Biopesticide based sustainable pest management for safer production of vegetable legumes and brassicas in Asia and Africa

Vegetables are one of the important crops which could alleviate poverty and malnutrition among the smallholder farmers in tropical Asia and Africa. However, a plethora of pests limit the productivity of these crops, leading to economic losses. Vegetable producers overwhelmingly rely on chemical pesticides in order to reduce pest-caused economic losses. However, over-reliance on chemical pesticides poses serious threats to human and environmental health. Hence, biopesticides offer a viable alternative to chemical pesticides in sustainable pest management programs. Baculoviruses such as nucleopolyhedrovirus (NPV) and granulovirus (GV) have been exploited as successful biological pesticides in agriculture, horticulture and forestry. Maruca vitrata multiple nucleocapsid NPV (MaviMNPV) was found to be a unique baculovirus specifically infecting pod borer on food legumes, and it has been successfully developed as a biopesticide in Asia and Africa. Entomopathogenic fungi also offer sustainable pest management options. Several strains of Metarhizium anisopliae and Beauveria bassiana have been tested and developed as biopesticides in Asia and Africa. This review specifically focuses on the discovery and development of entomopathogenic virus and fungi-based biopesticides against major pests of vegetable legumes and brassicas in Asia and Africa. © 2019 Society of Chemical Industry.

Effects of Earthworms and Agricultural Plant Species on the Soil Nematode Community in a Microcosm Experiment

Both earthworms and plants may affect the soil nematode community. However, the effects of earthworms and plant species interactions on soil nematode community are poorly understood. We explored how an epigeic earthworm Eisenia fetida affects the soil nematode community in systems with three representative plants (wheat, cotton and cabbage) which were grown in pots with or without added earthworms under greenhouse conditions. Earthworm presence decreased the abundance of total nematode and all four nematode trophic groups, except for the fungivore and predator/omnivore nematodes in wheat systems, but increased the genus richness of nematode in all treatments. Due to plant identity and different root exudates, plants had significant effects on soil nematode abundance. Compared with the no plant and without earthworm treatment, wheat and cabbage had the higher stimulation of the abundance of total nematode, bacterivores and fungivores, and cotton had the higher stimulation of the abundance of fungivores and predators-omnivores; whereas earthworm presence mostly weakened the stimulation effects of plant species on soil nematode abundance which indicated earthworms had the enhanced effects in the presence of plants. The interaction affected soil nematode abundance (total nematodes, bacterivore, fungivore and omnivore-predators) and community diversity indices (diversity index H', evenness index J', community maturity index ∑MI, Simpson dominance index λ and nematode channel ratio NCR). Principal component analysis showed that plant species affected soil nematode community composition. Redundancy analysis indicated plant species and biomass accounted for 41.60% and 34.13% of the variation in soil nematode community structure, respectively; while earthworms explained only 6.13%. Overall, current study suggest that earthworm could inhibit nematode abundance; whereas, plants have exerted greater influences on nematode community structure than earthworm presence due to their species-specific effects on different trophic groups of nematodes.

Potential toxicity of trace elements and nanomaterials to Chinese cabbage in arsenic- and lead-contaminated soil amended with biochars

To our knowledge, this is the first report on exploring the interactive effects of various biochars (BCs) and nanomaterials (NMs) on plant growth and bioavailability of trace elements in soil. This study evaluated the bioavailability and toxicity of arsenic (As), lead (Pb), and NMs to cabbage plants. The BCs were produced from rice husk (RB), sewage sludge, and bamboo wood (WB). The BCs at 2.5 and 5% (w w^-1), NMs for removing As (NMs-As) and heavy metals (NMs-HM) at 3000 mg kg^-1, and multi-walled carbon nanotubes (CNT) at 1000 mg kg^-1 were applied in bioassay and incubation experiments (40 days), along with the unamended soil as the control. Results showed that the NMs-As and NMs-HM decreased seed germination at 3 days after sowing; however, their toxicity was eliminated by BCs. Growth parameters of cabbage revealed that the CNT was the most toxic NMs, as it was translocated in root and leaf cells, which was confirmed by transmission electron microscopic images. Bioavailable Pb was reduced by 1.2-3.8-folds in all amended rhizosphere and bulk soils. Amendments of 2.5% WB + NMs-As and 2.5% RB + NMs-As significantly decreased both bioavailable As and Pb.

