Robin Gogoi

Nanosulfur: A Potent Fungicide Against Food Pathogen, Aspergillus niger

Elemental sulfur (S0), man’s oldest eco‐friendly fungicide for curing fungal infections in plants and animals, is registered in India as a non‐systemic and contact fungicide. However due to its high volume requirement, Indian agrochemical industry and farmers could not effectively use this product till date. We hypothesize that intelligent nanoscience applications might increase the visibility of nanosulfur in Indian agriculture as a potent and eco‐safe fungicide. Sulfur nanoparticles (NPs) were synthesized bottom‐up via a liquid synthesis method with average particle size in the range of 50–80 nm and the shapes of the NPs were spherical. A comparative study of elemental and nano‐sulfur produced has been tested against facultative fungal food pathogen, Aspergillus niger. Results showed that nanosulfur is more efficacious than its elemental form.

Endophytes: exploitation as a tool in plant protection

Endophytes are symptomless fungal or bacterial microorganisms found in almost all living plant species reported so far. They are the plant-associated microbes that form symbiotic association with their host plants by colonizing the internal tissues, which has made them valuable for agriculture as a tool in improving crop performance. Many fungal endophytes produce secondary metabolites such as auxin, gibberellin etc that helps in growth and development of the host plant. Some of these compounds are antibiotics having antifungal, antibacterial and insecticidal properties, which strongly inhibit the growth of other microorganisms, including plant pathogens. This article reviews the endophyte isolated from different plants, mode of endophytic infection and benefits derived by the host plant as a result of endophytism.

Suitability of Nano-sulphur for Biorational Management of Powdery mildew of Okra (Abelmoschus esculentus Moench) caused by Erysiphe cichoracearum

New nano-sulphur synthesized at IARI and three other commercial products namely commercial sulphur (Merck), commercial nano-sulphur (M K Impex, Canada) and Sulphur 80 WP (Corel Insecticide) were evaluated in vitro for fungicidal efficacy at 1000 ppm against Erysiphe cichoracearum of okra. All the sulphur fungicides significantly reduced the germination of conidia of E. cichoracearum as compared to control. Least conidial germination was recorded in IARI nano-sulphur (4.56%) followed by Canadian nanosulphur (14.17%), Merck sulphur (15.53%), sulphur 80 WP (15.97%) and control (23.09%). Non-germinated conidia count was also high in case of IARI nanosulphur followed by Canadian nano-sulphur, Merck sulphur and Sulphur 80WP. Apart from inhibition of conidial germination, cleistothecial appendages were also disrupted in contact with nano-sulphur and the cleistothecia became sterile. The study proved that IARI nano-sulphur is more effective than the commercial formulations and could be applied at lower amount for controlling powdery mildew disease for its better efficacy.

Effect Sulfur and ZnO Nanoparticles on Stress Physiology and Plant (Vignaradiata) Nutrition

Phytotoxic and agro beneficial properties of antimicrobially efficient Sulfur nanoparticles (SNPs) and ZnO nanoparticles (ZNPs) were evaluated on Mung (Vigna radiata). Mung seeds were germinated with an increasing concentration gradient of nanoparticles. The extent of phtotoxicity were assessed depending upon the effect of used nanoparticles on physical factors (relative root and shoot length, dry weight and area of leaves), photosynthetic pigments (chlorophyll, carotene and xanthophyll content) and mitochondrial stress indicator level (thiol), A simultaneous study was undertaken to understand the effect of SNPs and ZNPs on overall plant growth and nutrition. The nutritive values of nanoparticles were determined in terms of total lipid and protein content. All the aforementioned biochemical assays were performed in triplicate for statistical viability.

Azomethine based nano-chemicals: Development, in vitro and in vivo fungicidal evaluation against Sclerotium rolfsii, Rhizoctonia bataticola and Rhizoctonia solani

Fungal diseases posing a severe threat to the production of pulses, a major protein source, necessitates the need of new highly efficient antifungal agents. The present study was aimed to develop azomethine based nano-fungicides for protecting the crop from fungal pathogens and subsequent yield losses. The protocol for the formation of nano-azomethines was generated and standardized. Technically pure azomethines were transformed into their nano-forms exploiting polyethylene glycol as the surface stabilizer. Characterization was performed by optical (imaging) probe (Zetasizer) and electron probe (TEM) characterization techniques. The mean particle sizes of all nano-fungicides were below 100nm. In vitro fungicidal potential of nano-chemicals was increased by 2 times in comparison to that of conventional sized azomethines against pathogenic fungi, namely, Rhizoctonia solani, Rhizoctonia bataticola and Sclerotium rolfsii. The performance of nano-chemicals in pot experiment study was also superior to conventional ones as antifungal agent.

