Drought Adaptation Research Articles

Drought Sensitivity of Sugarcane Cultivars Shapes Rhizosphere Bacterial Community Patterns in Response to Water Stress.

Rhizosphere bacteria, the main functional microorganisms inhabiting the roots of terrestrial plants, play important roles in regulating plant growth and environmental stress resistance. However, limited information is available regarding changes occurring within the structure of the root microbial community and the response mechanisms of host plants that improve adaptability to drought stress. In this study, we conducted an experiment on two sugarcane varieties with different drought tolerance levels under drought and control treatments and analyzed the rhizosphere bacterial communities using 16S rRNA high-throughput sequencing. Correlation analysis results clarified the influence of various factors on the rhizosphere bacterial community structure. Drought stress reduced the diversity of the bacterial community in the rhizosphere of sugarcane. Interestingly, the bacterial community of the drought-sensitive sugarcane cultivar GT39 changed more than that of the drought-tolerant cultivar ZZ9. In addition, ZZ9 had a high abundance of drought-resistant bacteria in the rhizosphere under optimal soil water conditions, whereas GT39 accumulated a large number of drought-resistant bacteria only under drought stress. GT39 mainly relied on Actinobacteria in its response to drought stress, and the abundance of this phylum was positively correlated with soil acid phosphatase and protease levels. In contrast, ZZ9 mainly relied on Bacilli in its response to drought stress, and the abundance of this class was positively correlated with only soil acid phosphatase levels. In conclusion, drought stress can significantly reduce the bacterial diversity and increase the abundance of drought-resistant bacteria in the sugarcane rhizosphere. The high abundance of drought-resistant bacteria in the rhizosphere of drought-tolerant cultivars under non-drought conditions is an important factor contributing to the high drought adaptability of these cultivars. Moreover, the core drought-resistant bacteria of the sugarcane rhizosphere and root exudates jointly affect the resistance of sugarcane to drought.

A draft genome provides hypotheses on drought tolerance in a keystone plant species in Western North America threatened by climate change.

Climate change presents distinct ecological and physiological challenges to plants as extreme climate events become more common. Understanding how species have adapted to drought, especially ecologically important nonmodel organisms, will be crucial to elucidate potential biological pathways for drought adaptation and inform conservation strategies. To aid in genome‐to‐phenome research, a draft genome was assembled for a diploid individual of Artemisia tridentata subsp. tridentata, a threatened keystone shrub in western North America. While this taxon has few genetic resources available and genetic/genomics work has proven difficult due to genetic heterozygosity in the past, a draft genome was successfully assembled. Aquaporin (AQP) genes and their promoter sequences were mined from the draft genome to predict mechanisms regulating gene expression and generate hypotheses on key genes underpinning drought response. Fifty‐one AQP genes were fully assembled within the draft genome. Promoter and phylogenetic analyses revealed putative duplicates of A. tridentata subsp. tridentata AQPs which have experienced differentiation in promoter elements, potentially supporting novel biological pathways. Comparison with nondrought‐tolerant congener supports enrichments of AQP genes in this taxon during adaptation to drought stress. Differentiation of promoter elements revealed that paralogues of some genes have evolved to function in different pathways, highlighting these genes as potential candidates for future research and providing critical hypotheses for future genome‐to‐phenome work.

Physiological Screening for Drought Tolerance Traits in Vegetable Amaranth (Amaranthus tricolor) Germplasm

Amaranth (Amaranthus tricolor), an underutilized climate smart crop, is highly nutritious and possesses diverse drought tolerance traits, making it an ideal crop to thrive in a rapidly changing climate. Despite considerable studies on the growth and physiology of plants subjected to drought stress, a precise trait phenotyping strategy for drought tolerance in vegetable amaranth is still not well documented. In this study, two drought screening trials were carried out on 44 A. tricolor accessions in order to identify potential drought-tolerant A. tricolor germplasm and to discern their physiological responses to drought stress. The findings revealed that a change in stem biomass was most likely the main mechanism of drought adaptation for stress recovery, and dark-adapted quantum yield (Fv/Fm) could be a useful parameter for identifying drought tolerance in amaranth. Three drought tolerance indices: geometric mean productivity (GMP), mean productivity (MP) and stress tolerance index (STI) identified eight drought-tolerant accessions with stable performance across the two screening trials. The highly significant genotypic differences observed in several physiological traits among the amaranth accessions indicate that the amaranth panel used in this study could be a rich source of genetic diversity for breeding purposes for drought tolerance traits.