Benefits of phytoremediation amended with DC electric field. Application to soils contaminated with heavy metals

The objective of this study was to determine the influence of the DC electric current in the physicochemical properties of soil. The electric current may induce changes in pH and electric conductivity that will be reflected in the distribution of the electric potential in the soil specimen. This information will be used for the development of a phytoremediation technology amended with electric current. The results showed that low or moderate voltage gradients (0.67 V/cm) induced small changes in physicochemical properties of soil that do not compromise plant survival. The selected voltage gradient was used in electro-phytoremediation tests in soil contaminated with heavy metals (Cd, Co, Cr, Cu, Pb and Zn). Two plants species adapted to the soil and climate conditions were selected (Brassica rapa L. subsp. rapa and Lolium perenne L.). The electric field enhanced the plant growing, mainly in L. perenne, and increased the phytoremediation of the 6 metals. Mixed cultures of the two plant species showed interesting results for large scale applications.

Effect of cover crops on the yield and nutrient concentration of organic kale (Brassica oleracea L. var. acephala)

Kale is a leafy green vegetable regularly grown using non-organic agricultural systems. In recent years, organic kale demand has increased at near-doubling rates in the USA due to its perceived nutritional value. The objective of this study was to determine the effect of organic cover cropping systems on subsequent kale biomass production and nutrient composition (protein, mineral, and prebiotic carbohydrate concentrations) and to assess organic kale as a potential whole food source of daily essential mineral micronutrients and prebiotic carbohydrates. A single 100-g serving of fresh organic kale can provide mineral micronutrients (43-438 mg Ca; 11-60 mg Mg; 28-102 mg P; 0.5-3.3 mg Fe; 0.3-1.3 mg Mn; 1-136 µg Cu; and 0-35 µg Se) as well as 5.7-8.7 g of total prebiotic carbohydrates, including sugar alcohols (0.4-6.6 mg), simple sugars (6-1507 mg), raffinose and fructooligosaccharides (0.8-169 mg), hemicellulose (77-763 mg), lignin (0-90 mg), and unknown dietary fiber (5-6 g). Fresh organic kale has low to moderate concentrations of protein (1.3-6.0 g/100 g). Study results indicate that Starbor and Red Russian are the most suitable kale cultivars for organic production without considerable biomass and nutrient composition losses. Among the cover crops, faba bean results in the highest mineral, protein, and prebiotic carbohydrate concentrations in subsequent kale crops but ryegrass increases kale biomass production. Results also demonstrated a significant interaction between kale variety and organic cover crop with respect to biomass and nutrient concentration. Future organic nutritional breeding of kale is possible by selecting cultivars that perform well following different cover crops.

Agronomic performance, energy analysis, and carbon balance comparing different fertilization strategies in horticulture under Mediterranean conditions

Production capacity evaluation and environmental sustainability assessment allow defining both the most appropriate fertilization strategies and the agricultural systems management. The aims of this study were to investigate the following, in a cauliflower-lettuce rotation: (i) agricultural system agronomic performance, (ii) fertilization treatments environmental sustainability through the energy inputs/outputs analysis, and (iii) carbon footprint through the GHG emissions and carbon sequestration analyses. Three fertilization strategies were compared: (i) CM, compost from municipal solid waste; ii) MIN, mineral fertilizers; iii) MIX, the CM compost plus a mineral fertilizer. Cauliflower and lettuce responses to fertilization were influenced by climatic conditions from year to year, and among the fertilizer treatments, the CM demonstrated a better resilience to the extreme weather events. It also showed the highest renewable energy (44.3%), suggesting that the substitution of mineral fertilizers with organic ones may help to reduce the non-renewable energy depletion, thus promoting the sustainability in horticultural systems. The CM was the most efficient treatment, since the energy stocked as C in the soil (145,889 MJ ha-1) and the net energy and the energy efficiency for cauliflower and lettuce (113,106 MJ ha-1 and 3.1, respectively) were the highest. Our results suggest that the application of the tested sustainable practices makes the farm a "sink" for the atmospheric CO2.

Bioaugmentation of Exogenous Strain Rhodococcus sp. 2G Can Efficiently Mitigate Di(2-ethylhexyl) Phthalate Contamination to Vegetable Cultivation

This work developed a bioaugmentation strategy that simultaneously reduced soil di(2-ethylhexyl) phthalate (DEHP) pollution and its bioaccumulation in Brassica parachinensis by inoculating the isolated strain Rhodococcus sp. 2G. This strain could efficiently degrade DEHP at a wide concentration range from 50 to 1600 mg/L and transformed DEHP through a unique biochemical degradation pathway that distinguished it from other Rhodococcus species. Besides, strain 2G colonized well in the rhizosphere soil of the inoculated vegetable without competition with indigenous microbes, resulting in increased removal of DEHP from soil (∼95%) and reduced DEHP bioaccumulation in vegetables (∼75% in the edible part) synchronously. Improved enzyme activities and DOC content in the rhizosphere of the planting vegetable and inoculating strain 2G were responsible for the high efficiency in mitigating DEHP contamination to vegetable cultivation. This work demonstrated a great potential application to grow vegetables in contaminated soil for safe food production.

