Willow Species Research Articles

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Contrasting levels of β-diversity and underlying phylogenetic trends indicate different paths to chemical diversity in highland and lowland willow species

Growth Characteristics of Seven Willow Species Distributed in Eastern Japan in Response to Compost Application

To establish a short rotation coppice (SRC) system in the temperate region of East Asia, planting was conducted for cuttings from seven species, including Salix eriocarpa, S. gilgiana, S. gracilistyla, S. integra, S. sachalinensis, S. serissaefolia, and S. subfragilis, with wide distribution in eastern Japan. During cultivation, cheap compost derived from swine manure and containing high concentrations of various nutrients was added. Three treatment groups, including control, low manure (5 Mg ha−1), and high manure (10 Mg ha−1) treatments, were established, and seven willows were grown for two complete growing seasons to obtain the clone density of 10,000 cuttings ha−1. The manure treatments accelerated the growth of all the willow species after two growing seasons. The averages of annual biomass production of seven willows grown under the control, low manure, and high manure treatments were 0.2 Mg ha−1yr−1, 5.3 Mg ha−1yr−1, and 8.5 Mg ha−1yr−1, respectively. By comparing with the biomasses of seven willows, the largest annual biomass production rates of 14.1 and 13.7 Mg ha−1yr−1 were observed in the high manure treatments of S. sachalinensis and S. subfragilis, respectively. For two species under the high manure treatment, S. sachalinensis had the thickest shoots, and S. subfragilis had the tallest shoots. These growth characteristics of S. sachalinensis and S. subfragilis originate from their high biomass production. Overall, these results suggest that S. sachalinensis and S. subfragilis are potentially feasible candidates for the SRC system in temperate regions of East Asia.

Acetic acid enhances drought tolerance more in female than in male willows.

Drought is an important stress factor that limits plant growth and development. Female willows generally display stronger drought tolerance than males. The application of exogenous acetic acid (AA) has emerged as an efficient and eco-friendly approach to facilitate drought tolerance in willows. However, whether AA exerts sexually different effects on willows remains undefined. In this study, we comprehensively performed morphological and physiological analyses on three willow species, Salix rehderiana, Salix babylonica, and Salix matsudana, to investigate the sexually different responses to drought and AA. The results indicated that willow females were more drought-tolerant than males. AA application effectively enhanced willows' drought tolerance, and females applied with AA displayed greater root distribution and activity, stronger osmotic and antioxidant capacity and photosynthetic rate but less reactive oxygen species, or abscisic acid-mediated stomatal closure than males. In addition, AA application enhanced the jasmonic acid signaling pathway in females but inhibited it in males, conferring stronger drought defense capacity in female willows than in males. Overall, AA application improves drought tolerance more in female than in male willows, further enlarging the sexual differences in willows under drought-stressed conditions.

Genetic Diversity among Eight Species of Willow (Salix spp.) from Iran Based on SRAP Markers

This study reports the application of sequence-related amplified polymorphism (SRAP) technique in characterization of 8 species of Salix (spp) from Iran by screening 22 primer combinations (PCs). Twenty two SRAP primer combinations could amplify 116 scorable loci, of which 107 bands were polymorphic. The amplified DNA fragments were used for calculation and statistical analysis. The Complete linkage cluster was performed and dendrogram drawn with the help of NTSYS pc 2.02 software which revealed two main clusters and several sub-clusters. This investigation showed that genetic distance was relatively significant among these species. The Jaccard similarity coefficient ranged from 0.18 to 0.55. The results also propose that the SRAP marker is a useful tool for evaluation of genetic diversity and relationships among different Salix species.

De Novo Assembly and Annotation of 11 Diverse Shrub Willow (Salix) Genomes Reveals Novel Gene Organization in Sex-Linked Regions.

Poplar and willow species in the Salicaceae are dioecious, yet have been shown to use different sex determination systems located on different chromosomes. Willows in the subgenus Vetrix are interesting for comparative studies of sex determination systems, yet genomic resources for these species are still quite limited. Only a few annotated reference genome assemblies are available, despite many species in use in breeding programs. Here we present de novo assemblies and annotations of 11 shrub willow genomes from six species. Copy number variation of candidate sex determination genes within each genome was characterized and revealed remarkable differences in putative master regulator gene duplication and deletion. We also analyzed copy number and expression of candidate genes involved in floral secondary metabolism, and identified substantial variation across genotypes, which can be used for parental selection in breeding programs. Lastly, we report on a genotype that produces only female descendants and identified gene presence/absence variation in the mitochondrial genome that may be responsible for this unusual inheritance.

