Role of salt precursors for the synthesis of zinc oxide nanoparticles and in imparting variable antimicrobial activity

Synthesis of nanoparticles (NPs) having unique potentials and properties is of great importance in nanotechnology. The NP synthesis techniques may include the wet chemistry to microbial incubation reduction methods. This work reports generation of ZnO NPs by identical preparation including incubation of different zinc salts i.e. zinc acetate, zinc chloride and zinc sulphate as precursors with cell free extracts of Bacillus circulans MTCC 7906 (Bc7906) and Pleurotus florida (Pf). The synthesized NPs exhibited variation in their absorption peaks in UV-Vis spectra which appeared at 275 nm, 325 nm and 375 nm with P. florida for the three salt precursors respectively while the Bc7906 generated ZnO NPs showed peaks between 300-350 nm. A variation in ZnO NP morphology ranged from 50 to 120 nm in size and spherical, oval, cylindrical to trigonal anisotropic in shape by transmission EM. Further, the rough and corrugated surface topography of ZnO NPs was observed in Scanning EM. The % weight for Zn element surface composition as recorded by SEM-EDS was observed to be highest for zinc acetate (2.34%) and zinc sulphate (7.54 %) on microbial synthesis from Bc7906 and Pf respectively. The antimicrobial potential of the synthesized ZnO NPs on human pathogenic and plant beneficial bacteria was tested and it was observed to be highest for microbially synthesized ZnO NPs using zinc acetate (15 mm) and zinc sulphate (14 mm) as salt precursors @ 10 ppm. This is the first report on differential antimicrobial behavior of ZnO NPs on human pathogenic and plant beneficial microbes

Scanning electron microscopic studies of Beauveria bassiana against Lipaphis erysimi Kalt

This work was aimed to identify the LC50 of the indigenous fungal isolates for controlling L. erysimi infesta-tion in mustard aphid besides to probe the mechanism of action of the local isolates and comparison of the efficacy with the reference culture and commercial formulation ‘Mycojaal’. Three isolates of entomopathogenic fungi Beauveria bassiana were tested for infection on nymph of Lipaphis erysimi Kalt. using scanning electron microscopy (SEM) to record any variation. The SEM revealed adhesion of spores of B.bassiana followed by penetration of L.erysimi nymph surface. It was observed that all Beauveria isolates showed little variation with respect to penetration and adhesion at different time intervals. Further, lethal concentration (LC50) values of B. bassiana isolates against L. erysimi was recorded and was lowest (0.05x107 spores/ml) in B. bassiana MTCC 4495 and highest (0.11.X107 spores/ml) was recorded in native isolate F10 after 120 hours of treatment. The study has established the need for the isolation and evaluation of the indigenous Beauveria isolate. Moreover, it also exhibited the efficacy of the reference and commercially available biocontrol agents

Scanning Electron Microscopy study of root tissue of muskmelon: Transferring Fusarium wilt resistance from snapmelon to muskmelon

The overall aim of this study was to investigate the level of Fusarium oxysporum f. sp. Melonis (F.o.m.) infection by studying the Scanning electron micrographs of transverse sections of parent inbred lines and developed F1 hybrid. The current study involved KP4HM-15 (Fusarium wilt resistant inbred line) in a crossing program with well adapted muskmelon cv. Punjab Sunehri (PS) to develop FW resistant hybrid possessing high yield and quality traits. Fom infects melon root and trails through the cortical and endodermal cells to reach xylem vessels by penetrating through pits. This is the first SEM appraisal of the whole tap root of field grown melon accessions, KP4HM-15, PS and PSxKP4HM-15 (MH-41) (F1 hybrid) aimed to discern the role of the root morphometric characters for imparting FW resistance. The trend for root epidermo-cortical thickness was KP4HM-15>PS>MH-41 while for the xylem diameter was MH-41> KP4HM-15>PS. The F1 hybrid exhibited FW resistance intermediate among the two parents i.e. absence or presence of less mycelia as compared to the susceptible parent (PS). However, the extent of infection was higher than the resistant parent KP4HM-15, which shows that partial resistance was transferred from KP4HM-15 to MH-41. This study accentuates the resistance gene mining and use of wild melon accessions to introgress FW resistance in commercial melon cultivars

Antimycotic activity of biogenically synthesised metal and metal oxide nanoparticles against plant pathogenic fungus Fusarium moniliforme (F. fujikuroi)

263-270Consistent and injudicious application of antifungal agents to control fungal pathogens on crops results in off-target ill-effects on livestock and human health besides issues, such as disruption of ecological balance. In this context, development of novel specific antifungal agents such as metal or metal oxide nanoparticles without side effects becomes a necessity. Here, we attempted green synthesis of three different metal and metal oxide nanoparticles (NPs) (Ag, ZnO and FeO) by incubating metal salts with Trichoderma harzianum hyphal or mycelial extract (HE). The AgNPs were also generated using hyphal filtrate (HF). The synthesized nanoparticles were characterized by microscopy and spectroscopy techniques and evaluated by poisoned food technique/agar well diffusion technique under in vitro conditions on Czapek dox agar against plant pathogenic fungus Fusarium moniliforme. The tested NPs exhibited varied efficacy for curbing the growth of F. moniliforme. A NP concentration dependent increase in percent growth inhibition was recorded for the above mentioned three types of NPs. Moreover, the antimycotic efficacy of the microbial synthesized Ag NPs also varied for the T. harzianum cell free filtrate and hyphal extract formulations. Maximum percent hyphal growth inhibition (58.83%) was recorded for T. harzianum HE Ag NPs at 800 ppm followed by FeO NPs at 400 ppm (40.38%)