Substituting organic manure for compound fertilizer increases yield and decreases NH3 and N2O emissions in an intensive vegetable production systems

Substituting organic manure for compound fertilizer may play an important role in regulating the nitrogen (N) cycle and consequently affecting crop yield in agroecosystems. However, how substituting different organic manures for compound fertilizer affects crop yield and ammonia (NH₃) and nitrous oxide (N₂O) emissions in the vegetable system during the life-cycle production (including storage and field application) remains poorly elucidated. Thus, we conducted a greenhouse experiment to investigate the effects of substituting organic manure species, i.e., stored swine manure fertilizer (SS), swine manure covered by straw (CS), stored swine fertilizer mixed with biochar (BS), and stored swine manure fertilizer with void expansion (OS) for compound fertilizer (FC) on rapeseed yield and NH₃ and N₂O emissions in a rapeseed-cropping system in China. The results showed that the total gaseous N losses (NH₃ and N₂O) were 1.6, 1.4 and 1.1 times higher in SS, CS and OS than FC, respectively. However, total gaseous N losses in BS was 0.9 times less than FC. Compared with FC, rapeseed yield and N uptake in SS and CS were decreased by 17.2-20.2% and 16.0%-28.1%, respectively, but which were increased by 7.3% and 54.1% in BS, respectively. In addition, OS decreased rapeseed yield by 17.2%, but increased N uptake by 8.5%. Therefore, the effects of substituting organic manure for compound fertilizer on rapeseed yield, N uptake, NH₃ and N₂O varied regarding different organic manure species. Adopting stored swine fertilizer mixed with biochar might be a sound management practice to reduce gaseous N losses and enhance N uptake and yield in intensive vegetable production systems.

Creek to Table: Tracking fecal indicator bacteria, bacterial pathogens, and total bacterial communities from irrigation water to kale and radish crops

The impact of microbially contaminated irrigation water on risks to produce safety and public health is a complex issue that is not well understood. This study tracked fecal indicators, pathogenic bacteria, and total bacterial communities from a creek water irrigation source to irrigated produce to assess the impact of irrigation events on soil and produce-associated microbiota. Kale and radishes were drip-irrigated using Mid-Atlantic creek water in October 2017. Plant and soil samples were collected immediately before and after irrigation, and for 3 consecutive days thereafter. All samples (n = 134), including irrigation water, were tested for generic Escherichia coli and total coliforms (TC) using standard membrane filtration or direct plating, and for Salmonella enterica and Listeria monocytogenes by selective enrichment. DNA extracted from all samples was PCR-amplified for the V3-V4 region of the 16S rRNA gene for bacterial community profiling. In soil, TC levels were significantly higher immediately and 3 days post-irrigation compared to pre-irrigation (p < 0.01). E. coli levels in soil increased after irrigation, but the difference was not significant (p = 0.31), and die-off was not observed. No E. coli were detected on kale leaves. TC increased over the study period on radish roots (p < 0.01) but not kale leaves (p = 0.43). Although target pathogens were detected in irrigation water, S. enterica was detected from only one post-irrigation kale sample and L. monocytogenes was not detected in the field. The 16S rRNA gene sequencing data revealed differences in bacterial community structure and composition across sample types and showed that radish soil and root surface bacterial communities were more strongly influenced by irrigation compared to kale samples. This study provides insights into the impact of irrigation water on fresh produce microbiota, revealing that, although irrigation did influence crop-associated microbiota (especially below ground) in the field, bacterial pathogens were not likely transferred to the crop.

