Plant Bioassays Research Articles

Screening and field evaluation of white clover rhizobia for New Zealand pastures

Context Biological nitrogen (N) fixation through the rhizobia–legume symbiosis is a sustainable and cost-effective source of N for agriculture. In New Zealand (NZ), white clover (Trifolium repens) is a key component of pastures and rhizobial inoculation of clover is widely used. The current commercial inoculant for white clover, TA1, was isolated in Australia in the 1950s and may not be the best partner for modern white clover cultivars. Aims To identify Rhizobium leguminosarum bv. trifolii (Rlt) isolates suitable for use in NZ pastures. Methods The symbiotic potential of >230 isolates collected from throughout NZ was evaluated in plant bioassays. Selected isolates were further evaluated in pot and field trials. Key results Approximately 40% of NZ isolates supported better clover growth than TA1 under N-limited conditions in vitro. Of 24 Rlt isolates evaluated in a glasshouse trial, five produced significantly higher clover biomass than TA1. Three (S11N9, S20N7, S4N6) of nine isolates evaluated in two field trials in 2018–2019 significantly increased clover growth (12–38%) compared with paired uninoculated clover at several harvests, whereas inoculation with TA1 did not improve yield. In a third trial in 2020, S11N9 and S20N7 increased clover growth compared with the uninoculated control at two of three harvests; S4N6 performed better than TA1 at one harvest. When tested with four white clover cultivars, five Rlt isolates had higher symbiotic potential than TA1. Conclusions Inoculating white clover would be beneficial if improved inoculant isolates were available. Implications We recommend some NZ Rlt isolates could be developed into commercial inoculants to improve white clover performance in NZ.

Bacillus cereus EC9 protects tomato against Fusarium wilt through JA/ET-activated immunity.

The mechanisms of action and the limitations of effectiveness of natural biocontrol agents should be determined in order to convert them into end products that can be used in practice. Rhizosphere Bacillus spp. protect plants from various pathogens by displaying several modes of action. However, the ability of Bacillus spp. to control plant diseases depends on the interaction between the bacteria, host, and pathogen, and the environmental conditions. We found that soil drenching of tomato plants with the non-antifungal Bacillus cereus strain EC9 (EC9) enhances plant defense against Fusarium oxysporum f. sp. lycopersici (Fol). To study the involvement of plant defense-related phytohormones in the regulation of EC9-activated protection against Fol, we conducted plant bioassays in tomato genotypes impaired in salicylic acid (SA) accumulation, jasmonic acid (JA) biosynthesis, and ethylene (ET) production, and analyzed the transcript levels of pathways-related marker genes. Our results indicate that JA/ET-dependent signaling is required for EC9-mediated protection against Fol in tomato. We provide evidence that EC9 primes tomato plants for enhanced expression of proteinase inhibitor I (PI-I) and ethylene receptor4 (ETR4). Moreover, we demonstrated that EC9 induces callose deposition in tomato roots. Understanding the involvement of defense-related phytohormones in EC9-mediated defense against Fusarium wilt has increased our knowledge of interactions between non-antifungal plant defense-inducing rhizobacteria and plants.

Geochemical analyses of metal(loid) fractions do not predict plant uptake behavior: Are plant bioassays better tools to predict mine rehabilitation success?