Genotype accounts for intraspecific variation in the timing and duration of multiple, sequential life-cycle events in a willow species.

Phenological variation among individuals within populations is common and has a variety of ecological and evolutionary consequences, including forming the basis for population-level responses to environmental change. Although the timing of life-cycle events has genetic underpinnings, whether intraspecific variation in the duration of life-cycle events reflects genetic differences among individuals is poorly understood. We used a common garden experiment of 10 genotypes of Salix hookeriana (coastal willow) from northern California, USA to investigate the extent to which genetic variation explains intraspecific variation in the timing and duration of multiple, sequential life-cycle events: flowering, leaf budbreak, leaf expansion, fruiting, and fall leaf coloration. We used seven clones of each genotype, for a total of 70 individual trees. Genotype affected each sequential life-cycle event independently and explained on average 62% of the variation in the timing and duration of vegetative and reproductive life-cycle events. All events were significantly heritable. A single genotype tended to be 'early' or 'late' across life-cycle events, but there was no consistent response within genotypes for event durations. This research demonstrates that genetic variation can be a major component underlying intraspecific variation in the timing and duration of life-cycle events. It is often assumed that the environment affects durations, but we show that genetic factors also play a role. Because the timing and duration of events are independent of one another, our results suggest that the effects of environmental change on one event will not necessarily cascade to subsequent events. This article is protected by copyright. All rights reserved.

Food Preference of Termite (Microcerotermes diversus Silv.) for Forest Trees in Erbil Governorate

The current study investigated the sensitivity of different wood species to the termite, Microcerotermes diversus, in two different locations. The results showed that both softwood and hardwood of White Willow, Salix alba; Melia, Melia azedarach; pine, Pinus brutia and Mediterranean Cypress, Cupressus sempervirens are highly susceptible to the termite invasion under physically infection conditions in Sami Abdulrahman Park, Erbil city, Iraq. Moreover, the sensitivity of the species to the termite invasion was significantly different under natural infection in Grdarasha after 22 weeks from early April to the end of September 2017. In addition, the White Willow (Salix alba) species showed more sensitivity to the termite infection in comparison with others species, where the mean of wood green weight, wood dry weight (before infection), wood dry weight (after infection) and specific gravity loss during the period of experiment of the White Willow were 2.2609g, 2.1584g, 1.5983g and 0.5139 respectively. Furthermore, Cupressus sempervirens was more resistant in comparison with other wood species to the termite in both locations where green weight of wood 3.010g and Dry weight of wood (after infection) 2.287g, Dry weight of wood (befor infection) 2.877g and Specific gravity 0.685. Generally, this study revealed that there is no definite association between both physical properties and moisture content of softwoods and hardwoods with termite preference.
 

RETRACTED: Lamine, S.; Saunders, I. Phytoremediation of Heavy-Metals-Contaminated Soils: A Short-Term Trial Involving Two Willow Species from Gloucester WillowBank in the UK. Minerals 2022, 12, 519

The journal retracts the article “Phytoremediation of Heavy-Metals-Contaminated Soils: A Short-Term Trial Involving Two Willow Species from Gloucester WillowBank in the UK” [...]

Chemical profiling and biological activities of “green” extracts of willow species (Salix L., Salicaceae): Experimental and chemometric approaches

Willow bark extract (Salix spp., Salicaceae) has been used since ancient times as an analgesic, antipyretic and anti-inflammatory agent. In this paper, microwave-assisted extraction (MAE) was applied for the extraction of little-studied leaves and bark of six different species of the genus Salix with potential medicinal value. MAE extracts were evaluated in terms of their content of total phenolics, total flavonoids, selected phenolic constituents (salicin, chlorogenic acid, rutin, quercetin, naringenin) and antioxidant activity. Extracts with the highest content of target compounds were assessed for acetylcholinesterase inhibitory potential. Chemometric analysis was performed to identify clusters of samples based on the quantities of target phenolic compounds. Chemical composition varied among the analyzed species, as well as between leaves and bark of the same willow species. The extracts exhibited significant scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH) radicals. Chemometric tools enabled selection of species and plant part (leaf or bark) with the most favorable chemical profile, which could be further explored as sources of bioactive compounds for nutraceutical and pharmaceutical purposes.

The Search for Suitable Habitats for Endangered Species at Their Historical Sites-Conditions for the Success of Salix lapponum and Salix myrtilloides Reintroduction.

Restoring endangered plant species to their historical sites is not always possible due to constantly changing habitat conditions. The aim of this study was to test the effects of reintroduction of two relict willow species in eastern Poland. The experiment consisted of planting 48 individuals of Salix lapponum and S. myrtilloides, obtained by micropropagation, at each of the two selected sites and observing their survival after one year. At the same time, selected physicochemical and biocenotic factors of the environment were monitored. About 70% of S. lapponum individuals and 50% of S. myrtilloides plants survived the one-year period. This result can be considered satisfactory and confirms the effectiveness of this means of active protection. The results of measurements of selected abiotic factors of the environment and the observations and ecological analysis of the flora indicated that the habitat conditions of both historical sites have changed, resulting in accelerated succession of vegetation. However, complete habitat degradation did not occur, although the development of a multi-story structure of one of the phytocenoses intensified competition for light and other environmental resources, which narrowed the potential ecological niche of the reintroduced species.

Результаты первой попытки привлечения пары орлана-белохвоста в искусственное гнездовье

Результаты первой попытки привлечения пары орлана-белохвоста в искусственное гнездовье

Evolution of a hybrid zone of two willow species (Salix L.) in the European Alps analyzed by RAD-seq and morphometrics.

Natural hybridization of plants can result in many outcomes with several evolutionary consequences, such as hybrid speciation and introgression. Natural hybrid zones can arise in mountain systems as a result of fluctuating climate during the exchange of glacial and interglacial periods, where species retract and expand their territories, resulting in secondary contacts. Willows are a large genus of woody plants with an immense capability of interspecific crossing. In this study, the sympatric area of two diploid sister species, S.foetida and S.waldsteiniana in the eastern European Alps, was investigated to study the genomic structure of populations within and outside their contact zone and to analyze congruence of morphological phenotypes with genetic data. Eleven populations of the two species were sampled across the Alps and examined using phylogenetic network and population genetic structure analyses of RAD Seq data and morphometric analyses of leaves. The results showed that a homoploid hybrid zone between the two species was established within their sympatric area. Patterns of genetic admixture in homoploid hybrids indicated introgression with asymmetric backcrossing to not only one of the parental species but also one hybrid population forming a separate lineage. The lack of F1 hybrids indicated a long-term persistence of the hybrid populations. Insignificant isolation by distance suggests that gene flow can act over large geographical scales. Morphometric characteristics of hybrids supported the molecular data and clearly separated populations of the parental species, but showed intermediacy in the hybrid zone populations with a bias toward S.waldsteiniana. The homoploid hybrid zone might have been established via secondary contact hybridization, and its establishment was fostered by the low genetic divergence of parental species and a lack of strong intrinsic crossing barriers. Incomplete ecological separation and the ability of long-distance dispersal of willows could have contributed to the spatial expansion of the hybrid zone.

Exploring willow decline in an over-greening riparian corridor (River Jarama, Spain)

The analysis of willow forest decline in the Jarama River has been assessed through the study of morphological river conditions in three periods (1956, 1998 and 2018) together with active channel mobility ratios and changes in channel planform and vegetation coverage. Species composition of current riparian corridors at river segment scale and monitored natural recruitment of pioneer species at local scale have been studied. Jarama River has changed from wide active wandering towards narrower meandering channels with dense and continuous riparian over-greening corridors, in which willow formations are threatened, and drought-tolerant species have colonised it. Landform evolution shows an intensive ‘maturation’ associated with ‘anthropisation’ processes during the first period, while stability dominates nowadays. Results show a generalised aging and progressive mortality of shrub willows and the expansion of forests dominated by Fraxinus angustifolia, likely associated to the progressive reduction of channel mobility and the lack of bare gravel bars for pioneer recruitment. The dominant willow species is Salix salviifolia, a drought tolerant willow that has been able to withstand the processes of 'maturation’ and channel narrowing being widely distributed throughout the riparian section. On the other hand, other strict pioneer willows such as Salix eleagnos and Salix purpurea are very rare and are found in the few gravel banks that remain on the shore. Results predict a gradual disappearance of willows in the Jarama River as there is no significant recruitment, and they would last as long if those old specimens may survive.