Crop Residues in Wheat-Oilseed Rape Rotation System: a Pivotal, Shifting Platform for Microbial Meetings

Crop residues are a crucial ecological niche with a major biological impact on agricultural ecosystems. In this study, we used a combined diachronic and synchronic field experiment based on wheat-oilseed rape rotations to test the hypothesis that plant is a structuring factor of microbial communities in crop residues, and that this effect decreases over time with their likely progressive degradation and colonisation by other microorganisms. We characterised an entire fungal and bacterial community associated with 150 wheat and oilseed rape residue samples at a plurennial scale by metabarcoding. The impact of plant species on the residue microbiota decreased over time and our data revealed turnover, with the replacement of oligotrophs, often plant-specific genera (such as pathogens) by copiotrophs, belonging to more generalist genera. Within a single cropping season, the plant-specific genera and species were gradually replaced by taxa that are likely to originate from the soil. These changes occurred more rapidly for bacteria than for fungi, known to degrade complex compounds. Overall, our findings suggest that crop residues constitute a key fully-fledged microbial ecosystem. Taking into account this ecosystem, that has been neglected for too long, is essential, not only to improve the quantitative management of residues, the presence of which can be detrimental to crop health, but also to identify groups of beneficial microorganisms. Our findings are of particular importance, because the wheat-oilseed rape rotation, in which no-till practices are frequent, is particularly widespread in the European arable cropping systems.

Survival and internalization of Salmonella and Escherichia coli O157:H7 sprayed onto different cabbage cultivars during cultivation in growth chambers

BACKGROUND

Cabbage may become contaminated with enteric pathogens during cultivation. Using multiple cabbage cultivars at two maturity stages (small plants or plants with small heads) in growth chamber studies, the fate (internalization or surface survival) of Salmonella and Escherichia coli O157:H7 (0157) were examined in conjunction with any potential relationships to the plant's antimicrobial content.

RESULTS

Internalized Salmonella was detected in cabbage within 24 h with prevalence ranging from 62% (16 of 26) for the 'Super Red 80' cultivar to 92% (24 of 26) for the 'Red Dynasty' cultivar. Surface survival of pathogens on small cabbage plants over nine days was significantly affected by cultivar with both pathogens surviving the most on the 'Farao' cultivar and Salmonella and O157 surviving the least on the 'Super Red 80' and 'Capture' cultivars, respectively (P < 0.05). Survival of O157 was slightly higher on cabbage heads for O157 than small plants suggesting that the maturity stage may affect this pathogen's fate. An inverse relationship existed between antimicrobial levels and the pathogen's surface survival on cabbage heads (P < 0.05).

CONCLUSIONS

The fate of pathogens varied with the cabbage cultivar in growth chamber studies highlighting the potential to explore cultivar in field studies to reduce the risk of microbiological contamination in this crop. © 2019 Society of Chemical Industry.

Lower cadmium accumulation and higher antioxidative capacity in edible parts of Brassica campestris L. seedlings applied with glutathione under cadmium toxicity

Glutathione (GSH) is involved in not only plant developmental processes but also plant responses to abiotic stresses. A hydroponic experiment was performed to explore the protective roles of exogenous GSH in mitigating cadmium (Cd) stress in Brassica campestris L. seedlings by analyzing the morphological and physiological parameters. Results showed that Cd caused severe growth inhibition and Cd accumulation. However, application of GSH significantly mitigated toxic symptoms induced by Cd, including the improvement of the photosynthesis-, plant growth-, and root morphology-related parameters in seedlings under Cd stress. These responses were associated with a striking increase in activities of representative antioxidative enzymes and contents of corresponding non-enzymatic antioxidants. In vivo imaging of O₂^.- and H₂O₂, and the detection of lipid peroxidation further demonstrated that increased ability by GSH for Brassica campestris L. seedlings to endure Cd stress was consistent with a striking elevation of ratios of reduced to oxidized glutathione (GSH/GSSG) and ascorbic acid to dehydroascorbic acid (AsA/DHA). Additionally, GSH application increased Cd retained in roots, thus significantly decreased its translocation from root to shoot, ultimately decreased Cd accumulation in shoots. Taken together, our results proved evidence for GSH in ameliorating Cd toxicity via reducing Cd accumulation in shoots and increasing oxidation resistance. Accordingly, application of GSH could be a high-efficiency and promising strategy to decrease Cd concentration in edible parts of Brassica campestris L. in agricultural production.