Management of metal(loid) tailings at historic sites presents environmental hazards usually requiring rehabilitation to mitigate pollution risks. Strategies employed include capping or establishing vegetation directly, which requires tailings assessments to determine suitable rehabilitation approaches. Assessments are typically geochemical analyses, but plant based approaches may provide a more accurate measure of revegetation success although they are often limited to germination indices. This study uses the plant bioassay (Rhizotest™) with common geochemical assessment to predict plant uptake of metal(loid)s and the subsequent likely rehabilitation success. Pb/Zn tailings from five legacy sites within the UK and Ireland were characterized for pH, EC, water soluble and CaCl2-extractable content and aqua regia extractable content. Uptake of Sb, As, Cd, Cu, Ca, Mg, Mn, Zn, Pb was determined in shoots and roots of Lolium perenne.Total Zn, Pb, Sb, Cd and As in tailings ranged from 694 to 2683 mg kg−1, 1252 to 8072 mg kg−1, 14 to 148 mg kg−1, 1.3 to 44 mg kg−1 and 1.3 to 45 mg kg−1, respectively. The only correlation found between total and water soluble or CaCl2-extractable metal(loid) contents was for Cd, where r = 0.8 for total and CaCl2-extractable fractions. Limited uptake and translocation risk was identified for major contaminants Zn and Pb in most tailings samples but in some cases exceedance of phytotoxic threshold values occurred that was not reflected in geochemical analysis. Crucially, although total Cd and Sb content was relatively low (< 20 mg kg−1) in some tailings, elevated plant content for some samples highlights phytotoxic risk from minor elements. Results indicate that screening based on geochemical content is not sufficiently predictive of metal(loid) phytoavailability to reliably inform mine rehabilitation strategies. We therefore strongly recommend that geochemical analyses are supplemented with plant based bioassay to plan mine tailings revegetation and reduce risk of wider ecosystem metal(loid) transfer.

Field evaluation of spray drift and nontargeted soybean injury from unmanned aerial spraying system herbicide application under acceptable operation conditions.

Droplets of plant production products sprayed from unmanned aerial spraying system (UASS) applications are prone to drift, threatening nontarget crops, humans, and environment. There are few studies that have investigated plant bioassay of UASS spray drift, and even fewer when it comes to herbicide application. This work reports a combined field-scale evaluation of spray drift and plant bioassay for a rice herbicide florpyrauxifen-benzyl application using a six-rotor motor UASS under acceptable operating conditions. An artificial rice canopy was built to simulate a practical field application scenario and the soybean was applied to assess the nontargeted crop injury. The effects of nozzle type (droplet size), flight height, and adjuvant on spray deposition, sedimenting drift, airborne drift, and soybean injury were studied to explore the feasibility of UASS herbicide application. Under an average wind speed of 1.2-1.5m s-1 , reduced flight height, increased droplet size, and adding nonionic surfactant resulted in greater deposition, lower drift, and less injury to soybean. Increasing droplet size by changing the nozzle was more effective compared with adding adjuvant and reducing the flight height, which offers greater flexibility and can accomplish better spray performance. The correlations between sedimenting drift and soybean injury percentage were highly significant (P < 0.01, r > 0.96). The calculated buffer distances of 7.7-18.9m were to varying degrees less than the soybean safety distances of 10.0-20.0m. The results of this study provide a reference basis for determining optimum working parameters and establishing buffer zones for the rice herbicide application of UASS. © 2022 Society of Chemical Industry.

Herbicides in unexpected places: non-target impacts from tree root exudation of aminopyralid and triclopyr following basal bark treatments of invasive chokecherry (Prunus padus) in Alaska

AbstractBasal bark treatment of invasive trees is an approach designed to limit damage to non-target vegetation in the vicinity, but non-target injury is still documented. No study of basal bark treatments has examined the release of herbicide residues from roots of treated plants and resulting non-target impacts. Studies were conducted in Alaska interior and coastal boreal forests on basal bark treatments with aminopyralid and triclopyr on active-growth and dormant invasive chokecherry (Prunus padus L.). The study assessed non-target damage and soil herbicide residue using a combination of visual evaluations, bioassays, and soil residue analyses. Non-target damage from herbicide residues were identified in 40% of treatments containing aminopyralid with triclopyr, 60% of treatments containing aminopyralid alone, and 5% of treatments containing only triclopyr. Laboratory studies of aminopyralid treatments to saplings isolated the effects of herbicide exudation from roots, which was found to be significant, and the magnitude was dependent on dose. Herbicide soil residues in field and laboratory experiments were quantified with analytical detection and plant bioassays. Aminopyralid soil residues were identified in 57% of field treatments receiving 8 to 60 ml of herbicide solution (2% ai) and 70% of laboratory treatments receiving 10 µl of herbicide solution (2% to 16% ai). Triclopyr residues were found from one field treatment following dosage with 28 ml of herbicide solution (18.5% ai). Anatomically, plants grown in soils associated with herbicide-treated trees, both in the field and lab, grew less dry mass than non–herbicide treated controls. This study provides the first evidence that root exudation of herbicide following basal bark treatments contributes to non-target damage of adjacent vegetation and to accumulation of soil herbicide residues. This is an important new factor for integrated pest management within basal bark treatment systems and has implications for other herbicide application types such as injections and frill, as well as determining whether root exudation is species or herbicide specific.

