Breeding Crops for Enhanced Food Safety

Rhizosphere microbiomes and metabolomes are influenced by host genotype and developmental stage. However, there has been limited research that simultaneously profiles the rhizosphere microbiome and metabolism of rice across different genotypes and developmental stages. Furthermore, the interactions between rhizosphere microbiomes and metabolism in various plant genotypes and developmental stages are not well understood. Here, we investigated the diversity and composition of rhizosphere microbial community and metabolism across three hybrid rice varieties and their respective parent lines during three developmental stages (tillering, heading, and mature) using amplicon sequencing and untargeted metabolomics analyses. Plant developmental stages and genotypes significantly influence the rhizosphere microbiome and metabolome, with the impact of developmental stages being more pronounced. The composition of microbial communities and metabolites in the rhizosphere exhibited significant differences between the tillering stage and other developmental stages, with these differences becoming less distinct as the growth period continued. Hybrid rice displayed heterosis characteristics in their rhizosphere microorganisms compared to their parent varieties, as reflected by the significant enrichment of microbial species and the enhanced potential for microbial interactions within the co-occurrence network. Moreover, the differential microorganisms between the tillering and heading stages showed significant correlations with differential metabolites and soil chemical properties, including total phosphorus (TP), available phosphorus (AP), and nitrate nitrogen (NN). Taken together, this study contributes to our understanding of plant-microbiota-metabolome associations and provides a foundation for developing beneficial plant microbiomes and compounds to promote sustainable agricultural production.

Beneficial bacteria interact with plants by colonizing the rhizosphere and roots followed by further spread through the inner tissues, resulting in endophytic colonization. The major factors contributing to these interactions are not always well understood for most bacterial and plant species. It is believed that specific bacterial functions are required for plant colonization, but also from the plant side specific features are needed, such as plant genotype (cultivar) and developmental stage. Via multivariate analysis we present a quantification of the roles of these components on the composition of root-associated and endophytic bacterial communities in potato plants, by weighing the effects of bacterial inoculation, plant genotype and developmental stage. Spontaneous rifampicin resistant mutants of two bacterial endophytes, Paenibacillus sp. strain E119 and Methylobacterium mesophilicum strain SR1.6/6, were introduced into potato plants of three different cultivars (Eersteling, Robijn and Karnico). Densities of both strains in, or attached to potato plants were measured by selective plating, while the effects of bacterial inoculation, plant genotype and developmental stage on the composition of bacterial, Alphaproteobacterial and Paenibacillus species were determined by PCR-denaturing gradient gel-electrophoresis (DGGE). Multivariate analyses revealed that the composition of bacterial communities was mainly driven by cultivar type and plant developmental stage, while Alphaproteobacterial and Paenibacillus communities were mainly influenced by bacterial inoculation. These results are important for better understanding the effects of bacterial inoculations to plants and their possible effects on the indigenous bacterial communities in relation with other plant factors such as genotype and growth stage.

Heavy metal contamination of soil, water, and crops, and their health impact on residents, is a persistent social issue, and several studies have identified health risks of residents living near abandoned mines. In this study, the heavy metal concentrations in the soil and plants of abandoned gold mines of the primary goldmine and the secondary goldmine, Ilesa-Osun State Nigeria of latitude 7°, 27’N to 7°,35’N and longitude 4°, 47’E to 4°,53’E was investigated. A total of 20 soil samples in replicates of two [both surface (0 to15 cm) and subsurface (15 to 30 cm)] were collected from both sites and eight plant samples were also collected from both sites for this study. Metal concentration was determined using the Inductively Coupled Plasma/ Optical Emission Spectrometry (ICP/OES) technique. The trend of metal concentration was, Cr >Zn >Cu >Co >Pb >As >Cd. Soils in the secondary goldmine had mean values for Cu, Cr and Co higher than NCI standards for soil, which is indicative of Cu, Cr Co contamination in general. Chromium concentration of 79.4 mg/kg was observed in the soils of the secondary goldmine indicating chromium toxicity, at both 0 to 15 cm and 15 to 30 cm depths. While in plants, metal concentration was Zn >Cu >Pb> Cr >Co >As >Cd >Cd. Cd. Cu and Zn contamination in plants from the primary goldmine, were above the normal concentration of metals found in plants, with Cu considered to be at a high level, also (21 mg/kg). The plants considered in this study were observed to have high potential for phytoextraction of certain heavy metals. Key words: Heavy metals, goldmines, contamination, soil, plants