Biochar DOM for plant promotion but not residual biochar for metal immobilization depended on pyrolysis temperature

While biochar on metal immobilization was well understood, a small pool of dissolvable organic matter (DOM) from biochar was recently recognized as a bioactive agent for plant growth promotion. However, how the molecular composition and plant effects of this fraction and the performance for metal immobilization of the DOM-removed biochar could vary with pyrolysis temperature had been not well addressed. In this study, wheat straw biochar pyrolyzed at a temperature of 350 °C, 450 °C, 550 °C were extracted with hot water to separate the DOM fraction. The obtained biochar extracts (BE350, BE450, and BE550) were tested as foliar amendment to Chinese cabbage while the extracted (DOM-removed) biochars were tested for heavy metal immobilization in a contaminated soil. The results showed that BE350 was higher in organic matter content, abundance of organic molecules and mineral nutrients than BE450 and BE550. Compared to control, foliar application of BE350 significantly enhanced the shoot biomass (by 89%), increased leaf soluble sugar content (by 83%) but reduced leaf content of nitrate (by 34%) and of potential toxic metals (by 49% for Cd and by 30% for Pb). Moreover, BE350 treatment increased gene expression of nitrate reductase and glutamine synthetase enzyme activity of the tested plant. Meanwhile, soil amendment of DOM-extracted biochars significantly decreased soil CaCl₂ extractable pool of Cd, Pb, Cu and Zn in a range of 27%-78%. Thus, the performance of DOM extract of biochar on plant growth promotion was indeed dependent of pyrolysis temperature, being greater at 350 °C than at higher temperatures. In contrast, metal immobilizing capacity of biochar was regardless of pyrolysis temperature and DOM removal. Therefore, pyrolyzing wheat straw at low temperature could produce a biochar for valorized separation of a significant DOM pool for use in vegetable production, leaving the residual biochar for amendment to metal contaminated soil.

Municipal Sludge-induced Phytotoxicity

Municipal sludge (MS), containing various types of environmental pollutants, can exert phytotoxic effects in plants. Seed germination, chlorophyll content, plant weight, root and shoot growth, and metal levels, were measured as endpoints to assess the phytotoxic effects of leachates of MS from Lucknow city in three plants, Triticum aestivum, Brassica campestris and Phaseolus aureus. Among the five metals analysed, lead was found to be present at the highest concentration, and chromium at the lowest. Aqueous MS leachates had lower amounts of metals than pure MS. Seed germination was inhibited significantly in all three plants. The greatest inhibition of root and shoot growth was observed in B. campestris and T. aestivum. Total chlorophyll was depleted in all three plants, but the maximum depletion was observed in T. aestivum exposed to 10% leachate. Symptoms such as necrosis, leaf discoloration and root curling were also observed after exposure to 10% leachate, and plant weight was reduced significantly. It is evident that MS from Lucknow city exerted phytotoxic effects on all three test plant species.

Global implications of regional grain production through virtual water trade

Crop yields (Y) and virtual water content (VWC) of agricultural production are affected by climate variability and change, and are highly dependent on geographical location, crop type, specific planting and harvesting practice, soil property and moisture, hydro-geologic and climate conditions. This paper assesses and analyzes historical (1985-2009) and future (2040-2064) Y and VWC of three cereal crops (i.e., wheat, barley, and canola) with high spatial resolution in the highly intensive agricultural region of Alberta, Canada, using the Soil and Water Assessment Tool (SWAT). A calibrated and validated SWAT hydrological model is used to supplement agricultural (rainfed and irrigation) models to simulate Y and crop evapotranspiration (ET) at the sub-basin scales. The downscaled climate projections from nine General Climate Models (GCMs) for RCP 2.6 and RCP 8.5 emission scenarios are fed into the calibrated SWAT model. Results from an ensemble average of GCMs show that Y and VWC are projected to change drastically under both RCPs. The trade (export-import) of wheat grain from Alberta to more than a hundred countries around the globe led to the annual saving of ~5 billion m³ of virtual water (VW) during 1996-2005. Based on the weighted average of VWC for both rainfed and irrigated conditions, future population and consumption, our projections reveal an annual average export potential of ~138 billion m³ of VW through the flow of these cereal crops in the form of both grain and other processed foods. This amount is expected to outweigh the total historical provincial water yield of 66 billion m³ and counts for 47% of total historical precipitation and 61% of total historical actual ET. The research outcome highlights the importance of local high-resolution inputs in regional modeling and understanding the local to global water-food trade policy for sustainable agriculture.

Genome wide analysis of MADS-box gene family in Brassica oleracea reveals conservation and variation in flower development

BACKGROUND

MADS-box genes play important roles in vegetative growth and reproductive development and are essential for the correct development of plants (particularly inflorescences, flowers, and fruits). However, this gene family has not been identified nor their functions analyzed in Brassica oleracea.