Rainfall Recovery in North-East Arid Zone of Nigeria: Comparative Analysis of Drought and Post Drought Decades

This study used annual rainfall records from three stations within the North East Arid Zone of Nigeria for the period (1957-2017) to measure the extent of the rainfall recovery by comparing the drought decades and post drought decades rainfall patterns. Monthly rainfall records from Potiskum, Maiduguri and Nguru Stations were used. Descriptive and inferential statistical tools were employed in analysing the data. The findings of the study revealed a significant year-to-year variability in rainfall characteristics around 61 years (1957-2017) averages. The variability was large in 1970s up till 1990s, and lower in 1960s and from 2000 to 2018. Decreasing trend in annual rainfall amount was observed during the study period while a stability in onset and cessation dates were observed. The differences between 1957-1986 and 1987-2017 climatic season were found to be statistically insignificant. The study concluded that the reported rainfall recovery from drought is statistically insignificant and the observed long term mean trend revealed a decreasing trend. Therefore, the theory of Sahel rainfall recovery can be better termed as a ‘’break of the series of drought or decline in frequency and magnitude of occurrence of drought’’ The research recommended the continuations with the drought adaptation and mitigation strategies adopted by local population, decisions makers and organizations following the series Sahelian droughts of 1970s and 1980s.

New drought‐adaptive loci underlying candidate genes on wheat chromosome 4B with improved photosynthesis and yield responses

Flag leaf serves as an essential source of assimilates during grain filling, thereby contributing to grain yield up to 48%. Thus, high-throughput phenotyping of flag leaves is crucial to determine their physiological and genetic basis of yield formation and drought adaptation. Here, we utilized 200 wheat cultivars to identify drought-adaptive loci underlying candidate genes associated with flag leaf biomass and photosynthesis-related traits using a genome-wide association study (GWAS). GWAS revealed 21 significant marker-trait associations for key photosynthetic traits in response to drought stress. Analysis of linkage disequilibrium (LD) in these SNPs intervals discovered 103 significant SNPs that established distinct LD blocks containing a total of 382 candidate genes putatively involved in physiological processes, including photosynthesis and water responses. Further, in silico transcript analysis identified two candidate genes in locus AX-580365925 on chromosome 4B, those were found to be highly expressed under drought and associated with proton-transporting ATP synthase activity and stress response pathways. Accordingly, we identified significant allelic haplotype differences on this same locus. The tolerant haplotype (higher chlorophyll content under drought) representing major allele was more abundant and stably increased photosynthetic efficiency and yield under drought scenarios. Collectively, this study offers new adaptive loci and beneficial alleles to reshape the flag leaf physiological and associated photosynthetic components for better yield and sustainability to water-deficit stress.

Response of Sugarcane Rhizosphere Bacterial Community to Drought Stress.

Sugarcane is an important sugar and energy crop, and its yield is greatly affected by drought. Although a large number of studies have shown that rhizosphere microorganisms can help improve the adaptability of plants to biotic or abiotic stresses, there is a lack of studies on the adaptability of sugarcane rhizosphere microbial communities to host plants. Therefore, we conducted drought stress treatment and normal irrigation treatment on three sugarcane varieties GT21, GT31, and GT42 widely cultivated in Guangxi. Using 16S rDNA sequencing technology to analyze the changes in abundance of the sugarcane rhizosphere bacterial community under different treatments, combined with the determination of soil enzyme activity, soil nutrient content, and sugarcane physiological characteristics, we explored the sugarcane rhizosphere bacterial community response to drought stress. In addition, we used the structural equation model to verify the response path of sugarcane rhizosphere bacteria. The results show that the bacterial community structure in the rhizosphere of sugarcane is stable under normal water conditions. The change in the bacterial community structure under drought stress has a 25.2% correlation with the drought adaptability of sugarcane, but the correlation with drought stress is as high as 42.17%. The changes in abundance of rhizosphere bacteria under drought stress are mainly concentrated in the phylum Rhizobiales and Streptomycetales. This change is directly related to the physiological state of the host plant under drought stress, soil available phosphorus, soil urease and soil acid protease. We investigated the response species of rhizosphere microorganisms and their response pathways under drought stress, providing a scientific basis for rhizosphere microorganisms to assist host plants to improve drought adaptability.

