Isolation and characterization of PGPR obtained from different arsenic-contaminated soil samples and their effect on photosynthetic characters of maize grown under arsenic stress.

Contamination of the environment due to speedup of anthropogenic activities has become a serious threat to modern humanity. Among the contaminants, the new emerging concern is the heavy metal (HM) contamination in the environment. Because the persistence and harmfulness of heavy metals affect the ecosystem and the health of plants, animals, and humans, they are the most toxic substances in the environment. Among them, Arsenic (As) emerged as major environmental constraint leading to enormous negative effects on the plant, animal, and human health. Even in minute quantity, As is known to cause various critical diseases in humans and toxicity in plants. Research was performed to observe the capability of plant growth-promoting strains of bacteria in enhancing Zea mays (L.) growth in arsenic polluted soil. Total 30 bacterial strains were isolated from the polluted soils, screened for plant growth promotion potential and arsenic tolerance. Eighteen isolates showed resistance to different levels of sodium arsenate (ranging from 0 to 50 mM) in agar plate using LB media. Of 18 isolates, 83.3% produced IAA, methyl red, and hydrogen cyanide; 55.5% exhibited catalase activity; 61.1% showed siderophore production; 88.8% showed phosphate solubilization; and 44.4% showed oxidase, Voges proskauer activity, and KOH solubility. The most efficient isolates SR3, SD5, and MD3 with significant arsenic tolerance and plant growth-promoting (PGP) activity were examined via sequencing of amplified 16S rRNA gene. Isolates of bacteria, i.e., SR3, SD5, and MD3, showing multiple PGP-traits were identified as Bacillus pumilus (NCBI accession number: OR459628), Paenibacillus faecalis (NCBI accession number: OR461560), and Pseudochrobactrum asaccharolyticum (NCBI accession number: OR458922), respectively. Maize seeds treated with these PGPR strains were grown in pots contaminated with 50 ppm and 100 ppm sodium arsenate. Compared to untreated arsenic stressed plants, bacterial inoculation P. asaccharolyticum (MD3) resulted 20.54%, 18.55%, 33.45%, 45.08%, and 48.55% improvement of photosynthetic pigments (carotenoid content, chlorophyll content, stomatal conductance (gs), substomatal CO2, and photosynthetic rate), respectively. Principal component analysis explained that first two components were more than 96% of the variability for each tested parameter. The results indicate that in comparison to other isolates, P. asaccharolyticum isolate can be used as efficient agent for improving maize growth under arsenic polluted soil.

Organic amendments improve salinity-induced osmotic and oxidative stress tolerance in Okra (Abelmoschus esculentus (L.)Moench).

AIMS: Salinity adversely affects okra [Abelmoschus esculentus (L.) Moench] plants by inducing osmotic and oxidative stresses. This study was designed to enhance salinity-induced osmotic and oxidative stress tolerance in okra plants by applying organic amendments. METHODS: The effects of different organic amendments (municipal solid waste compost, farmyard manure (FYM) and press mud) on osmotic potential, water use efficiency, activities of antioxidant enzymes, total soluble sugar, total soluble proline, total soluble protein and malondialdehyde (MDA) contents of okra plants grown under saline conditions (50 mM sodium chloride) were evaluated in a pot experiment. The organic amendments were applied each at the rate of 5% and 10% per pot or in various combinations (compost + FYM, FYM + press mud and compost + press mud each at the rate of 2.5% and 5% per pot). RESULTS: As compared to control, high total soluble sugar (60.41), total soluble proline (33.88%) and MDA (51%) contents and increased activities of antioxidant enzymes [superoxide dismutase (83.54%), catalase (78.61%), peroxidase (53.57%] in salinity-stressed okra plants, were indicative of oxidative stress. Salinity significantly reduced the osmotic potential (41.78%) and water use efficiency (4.75%) of okra plants compared to control. Under saline conditions, 5% (farmyard manure + press mud) was the most effective treatment, which significantly improved osmotic potential (27.05%), total soluble sugar (4.20%), total soluble protein (73.62%) and total soluble proline (23.20%) contents and superoxide dismutase activity (32.41%), compared to saline soil. Application of 2.5% (FYM + press mud), 5% press mud, and 10% compost significantly reduced MDA content (27%) and improved activities of catalase (38.64%) and peroxidase (48.29%), respectively, compared to saline soil, thus facilitated to alleviate oxidative stress in okra plants. CONCLUSIONS: Using organic amendments (municipal solid waste compost, farmyard manure and press mud) was a cost-effective approach to improve salinity-induced osmotic and oxidative stress tolerance in okra plants.