RESULTS

In this study, we performed a whole-genome survey of the complete set of MADS-box genes in B. oleracea. In total, 91 MADS-box transcription factors (TFs) were identified and categorized as type I (Mα, Mβ, Mγ) and type II (MIKCC, MIKC*) groups according to the phylogeny and gene structure analysis. Among these genes, 59 were randomly distributed on 9 chromosomes, while the other 23 were assigned to 19 scaffolds and 9 genes from NCBI had no location information. Both RNA-sequencing and quantitative real-time-PCR analysis suggested that MIKC genes had more active and complex expression patterns than M type genes and most type II genes showed high flowering-related expression profiles. Additional quantitative real-time-PCR analysis of pedicel and four flower whorls revealed that the structure of the B.oleracea MIKC genes was conserved, but their homologues showed variable expression patterns compared to those in Arabidopsis thaliana.

CONCLUSION

This paper gives a detailed overview of the BolMADS genes and their expression patterns. The results obtained in this study provide useful information for understanding the molecular regulation of flower development and further functional characterization of MADS-box genes in B. oleracea.

Estimation of genetic architecture of biochemical traits in mid-late cauliflower (Brassica oleracea L. var. botrytis) under sub-temperate conditions of north western Himalayas

Understanding the genetic basis of biochemical traits of different cauliflower genotypes is essential for planning the effective breeding strategies in genetic improvement. To determine the mode of inheritance of dry matter content and biochemical traits, we made crosses using four genotypes of cauliflower, and obtained F₁, F₂, BC₁ and BC₂ populations. The six generations obtained were replicated thrice and evaluated in a randomized block design. The generation mean analysis of data showed the presence of duplicate epistasis in dry matter content which suggested the adoption of reciprocal recurrent selection and biparental mating for the improvement of the trait. However, in case of vitamin C, complementary type of epistasis was reported in three crosses, which indicated the exploitation of heterosis breeding of enhancing vitamin C. It can be concluded that the role of gene action was in general more complex for the traits studied. The nature and magnitude of gene effects varies character-wise as well as cross-wise. Hence, for the improvement of dry matter content and biochemical traits in a particular cross, a specific breeding strategy has to be implemented.

Sorting out the Value of Cruciferous Sprouts as Sources of Bioactive Compounds for Nutrition and Health

Edible sprouts with germinating seeds of a few days of age are naturally rich in nutrients and other bioactive compounds. Among them, the cruciferous (Brassicaceae) sprouts stand out due to their high contents of glucosinolates (GLSs) and phenolic compounds. In order to obtain sprouts enriched in these phytochemicals, elicitation is being increasing used as a sustainable practice. Besides, the evidence regarding the bioavailability and the biological activity of these compounds after their dietary intake has also attracted growing interest in recent years, supporting the intake of the natural food instead of enriched ingredients or extracts. Also, there is a growing interest regarding their uses, consumption, and applications for health and wellbeing, in different industrial sectors. In this context, the present review aims to compile and update the available knowledge on the fundamental aspects of production, enrichment in composition, and the benefits upon consumption of diverse edible cruciferous sprouts, which are sources of phenolic compounds and glucosinolates, as well as the evidence on their biological actions in diverse pathophysiological situations and the molecular pathways involved.

Evaluation of phytotoxicity of three organic amendments to collard greens using the seed germination bioassay

Small-scale vegetable and fruit crop producers in the USA use locally available commercial organic fertilizers and soil amendments recycled from municipal and agricultural wastes. Organic soil amendments provide crops with their nutrient needs and maintain soil health by modifying its physical, chemical, and biological properties. However, organic soil amendments might add unwanted elements such as toxic heavy metals or salts, which might inhibit crop growth and reduce yield. Therefore, the objective of this study was to evaluate phytotoxicity of three commercial organic amendments, chicken manure, milorganite, and dairy manure, to collard greens using the seed germination bioassay and chemical analysis of the organic amendments. The seed germination bioassay was conducted by incubating collard greens seeds to germinate in 1:10 (w/v) organic amendment aqueous extracts. Results of this work identified phytotoxic effects of chicken manure and milorganite, but not dairy manure, to collard greens. Potentially phytotoxic chemicals such as copper, zinc, nickel, and salts were also higher in chicken manure and milorganite compared to dairy manure. In particular, nickel in chicken manure and milorganite aqueous extracts was 28-fold and 21-fold, respectively, higher than previously reported toxic levels to wheat seedlings. The results demonstrate the need for more research on phytotoxicity of commercial organic soil amendments to ensure their safe use in vegetable and fruit crop production systems.

