Biocontrol Screening of Endophytes: Applications and Limitations.

The considerable loss of crop productivity each year due to plant disease or pathogen invasion during pre- or post-harvest storage conditions is one of the most severe challenges to achieving the goals of food security for the rising global population. Although chemical pesticides severally affect the food quality and health of consumers, a large population relies on them for plant disease management. But currently, endophytes have been considered one of the most suitable biocontrol agents due to better colonization and acclimatization potential. However, a very limited number of endophytes have been used commercially as biocontrol agents. Isolation of endophytes and their screening to represent potential characteristics as biocontrol agents are considered challenging by different procedures. Through a web search using the keywords "endophytes as biocontrol agents" or "biocontrol mechanism of endophytes," we have succinctly summarised the isolation strategies and different in vitro and in vivo biocontrol screening methods of endophytic biocontrol agents in the present review. In this paper, biocontrol mechanisms of endophytes and their potential application in plant disease management have also been discussed. Furthermore, the registration and regulatory mechanism of the endophytic biocontrol agents are also covered.

Effect of Microbial Consortium Constructed with Lignolytic Ascomycetes Fungi on Degradation of Rice Stubble.

Microbial degradation is an effective, eco-friendly and sustainable approach for management of the rice residue. After harvesting a rice crop, removal of stubble from the ground is a challenging task, that forces the farmers to burn the residue in-situ. Therefore, accelerated degradation using an eco-friendly alternative is a necessity. White rot fungi are the most explored group of microbes for accelerated degradation of lignin but they are very slow in growth. The present investigation focuses on degradation of rice stubble using a fungal consortium constructed with highly sporulating ascomycetes fungi, namely, Aspergillus terreus, Aspergillus fumigatus and Alternaria spp. All three species were successful at colonizing the rice stubble. Periodical HPLC analysis of rice stubble alkali extracts revealed that incubation with ligninolytic consortium released various lignin degradation products such as vanillin, vanillic acid, coniferyl alcohol, syringic acid and ferulic acid. The efficiency of the consortium was further studied at different dosages on paddy straw. Maximum lignin degradation was observed when the consortium was applied at 15% volume by weight of rice stubble. Maximum activity of different lignolytic enzymes such as lignin peroxidase, laccase and total phenols was also found with the same treatment. FTIR analysis also supported the observed results. Hence, the presently developed consortium for degrading rice stubble was found to be effective in both laboratory and field conditions. The developed consortium or its oxidative enzymes can be used alone or combined with other commercial cellulolytic consortia to manage the accumulating rice stubble effectively.

Exploring Potent Fungal Isolates from Sanitary Landfill Soil for In Vitro Degradation of Dibutyl Phthalate.

Di-n-butyl phthalate (DBP) is one of the most extensively used plasticizers for providing elasticity to plastics. Being potentially harmful to humans, investigating eco-benign options for its rapid degradation is imperative. Microbe-mediated DBP mineralization is well-recorded, but studies on the pollutant's fungal catabolism remain scarce. Thus, the present investigation was undertaken to exploit the fungal strains from toxic sanitary landfill soil for the degradation of DBP. The most efficient isolate, SDBP4, identified on a molecular basis as Aspergillus flavus, was able to mineralize 99.34% dibutyl phthalate (100 mg L-1) within 15 days of incubation. It was found that the high production of esterases by the fungal strain was responsible for the degradation. The strain also exhibited the highest biomass (1615.33 mg L-1) and total soluble protein (261.73 µg mL-1) production amongst other isolates. The DBP degradation pathway scheme was elucidated with the help of GC-MS-based characterizations that revealed the formation of intermediate metabolites such as benzyl-butyl phthalate (BBP), dimethyl-phthalate (DMP), di-iso-butyl-phthalate (DIBP) and phthalic acid (PA). This is the first report of DBP mineralization assisted with A. flavus, using it as a sole carbon source. SDBP4 will be further formulated to develop an eco-benign product for the bioremediation of DBP-contaminated toxic sanitary landfill soils.

Microbes-mediated integrated nutrient management for improved rhizo-modulation, pigeonpea productivity, and soil bio-fertility in a semi-arid agro-ecology.