Evaluation of commonly used nematicides with combined in in vitro and in planta bioassays

Summary For efficient use of available synthesised nematicides, bioassay-guided analysis is required to understand the behaviours of nematicides. In this study, the key nematicides on the market, including avermectin B1a, avermectin B2a, emamectin benzoate, fluensulfone, fluopyram and fosthiazate, were evaluated by both in vitro and in planta approaches with optimised solvent and nematode inoculum. We found that acetone was the only one of the six solvents tested safe for both root-knot nematode (RKN) second-stage juveniles (J2) and cucumber at the tested concentration. The optimal numbers of RKN J2 for inoculation on cucumber seedlings in the glass-tube assay, cup assay and microplot experiment were 200, 700 and 1250, respectively. No obvious phytotoxicity symptoms were observed in the in planta assays for all nematicides selected at the tested concentration in the soil drench application. When the substrate changed from pure sand to matrix-sand, the EC50 and EC90 of all six nematicides increased. Among them, fluopyram rose the most. In the microplot experiment, avermectin B2a showed the lowest EC50 but the EC90 of avermectin B2a, fluensulfone, fluopyram and fosthiazate were similar. The results are useful as a guide to the application of commonly used nematicides in the field.

Agronomic Efficiency of Phosphorus Fertilisers Recovered from Milk Processing Waste

The recovery of phosphorus (P) from milk processing flotation sludges (MFS) using pyrolysis can contribute to a sustainable reuse of P by converting waste to fertiliser. The objectives of this study were to quantify the recovery and transformation of P following MFS pyrolysis and compare the efficacy of raw and pyrolysed MFS as organic P fertilisers. Phosphorus retention in biochars was high (98 ± 0.73% yield), leading to the enrichment of P relative to the raw MFS by a factor of 4.3–4.5. Pyrolysis of the MFS at 450 °C led to a 3-fold increase in the proportion of P in the HCl-extractable fraction (65 ± 0.32%), a 2-fold reduction in NaOH-P (30 ± 2.1%), and negligible amounts of P in the H2O-P and NaHCO3-P fractions. The bioavailability of P in raw MFS and 450 °C biochar was compared to a soluble P fertiliser in P-limiting plant bioassays. In the short-term (70 day) trial where ryegrass was grown on three soil types (Arenosol, Vertisol or Ferralsol), biochar MFS showed higher efficacy as a P fertiliser than raw MFS in the acidic Ferralsol, whereas the opposite response was observed in the near-neutral Arenosol. In the Vertisol, neither the raw MFS nor biochar produced more cumulative biomass or P uptake than any of the nil P controls. Over a longer 200-day period, raw MFS and biochar applied to the Arenosol were about 20% as efficient at providing P to ryegrass plants as the water-soluble K2PO4, suggesting that higher application rates of MFS or biochar would be required to match synthetic fertilisers in the short term.

Effect of Long Term Fertilization Practices on Tembotrione Movement in Soil: Assessment by Plant Bioassay