LED lighting optimization as applied to a vitamin space plant growth facility

An algorithm of determining optimal LED lighting parameters for leafy crops (Chinese cabbage Brassica chinensis L. was taken as a model) in a vitamin space Plant Growth Facility is proposed. The lighting parameters to optimize were the level of photosynthetic photon flux density (PPFD), red and white LEDs PPFD ratio and pulse repetition period with a fixed pulse length 30 µs. Optimal lighting parameters should allow achieving a high biomass yield per consumed light energy, as well as high vitamin C content in the crop biomass. A quantitative optimality criterion for estimating the lighting parameters quality is suggested. For Chinese cabbage crop the maximum value of this criterion was obtained at the following lighting conditions parameters: PPFD - 500 μmol m^-2 s^-1, red/white ratio - 1.5, and pulse repetition period - 501 µs.

Pol III-Dependent Cabbage BoNR8 Long ncRNA Affects Seed Germination and Growth in Arabidopsis

Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts longer than 200 nt that are distributed widely in organisms and play many physiological roles. The BoNR8 lncRNA is a 272 nt long transcript yielded by RNA polymerase III in cabbage that was identified as the closest homolog of the AtR8 lncRNA in Arabidopsis. The BoNR8 lncRNA was expressed extensively in the epidermal tissue in the root elongation zone of germinated seeds, and its accumulation was induced by abiotic stresses, auxins and ABA. To investigate the correlation between the BoNR8 lncRNA and germination, BoNR8-overexpressing Arabidopsis plants (BoNR8-AtOX) were prepared. Three independent BoNR8-AtOX lines showed less primary root elongation, incomplete silique development and decreased germination rates. The germination efficiencies were affected strongly by ABA and slightly by salt stress, and ABA-related gene expression was changed in the BoNR8-AtOX lines.

Toxicity assessment of molybdenum slag as a mineral fertilizer: A case study with pakchoi (Brassica chinensis L.)

Large quantities of molybdenum (Mo) slag are generated as a by-product during mining and smelting, which not only occupy huge stretches of arable land and natural habitats but also threaten the local ecosystem and environment. How to recycle this Mo slag is becoming an urgent issue. Here, we reported the toxicity assessment of Mo slag as a mineral fertilizer for slag recycling in agricultural practices. The results showed the following: (1) Lower rates of slag (1.0%, 2.5%, and 5.0%) fertilization, especially 5.0% slag, increased the activities of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), the contents of chlorophyll, and both the maximum quantum yield and quantum efficiency of photosystem II; decreased the content of malondialdehyde and the non-photochemical quenching of photosystem II; and eventually increased the height, leaf area, and biomass of pakchoi seedlings; (2) Higher rates (7.5% and 10.0%) of Mo slag application resulted in a reduction in the aforementioned physiological and morphological parameters (except for peroxidase activity) of pakchoi seedlings; and (3) Although fertilization with 5.0% slag increased the accumulation of the non-essential elements arsenic (As), lead (Pb), and cadmium (Cd) in pakchoi seedlings, their contents were still lower than the maximum levels of the Codex Alimentarius Commission, European Union, and standards of China. From the perspectives of plant nutrition and food safety, our results showed that Mo slag fertilization at rates lower than 5.0% can be applied as a mineral fertilizer for pakchoi grown on calcareous soils.

Genome-wide characterization and expression profiling of SWEET genes in cabbage (Brassica oleracea var. capitata L.) reveal their roles in chilling and clubroot disease responses

BACKGROUND

The SWEET proteins are a group of sugar transporters that play a role in sugar efflux during a range of biological processes, including stress responses. However, there has been no comprehensive analysis of the SWEET family genes in Brassica oleracea (BoSWEET), and the evolutionary pattern, phylogenetic relationship, gene characteristics of BoSWEET genes and their expression patterns under biotic and abiotic stresses remain largely unexplored.

RESULTS

A total of 30 BoSWEET genes were identified and divided into four clades in B. oleracea. Phylogenetic analysis of the BoSWEET proteins indicated that clade II formed first, followed by clade I, clade IV and clade III, successively. Clade III, the newest clade, shows signs of rapid expansion. The Ks values of the orthologous SWEET gene pairs between B. oleracea and Arabidopsis thaliana ranged from 0.30 to 0.45, which estimated that B. oleracea diverged from A. thaliana approximately 10 to 15 million years ago. Prediction of transmembrane regions showed that eight BoSWEET proteins contain one characteristic MtN3_slv domain, twenty-one contain two, and one has four. Quantitative reverse transcription-PCR (qRT-PCR) analysis revealed that five BoSWEET genes from clades III and IV exhibited reduced expression levels under chilling stress. Additionally, the expression levels of six BoSWEET genes were up-regulated in roots of a clubroot-susceptible cabbage cultivar (CS-JF1) at 7 days after inoculation with Plasmodiophora brassicae compared with uninoculated plants, indicating that these genes may play important roles in transporting sugars into sink roots associated with P. brassicae colonization in CS-JF1. Subcellular localization analysis of a subset of BoSWEET proteins indicated that they are localized in the plasma membrane.