Chlorophyll Pigment and Leaf Macronutrient Trait Variation of Four Salix Species in Elevated CO2, under Soil Moisture Stress and Fertilization Treatments

Leaf chlorophyll pigment and macronutrient concentrations were quantified for four willow species (Salix cordata (COR), S. discolor (DIS), S. eriocephala (ERI) and S. interior (INT)) while growing under 2 × 2 factorial of ambient and elevated CO2 and well-watered and drought-stressed soil moisture treatments (Expt. 1). After the first year, we saw no difference in stem biomass between CO2 treatments. In the following year, a second experiment was conducted on a subset of well-watered willows as a 2 × 2 factorial of atmospheric CO2 and soil fertilization (FERT). For both years of Expt. 1, chlorophyll a, b, a + b (TCC) and carotenoids (CAR) significantly downregulated in response to elevated CO2 (eCO2) and upregulated in response to drought (DRT). In Expt. 2, FERT mitigated CO2 downregulation of TCC and CAR, and upregulated TCC and CAR. Across species, ERI had the greatest pigment concentrations followed by either COR or DIS. Except for one case, INT had the lowest pigment concentrations. A significant species x FERT interaction was due to magnitude effects. The CHLa:b ratio was not affected by CO2 or DRT but did increase in response to FERT. INT had the greatest CHLa:b ratio followed by DIS, then either ERI or COR. In the second year, TCC:CAR ratio decreased in response to eCO2 and increased in response to DRT and FERT. In Expt. 1, leaf N was the only nutrient to significantly downregulate in response to eCO2; whereas all other nutrient levels remained unchanged. In response to DRT, leaf N and Mg upregulated; whereas leaf P, K, and Ca were downregulated. In response to eCO2 in Expt. 2, again only leaf N downregulated; whereas all other nutrients remained unchanged. All leaf nutrients upregulated in response to FERT. Of the four species, INT had the greatest leaf N and K, and the lowest Ca. Species variation was important, but so to was clonal variation in response to change. Indeed, INT leaf chlorophyll and macronutrients are significantly different or segregated from the other three willow species and this may be related to the evolutionary origins of INT, and other species of the taxonomic section Longifoliae, in the arid southwest USA and Mexico. Furthermore, under low nutrient conditions, it may be necessary to fertilize the plants to see a biomass response to eCO2.

Conservation genetics of montane willow populations in Scotland—limited natural recovery despite long-distance gene flow and high genetic diversity

Plant species around the world are negatively affected by habitat fragmentation and climate change. Montane willow populations in the UK have declined primarily due to grazing, as well as climate change and muirburn in certain areas. Only small, isolated populations remain, scattered across steep ledges where shrubs escape most grazing animals. We explored the genetic effects of habitat fragmentation on gene flow and genetic diversity in the largest remaining patches in the UK, which lie in Scotland, for two now restricted and rare montane willow species—Salix myrsinites and Salix lapponum. Using ten microsatellite loci and an almost complete genetic inventory in the central Cairngorms area (S. myrsinites n = 186, S. lapponum n = 91) we showed that genetic diversity (heterozygosity and allelic richness) is relatively high in both species, particularly high for the decaploid S. myrsinites, and clonal reproduction low. Historic gene flow between populations could be demonstrated. Significant inbreeding was detected in both species and observed seed set and numbers of juveniles in the field are low, possibly indicating signs of inbreeding depression. Both species have extremely low numbers of individuals at each site, with many being smaller than ten, and in some cases combined with skewed sex-ratios (mainly female biased). This will likely cause more severe reproductive failures in the next generations unless population numbers are increased. Reinforcing populations of both species under low grazing pressure with new, unrelated individuals, as well as creating new stepping-stone populations will be necessary to help the recovery of these species. Results from this study will inform restoration work in Scotland aiming to create continuous woodland habitats from pinewoods at lower altitudes through to higher altitude downy birch woodlands merging with montane willows.

Mixed growth of Salix species can promote phosphate-solubilizing bacteria in the roots and rhizosphere.