Influence of silicon nano-particles on Avena sativa L. to alleviate the biotic stress of Rhizoctonia solani.

Avena sativa L. a cereal crop that is badly affected by several abiotic and biotic stresses. In the current study, silicon nanoparticles are used to mitigate the harmful effects of root rot disease caused by Rhizoctonia solani Kuhn on the growth of A. sativa. In vitro (Petri plates) and in vivo (pots experiment) were performed to measure the various physiological and biochemical parameters i.e. osmotic potential, chlorophyll, proline content, growth parameters, sugar, fresh and dry weight, and disease index. Results revealed that physiological and biochemical parameters were reduced under fungal stress with silicon nanoparticles treatment as compared to the control group. Si nanoparticles helped to alleviate the negative effects caused by fungus i.e. germination percentage upto 80%, germination rate 4 n/d, radical and plumule length was 4.02 and 5.46, dry weight 0.08 g, and relative water content was (50.3%) increased. Fungus + Si treatment showed the maximum protein content, i.e. 1.2 µg/g as compared to Fungus (0.3 µg/g) treated group. The DI was maximum (78.82%) when the fungus directly attacked the target plant and DI reduced (44.2%) when the fungus was treated with Si nanoparticles. Thus, silicon nanoparticles were potentially effective against the stress of R. solani and also used to analyze the plant resistance against fungal diseases. These particles can use as silicon fertilizers, but further studies on their efficacy under field conditions and improvement in their synthesis are still needed.

GC-MS analysis & antifungal activity of Datura metel L. against Rhizoctonia solani Kuhn.

The current study was designed to evaluate the antifungal properties of Datura metel L. against Rizoctonia solani Kuhn. To achieve this objective, six concentrations of leaves & stem methanol extract of D. metel viz. 1%, 1.5%, 2%, 2.5%, 3% & 3.5% were tested against R. solani in vitro. Leaf extract of D. metel was found more effective as its 3.5% concentration caused 75% retardation in test fungal growth as compared to the stem extract. D. metel methanolic leaf extract was fractioned between n-butanol, n-hexane, chloroform & ethyl acetate & bioactivities of isolated fractions were tested against R. solani. The chloroform fraction was found highly effective, as its concentrations 0.1% & 0.01% caused 27% & 21% growth inhibition respectively. So, this particular chloroform fraction was further analyzed to identify various chemical constituents through GC-MS (Gas chromatography mass spectroscopic) analysis. Twelve phyto-constituents viz. eugenol, 2-pentadecanone 6,10,14 trimethyl, pentadecanoic acid, pentadecanoic acid, 1 4-methyl- methyl ester, phytol, 9,12,15-octadecatrienoic acid, heptacosane, n-hexadecanoic, 6-octadecanoic acid, 9, 12 octadecanoic acid, dodecanoic & tetradecanoic acids were identified. So, the present study concluded that the presence of these bioactive constituents make D. metel as an effective antifungal agent against R. solani.

Isolation and molecular characterization of causal agent of blue mold on Allium cepa L. and its control by Pennisetum flaccidum Griseb.

Blue mold pathogen, isolated from infected Allium cepa L., was identified as a Penicillium species through morphological and molecular characterisation. Internal Transcribed spacer (ITS) region of ribosomal DNA (rDNA) was utilised for DNA sequencing. Basic Local Alignment Search Tool (BLAST) analysis has found the maximum similarity index of the fungus to be 82.39% with the Uncultured Penicillium clone (Accession: MF535522). So, the isolated Penicillium specie is the first reported specie of the genus that infects onion. A phylogenetic tree was constructed to establish a relationship of the isolated fungus with the most relevant species reported on GenBank. Extracts of Pennisetum flaccidum Griseb. were evaluated against the isolated fungus as a potential biocontrol agent. Among the five tested methanol concentrations (0.5%, 1%, 1.5%, 2% and 2.5%) of each plant part (root, inflorescence and foliage), 0.5% root extract showed maximum growth retardation, i.e. 89%. For bioassay-guided fractionation, the root extract was partitioned in n-hexane, chloroform, n-butanol and ethyl acetate. Ethyl acetate (1%) was proved to be the most potent one. Phytochemical screening has confirmed the occurrence of terpenoids, tannins, saponins and alkaloids. The applied molecular approach has deduced that the Penicillium specie collected from Pakistan might be novel. This study can be concluded that P. flaccidum contains potent phytochemicals which might be used as antifungal agent against Penicillium species.

Review: Microwave assisted extraction of phytochemicals an efficient and modern approach for botanicals and pharmaceuticals.

