Precision mapping and expression analysis of recessive bacterial blight resistance gene xa-45(t) from Oryza glaberrima.

BACKGROUND: Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating diseases of rice leading to huge yield losses in Southeast Asia. The recessive resistance gene xa-45(t) from Oryza glaberrima IRGC102600B, mapped on rice chromosome 8, spans 80 Kb with 9 candidate genes on Nipponbare reference genome IRGSP-1.0. The xa-45(t) gene provides durable resistance against all the ten Xanthomonas pathotypes of Northern India, thus aiding in the expansion of recessive bacterial blight resistance gene pool. Punjab Rice PR127, carrying xa-45(t), was released for wider use in breeding programs. This study aims to precisely locate the target gene among the 9 candidates conferring resistance to bacterial blight disease. METHODS AND RESULTS: Sanger sequencing of all nine candidate genes revealed seven SNPs and an Indel between the susceptible parent Pusa 44 and the resistant introgression line IL274. The genotyping with polymorphic markers identified three recombinant breakpoints for LOC_Os08g42370, and LOC_Os08g42400, 15 recombinants for LOC_Os08g423420 and 26 for LOC_Os08g42440 out of 190 individuals. Relative expression analysis across six time intervals (0, 8, 24, 48, 72, and 96 h) after bacterial blight infection showed over expression of LOC_Os08g42410-specific transcripts in IL274 compared to Pusa 44, with a significant 4.46-fold increase observed at 72 h post-inoculation. CONCLUSIONS: The Indel marker at the locus LOC_Os08g42410 was found co-segregating with the phenotype, suggesting its candidacy towards xa-45(t). The transcript abundance assay provides strong evidence for the involvement of LOC_Os08g42410 in the resistance conferred by the bacterial blight gene xa-45(t).

Einkorn genomics sheds light on history of the oldest domesticated wheat.

Einkorn (Triticum monococcum) was the first domesticated wheat species, and was central to the birth of agriculture and the Neolithic Revolution in the Fertile Crescent around 10,000 years ago1,2. Here we generate and analyse 5.2-Gb genome assemblies for wild and domesticated einkorn, including completely assembled centromeres. Einkorn centromeres are highly dynamic, showing evidence of ancient and recent centromere shifts caused by structural rearrangements. Whole-genome sequencing analysis of a diversity panel uncovered the population structure and evolutionary history of einkorn, revealing complex patterns of hybridizations and introgressions after the dispersal of domesticated einkorn from the Fertile Crescent. We also show that around 1% of the modern bread wheat (Triticum aestivum) A subgenome originates from einkorn. These resources and findings highlight the history of einkorn evolution and provide a basis to accelerate the genomics-assisted improvement of einkorn and bread wheat.

Integration of genetic and genomics resources in einkorn wheat enables precision mapping of important traits.

Einkorn wheat (Triticum monococcum) is an ancient grain crop and a close relative of the diploid progenitor (T. urartu) of polyploid wheat. It is the only diploid wheat species having both domesticated and wild forms and therefore provides an excellent system to identify domestication genes and genes for traits of interest to utilize in wheat improvement. Here, we leverage genomic advancements for einkorn wheat using an einkorn reference genome assembly combined with skim-sequencing of a large genetic population of 812 recombinant inbred lines (RILs) developed from a cross between a wild and a domesticated T. monococcum accession. We identify 15,919 crossover breakpoints delimited to a median and average interval of 114 Kbp and 219 Kbp, respectively. This high-resolution mapping resource enables us to perform fine-scale mapping of one qualitative (red coleoptile) and one quantitative (spikelet number per spike) trait, resulting in the identification of small physical intervals (400 Kb to 700 Kb) with a limited number of candidate genes. Furthermore, an important domestication locus for brittle rachis is also identified on chromosome 7A. This resource presents an exciting route to perform trait discovery in diploid wheat for agronomically important traits and their further deployment in einkorn as well as tetraploid pasta wheat and hexaploid bread wheat cultivars.

Comparative genomic analysis of 5Mg chromosome of Aegilops geniculata and 5Uu chromosome of Aegilops umbellulata reveal genic diversity in the tertiary gene pool.

