zone of PGPRs showed fairly rich phenolic acids. A total of nine phenolic acids were detected in which caffeic acid was maximum (29.14 μg/g) followed by gallic (17.64 μg/g) and vanillic (3.52 μg/g) acids but others were in traces. In P. aeruginosa, antibiosis zone had seven phenolic acids where IAA was maximum (3.48 μg/g) followed by o-coumeric acid (2.08 μg/g), others were in traces. The medium of antibiosis zone of P. fluorescens 4 and P. fluorescens 4 new had eight phenolic acids in which IAA was maximum with other phenolic acids in traces.

The mixture of tertiary and quaternary alkaloids isolated from Argemone ochroleuca inhibits spore germination of some fungi

The mixture of tertiary and quaternary alkaloids isolated from Argemone ochroleuca was separately assessed against spore germination of some plant pathogenic fungi, e.g. Alternaria alternata, Alternaria brassicae, Alternaria cajani, Bipolaris sp., Curvularia lunata, Curvularia sp., Colletotrichum musae, Fusarium udum, Helminthosporium sp., Helminthosporium pennisetti and Helminthosporium speciferum. Spore germination of Fusarium udum and Helminthosporium sp. was completely inhibited at very low concentration (200 ppm). A similar effect was observed on A. alternata, C. musae and H. pennisetti at 600, 800 and 1000 ppm. With quaternary alkaloids, Curvularia sp. and Colletotrichum musae were most sensitive as complete inhibition of spore germination was observed at 400, 600, 800 and 1000 ppm and a similar effect was observed with A. brassicae and A. cajani at 600, 800 and 1000 ppm. The remaining fungi were also highly sensitive to the mixture at different concentrations.