Making research relevant: Sharing climate change research with rangeland advisors to transform results into drought resilience

• Public programs, strategies, and incentives to implement rangeland climate adaptation are more effective if they are tailored to local drought exposures, sensitivities, and adaptation opportunities. As such, local rangeland advisers who aid in climate adaptation are pivotal to the development of these resources. • We hosted a virtual workshop with rangeland advisors to share results from our climate vulnerability assessment, gain their insight on finding usability, and discuss visions for resource creation. • Climate adaptation resources should not follow a one-size-fits-all approach. Accommodating variety in resource development and outreach must consider multiple factors: variation in the ranching community, instability in the environment beyond climate, and rancher/manager identified variables in climate vulnerability assessment analyses.

Exploration of Candidate Genes Derived from SNPs Associated with Phenotypic Root Plasticity Using Philippine Rice Germplasm for Drought Adaptation

Phenotypic root plasticity is a crucial trait for stable growth, adaptability, and productivity under abiotic-stressed growing environments. However, the genetic determinants and mechanisms controlling the trait are largely unknown, thus limiting its breeding application. We previously found 17 single nucleotide polymorphism (SNPs) significantly associated with phenotypic root plasticity traits – particularly, total root length (TRL), total nodal root length (TNRL), and total lateral root length (TLRL) – under moderate and severe drought using selected Philippine rice germplasm by employing the genome-wide association studies (GWAS) approach. Here, we present around 92 candidate genes using these SNP data. The genes were derived from various functional categories and drought intensity dependent. These were further narrowed via Gene Ontology and gene expression profile at root apical regions using databases to those whose putative functions were likely to be associated with root development in response to drought stress. Sixteen (16) more interesting known or novel genes were selected and discussed. When these genes are validated, they can help improve rice adaptation to water-limited environments.

Physiological and Molecular Responses of 'Dusa' Avocado Rootstock to Water Stress: Insights for Drought Adaptation.

Avocado consumption is increasing year by year, and its cultivation has spread to many countries with low water availability, which threatens the sustainability and profitability of avocado orchards. However, to date, there is not much information on the behavior of commercial avocado rootstocks against drought. The aim of this research was to evaluate the physiological and molecular responses of ‘Dusa’ avocado rootstock to different levels of water stress. Plants were deficit irrigated until soil water content reached 50% (mild-WS) and 25% (severe-WS) of field capacity. Leaf water potential (Ψw), net CO2 assimilation rates (AN), transpiration rate (E), stomatal conductance (gs), and plant transpiration rates significantly decreased under both WS treatments, reaching significantly lower values in severe-WS plants. After rewatering, mild- and severe-WS plants showed a fast recovery in most physiological parameters measured. To analyze root response to different levels of drought stress, a cDNA avocado stress microarray was carried out. Plants showed a wide transcriptome response linked to the higher degree of water stress, and functional enrichment of differentially expressed genes (DEGs) revealed abundance of common sequences associated with water stress, as well as specific categories for mild-WS and severe-WS. DEGs previously linked to drought tolerance showed overexpression under both water stress levels, i.e., several transcription factors, genes related to abscisic acid (ABA) response, redox homeostasis, osmoprotection, and cell-wall organization. Taken altogether, physiological and molecular data highlight the good performance of ‘Dusa’ rootstock under low-water-availability conditions, although further water stress experiments must be carried out under field conditions.