Wheat is one of the most important cereal crops for the global food security. Due to its narrow genetic base, modern bread wheat cultivars face challenges from increasing abiotic and biotic stresses. Since genetic improvement is the most sustainable approach, finding novel genes and alleles is critical for enhancing the genetic diversity of wheat. The tertiary gene pool of wheat is considered a gold mine for genetic diversity as novel genes and alleles can be identified and transferred to wheat cultivars. Aegilops geniculata and Ae. umbellulata are the key members of the tertiary gene pool of wheat and harbor important genes against abiotic and biotic stresses. Homoeologous-group five chromosomes (5Uu and 5Mg) have been extensively studied from Ae. geniculata and Ae. umbellulata as they harbor several important genes including Lr57, Lr76, Yr40, Yr70, Sr53 and chromosomal pairing loci. In the present study, using chromosome DNA sequencing and RNAseq datasets, we performed comparative analysis to study homoeologous gene evolution in 5Mg, 5Uu, and group 5 wheat chromosomes. Our findings highlight the diversity of transcription factors and resistance genes, resulting from the differential expansion of the gene families. Both the chromosomes were found to be enriched with the "response to stimulus" category of genes providing resistance against biotic and abiotic stress. Phylogenetic study positioned the M genome closer to the D genome, with higher proximity to the A genome than the B genome. Over 4000 genes were impacted by SNPs on 5D, with 4-5% of those genes displaying non-disruptive variations that affect gene function.

Physical mapping of the wheat genes in low-recombination regions: radiation hybrid mapping of the C-locus.

KEY MESSAGE: This work reports the physical mapping of an important gene affecting spike compactness located in a low-recombination region of hexaploid wheat. This work paves the way for the eventual isolation and characterization of the factor involved but also opens up possibilities to use this approach to precisely map other wheat genes located on proximal parts of wheat chromosomes that show highly reduced recombination. Mapping wheat genes, in the centromeric and pericentromeric regions (~ 2/3rd of a given chromosome), poses a formidable challenge due to highly suppressed recombination. Using an example of compact spike locus (C-locus), this study provides an approach to precisely map wheat genes in the pericentromeric and centromeric regions that house ~ 30% of wheat genes. In club-wheat, spike compactness is controlled by the dominant C-locus, but previous efforts have failed to localize it, on a particular arm of chromosome 2D. We integrated radiation hybrid (RH) and high-resolution genetic mapping to locate C-locus on the short arm of chromosome 2D. Flanking markers of the C-locus span a physical distance of 11.0 Mb (231.0-242 Mb interval) and contain only 11 high-confidence annotated genes. This work demonstrates the value of this integrated strategy in mapping dominant genes in the low-recombination regions of the wheat genome. A comparison of the mapping resolutions of the RH and genetic maps using common anchored markers indicated that the RH map provides ~ 9 times better resolution that the genetic map even with much smaller population size. This study provides a broadly applicable approach to fine map wheat genes in regions of suppressed recombination.

Identification and high-resolution mapping of a novel tiller number gene (tin6) by combining forward genetics screen and MutMap approach in bread wheat.

Wheat (Triticum aestivum) is one of the most important food crops worldwide, providing up to 20% of the caloric intake per day. Developing high-yielding wheat cultivars with tolerance against abiotic and biotic stresses is important to keep up with the increasing human population. Tiller number is one of the major yield-related traits, directly affecting the number of grains produced per plant; however, only a small number of QTL and underlining genes have been identified for this important factor. Identification of novel genetic variation underlying contrasting traits and their precise genetic mapping in wheat is considered difficult due to the complexity and size of the genome; however, advancements in genomic resources have made efficient gene localization more possible. In this study, we report the characterization of a novel tillering number gene using a mutant identified in the forward genetic screen of an ethyl methane sulfonate (EMS)-treated population of cv. "Jagger." By crossing the low tillering mutant with the Jagger wild-type plant, we generated an F2 population and used the MutMap approach to identify a novel physical interval on 11 Mb on chromosome 2DS. Using an F2 population of 442 gametes and polymorphic SNP markers, we were able to delineate the tin6 locus to a 2.1 Mb region containing 22 candidate genes.

Wheat Pore-Forming Toxin-Like Protein Confers Broad-Spectrum Resistance to Fungal Pathogens in Arabidopsis.