The herbicide behavior in soils is executed nowadays via the chemical extraction and instrumental analysis. However, the biological availability and the dynamics of herbicide in soil could be studied effectively through bioassay in the absence of sophisticated techniques and also in situ conditions. Tembotrione is one of the recently registered triketone herbicide and its movement behavior was not studied much in India. Hence the present study was executed to understand the influence of long term fertilization practices on its transport and movement using the bioassay technique involving Randomized Block Design (RBD). The plot wise soil samples were collected from the 50 years old long term fertilization experiment, processed and used to conduct the leaching column (made of PVC) experiment under controlled condition for 30 days. Soil samples were dissected depth wise and residue of tembotrione in each depth was obtained by conducting bioassay using green gram and sunflower as test species. For calibration curve preparation, a separate bioassay was conducted by fortifying tembotrione in control soil at different concentrations. The recorded plant parameters viz., germination percent and biomass after 15th day of both the test species predicted the tembotrione transport efficiently and the results of both the test species were comparable. The tembotrione has shown movement upto 30 cm soil depth and the concentration of residue decreased with increase in soil depth. The long term fertilization practices with the balanced nutrients supply viz., 100% NPK with hand weeding, Zn, FYM showed significant effect on the transport of tembotrione in soil at various depths.&#x0D; The study concludes that the plant bioassay technique using green gram and sunflower could be very well used to investigate the transport behavior of Tembotrione in soil. Based on data, tembotrione was identified as moderately mobile compound in sandy clay loam and its movement has been altered by the long term fertilization practices.

Stress-Tolerant Endophytic Isolate Priestia aryabhattai BPR-9 Modulates Physio-Biochemical Mechanisms in Wheat (Triticum aestivum L.) for Enhanced Salt Tolerance.

In efforts to improve plant productivity and enhance defense mechanisms against biotic and abiotic stresses, endophytic bacteria have been used as an alternative to chemical fertilizers and pesticides. In the current study, 25 endophytic microbes recovered from plant organs of Triticum aestivum L. (wheat) were assessed for biotic (phyto-fungal pathogens) and abiotic (salinity, drought, and heavy metal) stress tolerance. Among the recovered isolates, BPR-9 tolerated maximum salinity (18% NaCl), drought (15% PEG-6000), and heavy metals (µg mL−1): Cd (1200), Cr (1000), Cu (1000), Pb (800), and Hg (30). Based on phenotypic and biochemical characteristics, as well as 16S rDNA gene sequencing, endophytic isolate BPR-9 was recognized as Priestia aryabhattai (accession no. OM743254.1). This isolate was revealed as a powerful multi-stress-tolerant crop growth promoter after extensive in-vitro testing for plant growth-promoting attributes, nutrient (phosphate, P; potassium, K; and zinc, Zn) solubilization efficiency, extracellular enzyme (protease, cellulase, amylase, lipase, and pectinase) synthesis, and potential for antagonistic activity against important fungal pathogens viz. Alternaria solani, Rhizoctonia solani, Fusarium oxysporum, and Ustilaginoidea virens. At elevated salt levels, increases were noted in indole-3-acetic acid; siderophores; P, K, and Zn-solubilization; ACC deaminase; and ammonia synthesized by Priestia aryabhattai. Additionally, under in-vitro plant bioassays, wheat seedlings inoculated with P. aryabhattai experienced superior growth compared to non-inoculated seedlings in high salinity (0–15% NaCl) environment. Under NaCl stress, germination rate, plant length, vigor indices, and leaf pigments of wheat seedlings significantly increased following P. aryabhattai inoculation. Furthermore, at 2%-NaCl, B. aryabhattai greatly and significantly (p ≤ 0.05) decreased relative leaf water content, membrane damage, and electrolyte leakage compared with the non-inoculated control. Catalase, superoxide dismutase, and peroxidase activity increased by 29, 32, and 21%, respectively, in wheat seedlings exposed to 2% NaCl and inoculated with the bacteria. The present findings demonstrate that endophytic P. aryabhattai strains might be used in the future as a multi-stress reducer and crop growth promoter in agronomically important crops including cereals.

Conversion of sheath blight susceptible indica and japonica rice cultivars into moderately resistant through expression of antifungal β-1,3-glucanase transgene from Trichoderma spp.

