Enza Zaden (Netherlands)

The environmental persistence of polymers in liquid formulations (PLFs) can present a significant challenge for sustainability, particularly given their widespread use and limited post-use recovery.

Weight loss is an important subject in horticulture. We propose a kinetic model, consisting of two processes to describe tomato weight loss. The first process describes the conversion of ‘bound’ to ‘free’ water within the fruit, the second process describes the interaction with the outside environment as affected by temperature and relative humidity (RH). We conducted repeated weight measurements of ‘Brioso,’ ‘Capricia,’ and ‘Roterno’ tomatoes, stored at three temperatures and exposed to five RH levels (applied continuously or by switching from one to another RH level) over a 30-day period. Minimal loss was induced by storage at 100 % RH and 1-MCP (1.5 ppm for 24 h). Maximal weight loss was accomplished by storage at 0 % RH and ethylene (100 ppm for 24 h). The calibrated model accounted for 99.7 % of the encountered variation. A simplified weight loss model was applied to phenotype the weight loss of 66 tomato genotypes from three independent harvests. Weight loss was recorded during 35 days of storage at 16 °C and 85 % RH. This model described weight loss of each of the genotypes for more than 98 % of the encountered variation. The negative correlation between the rate constants for the conversion of ‘bound’ to ‘free’ water and the transport through the skin might indicate that a high rate of water availability is met with increased skin resistance to limit water loss (and vice versa). Weight loss phenotyping by kinetic modelling opens a new approach to investigate the genetic background of weight loss. • A kinetic modelling approach is proposed for postharvest weight loss in tomato. • The model includes both water loss to and uptake from the environment. • The model includes conversion of bound to free water and skin resistance. • Bound to free water conversion limits weight loss more than skin resistance. • High availability of free water is linked to higher skin resistance in 66 genotypes.

Biological control of seedborne pathogens and soilborne seedling pathogens through antagonists applied on seeds is an alternative to chemical seed treatments. The survival of coated microorganisms during the various seed processing, storage and distribution steps is essential for the use of beneficial fungi or bacteria on seeds. A study was done to gain insight into the survival potential and variability in survival of representatives of different microbial groups during storage of coated seeds of different crops. Survival of inocula on seeds of Brassica, onion, spinach and perennial ryegrass was tested by plating and for a subset of coated seeds by viability qPCR. A close correlation was found for CFU counts per seed and the estimated number of viable conidia based on strain-specific or generic fungal viability qPCR for conidia of Cladosporium cladosporioides H39 coated on various seed lots. For Lysobacter enzymogenes 3.1 T8, viability qPCR showed survival of cells on coated seeds. However, only few colonies were produced on Tryptone soy agar. Generic fungal and bacterial qPCR and viability qPCR assays with non-coated seeds indicated that only a proportion of the seed microbiota, frequently less than 10 %, are viable. Survival of inocula coated on seeds and stored for three to six months differed between applied microbial groups, formulation of inocula and between laboratories conducting the experiments. From the obtained results it can be concluded that there is a promising potential to improve the often envisaged low survival of inocula coated on seeds. Improved strains selection, improved and adapted seed processing technologies, and developing expertise in microbial seed processing will allow the use of a broader range of fungal and bacterial groups. The application of viability qPCR will support this development as a fast and reliable tool to monitor the survival of microbial inocula coated on seeds.

SUMMARYMicrospore embryogenesis is a type of in vitro totipotency in which the immature male gametophyte (pollen) develops into a haploid embryo after an abiotic stress treatment. In Brassica napus, heat‐stress treatment of male gametophytes induces the development of different types of multicellular embryogenic structures, each with different cellular characteristics and the capacity to form a differentiated embryo. The origin and early development of these different embryogenic structures have not been determined. We used two‐photon excitation fluorescence microscopy and time‐lapse imaging of cells expressing either a LEAFY COTYLEDON1 (LEC1) embryo identity reporter or a DR5v2 auxin response reporter to follow the development of embryogenic structures starting at the single‐ to few‐cell stage. We show for the first time that the developmental fate of embryogenic structures is defined by the symmetry of the first embryogenic division and that the division plane also predicts the timing of subsequent pollen wall (exine) rupture: suspensorless embryos develop after a symmetric division and undergo late exine rupture, while suspensor‐bearing embryos and embryogenic callus develop after an asymmetric division and undergo early exine rupture. Live imaging also captured previously unknown dynamic LEC1 and DR5v2 expression patterns that are associated with changes in exine integrity. This study highlights the developmental plasticity of cultured pollen and uncovers new roles for the first embryogenic cell division plane and the exine in defining and maintaining cell fate during microspore embryogenesis.

