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.

Analysis of ambient temperature-responsive transcriptome in shoot apical meristem of heat-tolerant and heat-sensitive broccoli inbred lines during floral head formation

BACKGROUND

Head formation of broccoli (Brassica oleracea var. italica) is greatly reduced under high temperature (22 °C and 27 °C). Broccoli inbred lines that are capable of producing heads at high temperatures in summer are varieties that are unique to Taiwan. However, knowledge of the early-activated pathways of broccoli head formation under high temperature is limited.

RESULTS

We compared heat-tolerant (HT) and heat-sensitive (HS) transcriptome of broccoli under different temperatures. Weighted gene correlation network analysis (WGCNA) revealed that genes involved in calcium signaling pathways, mitogen-activated protein kinase (MAPK) cascades, leucine-rich repeat receptor-like kinases (LRR-RLKs), and genes coding for heat-shock proteins and reactive oxygen species homeostasis shared a similar expression pattern to BoFLC1, which was highly expressed at high temperature (27 °C). Of note, these genes were less expressed in HT than HS broccoli at 22 °C. Co-expression analysis identified a model for LRR-RLKs in survival-reproduction tradeoffs by modulating MAPK- versus phytohormones-signaling during head formation. The difference in head-forming ability in response to heat stress between HT and HS broccoli may result from their differential transcriptome profiles of LRR-RLK genes. High temperature induced JA- as well as suppressed auxin- and cytokinin-related pathways may facilitate a balancing act to ensure fitness at 27 °C. BoFLC1 was less expressed in HT than HS at 22 °C, whereas other FLC homologues were not. Promoter analysis of BoFLC1 showed fewer AT dinucleotide repeats in HT broccoli. These results provide insight into the early activation of stress- or development-related pathways during head formation in broccoli. The identification of the BoFLC1 DNA biomarker may facilitate breeding of HT broccoli.

CONCLUSIONS

In this study, HT and HS broccoli genotypes were used to determine the effect of temperature on head formation by transcriptome profiling. On the basis of the expression pattern of high temperature-associated signaling genes, the HS transcriptome may be involved in stress defense instead of transition to the reproductive phase in response to heat stress. Transcriptome profiling of HT and HS broccoli helps in understanding the molecular mechanisms underlying head-forming capacity and in promoting functional marker-assisted breeding.

Comparison of foliar silicon and selenium on cadmium absorption, compartmentation, translocation and the antioxidant system in Chinese flowering cabbage

Silicon (Si) and selenium (Se) are beneficial for many higher plants when grown on stress conditions. However, the mechanisms underlying the differential effects between foliar Si and Se in alleviation of plant toxicity exposed to cadmium (Cd) stress are remained unclear. In this study, we investigated the discrepant mechanisms of foliar Si and Se on Cd absorption and compartmentation by roots, its translocation in xylem, and the antioxidant system within Chinese flowering cabbage (Brassica campestris L. ssp. chinensis var. utilis) under low and high Cd stress. Results showed that plant growth was significantly enhanced by foliar additions of Si or/and Se according to an increased plant tissue biomass at high Cd exposure. In addition, the foliar coupled addition of Si and Se showed little effects on the concentrations of Si or Se in plant tissues in comparison with the single addition of foliar Si or Se respectively. The foliar Si alone or combined with Se markedly reduced the Cd concentrations in plant shoots under two Cd treatments. This might be explained by the lower Cd concentrations in symplast and apoplast and the higher Cd concentrations in cell walls of plant roots, and the lower Cd concentrations in xylem sap. However, no great changes in these values were observed under the treatments of foliar Se alone. Moreover, the foliar additions of Si or/and Se all increased the antioxidant enzyme activities of SOD, CAT and APX in plant tissues, especially at high Cd dosage. No significant differences in the increasing degrees of these three antioxidant enzymes were found between the foliar Si and Se treatments. However, only the foliar Se alone or combined with Si markedly promoted the antioxidant enzyme activities of GR and DHAR in plant tissues. Our findings demonstrate that the alleviation of Cd toxicity by foliar Si maybe mainly responsible for inhibition of Cd absorption and its translocation to plant shoots, reinforcing its compartmentation into root cell walls, whilst enhancing the antioxidant enzyme system may be employed by foliar Se.