Excessive dependence on chemical fertilizers and ignorance to organic and microbial inputs under intensive cropping systems are the basic components of contemporary agriculture, which evolves several sustainability issues, such as degraded soil health and sub-optimal crop productivity. This scenario urges for integrated nutrient management approaches, such as microbes-mediated integrated plant nutrition for curtailing the high doses as chemical fertilizers. Rationally, experiment has been conducted in pigeonpea at ICAR-IARI, New Delhi, with the aim of identifying the appropriate nutrient management technique involving microbial and organic nutrient sources for improved rhizo-modulation, crop productivity, and soil bio-fertility. The randomized block-designed experiment consisted nine treatments viz. Control, Recommended dose of fertilizers (RDF), RDF+ Microbial inoculants (MI), Vermicompost (VC), Farm Yard Manure (FYM), Leaf Compost (LC), VC + MI, FYM + MI, and LC + MI. Rhizobium spp., Pseudomonas spp., Bacillus spp., and Frateuria aurantia were used as seed-inoculating microbes. The results indicated the significant response of integration following the trend VC + MI > FYM + MI > LC + MI > RDF + MI for various plant shoot-root growth attributes and soil microbial and enzymatic properties. FYM + MI significantly improved the water-stable aggregates (22%), mean weight diameter (1.13 mm), and geometric mean diameter (0.93 mm), soil organic carbon (SOC), SOC stock, and SOC sequestration. The chemical properties viz. available N, P, and K were significantly improved with VC + MI. The study summarizes that FYM + MI could result in better soil physico-chemical and biological properties and shoot-root development; however; VC + MI could improve available nutrients in the soil and may enhance the growth of pigeonpea more effectively. The outcomes of the study are postulated as a viable and alternative solution for excessive chemical fertilizer-based nutrient management and would also promote the microbial consortia and organic manures-based agro-industries. This would add to the goal of sustainable agricultural development by producing quality crop produce, maintaining agro-biodiversity and making the soils fertile and healthy that would be a "gift to the society."

Nitrogen-enriched biochar co-compost for the amelioration of degraded tropical soil.

Tropical soils are often deeply weathered and vulnerable to degradation having low pH and unfavorable Al/Fe levels, which can constrain crop production. This study aims to examine nitrogen-enriched novel biochar co-composts prepared from rice straw, maize stover, and gram residue in various mixing ratios of the biochar and their feedstock materials for the amelioration of acidic tropical soil. Three pristine biochar and six co-composts were prepared, characterized, and evaluated for improving the chemical and biological quality of the soil against a conventional lime treatment. The pH, cation exchange capacity (CEC), calcium carbonate equivalence (CCE) and nitrogen content of co-composts varied between 7.78-8.86, 25.3-30.5 cmol (p+) kg-1, 25.5-30.5%, and 0.81-1.05%, respectively. The co-compost prepared from gram residue biochar mixed with maize stover at a 1:7 dry-weight ratio showed the highest rise in soil pH and CEC, giving an identical performance with the lime treatment and significantly better effect (p < .05) than the unamended control. Agglomerates of calcite and dolomite in biochar co-composts, and surface functional groups contributed to pH neutralization and increased CEC of the amended soil. The co-composts also significantly (p < .05) increased the dehydrogenase (1.87 µg TPF g-1 soil h-1), ß-glucosidase (90 µg PNP g-1 soil h-1), and leucine amino peptidase (3.22 µmol MUC g-1 soil h-1) enzyme activities in the soil, thereby improving the soil's biological quality. The results of this study are encouraging for small-scale farmers in tropical developing countries to sustainably reutilize crop residues via biochar-based co-composting technology.

Potential Anti-Mycobacterium tuberculosis Activity of Plant Secondary Metabolites: Insight with Molecular Docking Interactions.

Tuberculosis (TB) is a recurrent and progressive disease, with high mortality rates worldwide. The drug-resistance phenomenon of Mycobacterium tuberculosis is a major obstruction of allelopathy treatment. An adverse side effect of allelopathic treatment is that it causes serious health complications. The search for suitable alternatives of conventional regimens is needed, i.e., by considering medicinal plant secondary metabolites to explore anti-TB drugs, targeting the action site of M. tuberculosis. Nowadays, plant-derived secondary metabolites are widely known for their beneficial uses, i.e., as antioxidants, antimicrobial agents, and in the treatment of a wide range of chronic human diseases (e.g., tuberculosis), and are known to "thwart" disease virulence. In this regard, in silico studies can reveal the inhibitory potential of plant-derived secondary metabolites against Mycobacterium at the very early stage of infection. Computational approaches based on different algorithms could play a significant role in screening plant metabolites against disease virulence of tuberculosis for drug designing.

Sludge Amendment Affect the Persistence, Carbon Mineralization and Enzyme Activity of Atrazine and Bifenthrin.

Atrazine and bifenthrin persistence study was carried out in three sludge amended soil under laboratory condition. Atrazine persisted shorter in sludge amended soil sludge-3 (half-life 23.4 days) followed by sludge-2 (half-life 30.1 days) and sludge-1 (half-life 37.1 days) than unamended control (half-life 150.5 days). Bifenthrin followed the similar pattern with sludge-3 (half-life 43.1 days) which increased to 50.3, 60.2 and 75.2 days, respectively in sludge-2, sludge-1 and unamended control representing an immense influence of sludges on degradation. Duncan's Multiple Range Test revealed that carbon mineralization process was significantly influenced by all the sludges (p < 0.0001). Sludge-3 indicated highest Cmin (initial 118.16 to final 133.64 mg CO2-C/kg) in bifenthrin and 129.91 mg CO2-C/kg in atrazine. The relatively high Cmin rate in sludge amended soil than unamended control suggested a lower persistency of both the pesticides and thus decreasing its potential ecological risk. Sludge-3 sludge amended soil increased the dehydrogenase enzyme activity as compared to sludge-1 and sludge-2 sludge in atrazine.