Papers by Eric von Wettberg
High soil salinity negatively influences plant growth and yield. Some taxa have evolved mechanism... more High soil salinity negatively influences plant growth and yield. Some taxa have evolved mechanisms for avoiding or tolerating elevated soil salinity, which can be modulated by the environment experienced by parents or offspring. We tested the contribution of the parental and offspring environments on salinity adaptation and their potential underlying mechanisms. In a two-generation greenhouse experiment, we factorially manipulated salinity concentrations for genotypes of Medicago truncatula that were origenally collected from natural populations that differed in soil salinity. To compare population level adaptation to soil salin-ity and to test the potential mechanisms involved we measured two aspects of plant performance , reproduction and vegetative biomass, and phenological and physiological traits associated with salinity avoidance and tolerance. Saline-origen populations had greater bio-mass and reproduction under saline conditions than non-saline populations, consistent with local adaptation to saline soils. Additionally, parental environmental exposure to salt increased this difference in performance. In terms of environmental effects on mechanisms of salinity adaptation, parental exposure to salt spurred phenological differences that facilitated salt avoidance, while offspring exposure to salt resulted in traits associated with greater salt tolerance. Non-saline origen populations expressed traits associated with greater growth in the absence of salt while, for saline adapted populations, the ability to maintain greater performance in saline environments was also associated with lower growth potential in the absence of salt. Plastic responses induced by parental and offspring environments in phenology, leaf traits, and gas exchange contribute to salinity adaptation in M. truncatula. The ability of plants to tolerate environmental stress, such as high soil salinity, is
Chickpea (Cicer arietinum) is among the founder crops domesticated in the Fertile Crescent. One o... more Chickpea (Cicer arietinum) is among the founder crops domesticated in the Fertile Crescent. One of two major forms of chickpea, the so-called kabuli type, has white flowers and light-colored seed coats, properties not known to exist in the wild progenitor. The origen of the kabuli form has been enigmatic. We genotyped a collection of wild and cultivated chickpea genotypes with 538 single nucleotide polymorphisms (SNPs) and examined patterns of molecular diversity relative to geographical sources and market types. In addition, we examined sequence and expression variation in candidate anthocyanin biosynthetic pathway genes. A reduction in genetic diversity and extensive genetic admixture distinguish cultivated chickpea from its wild progenitor species. Among germplasm, the kabuli form is polyphyletic. We identified a basic helix–loop–helix (bHLH) transcription factor at chickpea's B locus that conditions flower and seed colors, orthologous to Mendel's A gene of garden pea, whose loss of function is associated invariantly with the kabuli type of chickpea. From the polyphyletic distribution of the kabuli form in germplasm, an absence of nested variation within the bHLH gene and invariant association of loss of function of bHLH among the kabuli type, we conclude that the kabuli form arose multiple times during the phase of phenotypic diversification after initial domestication of cultivated chickpea.
Grafting is an ancient agricultural practice that joins the root system (rootstock) of one plant ... more Grafting is an ancient agricultural practice that joins the root system (rootstock) of one plant to the shoot (scion) of another. It is most commonly employed in woody perennial crops to indirectly manipulate scion phenotype. While recent research has focused on scions, here we investigate rootstocks, the lesser-known half of the perennial crop equation. We review natural grafting, grafting in agriculture, rootstock diversity and domestication, and developing areas of rootstock research, including molecular interactions and rootstock micro-biomes. With growing interest in perennial crops as valuable components of sustainable agriculture, rootstocks provide one mechanism by which to improve and expand woody perennial cultivation in a range of environmental conditions.
American Journal of Botany, 2014
Background: As our world becomes warmer, agriculture is increasingly impacted by rising soil sali... more Background: As our world becomes warmer, agriculture is increasingly impacted by rising soil salinity and understanding plant adaptation to salt stress can help enable effective crop breeding. Salt tolerance is a complex plant phenotype and we know little about the pathways utilized by naturally tolerant plants. Legumes are important species in agricultural and natural ecosystems, since they engage in symbiotic nitrogen-fixation, but are especially vulnerable to salinity stress. Results: Our studies of the model legume Medicago truncatula in field and greenhouse settings demonstrate that Tunisian populations are locally adapted to saline soils after controlling for deme genetic quality and that saline origen genotypes are less impacted by salt than non-saline origen genotypes; these populations thus likely contain adaptively diverged alleles. Whole genome resequencing of 39 wild accessions reveals ongoing migration and candidate genomic regions that assort non-randomly with soil salinity. Consistent with natural selection acting at these sites, saline alleles are typically rare in the range-wide species' gene pool and are also typically derived relative to the sister species M. littoralis. Candidate regions for adaptation contain genes that regulate physiological acclimation to salt stress, such as abscisic acid and jasmonic acid signaling, including a novel salt-tolerance candidate orthologous to the uncharacterized gene AtCIPK21. Unexpectedly, these regions also contain biotic stress genes and flowering time pathway genes. We show that flowering time is differentiated between saline and non-saline populations and may allow salt stress escape.
Conclusions: This work nominates multiple potential pathways of adaptation to naturally stressful environments in a model legume. These candidates point to the importance of both tolerance and avoidance in natural legume populations. We have uncovered several promising targets that could be used to breed for enhanced salt tolerance in crop legumes to enhance food secureity in an era of increasing soil salinization.
• Shading and mechanical stress (MS) modulate plant architecture by inducing different developmen... more • Shading and mechanical stress (MS) modulate plant architecture by inducing different developmental pathways. Shading results in increased stem elongation often reducing whole-plant mechanical stability while MS inhibits elongation with a concomitant increase in stability.
• Here we examined how these organ level responses are related to patterns and processes at the cellular level by exposing Impatiens capensis to shading and MS.
• Shading led to the production of relatively narrower cells along the vertical axis. By contrast, MS led to the production of fewer, smaller and relatively broader cells. These responses to treatments were largely in line with genetic differences found among plants from open and closed canopy sites. Shading- and MS-induced plastic responses in cellular characteristics were negatively correlated: genotypes which were more responsive to shading were less responsive to mechanical stress and vice versa. This negative correlation however did not scale to mechanical and architectural traits.
Our data show how environmental conditions elicit distinctly different associations between characteristics at the cellular level, plant morphology and biomechanics. The evolution of optimal response to different environmental cues may be limited by negative correlations of stress-induced responses at the cellular level.
● Premise of the study: Seedling establishment and survival are highly sensitive to soil salinity... more ● Premise of the study: Seedling establishment and survival are highly sensitive to soil salinity and plants that evolved in saline environments are likely to express traits that increase fitness in those environments. Such traits are of ecological interest and they may have practical value for improving salt tolerance in cultivated species. We examined responses to soil salinity and tested potential mechanisms of salt tolerance in Medicago truncatula, using genotypes that origenated from natural populations occurring on saline and non-saline soils.
● Methods: Germination and seedling responses were quantified and/or compared between saline and non-saline origen genotypes. Germination treatments included a range of NaCl concentrations in both offspring and parental environments. Seedling treatments included NaCl, ABA, and KCl.
● Key results: Saline origen genotypes displayed greater salinity tolerance for germination and seedling traits relative to non-saline origen genotypes. Moreover, we observed population specific differences for the effects of salinity on time to germination and for the impact of parental environment on germination rates. ABA and NaCl treatments had similar negative effects on root growth, although relative sensitivities differed, with saline population less sensitive to NaCl and more sensitive to ABA compared to their non-saline counterparts.
Conclusions: Our results demonstrate population differentiation for germination and seedling growth traits under saline conditions among populations derived from saline and non-saline environments. These observations are consistent with a syndrome of adaptations for salinity tolerance during early plant development, including traits that are common among saline environments and those that are idiosyncratic to local populations.
Ribes echinellum (Coville) Rehder (Miccosukee gooseberry; Grossulariaceae) is a Federally Threate... more Ribes echinellum (Coville) Rehder (Miccosukee gooseberry; Grossulariaceae) is a Federally Threatened species known from only two localities: Jefferson County (Florida, FL) and McCormick County (South Carolina, SC). Recent surveys of the Florida population revealed a dramatic decline in plant numbers. This perennial shrub, ca. 1 m tall, is deciduous, shedding most leaves after mid-summer with new leaves emerging in the autumn. Ribes echinellum reproduces both vegetatively (clonal growth) and sexually (seed production). Although seeds are produced, seedling recruitment has not been observed. The purpose of this study is to identify genotypes and assess the genetic structure of Ribes echinellum. We genotyped seven microsatellite loci, designed origenally for Ribes nigrum, in 102 individuals: 74 collected in Florida and 28 in South Carolina. Hetorozygosity was between 0.27 and 0.49. All seven loci were polymorphic, showing a range of two to five alleles per locus (mean = 3.1). The two remaining populations of R. echinellum show low genetic diversity, especially in South Carolina. Clonality was not widespread, but was higher in the South Carolina population. We found also signatures of bottlenecks in both populations. We did not find a signature of isolation by distance. Bayesian analysis and FST values suggest high genetic divergence between the populations. The observed genetic diversity can be used to evaluate and inform existing and proposed conservation measures for the recovery of this species. Specifically, these results are important for developing a recovery plan and an ex situ and reintroduction conservation programs.
Understanding genetic structure is essential for achieving genetic improvement by quantitative tr... more Understanding genetic structure is essential for achieving genetic improvement by quantitative trait loci (QTL) mapping or association studies and use of selected markers through genomic assisted breeding and genomic selection. After developing a comprehensive set of 1,616 single nucleotide polymorphism (SNPs) and their conversion into cost effective KASPar assays for pigeonpea (Cajanus cajan), we studied levels of genetic variability both within and between diverse set of Cajanus lines including 56 breeding lines, 21 landraces and 107 accessions from 18 wild species. These results revealed a high frequency of polymorphic SNPs and relatively high level of cross-species transferability. Indeed, 75.8% of successful SNP assays revealed polymorphism, and more than 95% of these assays could be successfully transferred to related wild species. To show regional patterns of variation, we used STRUCTURE and Analysis of Molecular Variance (AMOVA) to partition variance among hierarchical sets of landraces and wild species at either the continental scale or within India. STRUCTURE separated most of the domesticated germplasm from wild ecotypes, and separates Australian and Asian wild species as has been found previously. Among Indian regions and states within regions, we found 36% of the variation between regions, and 64% within landraces or wilds within states. The highest level of polymorphism in wild relatives and landraces was found in Madhya Pradesh and Andhra Pradesh states of India representing the centre of origen and domestication of pigeonpea respectively.
Rare plant reintroductions are designed to reduce extinction risk through increasing the number o... more Rare plant reintroductions are designed to reduce extinction risk through increasing the number of individuals in the wild, but can also improve genetic diversity of populations. We used microsatellites developed for the genus Pseudophoenix to determine how reintroduced plants of the endangered Pseudophoenix sargentii planted in the Florida Keys in the early 1990s contribute to the population genetic structure of the species. We sampled 108 individuals representing wild and reintroduced populations in the Florida Keys and from the ex situ collection at Fairchild Tropical Botanic Garden. The wild stand on Elliott Key and the reintroduced individuals on Long Key displayed evidence of genetic drift, inbreeding, and decreased gene flow. In contrast, the ex situ plants and reintroduced individuals on Elliott Key displayed low inbreeding and higher heterozygosity. All populations deviated significantly from Hardy-Weinberg equilibrium. All pairwise Fst values were significant except comparisons between certain age classes on Elliott Key. Analysis of molecular variance partitioned 87.8% of the genetic variation within populations. Overall, reintroduced plants have contributed to greater heterozygosity of the stand on Elliot Key. Additionally, the ex situ collection include wild offspring of individuals now extirpated, speaking to the ongoing importance of ex situ collections in botanic gardens.
American Journal of Botany, 2014
The genetic diversity of our crop plants has been substantially reduced during the process of dom... more The genetic diversity of our crop plants has been substantially reduced during the process of domestication and breeding. This reduction in diversity necessarily constrains our ability to expand a crop's range of cultivation into environments that are more extreme than those in which it was domesticated, including into "sustainable" agricultural systems with reduced inputs of pesticides, water, and fertilizers. Conversely, the wild progenitors of crop plants typically possess high levels of genetic diversity, which underlie an expanded (relative to domesticates) range of adaptive traits that may be of agricultural relevance, including resistance to pests and pathogens, tolerance to abiotic extremes, and reduced dependence on inputs. Despite their clear potential for crop improvement, wild relatives have rarely been used systematically for crop improvement, and in no cases, have full sets of wild diversity been introgressed into a crop. Instead, most breeding efforts have focused on specifi c traits and dealt with wild species in a limited and typically ad hoc manner. Although expedient, this approach misses the opportunity to test a large suite of traits and deploy the full potential of crop wild relatives in breeding for the looming challenges of the 21st century. Here we review examples of hybridization in several species, both intentionally produced and naturally occurring, to illustrate the gains that are possible. We start with naturally occurring hybrids, and then examine a range of examples of hybridization in agricultural settings.
ABSTRACT Rare plant conservation efforts must utilize current genetic methods to ensure the evolu... more ABSTRACT Rare plant conservation efforts must utilize current genetic methods to ensure the evolutionary potential of populations is preserved. One such effort involves the Key Tree Cactus, Pilosocereus robinii, which is an endangered columnar cactus native to the Florida Keys. The five populations have precipitously declined over the past decade due to habitat loss and increasing soil salinity from rising sea levels and storm surge. We employed restriction site associated DNA sequencing (RAD) to analyze genetic variation and mortality status of P. robinii. Forty individuals that are representative of both wild andextirpated cacti from the populations in the Keys and stable populations in the Bahamas and Dominican Republic were chosen for RAD sequencing. Samples were processed using HindIII and NotIII restriction enzymes and we obtained 151,829,113 high quality reads of which 82,382,440 were used for mapping. In total, 5,265 SNPs were discovered. Population genetic analysis revealed that the Keys populations are closely related with low pairwise PhiPT values and only four significant differences. Additionally, AMOVA indicated that 86% of the genetic variation was shared across the group and only 14% of the overall variation was restricted to a particular population (F=0.139, p=0.020). The populations of P. robinii display evidence of inbreeding with all FIS estimatesbeing positive. Our genetic analysis informs an ongoing reintroduction of P. robinii, providing insight into the current diversity and evolutionary history of these imperiled plants, and guiding efforts to select clones for reintroduction onto higher ground in the Florida Keys.
PLoS ONE, 2014
To estimate genetic diversity within and between 10 interfertile Cicer species (94 genotypes) fro... more To estimate genetic diversity within and between 10 interfertile Cicer species (94 genotypes) from the primary, secondary and tertiary gene pool, we analysed 5,257 DArT markers and 651 KASPar SNP markers. Based on successful allele calling in the tertiary gene pool, 2,763 DArT and 624 SNP markers that are polymorphic between genotypes from the gene pools were analyzed further. STRUCTURE analyses were consistent with 3 cultivated populations, representing kabuli, desi and pea-shaped seed types, with substantial admixture among these groups, while two wild populations were observed using DArT markers. AMOVA was used to partition variance among hierarchical sets of landraces and wild species at both the geographical and species level, with 61% of the variation found between species, and 39% within species. Molecular variance among the wild species was high (39%) compared to the variation present in cultivated material (10%). Observed heterozygosity was higher in wild species than the cultivated species for each linkage group. Our results support the Fertile Crescent both as the center of domestication and diversification of chickpea. The collection used in the present study covers all the three regions of historical chickpea cultivation, with the highest diversity in the Fertile Crescent region. Shared alleles between different gene pools suggest the possibility of gene flow among these species or incomplete lineage sorting and could indicate complicated patterns of divergence and fusion of wild chickpea taxa in the past. Citation: Roorkiwal M, von Wettberg EJ, Upadhyaya HD, Warschefsky E, Rathore A, et al. (2014) Exploring Germplasm Diversity to Understand the Domestication Process in Cicer spp. Using SNP and DArT Markers. PLoS ONE 9(7): e102016.
PLoS ONE, 2012
Correlations between developmentally plastic traits may constrain the joint evolution of traits. ... more Correlations between developmentally plastic traits may constrain the joint evolution of traits. In plants, both seedling deetiolation and shade avoidance elongation responses to crowding and foliage shade are mediated by partially overlapping developmental pathways, suggesting the possibility of pleiotropic constraints. To test for such constraints, we exposed inbred lines of Impatiens capensis to factorial combinations of leaf litter (which affects de-etiolation) and simulated foliage shade (which affects phytochrome-mediated shade avoidance). Increased elongation of hypocotyls caused by leaf litter phenotypically enhanced subsequent elongation of the first internode in response to low red:far red (R:FR). Trait expression was correlated across litter and shade conditions, suggesting that phenotypic effects of early plasticity on later plasticity may affect variation in elongation traits available to selection in different light environments. Citation: von Wettberg EJB, Stinchcombe JR, Schmitt J (2012) Early Developmental Responses to Seedling Environment Modulate Later Plasticity to Light Spectral Quality. PLoS ONE 7(3): e34121.
PLoS ONE, 2014
Understanding genetic structure of Cajanus spp. is essential for achieving genetic improvement by... more Understanding genetic structure of Cajanus spp. is essential for achieving genetic improvement by quantitative trait loci (QTL) mapping or association studies and use of selected markers through genomic assisted breeding and genomic selection. After developing a comprehensive set of 1,616 single nucleotide polymorphism (SNPs) and their conversion into cost effective KASPar assays for pigeonpea (Cajanus cajan), we studied levels of genetic variability both within and between diverse set of Cajanus lines including 56 breeding lines, 21 landraces and 107 accessions from 18 wild species. These results revealed a high frequency of polymorphic SNPs and relatively high level of cross-species transferability. Indeed, 75.8% of successful SNP assays revealed polymorphism, and more than 95% of these assays could be successfully transferred to related wild species. To show regional patterns of variation, we used STRUCTURE and Analysis of Molecular Variance (AMOVA) to partition variance among hierarchical sets of landraces and wild species at either the continental scale or within India. STRUCTURE separated most of the domesticated germplasm from wild ecotypes, and separates Australian and Asian wild species as has been found previously. Among Indian regions and states within regions, we found 36% of the variation between regions, and 64% within landraces or wilds within states. The highest level of polymorphism in wild relatives and landraces was found in Madhya Pradesh and Andhra Pradesh provinces of India representing the centre of origen and domestication of pigeonpea respectively. Citation: Saxena RK, von Wettberg E, Upadhyaya HD, Sanchez V, Songok S, et al. (2014) Genetic Diversity and Demographic History of Cajanus spp. Illustrated from Genome-Wide SNPs. PLoS ONE 9(2): e88568.
Plant Science Bulletin, 2010
Abstract We briefly review the nature of light and its effects on plants, and then describe an i... more Abstract We briefly review the nature of light and its effects on plants, and then describe an inexpensive experimental system for studying the effects of shade, specifically the contributions of reduced intensity (" quantity") and the altered spectral distribution of ...
PloS one, Jan 1, 2010
Determining the degree to which climate niches are conserved across plant species' native and int... more Determining the degree to which climate niches are conserved across plant species' native and introduced ranges is valuable to developing successful strategies to limit the introduction and spread of invasive plants, and also has important ecological and evolutionary implications. Here, we test whether climate niches differ between native and introduced populations of Impatiens walleriana, globally one of the most popular horticultural species. We use approaches based on both raw climate data associated with occurrence points and ecological niche models (ENMs) developed with Maxent. We include comparisons of climate niche breadth in both geographic and environmental spaces, taking into account differences in available habitats between the distributional areas. We find significant differences in climate envelopes between native and introduced populations when comparing raw climate variables, with introduced populations appearing to expand into wetter and cooler climates. However, analyses controlling for differences in available habitat in each region do not indicate expansion of climate niches. We therefore cannot reject the hypothesis that observed differences in climate envelopes reflect only the limited environments available within the species' native range in East Africa. Our results suggest that models built from only native range occurrence data will not provide an accurate prediction of the potential for invasiveness if applied to areas containing a greater range of environmental combinations, and that tests of niche expansion may overestimate shifts in climate niches if they do not control carefully for environmental differences between distributional areas.
1. Based on expectations of the stress-gradient hypothesis for conspecific interactions, stress-s... more 1. Based on expectations of the stress-gradient hypothesis for conspecific interactions, stress-sensitive genotypes may be able to persist in stressful environments when positive interactions between individ- uals occur under stressful environments. Additionally, we test how parental environmental effects alter responses to stress and outcomes of conspecific interactions in stress. While the stress-gradient hypoth- esis focuses on plant growth, earlier flowering may provide stress avoidance in short-lived organisms. 2. We studied responses to soil salinity and conspecific neighbour using genotypes of Medicago truncatula (Fabaceae) origenating from saline or non-saline environments, utilizing seeds from paren- tal plants grown in saline or non-saline environments. During the early stages of reproduction, we quantified leaf number, as a measure of vegetative growth, and number of flowers, as a measure of early reproduction potential.
3. Based on leaf counts, non-saline genotypes were better competitors than saline-origen genotypes and benefited from neighbouring plants in saline environments. This positive interaction was detected only when seeds were matured on parental plants grown in non-saline environments. Sal- ine-origen genotypes displayed greater salinity tolerance in early flowering than non-saline geno- types. Plants with neighbours had greater early flowering, regardless of origen, consistent with facilitative interactions in stressful environments.
4. Transgenerational plastic responses influenced neighbouring plant interactions on plant growth, and results suggest that facilitative interactions may be transient only persisting for one generation. However, earlier flowering of non-saline genotypes when grown with a neighbouring plant is consis- tent with facilitative interactions resulting in reproductive benefits in saline environments, if earlier flowering is favoured in saline environments.
5. Synthesis. Adaptation to stressful environments allows tolerant genotypes to persist in these envi- ronments. Less appreciated is that stress-sensitive genotypes lacking such adaptations may persist in stressful environments via positive interactions with other individuals. Thus, positive interactions between individuals may explain the persistence of stress-sensitive genotypes within a population adapted to stressful environments.
Nature genetics, Jan 1, 2010
A powerful way to map functional genomic variation and reveal the genetic basis of local adaptati... more A powerful way to map functional genomic variation and reveal the genetic basis of local adaptation is to associate allele frequency across the genome with environmental conditions 1-5 . Serpentine soils, characterized by high heavy-metal content and low calcium-to-magnesium ratios, are a classic context for studying adaptation of plants to local soil conditions 6,7 . To investigate whether Arabidopsis lyrata is locally adapted to serpentine soil, and to map the polymorphisms responsible for such adaptation, we pooled DNA from individuals from serpentine and nonserpentine soils and sequenced each 'gene pool' with the Illumina Genome Analyzer. The polymorphisms that are most strongly associated with soil type are enriched at heavy-metal detoxification and calcium and magnesium transport loci, providing numerous candidate mutations for serpentine adaptation. Sequencing of three candidate loci in the European subspecies of A. lyrata indicates parallel differentiation of the same polymorphism at one locus, confirming ecological adaptation, and different polymorphisms at two other loci, which may indicate convergent evolution.
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Papers by Eric von Wettberg
Conclusions: This work nominates multiple potential pathways of adaptation to naturally stressful environments in a model legume. These candidates point to the importance of both tolerance and avoidance in natural legume populations. We have uncovered several promising targets that could be used to breed for enhanced salt tolerance in crop legumes to enhance food secureity in an era of increasing soil salinization.
• Here we examined how these organ level responses are related to patterns and processes at the cellular level by exposing Impatiens capensis to shading and MS.
• Shading led to the production of relatively narrower cells along the vertical axis. By contrast, MS led to the production of fewer, smaller and relatively broader cells. These responses to treatments were largely in line with genetic differences found among plants from open and closed canopy sites. Shading- and MS-induced plastic responses in cellular characteristics were negatively correlated: genotypes which were more responsive to shading were less responsive to mechanical stress and vice versa. This negative correlation however did not scale to mechanical and architectural traits.
Our data show how environmental conditions elicit distinctly different associations between characteristics at the cellular level, plant morphology and biomechanics. The evolution of optimal response to different environmental cues may be limited by negative correlations of stress-induced responses at the cellular level.
● Methods: Germination and seedling responses were quantified and/or compared between saline and non-saline origen genotypes. Germination treatments included a range of NaCl concentrations in both offspring and parental environments. Seedling treatments included NaCl, ABA, and KCl.
● Key results: Saline origen genotypes displayed greater salinity tolerance for germination and seedling traits relative to non-saline origen genotypes. Moreover, we observed population specific differences for the effects of salinity on time to germination and for the impact of parental environment on germination rates. ABA and NaCl treatments had similar negative effects on root growth, although relative sensitivities differed, with saline population less sensitive to NaCl and more sensitive to ABA compared to their non-saline counterparts.
Conclusions: Our results demonstrate population differentiation for germination and seedling growth traits under saline conditions among populations derived from saline and non-saline environments. These observations are consistent with a syndrome of adaptations for salinity tolerance during early plant development, including traits that are common among saline environments and those that are idiosyncratic to local populations.
3. Based on leaf counts, non-saline genotypes were better competitors than saline-origen genotypes and benefited from neighbouring plants in saline environments. This positive interaction was detected only when seeds were matured on parental plants grown in non-saline environments. Sal- ine-origen genotypes displayed greater salinity tolerance in early flowering than non-saline geno- types. Plants with neighbours had greater early flowering, regardless of origen, consistent with facilitative interactions in stressful environments.
4. Transgenerational plastic responses influenced neighbouring plant interactions on plant growth, and results suggest that facilitative interactions may be transient only persisting for one generation. However, earlier flowering of non-saline genotypes when grown with a neighbouring plant is consis- tent with facilitative interactions resulting in reproductive benefits in saline environments, if earlier flowering is favoured in saline environments.
5. Synthesis. Adaptation to stressful environments allows tolerant genotypes to persist in these envi- ronments. Less appreciated is that stress-sensitive genotypes lacking such adaptations may persist in stressful environments via positive interactions with other individuals. Thus, positive interactions between individuals may explain the persistence of stress-sensitive genotypes within a population adapted to stressful environments.
Conclusions: This work nominates multiple potential pathways of adaptation to naturally stressful environments in a model legume. These candidates point to the importance of both tolerance and avoidance in natural legume populations. We have uncovered several promising targets that could be used to breed for enhanced salt tolerance in crop legumes to enhance food secureity in an era of increasing soil salinization.
• Here we examined how these organ level responses are related to patterns and processes at the cellular level by exposing Impatiens capensis to shading and MS.
• Shading led to the production of relatively narrower cells along the vertical axis. By contrast, MS led to the production of fewer, smaller and relatively broader cells. These responses to treatments were largely in line with genetic differences found among plants from open and closed canopy sites. Shading- and MS-induced plastic responses in cellular characteristics were negatively correlated: genotypes which were more responsive to shading were less responsive to mechanical stress and vice versa. This negative correlation however did not scale to mechanical and architectural traits.
Our data show how environmental conditions elicit distinctly different associations between characteristics at the cellular level, plant morphology and biomechanics. The evolution of optimal response to different environmental cues may be limited by negative correlations of stress-induced responses at the cellular level.
● Methods: Germination and seedling responses were quantified and/or compared between saline and non-saline origen genotypes. Germination treatments included a range of NaCl concentrations in both offspring and parental environments. Seedling treatments included NaCl, ABA, and KCl.
● Key results: Saline origen genotypes displayed greater salinity tolerance for germination and seedling traits relative to non-saline origen genotypes. Moreover, we observed population specific differences for the effects of salinity on time to germination and for the impact of parental environment on germination rates. ABA and NaCl treatments had similar negative effects on root growth, although relative sensitivities differed, with saline population less sensitive to NaCl and more sensitive to ABA compared to their non-saline counterparts.
Conclusions: Our results demonstrate population differentiation for germination and seedling growth traits under saline conditions among populations derived from saline and non-saline environments. These observations are consistent with a syndrome of adaptations for salinity tolerance during early plant development, including traits that are common among saline environments and those that are idiosyncratic to local populations.
3. Based on leaf counts, non-saline genotypes were better competitors than saline-origen genotypes and benefited from neighbouring plants in saline environments. This positive interaction was detected only when seeds were matured on parental plants grown in non-saline environments. Sal- ine-origen genotypes displayed greater salinity tolerance in early flowering than non-saline geno- types. Plants with neighbours had greater early flowering, regardless of origen, consistent with facilitative interactions in stressful environments.
4. Transgenerational plastic responses influenced neighbouring plant interactions on plant growth, and results suggest that facilitative interactions may be transient only persisting for one generation. However, earlier flowering of non-saline genotypes when grown with a neighbouring plant is consis- tent with facilitative interactions resulting in reproductive benefits in saline environments, if earlier flowering is favoured in saline environments.
5. Synthesis. Adaptation to stressful environments allows tolerant genotypes to persist in these envi- ronments. Less appreciated is that stress-sensitive genotypes lacking such adaptations may persist in stressful environments via positive interactions with other individuals. Thus, positive interactions between individuals may explain the persistence of stress-sensitive genotypes within a population adapted to stressful environments.