The final quality of pharmaceutically active herbal preparation is significantly contributed by extraction procedures. Hence in the last decade Microwave assisted extraction (MAE) has been introduced. This is an efficient and modern tool with multiple benefits as compared to the traditional methods of extraction. The benefits are in terms of reduction in cost, time of extraction, amount of solvent used, energy consumptions and low CO2 emission. Therefore present study was planned to give brief overview on applications of microwave assisted extraction of natural products. It is also discussed that how the various parameters of microwave assisted extraction like nature of the solvent, temperature, particle size, power level of microwaves and time of irradiation influences the extract yields of plant parts. This review also emphasizes the application of MAE for increased production of phyto-medicines, sweeteners, spices and all other commercial products related to botanicals.

BIOPESTICIDAL ACTIVITY OF Calotropis procera L. AGAINST Macrophomina phaseolina.

BACKGROUND: Mungbean [Vigna radiata (L.) Wilczek] is an important pulse crop globally. This imperative crop is severely affected by charcoal rot disease caused by Macrophomina phaseolina (Tassi) Goid. In the present study, the leaves of Calotropis procera L. were tested for their antifungal potential against M. phaseolina. MATERIALS AND METHODS: Various concentrations i.e. 1%, 2.5%, 4%, 5.5% and 7% of methanolic extract of C. procera leaves were prepared and their in vitro bioactivity was examined against the test fungus. Methnolic leaf extract was partitioned using n-hexane, chloroform, ethyl acetate and n-butanol and antifungal activity of each fraction was evaluated. n-Hexane fraction was subjected to GC-MS analysis. RESULTS: The higher concentration of methanolic leaf extract (7%) caused maximum inhibition in the diameter of M. phaseolina i.e. 38%. The n-hexane fraction of methanolic leaf extract was found to be the most effective against M. phaseolina. Seven compounds belonging to classes of chlorocarbon, aromatic hydrocarbon, azocompounds, aromatic carboxylic acids and fatty acids were identified in GC-MS analysis of n-hexane fraction. CONCLUSION: Antifungal activity of the methanolic leaf extract of C. procera might be due to the presence of the identified compounds in n-hexane fraction of methanolic leaf extract.

Antifungal compounds from Melia azedarach leaves for management of Ascochyta rabiei, the cause of chickpea blight.

The antifungal activity of Melia azedarach L. leaves was investigated against Ascochyta rabiei (Pass.) Lab., the cause of destructive blight disease of chickpea (Cicer arietinum L.). Bioassay guided fractionation revealed that the chloroform fraction of the methanolic extract of M. azedarach leaves was highly effective against A. rabiei. Six compounds, namely ß-sitosterol (1), ß-amyrin (2), ursolic acid (3), benzoic acid (4), 3,5 dimethoxybenzoic acid (5) and maesol (6) were isolated from the chloroform fraction through column chromatography. The in vitro antifungal activity of compounds 2-5 was evaluated against A. rabiei. A commercial fungicide, mancozeb, was used as a positive control. Different concentrations of mancozeb and the isolated compounds, ranging from 0.0039 to 4 mg mL(-1), were used in the antifungal bioassay, and data regarding minimum inhibitory concentration (MIC) was recorded 24, 48 and 72 h after incubation. All concentrations of mancozeb inhibited the fungal spore germination at all three incubation periods. The tested compounds exhibited variable antifungal activity against the target fungal pathogens. All compounds showed their highest antifungal activity after 24 h of incubation. Compound 2 was found to be the most effective, with an MIC of 0.0156 mg mL(-1), followed by compounds 3, 4 and 5, with MIC values of 0.0312, 0.25 and 0.125 mg mL(-1), respectively.

Antifungal activity of Syzygium cumini against Ascochyta rabiei-the cause of chickpea blight.

Aqueous, ethanol and n-hexane extracts from leaves, fruit, root-bark and stem-bark of Syzygium cumini (L.) Skeels were tested for their antifungal activity against Ascochyta rabiei (Pass.) Lab., the cause of blight disease of the chickpea (Cicer arietinum L.). Different concentrations, namely 1, 2, ..., 5% of both aqueous and the two organic solvent extracts were used in this study. Aqueous extracts of all the four test plant parts, namely leaves, fruit, stem-bark and root-bark, showed significant antifungal activity resulting in 7-30%, 22-59%, 23-39% and 21-64% reduction in fungal growth, respectively. Similarly, n-hexane stem-bark extract, and ethanol root- and stem-bark extracts also significantly suppressed the growth of target fungal species, resulting in 17-39%, 24-30% and 12-32% suppression in fungal growth.