Fusarium head blight (FHB), caused by the hemibiotrophic fungus Fusarium graminearum, is one of the major threats to global wheat productivity. A wheat pore-forming toxin-like (PFT) protein was previously reported to underlie Fhb1, the most widely used quantitative trait locus in FHB breeding programs worldwide. In the present work, wheat PFT was ectopically expressed in the model dicot plant Arabidopsis. Heterologous expression of wheat PFT in Arabidopsis provided a broad-spectrum quantitative resistance to fungal pathogens including F. graminearum, Colletotrichum higginsianum, Sclerotinia sclerotiorum, and Botrytis cinerea. However, there was no resistance to bacterial or oomycete pathogens Pseudomonas syringae and Phytophthora capsici, respectively in the transgenic Arabidopsis plants. To explore the reason for the resistance response to, exclusively, the fungal pathogens, purified PFT protein was hybridized to a glycan microarray having 300 different types of carbohydrate monomers and oligomers. It was found that PFT specifically hybridized with chitin monomer, N-acetyl glucosamine (GlcNAc), which is present in fungal cell walls but not in bacteria or oomycete species. This exclusive recognition of chitin may be responsible for the specificity of PFT-mediated resistance to fungal pathogens. Transfer of the atypical quantitative resistance of wheat PFT to a dicot system highlights its potential utility in designing broad-spectrum resistance in diverse host plants. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

A wheat kinase and immune receptor form host-specificity barriers against the blast fungus.

Since emerging in Brazil in 1985, wheat blast has spread throughout South America and recently appeared in Bangladesh and Zambia. Here we show that two wheat resistance genes, Rwt3 and Rwt4, acting as host-specificity barriers against non-Triticum blast pathotypes encode a nucleotide-binding leucine-rich repeat immune receptor and a tandem kinase, respectively. Molecular isolation of these genes will enable study of the molecular interaction between pathogen effector and host resistance genes.

User experience study of an affordable manual standing wheelchair.

PURPOSE: The manual user-operated Arise Standing Wheelchair (SWC) is the end-result of multiple design iterations based on comments from user trials. The Arise SWC provides standing functionality, outdoor mobility, affordability, and customizability. This paper describes a user experience study of the Arise SWC's pre-commercial version. METHODS: Thirty participants (N = 30, 25 Male, 5 Female) were recruited for the study. All the participants were people with spinal cord injury. The study was conducted over a period of six weeks (five participants per week) within the hospital premises under the supervision of clinical personnel. A 30 min interactive training session involved thirteen activities. During the trial period, the participants were trained to perform twenty-two activities to familiarize themselves with the SWC. The participants were also trained to perform four functional usage activities with the SWC. At the end of the study, participant responses to ten outcome measures were captured using a smiley-based Likert-scale questionnaire. RESULTS: A majority of the participants (93.3%) felt happy when they stood in the SWC. The majority participants (83.3%) preferred the Arise SWC over their current wheelchair. Also, 80% participants anticipated that they could get more work done at home using the standing function of the wheelchair. CONCLUSIONS: A one-time fitting and training ensured optimal effort for the SWC operation, correct posture, and comfortable user experience. With proper dissemination and awareness, it is believed that the Arise SWC will benefit eligible users and improve their quality of life.IMPLICATIONS FOR REHABILITATIONThe Arise wheelchair provides standing functionality, outdoor mobility, affordability, and customizability.Study confirms that incorporating standing functionality can improve the quality of life for wheelchair users.The majority of users were happy, felt safe and expected to do more with the standing functionality.Study results support further testing in real world conditions beyond the hospital setting.

Micro-characteristics of a naturally ventilated classroom air quality under varying air purifier placements.