Laboratory Investigation of Cauliflower-Fungus-Insect Interactions for Cabbage Maggot Control

The cabbage maggot (also known as cabbage root fly [CRF]; Delia radicum L.) is a serious pest of brassicas. The pest's soil-dwelling larvae are especially damaging to young brassica transplants. In light of toxic soil insecticide phase-out novel biocontrol management solutions are sought for. Our research is focused on the development of a biological control strategy involving cauliflower plantlet inoculation with insect pathogenic fungi. This article presents the results of a laboratory investigation of cauliflower × microbe × CRF interactions. Seven isolates of fungi (entomopathogenic and rhizosphere-competent fungi and soil saprotrophs) were tested for their pathogenicity to CRF and their effects on cauliflower plantlets. The laboratory experiments were performed in sterilized substrate. Several strains significantly increased CRF mortality, some at par with a commercial bioinsecticide based on B. bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae). All strains colonized the rhizoplane, however to varying extent. Some isolates were also reisolated from within healthy plant tissues and thus identified as endophytes. The method of applying conidia had a significant effect on survival and weight of seedlings and rhizoplane and endophytic colonization rates. Two Metarhizium brunneum Petsch (Hypocreales: Clavicipitaceae) isolates exhibited plant growth promotion effects when ungerminated seeds were coated with conidia. The ecological implications of plant × microbe × pest interactions and options for improving the effectiveness of a fungal-based biological CRF management strategy are discussed.

Biochar amendment immobilizes arsenic in farmland and reduces its bioavailability

This study aimed to determine effects of biochar derived from wheat straw at 500 °C on arsenic immobilization in a soil-Brassica campestris L system. When the soils amended with 4% modified biochar (MBC), 0.5% Fe grit as zero-valent iron (ZVI), 0.5% Fe grit + 4% MBC (ZMBC), 0.5% ZVI + 4% biochar (ZBC), 4% biochar (BC), and control (without amendments), it confirmed that available arsenic concentration in soils occurred in the following order: ZMBC < MBC < ZVI < ZBC < Control < BC. Water-soluble As (WSAs) was reduced by 89.74% and 92.30% in MBC- and ZMBC-amended soils, respectively, compared to the control. When MBC applied into soil, As uptake of shoot and root decreased by 44.55% and 45.40%, respectively, and ZMBC resulted in 74.92% and 71.80% reduction in shoot and root As of Brassica campestris L. Immobilization effect of As in ZBC was also observed though BC elevated plant As uptake significantly. The immobilization effect of MBC was mainly attributed to Fe₂O₃ impregnation illustrated by x-ray diffraction (XRD) and scanning electron microscopy (SEM) images through sorption, precipitation, and coprecipitation. Such Fe containing complexes might impede As translocation from root to shoot and subsequently reduce As accumulation in the plant with modified biochar amendment.

Speed breeding in growth chambers and glasshouses for crop breeding and model plant research

'Speed breeding' (SB) shortens the breeding cycle and accelerates crop research through rapid generation advancement. SB can be carried out in numerous ways, one of which involves extending the duration of plants' daily exposure to light, combined with early seed harvest, to cycle quickly from seed to seed, thereby reducing the generation times for some long-day (LD) or day-neutral crops. In this protocol, we present glasshouse and growth chamber-based SB approaches with supporting data from experimentation with several crops. We describe the conditions that promote the rapid growth of bread wheat, durum wheat, barley, oat, various Brassica species, chickpea, pea, grass pea, quinoa and Brachypodium distachyon. Points of flexibility within the protocols are highlighted, including how plant density can be increased to efficiently scale up plant numbers for single-seed descent (SSD). In addition, instructions are provided on how to perform SB on a small scale in a benchtop growth cabinet, enabling optimization of parameters at a low cost.

Root colonization and growth promotion of soybean, wheat and Chinese cabbage by Bacillus cereus YL6

Although phosphate-solubilizing bacteria (PSBs) are used in agricultural production, comprehensive research on PSB that colonize the rhizosphere of different plants and promote plant growth is lacking. This study was conducted to examine the growth-promoting effects and colonizing capacity of strain YL6, a PSB. YL6 not only increased the biomass of soybean and wheat in pot experiments but also increased the yield and growth of Chinese cabbage under field conditions. The observed growth promotion was related to the capacity of YL6 to dissolve inorganic and organic phosphorus and to produce indole-3-acetic (IAA) and gibberellin (GA). After applying YL6 to soybean, wheat and Chinese cabbage, the rhizosphere soil available phosphorus (available P) content increased by 120.16%, 62.47% and 7.21%, respectively, and the plant total phosphorus content increased by 198.60%, 6.20% and 78.89%, respectively, compared with plants not treated with YL6. To examine plant colonization, YL6 labeled with green fluorescent protein (YL6-GFP) was inoculated into the plant rhizosphere and found to first colonize the root surface and hairs and then to penetrate into the intercellular spaces and vessels. Collectively, these results demonstrate that YL6 promotes the growth of three different crops and colonizes them in a similar manner. The findings therefore provide a solid foundation for probing the mechanisms by which PSB affect plant growth.