Although plants harbor a huge phytochemical diversity, only a fraction of plant metabolites is functionally characterized. In this work, we aimed to identify the genetic basis of metabolite functions during harsh environmental conditions in Arabidopsis thaliana. With machine learning algorithms we predicted stress-specific metabolomes for 23 (a)biotic stress phenotypes of 300 natural Arabidopsis accessions. The prediction models identified several aliphatic glucosinolates (GLSs) and their breakdown products to be implicated in responses to heat stress in siliques and herbivory by Western flower thrips, Frankliniella occidentalis. Bivariate GWA mapping of the metabolome predictions and their respective (a)biotic stress phenotype revealed genetic associations with MAM, AOP, and GS-OH, all three involved in aliphatic GSL biosynthesis. We, therefore, investigated thrips herbivory on AOP, MAM, and GS-OH loss-of-function and/or overexpression lines. Arabidopsis accessions with a combination of MAM2 and AOP3, leading to 3-hydroxypropyl dominance, suffered less from thrips feeding damage. The requirement of MAM2 for this effect could, however, not be confirmed with an introgression line of ecotypes Cvi and Ler, most likely due to other, unknown susceptibility factors in the Ler background. However, AOP2 and GS-OH, adding alkenyl or hydroxy-butenyl groups, respectively, did not have major effects on thrips feeding. Overall, this study illustrates the complex implications of aliphatic GSL diversity in plant responses to heat stress and a cell-content-feeding herbivore.

Abstract Plants host diverse microbial communities that can be influenced by their hosts to mitigate biotic stress. Previous research demonstrated that distinct laboratory cultures of Hyaloperonospora arabidopsidis (Hpa) on Arabidopsis thaliana , consistently harbor nearly identical bacteria. In this study, we analyzed the bacterial phyllosphere communities of laboratory-grown spinach plants infected by the downy mildew pathogen Peronospora effusa (Pe). Using 16S amplicon sequencing, we identified 14 Amplicon Sequence Variants (ASVs), with diverse taxonomies, that were enriched in at least 3 out of 5 investigated Pe cultures. This small set of 14 ASVs occupied on average 6.9% of the total bacterial communities in healthy spinach plants, and 43.1% in Pe-inoculated plants. A specific Rhodococcus and a Paenarthrobacter ASV were particularly prevalent and abundant. To validate these findings outside of the laboratory, we planted a susceptible variety of spinach in 4 agricultural fields and sampled leaves from Pe-infected plants in 2 fields where this pathogen naturally occurred. Comparative microbiome analysis of diseased and healthy plants revealed significant enrichment of 16 and 31 ASVs in these 2 fields, respectively. Among these, the Paenarthrobacter ASV was enriched in one field and the Rhodococcus ASV in the other field, suggesting that disease-associated microbiota that are abundantly detected in Pe laboratory cultures are also associated with Pe-infected field plants. Additionally, we observed an overlap of ASVs that were associated with both Pe and Hpa, indicating that similar bacteria are linked to downy mildew disease across different hosts.

The hormone salicylic acid (SA) plays a crucial role in plant immunity by activating responses that arrest pathogen ingress. SA accumulation also penalizes growth, a phenomenon visible in mutants that hyperaccumulate SA, resulting in strong growth inhibition. An important question, therefore, is why healthy plants produce basal levels of this hormone when defense responses are not activated. Here, we show that basal SA levels in unchallenged plants are needed for the expression of a number of immunity-related genes and receptors, such as RECEPTOR-LIKE PROTEIN 23 (RLP23). This was shown by depleting basal SA levels in transgenic Arabidopsis lines through the overexpression of the SA-inactivating hydroxylases DOWNY MILDEW-RESISTANT 6 (DMR6) or DMR6-LIKE OXYGENASE 1. RNAseq analysis revealed that the expression of a subset of immune receptor and signaling genes is strongly reduced in the absence of SA. The biological relevance of this was shown for RLP23: In SA-depleted and SA-insensitive plants, responses to the RLP23 ligand, the microbial pattern nlp24, were strongly reduced, whereas responses to flg22 remained unchanged. We hypothesize that low basal SA levels are needed for the expression of a subset of immune system components that enable early pathogen detection and activation of immunity.