Isolation of endophytic actinomycetes from Syzygium cumini and their antimicrobial activity against human pathogens

Isolation of endophytic actinomycetes is an important step to screen antimicrobial compounds to curb the threat of drug-resistant strains of human pathogens. Out of the 50 endophytic actinomycetes obtained from surface sterilized root, stem and leaf tissues of Syzygium cumini, 50 isolates (30%) exhibited antimicrobial activity. Antistaphylococcal activity was displayed by most of the isolates, with maximum percent inhibition by J-10 (Mean of Inhibition Factor=12.12 mm2). A total of 8 isolates (4 each) were able to hydrolyse protein (proteinase activity) and solubilize chitin (chitinase activity). Results of thin layer chromatography confirm the production of chloramphenicol family |antibiotic by the isolate J-5. This is the first report providing an insight into untapped endophytic actinomycete milieu of Syzygium cumini yet to be explored which might be a promising source for novel antimicrobial agents

Penicillum oxalicum spg1: A novel entomopathogenic fungus isolated from mummified Bemisia tabaci (Gennadius) of cotton

Whitefly has assumed the status of a serious pest of cotton in north India in recent past due to its severe attack on cotton crop. The productivity of cotton crop has fallen substantially from 574 kg ha-1 of lint in the year 2014 -15 to 197 kg ha-1 in the year 2015-16 in Punjab. During extensive epidemiological surveillance of whitefly on cotton crop in the month of September 2016, mummified whiteflies with fungus were noticed on both abaxial and adaxial surfaces of leaves of the infested cotton plant at village, Mandi Khurd, Mansa District of Punjab, India and at Punjab Agricultural University, Regional Research Station, Bathinda, India. The fungus was isolated and purified from the mummified white fly and characterized at molecular level by sequencing 633 bp D2 region of Large Subunit (LSU) rRNA gene and identified as Penicillium oxalicum spg1. The gene sequence has been submitted to NCBI, USA with accession no. KY214238. The microscopic studies (stereo- and scanning electron) of the cotton leaves with mummified whitefly further strengthen the entomopathogenic potential of P. oxalicum spg1. There are few reports of entomopathogenic potential of P. oxalicum spg1 against other insects and pests. To our knowledge, this is the first report of isolation and identification of P. oxalicum spg1 from mummified white fly. It’s potential as a biocontrol agent against white fly can be exploited in a promising way with nominal interference with biological equilibrium

Zinc-Based Nanomaterials for Diagnosis and Management of Plant Diseases: Ecological Safety and Future Prospects

A facet of nanorenaissance in plant pathology hailed the research on the development and application of nanoformulations or nanoproducts for the effective management of phytopathogens deterring the growth and yield of plants and thus the overall crop productivity. Zinc nanomaterials represent a versatile class of nanoproducts and nanoenabled devices as these nanomaterials can be synthesized in quantum amounts through economically affordable processes/approaches. Further, these nanomaterials exhibit potential targeted antimicrobial properties and low to negligible phytotoxicity activities that well-qualify them to be applied directly or in a deviant manner to accomplish significant antibacterial, antimycotic, antiviral, and antitoxigenic activities against diverse phytopathogens causing plant diseases. The photo-catalytic, fluorescent, and electron generating aspects associated with zinc nanomaterials have been utilized for the development of sensor systems (optical and electrochemical biosensors), enabling quick, early, sensitive, and on-field assessment or quantification of the test phytopathogen. However, the proficient use of Zn-derived nanomaterials in the management of plant pathogenic diseases as nanopesticides and on-field sensor system demands that the associated eco- and biosafety concerns should be well discerned and effectively sorted beforehand. Current and possible utilization of zinc-based nanostructures in plant disease diagnosis and management and their safety in the agroecosystem is highlighted

Isolation and biochemical characterization of microalgae from waterlogged areas of Southwest Punjab

700-707Microalgae are considered as a potential feedstock for producing sustainable biofuel. The high growth rate and ability to rapidly improve the strains for high lipid and carbohydrate content without competing for arable land, makes microalgae a viable option for sustainable fuel production. Five microalgae designated as MA-1, MA-2, MA-3, MA-4 and MA-5 were isolated from the waterlogged areas of villages Theri, Ghagga and Gurusar of district Muktsar, Punjab. On the basis of optical and scanning electron microscopy, these microalgal isolates were found to be round in shape, green coloured and unicellular in structure and were tentatively identified as Chlorella sp. Chlorella sp. MA-1 was found to be fast growing with maximum absorbance (A600nm), viable cell count and chlorophyll content of 3.26, 369.4×105 cfu/mL and 24.31 mg/g dry wt., respectively at 5 days after culturing (DAC) However, significantly high total soluble protein content of 11.42% was found in this isolate at 5 days after culturing. Chlorella sp. MA-3 showed significantly high total carbohydrate content of 5.10 percent at 5 days after culturing (DAC), whereas the total lipid content was found to be significantly high in Chlorella sp. MA- 2 (4.16%) at 7 DAC. Alteration in the environmental and culturing conditions can further improve the chemical constituents of these microalgal isolates to improve biofuel production