Sucrose Metabolism in Plants under Drought Stress Condition: A Review

Drought stress reduces photosynthetic rate and leading to depletion of the energy source and lowers the yield. Under drought stress, reduced turgor pressure cause inhibition of cell elongation and impaired mitosis leads to reduction in growth rate. Role of sucrose metabolism under drought adaptation and response of plants to stress in different tissues and at different developmental stages. Cytoplasmic sucrose synthesis is more under drought condition and there is differential expression in tolerant and susceptible cultivars. Under drought condition, plant start consuming its own sink for its survival thus reducing sucrose concentration. But reduction in sucrose concentration is less in drought tolerant plants. Drought stress induced an increase of the root/shoot ratio, which was due to the increased inhibition of biomass accumulation of shoots compared to roots. Drought stress enhanced the activities of sucrose metabolic enzymes and up-regulated the expression of genes such as SPS, SuSy and INV. In addition, drought stress up-regulated the expression levels of SWEET and SUC and promoted the transport of sucrose from source to sink.

Effect of progressive drought stress on physio-biochemical responses and gene expression patterns in wheat.

The online version contains supplementary material available at 10.1007/s13205-021-02991-6.

Genomic basis underlying the metabolome-mediated drought adaptation of maize

BackgroundDrought is a major environmental disaster that causes crop yield loss worldwide. Metabolites are involved in various environmental stress responses of plants. However, the genetic control of metabolomes underlying crop environmental stress adaptation remains elusive.ResultsHere, we perform non-targeted metabolic profiling of leaves for 385 maize natural inbred lines grown under well-watered as well as drought-stressed conditions. A total of 3890 metabolites are identified and 1035 of these are differentially produced between well-watered and drought-stressed conditions, representing effective indicators of maize drought response and tolerance. Genetic dissections reveal the associations between these metabolites and thousands of single-nucleotide polymorphisms (SNPs), which represented 3415 metabolite quantitative trait loci (mQTLs) and 2589 candidate genes. 78.6% of mQTLs (2684/3415) are novel drought-responsive QTLs. The regulatory variants that control the expression of the candidate genes are revealed by expression QTL (eQTL) analysis of the transcriptomes of leaves from 197 maize natural inbred lines. Integrated metabolic and transcriptomic assays identify dozens of environment-specific hub genes and their gene-metabolite regulatory networks. Comprehensive genetic and molecular studies reveal the roles and mechanisms of two hub genes, Bx12 and ZmGLK44, in regulating maize metabolite biosynthesis and drought tolerance.ConclusionOur studies reveal the first population-level metabolomes in crop drought response and uncover the natural variations and genetic control of these metabolomes underlying crop drought adaptation, demonstrating that multi-omics is a powerful strategy to dissect the genetic mechanisms of crop complex traits.

Breeding custom-designed crops for improved drought adaptation.

The current pace of crop improvement is inadequate to feed the burgeoning human population by 2050. Higher, more stable, and sustainable crop production is required against a backdrop of drought stress, which causes significant losses in crop yields. Tailoring crops for drought adaptation may hold the key to address these challenges and provide resilient production systems for future harvests. Understanding the genetic and molecular landscape of the functionality of alleles associated with adaptive traits will make designer crop breeding the prospective approach for crop improvement. Here, we highlight the potential of genomics technologies combined with crop physiology for high-throughput identification of the genetic architecture of key drought-adaptive traits and explore innovative genomic breeding strategies for designing future crops.

Spatio-Temporal Analysis of Drought Variability in Myanmar Based on the Standardized Precipitation Evapotranspiration Index (SPEI) and Its Impact on Crop Production

Drought research is an important aspect of drought disaster mitigation and adaptation. For this purpose, we used the Standardized Precipitation Evapotranspiration Index (SPEI) to investigate the spatial-temporal pattern of drought and its impact on crop production. Using monthly precipitation (Precip) and temperature (Temp) data from 1986–2015 for 39 weather stations, the drought index was obtained for the time scale of 3, 6, and 12 months. The Mann–Kendall test was used to determine trends and rates of change. Precip and Temp anomalies were investigated using the regression analysis and compared with the drought index. The link between drought with large-scale atmospheric circulation anomalies using the Pearson correlation coefficient (R) was explored. Results showed a non-uniform spatial pattern of dryness and wetness which varied across Myanmar agro-ecological zones and under different time scales. Generally, results showed an increasing trend for the SPEI in the three-time scales, signifying a high tendency of decreased drought from 1986–2015. The fluctuations in dryness/wetness might linked to reduction crop production between 1986–1999 and 2005, 2008, 2010, 2013 cropping years. Results show relationship between main crops production and climate (teleconnection) factors. However, the low correlation values (i.e., <0.49) indicate the extent of the relationship within the natural variability. However, readers are urged to interpret this result cautiously as reductions in crop production may also be affected by other factors. We have demonstrated droughts evolution and trends using weather stations, thus providing useful information to aid policymakers in developing spatially relevant climate change adaptation and mitigation management plans for Myanmar.