Abstract BackgroundAll species shed DNA into their environment during life or in death providing an opportunity to monitor biodiversity via its environmental DNA. Biodiversity monitoring using environmental DNA based technologies has become an important tool in understanding ecosystems. In recent years promising progress for non-invasive and, more importantly, non-destructive monitoring has been made by combining the retrieval of information transmitted by released environmental DNA with high-throughput sequencing technologies. Important ecosystems under continuous threat by disease but essential for food supplies are agricultural systems, often farmed as large monocultures and so highly vulnerable to disease outbreaks. Pest and pathogen monitoring in agricultural ecosystems is therefore key for efficient and early disease prevention and management. Air is rich in biodiversity, but has the lowest DNA concentration of all environmental media and yet it is required for windborne spread by many of the world’s most damaging crop pathogens. Our work and recent research suggests that ecosystems can be monitored efficiently using airborne nucleic acid information.ResultsHere we show that the airborne DNA of microbes can be recovered, sequenced and taxonomically classified, including down to the species level. Monitoring a field growing key crops we show that Air-seq can identify the presence of agriculturally significant pathogens and quantify their changing abundance over a period of 1.5 months often correlating with weather variables.ConclusionWe add to the evidence that aerial environmental DNA can be used as a source for biomonitoring in agricultural and more general terrestrial ecosystems. The ability to detect fluxes and occurrence patterns of species and strains with high throughput sample processing and analysis technologies highlights the value of airborne environmental DNA in monitoring biodiversity changes and tracking of taxa of human interest or concern.

Abstract Seed health is an indispensable prerequisite of food security. While the toolkit of plant protection products is currently limited, evidence suggests that the seed microbiome could protect seeds from pathogens. Thus, given their possible disease suppressive potential, we tested 11 different pathosystems to achieve the following proof-of-concept: seed microbiomes can be beneficial for seed health through conferring disease suppression. This study focused on beetroot, onion, spinach, pepper, coriander, red fescue and perennial ryegrass seeds, with each crop being challenged with one or two from a total of six pathogens, namely Pythium ultimum (or a Pythium sp.), Setophoma terrestris, Fusarium oxysporum, Phytophthora capsici, Laetisaria fuciformis and a mix of Puccinia sp. isolates. Each seed lot of each crop was tested with and without treatment with a disinfectant as a proxy for comparing intact seed microbiomes with seed microbiomes after partial elimination by disinfection. We found disease suppression in two pathosystems. Beetroot and spinach seed lots were able to suppress disease caused by P. ultimum when their microbiomes were intact but not after seed disinfection. We speculate that this relates to the microorganisms residing on and in the seed. Yet, seed microbiome disease suppression was not found in all pathosystems, highlighting the variation in seed morphology, plant cultivars, pathogens and seed disinfection treatments. A holistic understanding of the characteristics of seeds that harbour suppressive microbiomes as well as the pathogens that are sensitive to suppression could lead to more targeted and informed seed processing and treatment and, consequently, to the sustainable management of seedling diseases.

Over the last decade, viral metagenomic studies have resulted in the discovery of thousands of previously unknown viruses. These studies are likely to play a pivotal role in obtaining an accurate and robust understanding of how viruses affect the stability and productivity of ecosystems. Among the metagenomics-based approaches that have been developed since the beginning of the 21st century, shotgun metagenomics applied specifically to virion-associated nucleic acids (VANA) has been used to disentangle the diversity of the viral world. We summarize herein the results of 24 VANA-based studies, focusing on plant and insect samples conducted over the last decade (2010 to 2020). Collectively, viruses from 85 different families were reliably detected in these studies, including capsidless RNA viruses that replicate in fungi, oomycetes, and plants. Finally, strengths and weaknesses of the VANA approach are summarized and perspectives of applications in detection, epidemiological surveillance, environmental monitoring, and ecology of plant viruses are provided. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.