Rice is an important food crop for three billion people worldwide. The crop is vulnerable to several diseases. Sheath blight caused by fungal pathogen Rhizoctonia solani is a significant threat to rice cultivation accounting for up to 50% yield losses. The pathogen penetrates leaf blades and sheaths, leading to plant necrosis; and major disease resistance gene against the pathogen is not available. This study describes development of sheath blight resistant transgenic indica and japonica rice cultivars through introduction of antifungal β-1,3-glucanase transgene cloned from Trichoderma. The transgene integration and expression in transformed T0 rice plants was examined by PCR, RT-PCR, qRT-PCR demonstrating up to 5-fold higher expression as compared to non-transgenic plants. The bioassay of T0, T1 and homozygous T2 progeny plants with virulent R. solani isolate revealed that plants carrying high level of β-1,3-glucanase expression displayed moderately resistant reaction to the pathogen. The optical micrographs of leaf sheath cells from moderately resistant plant after pathogen inoculation displayed presence of a few hyphae with sparse branching; on the contrary, pathogen hyphae in susceptible non-transgenic plant cells were present in abundance with profuse hyphal branching and forming prominent infection cushions. The disease severity in T2 progeny plants was significantly less as compared to non-transgenic plants confirming role of β-1,3-glucanase in imparting resistance.

A Short Review of Anti-Rust Fungi Peptides: Diversity and Bioassays

Pucciniales are fungal pathogens of plants that cause devastating rust diseases in agriculture. Chemically-synthesized pesticides help farmers to control rust epidemics, but governing bodies aim at limiting their use over the next decade. Defense peptides with antimicrobial activities may help to innovate a next generation of phytosanitary products for sustainable crop protection. This review comprehensively inventories the proteins or peptides exhibiting a biochemically-demonstrated antifungal activity toward Pucciniales (i.e., anti-rust proteins or peptides; hereafter ‘ARPs’), and also analyses the bioassays used to characterize them. In total, the review scrutinizes sixteen publications, which collectively report 35 ARPs. These studies used either in vitro or in planta bioassays, or a combination of both, to characterize ARPs; mostly by evaluating their ability to inhibit the spore germination process in vitro or to inhibit fungal growth and rust disease development in planta. Also, the manuscript shows that almost no mode of action against rust fungi was elucidated, although some might be inferred from studies performed on other fungi. This short review may serve as a knowledge and methodological basis to inform future studies addressing ARPs.

Organic phosphorus immobilization in microbial biomass controls how N2-fixing trees affect phosphorus bioavailability in two tropical soils

• Enzyme-labile Po and plant bioassays were used as soil P bioavailability indicators. • Po immobilization in microbial biomass is greater in P-poor sites than in P-rich sites. • Positive effect of acacia on soil P bioavailability depends on locked microbial Po. Eucalyptus is the tree most widely planted in tropical countries to satisfy growing demand for wood products, but high yields require high fertilizer inputs. Introducing N 2 -fixing trees (NFT), such as Acacia mangium, has been proposed to improve soil fertility and aboveground tree biomass in Eucalyptus plantations. In addition to N inputs, NFT species may increase plant P nutrition through increased rates of organic P (Po) cycling. However, the positive effect of acacia on soil P availability and plant P nutrition was found to vary substantially between sites. The ability of acacia to improve P bioavailability might mainly depend on Po sequestration in microbial biomass, preventing Po mineralization by phosphatases and efficient Po recycling. This hypothesis was tested at two tropical sites, Itatinga (Brazil) and Kissoko (Congo) by measuring inorganic phosphate (Pi), Po and enzyme-labile Po in bicarbonate extracts from the topsoil collected from plots with Eucalyptus , acacias, or native vegetation. We used bicarbonate enzyme-labile Po after soil autoclaving as an indicator of microbial Po, and a Eucalyptus bioassay to measure the actual P bioavailability for Eucalyptus seedlings. At Itatinga, bicarbonate-Pi was very low, while Po was the main P form. Enzyme-labile Po was very weak in intact soils and high in autoclaved soils, indicating high immobilization in microbial biomass. At Kissoko, Po was highly enzyme-labile in both intact and autoclaved soils, especially from acacia plots, suggesting very low Po immobilization in microbial biomass. Growth and P accumulations in Eucalyptus seedlings were low in all soils at Itatinga and were the highest in Eucalyptus plants grown in acacia soils at Kissoko. Our results highlight the potential of acacia trees for improving P bioavailability for other tree species if labile Po enrichment in the soil provided by this N 2 -fixing tree is not locked into the microbial biomass.