A naturally-ventilated operational classroom was instrumented at 18 locations to assess spatial variations of classroom air pollution (CRAP), thermal comfort and ventilation indicators under 10 different scenarios (base scenario without air purifier (AP); three single AP scenarios; three scenarios with two APs at same locations; three scenarios with two APs at different locations). Unlike PM2.5, monitored PM10 and CO2 concentrations followed the diurnal occupancy profile. Highest vertical variation (38%) in CO2 was at the classroom entry zone at 40-300 cm height. CO2 increased until 225 cm before stratifying further. PM10 increased to highest levels at children sitting height (100 cm) before decreasing to adult breathing height (150 cm). Highest horizontal variations in CO2 (PM10) were 29% (22%) at 40 cm height between the entry and occupied zones. Teachers' exposure to CO2 (PM10) in breathing zone varied by up to 6% (3%); the corresponding variations across monitored locations were up to 14% (19%). Teachers' exposure to CO2 was up to 13% higher than that of children and 18% lower for PM10. Traffic emissions (PM2.5 and NOx), secondary pollutants (VOCs and O3), thermal comfort parameters and noise level in the classroom varied insignificantly among scenarios. PM10 reduction was not doubled by using two air purifiers, which were most effective when placed within the highest PM concentration zone. Cross-comparisons of scenarios showed: use of AP reduced classroom's spatial average PM10 up to 14%; PM10 was reduced by increasing the AP's filtration capacity; and AP had insignificant impact on spatial average CO2. PM10 showed a maximum reduction of 46% (teacher zone), 62% (occupied zone) and 50% (entry zone) at children's breathing height, depending on usage scenario. This study produced high-resolution data for validating the detailed numerical models for classrooms and informing decision-making on AP's placement to minimise children's exposure to CRAP and re-breathed CO2.

Interventions for improving indoor and outdoor air quality in and around schools.

Students spend nearly one third of their typical day in the school environment, where they may be exposed to harmful air pollutants. A consolidated knowledge base of interventions to reduce this exposure is required for making informed decisions on their implementation and wider uptake. We attempt to fill this knowledge gap by synthesising the existing scientific literature on different school-based air pollution exposure interventions, their efficiency, suitability, and limitations. We assessed technological (air purifiers, HVAC - Heating Ventilation and Air Conditioning etc.), behavioural, physical barriers, structural, school-commute and policy and regulatory interventions. Studies suggest that the removal efficiency of air purifiers for PM2.5, PM10, PM1 and BC can be up to 57 %, 34 %, 70 % and 58 %, respectively, depending on the air purification technology compared with control levels in classroom. The HVAC system combined with high efficiency filters has BC, PM10 and PM2.5 removal efficiency up to 97 %, 34 % and 30 %, respectively. Citizen science campaigns are effective in reducing the indoor air pollutants' exposure up to 94 %. The concentration of PM10, NO2, O3, BC and PNC can be reduced by up to 60 %, 59 %, 16 %, 63 % and 77 %, respectively as compared to control conditions, by installing green infrastructure (GI) as a physical barrier. School commute interventions can reduce NO2 concentration by up to 23 %. The in-cabin concentration reduction of up to 77 % for PM2.5, 43 % for PNC, 89 % for BC, 74 % for PM10 and 75 % for NO2, along with 94 % reduction in tailpipe emission of total particles, can be achieved using clean fuels and retrofits. No stand-alone method is found as the absolute solution for controlling pollutants exposure, their combined application can be effective in most of the scenarios. More research is needed on assessing combined interventions, and their operational synchronisation for getting the optimum results.

Exploring genetic diversity of wild and related tetraploid wheat species Triticum turgidum and Triticum timopheevii.

INTRODUCTION: The domestication bottleneck has reduced genetic diversity inwheat, necessitating the use of wild relatives in breeding programs. Wild tetraploid wheat are widely used in the breeding programs but with morphological characters, it is difficult to distinguish these, resulting in misclassification/mislabeling or duplication of accessions in the Gene bank. OBJECTIVES: The study aims to exploreGenotyping by sequencing (GBS) to characterize wild and domesticated tetraploid wheat accessions to generate a core set of accessions to be used in the breeding program. METHODS: TASSEL-GBS pipeline was used for SNP discovery, fastStructure was used to determine the population structure and PowerCore was used to generate a core sets. Nucleotide diversity matrices of Nie's and F-statistics (FST) index were used to determine the center of genetic diversity. RESULTS: We found 65 % and 47 % duplicated accessions in Triticum timopheevii and T. turgidum respectively. Genome-wide nucleotide diversity and FST scan uncovered a lower intra and higher inter-species differentiation. Distinct FST regions were identified in genomic regions belonging to domestication genes: non-brittle rachis (Btr1) and vernalization (VRN-1).Our results suggest that Israel, Jordan, Syria, and Lebanonas the hub of genetic diversity of wild emmer;Turkey, and Georgia for T. durum; and Iraq, Azerbaijan, and Armenia for theT. timopheevii. Identified core set accessions preserved more than 93 % of the available genetic diversity. Genome wide association study (GWAS) indicated the potential chromosomal segment for resistance to leaf rust in T. timopheevii. CONCLUSION: The present study explored the potential of GBS technology in data reduction while maintaining the significant genetic diversity of the species. Wild germplasm showed more differentiation than domesticated accessions, indicating the availability of sufficient diversity for crop improvement. With reduced complexity, the core set preserves the genetic diversity of the gene bank collections and will aid in a more robust characterization of wild germplasm.