Combining QTL mapping with transcriptome and metabolome profiling reveals a possible role for ABA signaling in resistance against the cabbage whitefly in cabbage

Whiteflies are among the world's most significant agricultural pests and chemical insecticides are extensively used to reduce crop damage to acceptable levels. However, nearly all insecticides pose a threat to the environment and alternative control methods, such as breeding of crop varieties that are inherently insect-resistant, are needed. Previously, a strong source of plant-age dependent resistance to the cabbage whitefly (Aleyrodes proletella) has been identified in the modern white cabbage (Brassica oleracea var. capitata) variety Rivera. However, nothing is known about the molecular mechanisms or the genes involved in this resistance. In the present study, a multidisciplinary approach combining transcriptome and metabolome profiling with genetic mapping was used to identify the molecular players of whitefly resistance in cabbage. Transcriptome profiles of young (susceptible) and older (resistant) Rivera plants were analyzed using RNA sequencing. While many genes involved in general processes were differentially expressed between both ages, several defense-related processes were overrepresented in the transcriptome profile of older plants. Hormone measurements revealed that jasmonic acid (JA) levels decreased upon whitefly infestation at both plant ages. Interestingly, abscisic acid (ABA) levels showed contrasting effects in response to whitefly infestation: ABA levels were reduced in young plants but induced in older plants upon whitefly feeding. Auxin levels were significantly lower in older plants compared with young plants, independent of whitefly presence, while glucosinolate levels were higher. Additionally, whitefly performance was monitored in an F2 population derived from a cross between Rivera and the susceptible white cabbage variety Christmas Drumhead. Significant QTL intervals were mapped on chromosome 2 and 9 for oviposition rate and whitefly adult survival, respectively. Several genes that were higher expressed in older plants and located in the identified QTL intervals were orthologous to Arabidopsis genes that have been related to ABA signaling, suggesting a role for ABA in the regulation of resistance towards whiteflies. Our results show that combining different omics approaches is a useful strategy to identify candidate genes underlying insect resistance.

Minimum tillage and organic fertilization for the sustainable management of Brassica carinata A. (Braun) in the Mediterranean environment

In recent years, the massive exploitation of agricultural land intended to meet growing food demand has led to a reduction in soil fertility through the depletion of nutrients and organic matter. To implement sustainable agriculture, it is necessary to reduce soil tillage and use residual biomasses that are easily available in the region as soil amendments. Furthermore, it is important to test these residual biomasses in order to exclude a possible increase of heavy metals in soils due to the incorporation of the aforementioned biomasses. The current study aimed to evaluate the effects on soil fertility and health following the application of organic fertilizers combined with different soil tillage practices and the agronomic response of Brassica carinata A. (Braun). The soil tillage treatments consisted of conventional (CT) and minimum tillage (MT), whereas the fertilization treatments were mineral fertilizer (N_min), municipal solid waste compost (N_comp), mixed compost and mineral fertilizer (N_mix), and sewage sludge (N_ss). These treatments were compared with an unfertilized control (N₀). The N_comp and N_ss treatments enhanced soil fertility, increasing the organic carbon and available phosphorus concentrations compared with N₀ and N_min, whereas no significant difference was showed between the soil tillage treatments in terms of soil fertility. In addition, N_ss did not show any significant difference compared to N_min in terms of crop biomass, whereas this parameter appeared higher in CT compared with MT. A principal component analysis showed that the concentrations of toxic elements applied by the organic amendments did not change the dynamic equilibrium of the soil-plant system. Over the short term, the replacement of CT and N_min with MT and N_ss can be achieved, thus guaranteeing the sustainable cultivation of Brassica, without significant changes in heavy metal concentration in soil.

Tissue culture and genetic transformation of cabbage (Brassica oleracea var. capitata): an overview

MAIN CONCLUSION

The main goal of this publication is an overview of the biotechnological achievements concerning in vitro cultures and transformation of Brassica oleracea var. capitata. Faced with the requirements of the global food market, intensified work on the genetic transformation of economically important plants is carried out in laboratories around the world. The development of efficient procedures for their regeneration and transformation could be a good solution for obtaining, in a shorter time than by traditional methods, plants with desirable traits. Furthermore, conventional breeding methods are insufficient for crop genetic improvement not only because of being time-consuming but also because they are severely limited by sexual incompatibility barriers. This problem has been overcome by genetic engineering, which seems to be a very good technique for cabbage improvement. Despite the huge progress that has been made in the field of plant regeneration and transformation methods, up to now, no routine transformation procedure has been developed in the case of cabbage. This problem stems from the fact that the efficiency of cabbage transformation is closely related to the genotype and some varieties are recalcitrant to transformation. It is obvious that it is not possible to establish one universal regeneration and transformation protocol for all varieties of cabbage. Therefore, it seems fully justified to develop the above-mentioned procedures for individual economically important cultivars. Despite the obstacles of cabbage transformation in laboratories of many countries, especially those where this vegetable is extremely popular (e.g., China, India, Korea, Malaysia, Pakistan), such attempts are made. This article reviews the achievements in the field of tissue culture and cabbage transformation from the last two decades.