Application of Pseudomonas Strains for Biocontrol of Commercial Crops Susceptible to Plant Pathogens: A Review

Indiscriminate use of chemicals as fertilizers and pesticides gives rise to substantial harm to the environment and ecosystem along with animals and humans. More importantly, to replace such hazardous agrochemicals, many biological solutions are available in nature which is present in the form of microorganisms having the capacity to promote plant growth substantially. Pseudomonas play a major role in plants like inducing systemic resistance, colonizing plant roots or tissue interior, helping in modulating plant hormone levels, biological control of pathogens and more over regulating the growth-related genes in plants. The fluorescent pseudomonads belong to plant growth-promoting rhizobacteria (PGPR) and many strains of pseudomonas are well known to enhance plant growth promotion and decrease the severity of many diseases. Biocontrol strains of pseudomonas in plant bioassays synthesize one or more several antibiotic compounds. In vitro, these antibiotics have been proven as inhibitory compounds and have exhibited active responses for plant health management in field conditions. The current study mainly relies on the effective use of Pseudomonas spp. as a potential biocontrol agent for the biological control of many diseases in agriculture and horticultural crops.

Bioinspired Rhamnolipid Protects Wheat Against Zymoseptoria tritici Through Mainly Direct Antifungal Activity and Without Major Impact on Leaf Physiology.

Rhamnolipids (RLs), glycolipids biosynthesized by the Pseudomonas and Burkholderia genera, are known to display various activities against a wide range of pathogens. Most previous studies on RLs focused on their direct antimicrobial activity, while only a few reports described the mechanisms by which RLs induce resistance against phytopathogens and the related fitness cost on plant physiology. Here, we combined transcriptomic and metabolomic approaches to unravel the mechanisms underlying RL-induced resistance in wheat against the hemibiotrophic fungus Zymoseptoria tritici, a major pathogen of this crop. Investigations were carried out by treating wheat plants with a bioinspired synthetic mono-RL with a 12-carbon fatty acid tail, dodecanoyl α/β-L-rhamnopyranoside (Rh-Est-C12), under both infectious and non-infectious conditions to examine its potential wheat defense-eliciting and priming bioactivities. Whereas, Rh-Est-C12 conferred to wheat a significant protection against Z. tritici (41% disease severity reduction), only a slight effect of this RL on wheat leaf gene expression and metabolite accumulation was observed. A subset of 24 differentially expressed genes (DEGs) and 11 differentially accumulated metabolites (DAMs) was scored in elicitation modalities 2, 5, and 15 days post-treatment (dpt), and 25 DEGs and 17 DAMs were recorded in priming modalities 5 and 15 dpt. Most changes were down-regulations, and only a few DEGs and DAMs associated with resistance to pathogens were identified. Nevertheless, a transient early regulation in gene expression was highlighted at 2 dpt (e.g., genes involved in signaling, transcription, translation, cell-wall structure, and function), suggesting a perception of the RL by the plant upon treatment. Further in vitro and in planta bioassays showed that Rh-Est-C12 displays a significant direct antimicrobial activity toward Z. tritici. Taken together, our results suggest that Rh-Est-C12 confers protection to wheat against Z. tritici through direct antifungal activity and, to a lesser extent, by induction of plant defenses without causing major alterations in plant metabolism. This study provides new insights into the modes of action of RLs on the wheat-Z. tritici pathosystem and highlights the potential interest in Rh-Est-C12, a low-fitness cost molecule, to control this pathogen.

Microcosm based bio-efficacy evaluation of biologically produced nano-Zn–Fe fertiliser

Chemical fertilisers are a significant component of agricultural inputs needed to achieve the highest possible yield and productivity. Fertilisers, on the other hand, change the nutrient balance and health of the soil. Furthermore, because of its low usage efficiency, this widespread use has a negative impact on ecosystems. In this study, nano-Zn–Fe fertiliser was synthesised in a microbial bioreactor and its key properties were determined, including actual particle size, elemental composition, zeta potential, and bioactive content. A microcosm plant bioassay system developed in-house was used to assess the bio-efficacy of biologically generated nano-Zn–Fe fertiliser. The fertiliser was applied to maize (at a rate of 1500 μg g−1 seeds) using a polymer-based seed coating technique and compared to commercial bulk and nano-fertilisers. The results indicate that nano-Zn–Fe fertiliser considerably improves seed germination, plant growth, and nutrient uptake in plants when compared to controls (polymer and feedstock material coated seeds) and commercial goods (bulk and nano-fertilisers). Additionally, we calculated the lead content of the plant system to verify that the produced material is non-toxic in accordance with global fertiliser permissible limit standards. As a result, nano-Zn-Fe fertilisers may be a more viable option for supplying an alternative source of zinc and iron fertilisers to balance global agricultural productivity constraints.