Spatiotemporal changes of snow metrics in mountainous data-scarce areas using reanalyses

Mountain snowmelt is a critical water resource for achieving food and water security in drylands. Climate change impacts the snowmelt and consequently water resources reliability in downstream communities in drylands. Data limitation is one of the main challenges for assessing such impacts. This study assessed the trend in snow depth (SD), snowy day to wet day (SDWD), and snow phenology-related metrics in data-scarce snowy areas of Iran over 1987–2017. Furthermore, the contribution of temperature warming, precipitation and Arctic Oscillation (AO) anomalies to the snow metrics trends was investigated. The analyses were performed using the more accurate reanalyses selected between ERA-Interim and ERA5. The trend magnitude and significance were also assessed during the December-January-February (DJF), March-April (MA), and December-January-February-March-April (DJFMA) using the Sen’s estimator and Mann-Kendall (MK) test, respectively. Given the ERA5′s superiority, this product was employed for the trend and contribution analyses. The SD, SDWD and snow cover duration (Sdur) had a decreasing trend at more than 90% of study area. Except for snow cover onset date (Ds), MK detected a significant trend in the snow metrics at 40% or more of the studied regions. The more humid regions experienced a greater SD reduction. The SDWDDJF also decreased by less than 1% for the areas having average winter wintertime temperature below the threshold of −2.80 °C. The downward trend in Sdur was largely due to the earlier snowmelt rather than later Ds. A decline of 5 > day per decade was found for Sdur at the areas with DJFMA temperature below the melting point. The SD, SDWD and phenology metrics changes can be accounted for by temperature warming in most regions. The SDWD-AO relationship was statistically significant for the majority of the cases. The AO anomalies seem to impact SDWD via affecting wintertime temperature. The decrease of snow metrics indicates the occurrence of more severe and frequent dry snow droughts in the studied sub-basins. Thus, drought adaptation strategies need to consider the patterns of snow metrics in addition to total precipitation under global warming. The ERA5 outputs can be applied for evaluating snow drought under data scarcity.

Breeding custom‐designed crops for improved drought adaptation

The current pace of crop improvement is inadequate to feed the burgeoning human population by 2050. Higher, more stable and sustainable crop production is required against a backdrop of drought stress, which causes significant losses in crop yields. Tailoring crops for drought adaptation may hold the key to address these challenges and provide resilient production systems for future harvests. Understanding the genetic and molecular landscape of the functionality of alleles associated with adaptive traits will make designer crop breeding the prospective approach for crop improvement. Here, we highlight the potential of genomics technologies combined with crop physiology for high-throughput identification of the genetic architecture of key drought-adaptive traits and explore innovative genomic breeding strategies for designing future crops.

Integrated nutrient management improves soil organic matter and agronomic sustainability of semiarid rainfed Inceptisols of the Indo‐Gangetic Plains

ABSTRACTBackgroundClimate and management practices impact the soil organic carbon (SOC) stocks of agricultural soils. Especially under the semiarid climate of India, organic matter is rapidly decomposed, and imbalanced nutrient input further exacerbates its depletion, thus facilitating the decline in soil quality and crop yields. Improving SOC contents through integrated nutrient management (INM), that is, conjunctive use of organic and chemical sources of nutrients, could ameliorate soil health and sustain crop yields.AimTo assess the potential of the INM approach to enhance the SOC status, soil quality, crop production, and drought adaptation of pearl millet under rainfed conditions.MethodsNutrient inputs were supplied through mineral fertilizers, organic manures, and a combination of both. SOC sequestration, sustainable yield index, plant‐available N, P, K, and water, bulk density, and KMnO4‐oxidizable C were estimated.ResultsHigher SOC sequestration rate (0.50 and 0.48 Mg ha−1 y−1 in 50% N (fertilizer) + 50% N (farmyard manure), and 50% N (fertilizer) + 50% N (crop residue), respectively) and significant increase in soil fertility were recorded in organically amended treatments. Improvement of 1 Mg ha−1 of SOC stock in the root zone (0.4 m depth) reduced the severity of drought and increased the yield by 38 kg ha−1. Plots under organic amendments suffered less yield losses under short‐duration droughts, but this positive effect could only be exploited when the rainfall deficit was up to 25%.ConclusionManagements that add up to 1.2 Mg ha−1 y−1 SOC are adaptive and climate‐resilient strategies in dry semiarid degraded Inceptisols of the Indo‐Gangetic Plains.