Evaluation of 19,460 Wheat Accessions Conserved in the Indian National Genebank to Identify New Sources of Resistance to Rust and Spot Blotch Diseases

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat–Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011–14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.

Sensitive and rapid determination of elemental nanosulfur/sulfur by liquid chromatography

In order to identify the most suitable method for the estimation of nanosulfur for studying its residue dynamics, the present work was taken up. HPLC and GC methods were explored for its analysis. A comparative study of the existing analytical methods for the quality control of nanosulfur was undertaken. UV spectrophotometry and HPLC methods were superior with lower LOD when compared to GC-MS, which was not satisfactory due to breakage of catenated S20 into S6 and S8 . The method has been validated by analyzing various nanosulfur formulations of known concentrations. The recovery of the UV and HPLC methods ranged from 80.71 to 109.51% and 82.31 to 109.84%, respectively. The LOD of UV, GC-MS, and HPLC is 4, 20, and 1 ppm, respectively. The retention time of sulfur was 13.77 (HPLC), 2.89 (ultra high performance liquid chromatography), and 12.715 + 21.524 min (GC-MS). The method was successfully utilized for estimating sulfur in natural samples such as water from a sulfur hot spring and wastewater. The method has been validated by following the method recommended by the American Society for Testing and Materials. The HPLC method emerged as the best analytical method for the estimation of elemental sulfur.

Characterization of Nanocomposites in Flyash for Possible Pesticide Application

Fly ash composed of crystalline abrasive silica alumina etc is a major source of pollution in and around Kolaghat thermal power plant, West Bengal. In an attempt to find ecofriendly use of fly ash, 300 kg of fly ash was taken to size range of 20–100 nm by (a) sieving, filtration followed by sonication and (b) long time low speed ball milling. Resultant slurry containing polydisperse naked nanoparticle mix was characterized using DLS, SEM, EDAX, and TEM etc. We hypothesized that immobilization of nanoflyash on solid matrix, and as a support for slow release of fumigants/fungicides/bactericides would usher in a variety of usages as value added low cost tiles in bathrooms and similar public utilities in India. Accordingly, we report here the preparation of metal and clay tiles with nanocomposite and nanoflyash. These tiles were impregnated with a number of other nanoparticles of choice.

Leaf rot disease of cauliflower caused by Choanephora cucurbitarum in India

Leaf rot of cauliflower caused by Choanephora cucurbitarum is reported for the first time in India. Koch’s postulates were fulfilled for the first time for this fungus-host association demonstrating that C. cucurbitarum, known to be the pathogen behind soft rot on numerous hosts is also a pathogen of cauliflower.

Characterization of yellow rust resistance genes by using gene postulation and assessment of adult plant resistance in some Indian wheat genotypes

The yellow rust caused by Puccinia striiformis f.sp. tritici is an important constraint to wheat production worldwide. Host resistance is the most economicalway to manage yellow rust. Race-specific resistance is short-lived and overcome by the evolution of new races of the pathogens. However, non-race-specific, or quantitative resistance, controlled by many genes and effective at the adult plant stage, is generally considered to be more durable and long-lasting. Such type of resistance should be of primary interest to wheat breeders around the world. With this background, old wheat genotypes/cultivars were evaluated against different pathotypes of Puccinia striiformis for resistance at both the seedling and adult plant stages. By applying the gene matching technique, three yellow rust resistance genes viz., Yr2, Yr9 and Yr18 were postulated. Adult plant resistancewas assessed through host response and epidemiological parameters i. e. final rust severity, relative area under rust progress curve, coefficient of infection and infection rate. Promising adult plant resistance was observed on the cultivars DBW 17, DBW 71, PDW 314, HS 507, VL 804, VL 829, VL 907, HPW 251, HPW 349, HD 2967, HD 2985, HD 3043, HD 3086, PBW 660, C 306, HI 1563, WH 1021, WH 1080 and Raj 4083 consistently during rabi seasons of 2013–15. All these promising yellow rust resistant cultivars at adult plant stage were susceptible at seedling stage to one or more pathotype(s) of yellow rust, which indicated the presence of adult plant resistance. At seedling stage, adult plant resistance gene Yr18 was characterized in eight cultivars, namely, HS 277, VL 804, VL 829, HD 2733, NI 5439, NIAW 34, PBW 175 and C 306 where, it occurred in combination with other genes in the seven cultivars. All these wheat cultivars exhibited effective adult plant resistance.