Whole genome resequencing and comparative genome analysis of three Puccinia striiformis f. sp. tritici pathotypes prevalent in India.

Stripe rust disease of wheat, caused by Puccinia striiformis f. sp. tritici, (Pst) is one of the most serious diseases of wheat worldwide. In India, virulent stripe rust races have been constantly evolving in the North-Western Plains Zone leading to the failure of some of the most widely grown resistant varieties in the region. With the goal of studying the recent evolution of virulent races in this region, we conducted whole-genome re-sequencing of three prevalent Indian Pst pathotypes Pst46S119, Pst78S84 and Pst110S119. We assembled 58.62, 58.33 and 55.78 Mb of Pst110S119, Pst46S119 and Pst78S84 genome, respectively and found that pathotypes were highly heterozygous. Comparative phylogenetic analysis indicated the recent evolution of pathotypes Pst110S119 and Pst78S84 from Pst46S119. Pathogenicity-related genes classes (CAZyme, proteases, effectors, and secretome proteins) were identified and found to be under positive selection. Higher rate of gene families expansion were also observed in the three pathotypes. A strong association between the effector genes and transposable elements may be the source of the rapid evolution of these strains. Phylogenetic analysis differentiated the Indian races in this study from other known United States, European, African, and Asian races. Diagnostic markers developed for the identification of three Pst pathotypes will help tracking of yellow rust at farmers field and strategizing resistance gene deployment.

Cloning of the broadly effective wheat leaf rust resistance gene Lr42 transferred from Aegilops tauschii.

The wheat wild relative Aegilops tauschii was previously used to transfer the Lr42 leaf rust resistance gene into bread wheat. Lr42 confers resistance at both seedling and adult stages, and it is broadly effective against all leaf rust races tested to date. Lr42 has been used extensively in the CIMMYT international wheat breeding program with resulting cultivars deployed in several countries. Here, using a bulked segregant RNA-Seq (BSR-Seq) mapping strategy, we identify three candidate genes for Lr42. Overexpression of a nucleotide-binding site leucine-rich repeat (NLR) gene AET1Gv20040300 induces strong resistance to leaf rust in wheat and a mutation of the gene disrupted the resistance. The Lr42 resistance allele is rare in Ae. tauschii and likely arose from ectopic recombination. Cloning of Lr42 provides diagnostic markers and over 1000 CIMMYT wheat lines carrying Lr42 have been developed documenting its widespread use and impact in crop improvement.

Current understanding of atypical resistance against fungal pathogens in wheat.

Pathogens and pests are a major challenge to global food security. Around one hundred different pests and pathogens challenge wheat, one of the most important food crops in the world. Traditional worldwide use of a few key resistance genes in wheat cultivars has necessitated a diversification of the toolbox of resistance genes in wheat varieties over the coming decades to meet the global production demands. Recent advances in gene discovery and functional characterization of genetic resistance mechanisms in wheat reveal great diversity in the types and effectiveness of the underlying resistance genes. This article summarizes the recent developments in the discovery of non-traditional "atypical" resistance genes in wheat against diverse fungal pathogens.

Menstrual changes after spinal cord injury.