Assessment of Pseudomonas spp. for Growth Promotion, Biocontrol and Stress Tolerance Applicability towards Organic and Inorganic Pollutants

Organic and inorganic pollutants have deleterious effect in the environment, crops productivity, microbiomeand soil fertility. The persistence uses of toxic compound like pesticides not only affect soil health but alsoagitated ecosystem. Use of Plant Growth Promoting rhizobacteria can play an important role towardsachieving the objectives of sustainable ecosystem. Pseudomonas group of bacteria are known for theirremediation properties but are lesser explored for their growth promotion attributes and to alleviate otherabiotic and biotic stress in the agriculture system. The paper presents multifarious potential of Pseudomonasisolates obtained from agriculture fields in the vicinity of Ghaziabad, U.P (PGPM2, 3, 4, 5). Biochemicaltests for identification suggested that these isolates belong to Pseudomonads group of organisms. Further,molecular characterization through 16S RNA gene sequence analysis confirmed their identity as PGPM2-Pseudomonas species, PGPM3- Pseudomonas plecoglosida, PGPM4- Pseudomonas and PGPM5- Pseudomonasrespectively. Production of essential hormones such as indole acetic acid, gibberellic acid and phosphatesolubilisation activity have endorsed the plant growth promotion attribute by these isolates. Production ofammonia and secretion of lytic enzymes like lipase by PGPM2 and PGPM3 indicate stronger bio-controlabilities in these isolates as compared to other isolates, all isolates showed positive for the bio-film formation,a positive attribute that helps in colonising and surviving harsh environments. Bangle method establishedthe strong antagonistic activity that these isolates possess against 3 important plant root pathogens namelyMacrophominaphaseolina (41%) followed by Sclerotium rolfsii (36-15%) and Fusarium oxysporum (21%)respectively. Isolates PGPM2 &amp; PGPM3 showed maximum tolerance against salt (500MM) while isolatesPGPM2 and PGPM4 showed better tolerance to Pesticides monocrotophos and dimethoate (PGPM2- MICand LD50 and PGPM3 –MIC AND LD50). Host plant bioassay with pearl millets (bajra) revealed maximumgrowth promoting efficiency (root length and shoot length) by PGPM2. The manuscript provides abiochemical and physiological evidence that native Pseudomonas isolates not only promote plant growthbut also possess unique ability to tolerate adverse abiotic stress conditions such as tolerance to salt, organic(pesticides) and inorganic pollutants thus offering multiple growth supporting advantages to the planthost.

Phytotoxicity complements chemical assessment for re-use and re-purposing of refinery wastes for soil amendment purposes after bioremediation

The objective of this study was to assess the suitability of onsite re-use of mature compost for landscaping and tree mulching, produced from the bioremediation of oily sludge from the refinery. Compost samples from the co-composting process were analysed for a range of contaminants, including a human health risk assessment fractionation (HRAF) of the remaining petroleum hydrocarbons, as well as a phytotoxicity test. The chemical characterisation demonstrated that the process removed more than 94% of the original petroleum hydrocarbons from the sludge, and the removal rates were high at 1155 mg/kg/day. The HRAF demonstrated no residual risks, posed by the petroleum hydrocarbons present in the compost to human health if used on-site when compared to the relevant Australian environmental investigation levels (ILs). However, the phytotoxicity assessment demonstrated that the compost was toxic to germinating lettuce. The gap in the literature this study addressed was to provide an estimate of the LD50 and no effect concentration (NEC) for the compost using a standard plant bioassay containing a range of residual (aged) and bioremediated refinery process wastes, including petroleum hydrocarbons. The values estimated for LD50 and NEC were approximately 125 and 43 mg/kg, respectively for compost containing residual petroleum hydrocarbon fractions, filling a gap in the current literature which has limited data on standard toxicity values that can be used in determining and informing commercial remediation strategies and their outcomes with aged sludges. Phytotoxicity was shown to be an important complement to conventional analyses and HRAF data when characterising the sludge, and understanding its potential for re-use. The novelty of the study is that it highlighted a gap in the complementary use of chemical and bioassay analyses for evaluating refinery waste remediation endpoints, which has potential for broader application to other projects.