Airborne antibiotics, antimicrobial resistance, and bacterial pathogens in a commercial composting facility: Transmission and exposure risk

Heavy metal and phthalate contamination and labeling integrity in a large sample of US commercially available cannabidiol (CBD) products

Antibiotic resistance in human pathogens can proliferate under selective pressures. Heavy metals in environmental reservoirs may contribute to selecting antibiotic-resistant strains. To determine the associations between heavy metals and antibiotic resistance, a literature review was conducted to systematically collect and categorize evidence for co-occurrence of resistance to heavy metals and antibiotics within human pathogenic bacteria in water, wastewater, and soil. In total, 42 publications adhered to inclusion criteria. Across the reservoirs, zinc and cadmium were the most commonly observed heavy metals associated with resistance to antibiotics. Pseudomonas aeruginosa and Escherichia coli were the most commonly studied bacteria with reported co-occurrence of resistance to several heavy metals and antibiotic classes. As co-selecting agents, prevalence of heavy metals in the environment can proliferate resistance to heavy metals and antibiotics through co-resistance and cross-resistance mechanisms. In comparing different reservoirs, soils and sediments harbor higher heavy metal and antibiotic resistances compared to water environments. Additionally, abiotic factors such as pH can affect the solubility and hence, the availability of heavy metals to bacterial pathogens. Overall, our review demonstrates heavy metals act as co-selecting agents in the proliferation of antibiotic resistance in human pathogens in multiple environmental reservoirs. More studies that include statistical data are needed to further describe the exposure-response relationships between heavy metals and antibiotic resistance in different environmental media. Moreover, integration of culture-based and molecular-based methods in future studies are recommended to better inform our understanding of bacterial co- and cross-resistance mechanisms to heavy metals and antibiotics.

Changes in non-structural carbohydrates before and during winter are one of the major plant responses to winter stress. However, the observed pattern of changes is variable, not only between grass species but also between different experiments. This study examined the effect of developmental stage on carbohydrate reserves during winter in two grass species differing in winter hardiness. Timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.), sown early or late in the growing season, were sampled for total non-structural carbohydrates (TNC) in late October (end of main growing season), and then in late January, early March and late April. Quantitative and qualitative patterns of carbohydrate accumulation in crown segments were influenced both by plant genotype and developmental stage of the plants prior to winter. TNC increased from October to March, demonstrating considerable cell activity during winter, and declined to their lowest level in April. Sucrose proved to be the major reserve carbohydrate, followed by fructans. The highest content of TNC was found in the most winter-hardy cultivars, particularly in January and March. Early-sown plants accumulated higher levels of fructans than of sucrose, whereas late-sown plants mainly accumulated sucrose. These differences persisted during the winter. It can be concluded that the pattern of carbohydrate accumulation during winter differed between the two species studied and it was strongly affected by both cultivar and plant-developmental stage.