STUDY DESIGN: This was a single-centre, prospective, descriptive, hospital-based study in females with spinal cord injuries (SCI). OBJECTIVES: To study menstrual changes after SCI. SETTING: The in-patient and out-patient services of the Department of Physical Medicine and Rehabilitation of a tertiary care institute in India between October 2018 and October 2020. METHODS: SCI females who were included in the study answered a questionnaire regarding amenorrhea after injury, menstrual cycle regularity, frequency, duration, flow, dysmenorrhoea and presence of autonomic dysreflexia during menstruation. All the study related data was analysed using SPSS version 24. A p value < 0.05 was considered as statistically significant. RESULTS: 40 females were included. 31 (77.5%) had amenorrhea. The mean duration of return of menstruation was 2.65 months. There was significant reduction in the duration of menstrual flow (p value < 0.001), amount of flow (p value = 0.041) and dysmenorrhea (p value < 0.001) after SCI. CONCLUSIONS: Amenorrhea was seen in 77.5% females. Most of them resumed their menstrual cycle. The menstruation duration and flow were reduced significantly. There is a need to address concerns and reassure females regarding resumption of menstruation after SCI.

Genotyping-by-sequencing and genomic selection applications in hexaploid triticale.

Triticale, a hybrid species between wheat and rye, is one of the newest additions to the plant kingdom with a very short history of improvement. It has very limited genomic resources because of its large and complex genome. Objectives of this study were to generate dense marker data, understand genetic diversity, population structure, linkage disequilibrium (LD), and estimate accuracies of commonly used genomic selection (GS) models on forage yield of triticale. Genotyping-by-sequencing (GBS), using PstI and MspI restriction enzymes for reducing genome complexity, was performed on a triticale diversity panel (n = 289). After filtering for biallelic loci with more than 70% genome coverage, and minor allele frequency (MAF) > 0.05, de novo variant calling identified 16,378 single nucleotide polymorphism (SNP) markers. Sequences of these variants were mapped to wheat and rye reference genomes to infer their homologous groups and chromosome positions. About 45% (7430), and 58% (9500) of the de novo identified SNPs were mapped to the wheat and rye reference genomes, respectively. Interestingly, 28.9% (2151) of the 7430 SNPs were mapped to the D genome of hexaploid wheat, indicating substantial substitution of the R genome with D genome in cultivated triticale. About 27% of marker pairs were in significant LD with an average r2 > 0.18 (P < 0.05). Genome-wide LD declined rapidly to r2 < 0.1 beyond 10 kb physical distance. The three sub-genomes (A, B, and R) showed comparable LD decay patterns. Genetic diversity and population structure analyses identified five distinct clusters. Genotype grouping did not follow prior winter vs spring-type classification. However, one of the clusters was largely dominated by winter triticale. GS accuracies were estimated for forage yield using three commonly used models with different training population sizes and marker densities. GS accuracy increased with increasing training population size while gain in accuracy tended to plateau with marker densities of 2000 SNPs or more. Average GS accuracy was about 0.52, indicating the potential of using GS in triticale forage yield improvement.

Production of Transgenic Handmade Cloned Goat (Capra hircus) Embryos by Targeted Integration into Rosa 26 Locus Using Transcription Activator-like Effector Nucleases.

Transgenic goats are ideal bioreactors for the production of therapeutic proteins in their mammary glands. However, random integration of the transgene within-host genome often culminates in unstable expression and unpredictable phenotypes. Targeting desired genes to a safe locus in the goat genome using advanced targeted genome-editing tools, such as transcription activator-like effector nucleases (TALENs) might assist in overcoming these hurdles. We identified Rosa 26 locus, a safe harbor for transgene integration, on chromosome 22 in the goat genome for the first time. We further demonstrate that TALEN-mediated targeting of GFP gene cassette at Rosa 26 locus exhibited stable and ubiquitous expression of GFP gene in goat fetal fibroblasts (GFFs) and after that, transgenic cloned embryos generated by handmade cloning (HMC). The transfection of GFFs by the TALEN pair resulted in 13.30% indel frequency at the target site. Upon cotransfection with TALEN and donor vectors, four correctly targeted cell colonies were obtained and all of them showed monoallelic gene insertions. The blastocyst rate for transgenic cloned embryos (3.92% ± 1.12%) was significantly (p < 0.05) lower than cloned embryos (7.84% ± 0.68%) used as control. Concomitantly, 2 out of 15 embryos of morulae and blastocyst stage (13.30%) exhibited site-specific integration. In conclusion, the present study demonstrates TALEN-mediated transgene integration at Rosa 26 locus in caprine fetal fibroblasts and the generation of transgenic cloned embryos using HMC.

Nature-based solutions efficiency evaluation against natural hazards: Modelling methods, advantages and limitations.

Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS.