An AFLP and RFLP linkage map and quantitative trait locus (QTL) analysis of growth traits in Salix

A genetic linkage map of Salix (2n = 38), composed of 325 AFLP and 38 RFLP markers has been constructed. The map was based on a population ( n = 87) derived from a cross between the male hybrid clone "Bj?rn" ( Salix viminalis x Salix schwerinii) and the female clone "78183" ( S. viminalis). Three hundred fifty seven AFLPs corresponding to DNA polymorphisms heterozygous in one parent and null in the other were scored. A total of 87 RFLP probes, most (83) derived from the Populus genome, yielded 39 and 11 polymorphic loci segregating in a 1:1 and 1:2:1 ratio respectively. Two maps, one for each parent, were constructed according to the "two-way pseudo-testcross" mapping strategy. The S. viminalis x S. schwerinii map (2,404 cM) included 217 markers and formed 26 major linkage groups while S. viminalis (1,844 cM) consisted of 146 markers placed on 18 major groups. In addition, eight and 14 additional minor linkage groups composed of less than four markers (doubles and triplets) were obtained in the S. viminalis x S. schwerinii and the S. viminalis maps, respectively. Both maps provided 70-80% genome coverage with an average density of markers of 14 cM. To investigate possible homologies between the parental maps, 20 AFLPs and 11 RFLPs segregating in 3:1 or 1:2:1 ratios were included in the linkage analysis. Eight linkage groups homologous between the two maps were detected. The present genetic map was used to identify quantitative trait loci (QTLs) affecting growth-related traits. Eleven QTLs were identified; seven QTLs for height growth, one QTL for stem diameter, one QTL for the height: diameter ratio, one QTL for the number of vegetative buds during flowering time and one QTL for the number of shoots. The estimated magnitude of the QTL effect ranged from 14 to 22% of the total phenotypic variance. One QTL associated with height growth and one affecting the height: diameter ratio were overlapping in the same marker interval with the QTL affecting stem diameter. QTL stability over years was estimated for traits measured in multiple years. Generally, QTLs were only significant in a single year although two QTLs for height growth were close to reaching the significance level in 2 consecutive years.     

Periodicity of bud bursting in willow (Salix viminalis) as affected by growth regulators

Saunders, P. F. and Barros, R. S. 1987. Periodicity of bud bursting in willow ( Salix viminalis ) as affected by growth regulators.
Lateral vegetative buds of willow ( Salix viminalis L.) were only innately dormant for 3–5 weeks in October; during this time their apices were correlatively inhibited by the bud leaflets. Exogenous gibberellins stimulated the opening of cultured buds when the plants were dormant or entering dormancy. As dormancy was being released, however, cultured buds became more responsive to exogenous cytokinins. Thus the demand for gibberellins and cytokinins for bud opening seemed to be sequential rather than simultaneous. Dormant buds cultured in the presence of abscisic acid remained unopened, but they opened after a chilling treatment. Subsequent growth of such buds as measured by dry matter accumulation, was observed only if a cytokinin was added to the medium.     

Development of a hydroponic screening technique to assess heavy metal resistance in willow (Salix)

A nutrient thin film hydroponic system has been developed which allows rapid screening of willow (Salix) clones for their resistance to heavy metals, and hence their use in phytoremediation. Two clones known to be different in their resistance to heavy metals (Salix burjatica (Germany) and S. triandra x viminalis (Q83)), could be distinguished on the basis of leaf biomass, root biomass and stem height after 6 weeks. There were also differences in the uptake of heavy metals between the two clones.     

A feasibility study of a Salix viminalis gravel hydroponic system to renovate primary settled wastewater

A Salix viminalis/gravel system based on hydroponics was developed for wastewater renovation in order to avoid the problems of soil damage and pollution associated with long-term application of wastewater to soil. For such a system to work the mineral elements applied must match closely the requirements of the tree species. To examine this the growth and nutrient uptake of S. viminalis in wastewater was compared with that in Long Ashton nutrient solution (1/4 strength). S. viminalis grew more slowly in wastewater than in Long Ashton solution, but exhibited no obvious deficiency or toxicity symptoms. Since industrial wastewaters often contain metals, the extent to which copper might inhibit wastewater treatment in this system was also examined. S. viminalis was grown in wastewater amended with 10 and 100 ppm copper. Trees were unaffected by wastewater with 10 ppm copper when compared to trees grown in wastewater alone. Wastewater containing with 100 ppm copper was too toxic for the trees to thrive and wastewater treatment was reduced. Treatment efficiencies for unamended wastewater were 57.7% for nitrogen, 90.6% for phosphorus and 24.9% for potassium. These efficiencies are much greater than those quoted for a Salix/soil system, and thus Salix/gravel systems may have potential for wastewater treatment in environmentally sensitive areas or situations.     