Heavy metals from natural and anthropogenic sources accumulate in soil and plants and as a consequence represent important environmental contamination problems. Nevertheless, food safety issues and adverse health risks make this one of the most serious environmental issues. The aim of the present study was to assess heavy metal contamination in the paddy plants from the northern area of Malaysia using Inductively Coupled Plasma Mass Spectrometry (ICPMS) and its risk assessment. In total, the heavy metals (As, Cd, Cu, Cr, and Pb) of the samples of paddy plants harvested from Kedah areas were extracted using an acid digestion method, while the heavy metals for soil samples using ammonium acetate. The heavy metal concentrations were then analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The enrichment (EF) and translocation factors (TF) of heavy metals were calculated, and health risk assessment (HRA) was performed. The EF values for heavy metals from the soil to roots, roots to stems, stems to leaves, and stems to grains followed the order Cu > As > Cr > Cd > Pb, whereas Cr and Pb were characterized by greater TF values from stem to grain than the other elements. The average daily dose (ADD) for both children and adults is below the safe value intake for each of the studied elements. The combined hazard index (HI) of five elements was beyond the acceptable value (HI >1). The carcinogenic risk, as exemplified by lifetime cancer risk (LCR), indicated that single exposure to As or Cr, in both adults and children, was greater than 10−4. The total cancer risk (CRt) resulting from multiple exposure to carcinogenic elements exceeded the acceptable value (CRt >1 ×10−4) in both adults and children. Overall, exposure to heavy metals through rice consumption poses potential non-carcinogenic and carcinogenic health risks to the local residents in the northern area; thus, regular monitoring of pollution in the area is crucial.

Plant genetic variation can have far‐reaching effects on associated communities and ecosystems. Heritable variation in ecologically relevant plant traits is often non‐randomly distributed across a species’ range and can exhibit geographic clines. In the event of range expansions and migration, previously unfamiliar genotypes may have large impacts on resident communities and ecosystems due to the introduction of novel and heritable phenotypic variation. Here we test the hypothesis that geographic origin of a focal plant genotype has effects on belowground invertebrate communities using a common garden field experiment. We sampled soil invertebrates from 103 Oenothera biennis genotypes, which were collected from across the species’ range and planted into a common garden field experiment at the northern range limit. We enumerated 24 000 individuals from 190 morphospecies and found that the diversity, abundance, and composition of soil invertebrate communities varied greatly among plant genotypes. Despite strong effects of plant genotype, we found few genetic correlations between plant traits and soil invertebrate community variables. However, herbivore damage was strongly related to variation in the soil invertebrate community. Geographic origin of plant genotypes had at most a weak effect on belowground communities. We speculate that predicting the extended effects of population movement on associated communities will require detailed knowledge of the trait variation occurring within focal species across particular environmental gradients.

Urban agroforestry and its potential integration into city planning efforts

Little is known about the influence of genetic diversity in plant populations on the dynamics of plant viruses, particularly those transmitted by insects. For these viruses, plant genetic diversity may affect virus incidence through impacts on the population dynamics of the vector insects or through impacts on vector feeding behavior, which determines transmission of the virus. This study was designed to explore the influence of plant genetic diversity on virus dispersal by aphid vectors and to examine the biological mechanisms responsible for that influence. In a set of field experiments using the aphid—transmitted barley yellow dwarf virus, I examined the influence of genetic diversity in oat (Avena sativa L.) populations on the spread of the virus and on the population dynamics and movement behavior of aphid vectors of the virus. Only at relatively high aphid abundance were the densities of aphid vectors influenced by plant genetic diversity. In one year out of three, densities of the oat—bird cherry aphid, Rhopalosiphum padi (L.), were significantly lower in the genetically diverse stand than in the genetically homogeneous stands. In no year were densities of the English grain aphid, Sitobion avenae (F.), influenced by the host—plant population. Despite these weak or absent effects on vector abundance, the incidence of the virus was consistently lower in the genetically diverse oat populations. Disease reduction in the diverse populations appears to depend upon changes in aphid movement behavior that affect the efficiency of virus transmission. Mark—release experiments with S. avenae demonstrated that movement rates were significantly higher and plant tenure times were significantly lower in the genetically diverse oat populations. Because the barley yellow dwarf virus requires several hours of aphid feeding for effective transmission, these reduced tenure times and increased travel time among plants led to a reduction of virus transmission. While plant genotype can clearly influence herbivorous insects dramatically, this study suggests that the effects on insects of genetic diversity per se in the host—plant population are likely to be subtle and not easily detected using standard field sampling techniques, except at high insect densities. Yet even at low vector densities, behavioral responses to plant genetic diversity can lead to significant effects on the spread of pathogens.