Assessment of the effects of fungicide (Thiram) on somatic cells of broad bean (Vicia faba L.)

Present study was carried out to know the impact of fungicide (Thiram) on somatic cells of broad bean (Vicia faba L.). Thiram is one of the most effective fungicide. Significant inhibition of mitotic index and increase in the frequencies of chromosome aberrations were observed. Results of the study indicate that both the plant bioassay found to be sensitive indicators for the genotoxicity assessment as the outcome of majority test system. Using plant bioassays for testing and monitoring environmental chemicals or pollution has many advantages. The mitotic index decreases due to exposure of plant extract with thiram in higher concentration as 150, 300, 550, 800 ppm for 8h and show reducing effect that is 21.00, 20.70, 18.61 and 16.77 in comparison to control that is 21.19. The higher concentrations of fungicide showed the genotoxic effects and damage the chromosomal integrity.

Characterization of field-scale spray drift deposition and non-target plant biological sensitivity: a corn herbicide (mesotrione/s-metolochlor) case study.

This work reports a combined, field-scale spray drift deposition and plant bioassay study for a pre-mixture of the herbicides mesotrione and s-metolachlor. Wind direction data and field dimensions were used to evaluate the potential for spray drift to bypass downwind sampling devices. Variability in resulting spray drift across downwind distances was assessed alongside wind speed measured at on-site weather stations. Measured wind angles were used to geometrically adjust traveled drift particle distances and enabling isolation of wind direction impact from wind speed. Further, the use of single and multiple in-field monitoring locations was compared to quantify the benefit of higher-resolution meteorological sampling. Generally, increased wind speed resulted in significantly greater herbicide deposition at distances proximal to the edge of the spray zone. According to the drift deposition curves that included wind speed data from single and multiple onsite weather stations, trials with relatively higher wind speeds were associated with greater spray drift deposition at relatively close sampling distances downwind from the application area. Only marginal improvement of linear mixed-effects model fit was observed when including data from three weather stations, compared to the fit from a single weather station or absence of weather data in the model. Using tomato and lettuce plant bioassay species, the overall no-effect distance was 3.0m (10ft). Results from this study are informative to refine pesticide risk assessment for non-target plants and indicate that a single weather station is sufficient to capture potential influential effects from wind speed and direction on spray drift. © 2022 Society of Chemical Industry.

A Loop-Mediated Isothermal DNA Amplification (LAMP) Assay for Detection of the Clubroot Pathogen Plasmodiophora brassicae.

Clubroot caused by Plasmodiophora brassicae is a serious threat to cruciferous crops around the world. The resting spores of P. brassicae are a primary source of infection and can survive in soil for many years. Detection of resting spores in soil is essential for forecasting clubroot prevalence. Detection of P. brassicae has been relying on plant bioassays or PCR-based methods. The loop-mediated isothermal DNA amplification (LAMP) is a promising approach for microorganism detection with the advantage of high sensitivity, accuracy, and convenience in viewing. In this study, we developed a LAMP assay for detection of P. brassicae in soil, roots, and seeds. This method can detect P. brassicae at a minimal amount of 1 fg of plasmid DNA or 10 resting spores in the soil. Compared with conventional PCR, the LAMP was more sensitive in detection of P. brassicae at the lower levels in soil samples. In conclusion, we elaborated a sensitive, accurate, and easy-to-use LAMP assay to detect P. brassicae, which will facilitate sustainable clubroot management and planning.