CONCLUSIONS

This study provides important insights into the evolution of the SWEET gene family in B. oleracea and other species, and represents the first study to characterize phylogenetic relationship, gene structures and expression patterns of the BoSWEET genes. These findings provide new insights into the complex transcriptional regulation of BoSWEET genes, as well as potential candidate BoSWEET genes that promote sugar transport to enhance chilling tolerance and clubroot disease resistance in cabbage.

Slightly Acidic Electrolyzed Water Treatment Enhances the Main Bioactive Phytochemicals Content in Broccoli Sprouts via Changing Metabolism

Changes in the content of bioactive phytochemicals in the broccoli sprouts subjected to different slightly acidic electrolyzed water (SAEW) treatments were investigated in the present study. The highest sulforaphane amount in broccoli sprouts treated with SAEW with an available chlorine concentration (ACC) of 50 mg/L was 11.49 mg/g in dry weight (DW), which increased by 61.2% compared to the control. SAEW treatment enhanced the sulforaphane content mainly by increasing the glucoraphanin (GRA) concentration due to the promotion of methionine metabolism and increased myrosinase activities. In addition, the relative anthocyanin contents of light-germinated broccoli under SAEW 50 treatment were 2.03 times that of broccoli sprouts with tap water treatment, and these contents were associated with an increase in phenylalanine ammonia lyase (PAL) activities and phenylalanine participation in biosynthesis. In summary, SAEW promotes metabolism to induce the accumulation of bioactive compounds in broccoli sprouts.

Sustainable biosurfactant produced by Serratia marcescens UCP 1549 and its suitability for agricultural and marine bioremediation applications

BACKGROUND

Biosurfactants are surface-active agents produced by microorganisms that have higher efficiency and stability, lower toxicity and higher biocompatibility and biodegradability than chemical surfactants. Despite its properties and potential application in a wide range of environmental and industrial processes, biosurfactants are still not cost-competitive when compared to their synthetic counterparts. Cost effective technologies and renewable raw substrates as agro-industrial and regional waste from northeast of Brazil as cassava flour wastewater, supplemented with lactose and corn oil are mainly the chemically media for growing microorganism and in turn the production of the biosurfactant of quality. This study aimed to obtained biosurfactant by Serratia marcescens UCP 1549 containing cassava flour wastewater (CWW), by application of a full-factorial design, as sustainable practices in puts the production process in promising formulation medium. The characterization of the biomolecule was carried out, as well as the determination of its stability and toxicity for cabbage seeds. In addition, its ability to stimulate seed germination for agriculture application and oil spill bioremediation were investigated.

RESULTS

Serratia marcescens showed higher reduction of surface tension (25.92 mN/m) in the new medium containing 0.2% lactose, 6% cassava flour wastewater and 5% corn waste oil, after 72 h of fermentation at 28 °C and 150 rpm. The substrate cassava flour wastewater showed a promising source of nutrients for biosurfactant production. The isolate biosurfactant exhibited a CMC of 1.5% (w/v) and showed an anionic and polymeric structure, confirmed by infrared spectra. The biomolecule demonstrated high stability under different temperatures, salinity and pH values and non-toxicity against to cabbage seeds. Thus, exploring biosurfactant their potential role in seeds germinations and the promotion and agricultural applications was investigated. In addition, the effectiveness of biosurfactant for removal burned motor oil adsorbed in sand was verified.

CONCLUSIONS

The use of medium containing CWW not only reduces the cost of process of biosurfactant production, but also the environmental pollution due to the inappropriate disposal of this residue. This fact, added to the high stability and non-toxicity of the biosurfactant produced by S. marcescens UCP 1549, confirms its high environmental compatibility, make it a sustainable biocompound that can be replace chemical surfactants in diverse industries. In addition, the effectiveness of biosurfactant for stimulate seed germination and removing burned motor oil from sand, suggests its suitability for agriculture and bioremediation applications.