Ensuring Safe Food for Infants: The Importance of an Integrated Approach to Monitor and Reduce the Risks of Biological, Chemical, and Physical Hazards

Variance in edibility among plant genotypes is expected to be a key driver of plant genetic diversity (PGD) effects on abundance of insect herbivores and resulting herbivory. Yet, herbivore foraging behavior and leaf consumption may be also context‐dependent and, in particular, influenced by herbivore density, which remains unexplored. We used a combination of field and laboratory experiments with saplings from four half‐sib families (henceforth, families) of pedunculate oak (Quercus robur) to test how PGD and herbivore density interactively affect herbivory. Insect herbivory was assessed in a common garden experiment with plots containing all possible combinations of individuals from one to four oak families. Herbivore density was manipulated by spraying insecticide in a factorial design. Complementary feeding trials with gypsy moth larvae (Lymantria dispar) were used to further explore the mechanisms underlying observed patterns in the field. Herbivory decreased with increasing PGD under normal herbivore density, but not under reduced herbivore abundance. The most damaged oak family in the field was also the most consumed in non‐choice tests and was consistently preferred over other families in choice tests. Trials showed that the presence of less edible families in the diet reduced overall consumption by gypsy moth larvae. Under field conditions, the most edible family consistently benefited most from being associated with less edible, neighboring genotypes. Our results demonstrate that small‐scale PGD can provide associational resistance to insect herbivory, probably through change in herbivore foraging activity. Importantly, they also reveal that the magnitude of genetic diversity effect depends on herbivore density.

A potting experiment was carried out in the plastic house using soil with a loam texture, for the purpose of studying the process of phytoremidation of soil contaminated with some heavy metals (Plumbum, Cadmium, and Nickel) using three ornamental plants: Ficu elastica (Fix) and Catharanthus vinca and Carissa, to evaluate the efficiency of above ornamental plants in absorbing and accumulating heavy metals from soil contaminated with them. Evaluation of soil and plant contamination with heavy metals based on concentration according to international standards. Seedlings of ornamental plants were planted at the same age and were fertilized with NPK elements according to the fertilizer recommendation. It was irrigated with tap water after depleting 35% of the prepared water. The experiment continued for four months and was carried out according to a completely randomized design (CRD) using three ornamental plants and three levels of three heavy metals Pb, Cd, and Ni are 0, 100, and 200 mg L-1 for Plumbum, 0, 10 and 15 mg L-1 for Cadmium, and 0, 50 and 100 mg L-1 for Nickel with four replications to make a number of experimental units 108. Soil samples were taken and after the end of the experiment, available and total heavy metals were estimated. Plant samples (leaves) were also taken after the end of the experiment, and concentrations of heavy metals were estimated. Results showed an increase in total and available concentrations of heavy metals in cultivated soil for all plants after the end of the experiment, directly with an increase in levels of added heavy metals. Plumbum, Cadmium, and Nickel (32.27, 28.62, and 33.56), (1.593, 1.009, 1.326) and (12.17, 8.41, and 10.61) mg kg-1 for heavy metals, respectively, for Ficus elastica (Fix) and Catharanthus vinca and Carissa, respectively. Plants can be arranged in terms of their efficiency in absorbing heavy metals as follows: Catharanthus vinca > Carissa > Ficus elastica, which indicates the high ability of plants to transport and accumulate heavy metals from soil to plant. Heavy elements can arrange according to the amount absorbed from them as follows: - Cadmium > Nickel > Plumbum. Keywords: polluted soil, heavy elements, biological reclamation, ornamental plants

Silicon and heavy metal dynamics in soil-rice systems: A taihu lake plain case study on silicon depletion.