Edge influence on the microclimate and vegetation of fragments of a north Amazonian forest

There are multiple pressures on Amazon forests due to, anthropic activities such as extensive cattle ranching, logging, and legal and illegal crops. These pressures generate highly fragmented landscapes that leads to an increase in forest edges. Thus, forest vegetation exposed to the surrounding open environment generates a series of direct effects that extend into the interior of the forest. Changes in the microclimate are among the most notable effects, and these can impact the composition and structure of the vegetation and affect the alteration of multiple ecological processes and ecosystem services. To better understand these consequences, we evaluated the distance of the edge influence on the microclimate, the composition of the vegetation, and the forest structure in the northern Amazon. We considered two types of edges according to adjacent cover: grasslands dedicated to extensive cattle ranching and rubber plantations (Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg.). We recorded significant differences in the composition and abundance of plants of all size categories. We found less richness and dominance of generalist species, that are characteristic of disturbed environments, in the forest sector adjacent to pastures. These edges had also lower humidity and higher temperatures than rubber plantations ones. The distance from the edge to the interior also affected the structure of the vegetation, with a higher density of individuals in the interior of the forest and significant differences in the diameter and height of individuals. We argue that the rubber plantations could be used as a forest management strategy of drought adaptation since it forms a less abrupt border and has a buffer function, keeping higher humidity values and lower temperatures than forest edges adjacent to pastures.

Assessment of meteorological drought change in the 21st century based on CMIP6 multi-model ensemble projections over mainland China

Understanding drought dynamics spatially and temporally is essential for environmental and socio-economic systems, especially under climate change with expected increasing drought. This study aims to update the knowledge about drought spatiotemporal changes over mainland China in the 21st century by utilizing the latest Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets. Precipitation from the nine CMIP6 models is first bias-corrected using a quantile mapping approach and then used to calculate the 3-month Standardized Precipitation Index (SPI) for the historical period and future three scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). We conduct a clustering algorithm to identify three-dimensional (i.e., latitude, longitude, and time) drought events to access the drought dynamics in both space and time. Results show that the drought events occur more frequently during June to September than the other months for both historical and future periods. The drought frequency is significantly increasing during Sep–Dec in the 21st century (increase by about 8.5%, p-value<0.05). Compared with the historical period, drought centers shift toward south under the future projections, indicating a relatively high drought frequency in south China. Additionally, drought events are projected to have shorter duration, smaller affected area, but higher intensity under all three scenarios. The study contributes to our comprehensive understanding of how future drought characteristics will change due to climate change from the perspective of spatiotemporal dynamics. These results are helpful to drought risk management and provide information for developing drought adaptation strategies.

Using a Serious Digital Game to Communicate Drought Risk in Singapore: An Experimental Study

This experimental study tested the effects of digital tactical messaging on 189 undergraduates’ drought risk responsiveness using a mobile serious game. In the game’s virtual household environment, treatment groups were exposed to message framings informed by risk psychological theories. Drought risk responsiveness was indicated by participants’ in-game water consumption levels. The first intervention entailed treatment groups receiving advisories about an impending drought whose magnitude and likelihood varied for different groups. Next, groups would either receive a message reinforcing the efficacy, or social acceptability, of conserving and rationing water during a drought condition. Lastly, groups received a message about a water rationing exercise that they could participate in. Factorial analyses showed that knowing the severity and likelihood of an impending drought did not affect drought risk responsiveness. However, norms- and efficacy-framed messages, as well as rationing exercises, influenced risk responsiveness. The study is expected to be instructive to policymakers and practitioners interested in digitally communicating drought risk and adaptation to the public.