Phosphorus (P) is an essential plant nutrient that can limit plant growth due to low availability in the soil. P-solubilizing bacteria in the roots and rhizosphere increase the P use efficiency of plants. This study addressed the impact of plant species, the level of plant association with bacteria (rhizosphere or root endophyte) and environmental factors (e.g., seasons, soil properties) on the abundance and diversity of P-solubilizing bacteria in short-rotation coppices (SRC) of willows (Salix spp.) for biomass production. Two willow species (S. dasyclados cv. Loden and S. schwerinii × S. viminalis cv. Tora) grown in mono-and mixed culture plots were examined for the abundance and diversity of bacteria in the root endosphere and rhizosphere during two seasons (fall and spring) in central Sweden and northern Germany. Soil properties, such as pH and available P and N, had a significant effect on the structure of the bacterial community. Microbiome analysis and culture-based methods revealed a higher diversity of rhizospheric bacteria than endophytic bacteria. The P-solubilizing bacterial isolates belonged mainly to Proteobacteria (85%), Actinobacteria (6%) and Firmicutes (9%). Pseudomonas was the most frequently isolated cultivable bacterial genus from both the root endosphere and the rhizosphere. The remaining cultivable bacterial isolates belonged to the phyla Actinobacteria and Firmicutes. In conclusion, site-specific soil conditions and the level of plant association with bacteria were the main factors shaping the bacterial communities in the willow SRCs. In particular, the concentration of available P along with the total nitrogen in the soil controlled the total bacterial diversity in willow SRCs. A lower number of endophytic and rhizospheric bacteria was observed in Loden willow species compared to that of Tora and the mix of the two, indicating that mixed growth of Salix species promotes P-solubilizing bacterial diversity and abundance. Therefore, a mixed plant design was presented as a management option to increase the P availability for Salix in SRCs. This design should be tested for further species mixtures.

Unweaving the population structure and genetic diversity of Canadian shrub willow

Perennial shrub willow are increasingly being promoted in short-rotation coppice systems as biomass feedstocks, for phytoremediation applications, and for the diverse ecosystem services that can accrue. This renewed interest has led to widespread willow cultivation, particularly of non-native varieties. However, Canadian willow species have not been widely adopted and their inherent diversity has not yet been thoroughly investigated. In this study, 324 genotypes of Salix famelica and Salix eriocephala collected from 33 sites of origin were analyzed using 26,016 single nucleotide polymorphisms to reveal patterns of population structure and genetic diversity. Analyses by Bayesian methods and principal component analysis detected five main clusters that appeared to be largely shaped by geoclimatic variables including mean annual precipitation and the number of frost-free days. The overall observed (HO) and expected (HE) heterozygosity were 0.126 and 0.179, respectively. An analysis of molecular variance revealed that the highest genetic variation occurred within genotypes (69%), while 8% of the variation existed among clusters and 23% between genotypes within clusters. These findings provide new insights into the extent of genetic variation that exists within native shrub willow species which could be leveraged in pan-Canadian willow breeding programs.

Repeated turnovers keep sex chromosomes young in willows

BackgroundSalicaceae species have diverse sex determination systems and frequent sex chromosome turnovers. However, compared with poplars, the diversity of sex determination in willows is poorly understood, and little is known about the evolutionary forces driving their turnover. Here, we characterized the sex determination in two Salix species, S. chaenomeloides and S. arbutifolia, which have an XY system on chromosome 7 and 15, respectively.ResultsBased on the assemblies of their sex determination regions, we found that the sex determination mechanism of willows may have underlying similarities with poplars, both involving intact and/or partial homologs of a type A cytokinin response regulator (RR) gene. Comparative analyses suggested that at least two sex turnover events have occurred in Salix, one preserving the ancestral pattern of male heterogamety, and the other changing heterogametic sex from XY to ZW, which could be partly explained by the “deleterious mutation load” and “sexually antagonistic selection” theoretical models. We hypothesize that these repeated turnovers keep sex chromosomes of willow species in a perpetually young state, leading to limited degeneration.ConclusionsOur findings further improve the evolutionary trajectory of sex chromosomes in Salicaceae species, explore the evolutionary forces driving the repeated turnovers of their sex chromosomes, and provide a valuable reference for the study of sex chromosomes in other species.