Host–pathogen relationship between Salix and Melampsora sheds light on the parentage of some biomass willows

The association between willow ( Salix ) and rust ( Melampsora ) is highly specific. Willows named Salix burjatica , S. dasyclados ( S. × dasyclados ) and S. × calodendron are important in renewable-energy plantations in the UK and western Europe. There has been much controversy over their origin, species status and nomenclature. It has been suggested that they have originated from hybridization between. S. caprea , S. viminalis and S. cinerea . In the present work, 59 willow clones were investigated through morphological examination and detached leaf inoculation using willow differentials, for their association, in southwest England, with M. capraearum and three pathotypes of Melampsora epitea (Me-A, B and C). M. capraearum was found on all clones of S. caprea and its hybrids with S. aurita ; Me-A on all S. viminalis clones; Me-B on wild S. cinerea , S. × calodendron , S. × dasyclados 'De Biardii 445' and S . 'Spaethii'; Me-C on all S. burjatica clones and most S. × dasyclados clones. Both M. caprearum and Me-A infected all S. × sericans ( S. caprea × viminalis ) clones and S. × dasyclados 'LA041/03'. We suggest that S. × dasyclados 'LA041/03' should be treated as S. × sericans ( S. caprea × S. viminalis ); S. burjatica , S. dasyclados and S. × dasyclados as synonyms; S. × dasyclados 'De Biardii 445' as S. × calodendron 'De Biardii 445'; and S . 'Spaethii' as S. × calodendron 'Spaethii'.     

Dasineura ingeris sp.n. (Diptera: Cecidomyiidae) on Salix viminalis in Sweden, including comparisons with some other Dasineura species on Salix

Infestations of an undescribed gall midge species were discovered in Southern Sweden in biomass plantations and nurseries of Salix viminalis L. Terminal leaf buds are damaged and side shoots subsequently develop. This midge, Dasineura ingeris sp.n., closely resembles three other species occurring on Salix: D.terminalis (H. Loew) on S.alba L. and S.fragilis L.; D.iteobia (Kieffer) recorded from S.caprea L. and S.cinerea L.; and D.schreiteri (Stelter) (= comb.n. for Rabdophaga schreiteri Stelter) originally found as an inquiline in the galls of another gall midge, Dasineura rosaria (H. Loew), on S.repens L. No qualitative differences in morphology were observed between these four gall midge species, but results of morphometric analyses show significant differences between all of them. In oviposition preference trials, which included host plants of all four midge species, D.ingeris laid eggs mainly on S. viminalis, D.schreiteri preferably on S.repens , and D.iteobia exclusively on S.caprea. In larval performance trials D.ingeris produced many galls on S. viminalis , one gall also on S.caprea , but no galls on either S.alba or S.repens.     

Influence of Ca/mg ratio on phytoextraction properties of Salix viminalis I. The effectiveness of Cd, Cu, Pb, and Zn bioaccumulation and plant growth

Phytoremediation and its efficiency--influenced by several factors-is prime concern in reduction of environment contamination with heavy metals. The aim of the study was to estimate in controlled conditions--in relation to the natural Ca/Mg ratio 4:1--the influence of different Ca/Mg ratios (1:1/4, 20:1, 1:10) on selected heavy metals (Cd, Cu, Pb, and Zn) accumulation efficiency shown by three morphological parts of Salix viminalis 'Cinamomea' (cane bark, shoots and roots). Accumulation of heavy metals in experimental conditions was significantly Ca/Mg ratio dependent, and occurred in the following order: 1:10 > 4:1 > 20:1 > 1:1/4. The highest accumulation under 0.5 mM solutions (as compared to 0.1 mM) was noted for copper and zinc, and the lowest for cadmium. Biometric parameters of Salix viminalis cuttings revealed the highest biomass productivity under 20:1 and 4:1 Ca/Mg ratios. In the case of shoot length increase, both metal concentration and kind of metal present in the solution were important. The results indicate that higher calcium ion concentration in solution (Ca/Mg 20:1) stimulates Salix viminalis growth by 3 fold when compared to other Ca/Mg ratio. It can be an important factor in remediation of the environment with this plant.     

Screening of willow species for resistance to heavy metals: comparison of performance in a hydroponics system and field trials

The aim of this study was to ascertain whether metal resistance in willow (Salix) clones grown in a hydroponics screening test correlated with data from the same clones grown independently in a field trial. If so, results from a short-term, glasshouse-based system could be extrapolated to the field, allowing rapid identification of willows suitable for planting in metal-contaminated substrates without necessitating longterm field trials. Principal Components Analysis was used to show groups of clones and to assess the relative importance of the parameters measured in both the hydroponics system and the field; including plant response factors such as increase in stem height, as well as metal concentrations in plant tissues. The clones tested fell into two distinct groups. Salix viminalis clones and the basket willow Black Maul (S. triandra) were less resistant to elevated concentrations of heavy metals than a group of hardier clones, including S. burjatica 'Germany,' S.x dasyclados, S. candida and S. spaethii. The more resistant clones produced more biomass in the glasshouse and field, and had higher metal concentrations in the wood. The less resistant clones had greater concentrations of Cu and Ni in the bark, and produced less biomass in the glasshouse and field. Significant relationships were found between the response of the same clones grown the in short-term glasshouse hydroponics system and in the field.     

Mapping of quantitative trait loci controlling timing of bud flush in Salix

Dormancy release is an important phenological stage, which determines plant growth and survival in northern temperate regions. Spring bud flushing was studied in a Salix pedigree (n=82) derived from a cross between the male hybrid clone "Bj?rn" (Salix viminalis x Salix schwerinii) and the female clone "78183" (Salix viminalis). The timing of bud flush was recorded outdoors in two consecutive years (1998, 1999) and indoor in the spring of 1998. Timing of bud flush was found to be under moderately strong genetic control (clonal mean heritabilities ranging from 0.43 to 0.72). Phenotypic correlations between height growth and bud flushing were negative but non-significant (r=0.1-0.3). Using a Salix linkage map composed of 325 AFLP and 38 RFLP markers, six quantitative trait loci (QTLs) and three unmapped marker loci associated with timing of bud flush were detected. Four QTLs were detected in the field experiment while two QTLs and three unmapped marker loci were identified in the indoor experiment. One QTL associated with indoor bud flushing coincided with one of the QTL detected from the field data. Individual QTL explained 6-16% of the phenotypic variance [corrected]. None of the bud flush QTLs coincided with QTLs controlling height growth identified previously in the same pedigree.     

Effects of summer and winter harvesting on element phytoextraction efficiency of Salix and Populus clones planted on contaminated soil

The clones of fast-growing trees (FGTs) were investigated for phytoextraction of soil contaminated with risk elements (REs), especially Cd, Pb, and Zn. As a main experimental factor, the potential effect of biomass harvesting time was assessed. The field experiment with two Salix clones (S1 – (Salix schwerinii × Salix viminalis) × S. viminalis, S2 – S. × smithiana) and two Populus clones (P1 – Populus maximowiczii × Populus nigra, P2 – P. nigra) was established in April 2009. Shoots of all clones were first harvested in February 2012. After two further growing seasons, the first half of the trees was harvested in September 2013 before leaf fall (summer harvest) and the second half in February 2014 (winter harvest). Remediation factors (RFs) for all clones and all REs (except Pb for clone S1) were higher in the summer harvest. The highest annual RFs for Cd and for Zn (1.34 and 0.67%, respectively) were found for clone S2 and were significantly higher than other clones. Although no increased mortality of trees harvested in the summer was detected in the following season, the effect of summer harvesting on the phytoextraction potential of FGTs clones should be investigated in long-term studies.     

The development of two flanking SCAR markers linked to a sex determination locus in Salix viminalis L

Most studies of sex determination systems in plants involve dioecious annuals that have known sex chromosomes. Despite the absence of such structures in the majority of dioecious plants, gender seems to be under relatively strict genetic control in some species. Genetic markers linked to a female sex-determination locus in Salix viminalis L. have been discovered through bulked segregant analysis of three full-sib families using approximately 1,000 arbitrary primers. Two RAPD markers that were present in the common female parent as well as in predominantly female progeny of these families were subsequently sequenced and converted to sequence characterized amplified region (SCAR) markers. The two SCAR markers are correlated with gender in the three full-sib families and are present in 96.4% of the female progeny and 2.2% of the males, providing evidence of linkage to a putative female-specific locus associated with gender determination in S. viminalis. Estimates of recombination suggest that the two markers are flanking a putative sex determination locus, SDL-II, in certain families of S. viminalis.     

Heat shock proteins in willow (Salix viminalis)

The heat shock response in three vegetatively propagated clones of Salix viminalis L. was studied. In the clone 78198, synthesis of a total of 58 proteins was induced or increased by heat shock. Of these proteins, 39 were found in both leaves and callus, 8 only in leaves, and 11 only in callus. The number of heat shock proteins differed between the three clones studied. The molecular weights of the heat shock proteins ranged from 18000 to over 94000. The optimal synthesis of heat shock proteins took place at 37–40°C, but several proteins could be induced at 25–30°C. The synthesis of the majority of the proteins present at a normal growth temperature (20°C) was not completely blocked by the heat shock. More than 12 h was needed for the reappearance of the normal protein synthesis pattern after heat shock.     

Strategies for the biological control of invasive willows (Salix spp.) in Australia

Abstract  Willows ( Salix spp.) are Weeds of National Significance in Australia where a large number of taxa are naturalised in temperate regions and can cause serious environmental degradation of riparian and wetland habitats. Several species are of economic or ornamental value and conflicts of interest could arise with planning their suppression. Biological control of six willow species ( S. alba L., S. cinerea L . , S. fragilis L., S. nigra Marshall, S. viminalis L., S . x  rubens Schrank) is under consideration in Australia using three approaches based on targeting different morphological structures. A rich phytophagous biota associated with Salix in their regions of origin indicate a range of organisms are available for development as biological control agents. Implementation strategies will depend on the host species targeted for biological control, their reproductive strategies, the level of control required to reduce environmental impacts and the level of conflict of interest associated with a biological control program.     

北京地区蒿柳的开花物候期及单花序开放过程中花粉活力和柱头可授性变化

Flowering phenology and flowering dynamics of female and male inflorescences of Salix viminalis Linn. in Beijing were observed in 2015 and 2016, and changes in pollen activity and stigma receptivity were also investigated. The results show that early flowering stage of S. viminalis in Beijing is happened in early?March, flowering period is 11-18 d, and flowering pattern is the first opening type of male flower. Flowering period of single inflorescence in male and female plants is 10-15 d and 8-10 d, respectively, which can be divided into five stages:emerging color stage, initial flowering stage, half flowering stage, full flowering stage and withered stage. Flowering date of male plant is earlier about 3-4 d than that of female plant. However, the difference of full flowering stage between male and female plants is only 1 d. Pollen germination rate and stigma receptivity show a trend of firstly increasing then decreasing during blossom process. Pollen germination rate reaches the highest of 72% at full flowering stage, and stigma receptivity is more than 90% at half and full flowering stages. Therefore, it is suggested that pollen collection and pollination in mid?March can improve success rate of cross breeding of S. viminalis.     

北京东灵山地区主要树生地衣调查初报

首次对北京森林生态定位站所在地东灵山小龙门林场主要森林树种上的地衣进行了调查研究,辽东栎,核桃楸,山杨,黄花柳,白腊和春榆等树种上的地衣覆盖度较大,其覆盖度多为３０％￣６０％,最高可达８０％。     

No phytochelatin (PC2 and PC3) detected in Salix viminalis

Phytochelatins (PCs) have been detected in a large range of plant species, but their role in heavy-metal tolerance is unclear. Various clones of Salix viminalis are differently tolerant to heavy metals, and the aim of this work was to investigate whether PCs were differently expressed in tolerant compared with sensitive clones. In a long-term study, five clones with high or low metal tolerance were cultivated 21 days without or with Cd (1 or 10 µ M ), Cu (0.3 or 7 µ M ), Ni (15 µ M ), Pb (7 µ M ) or Zn (10 or 100 µ M ). Controls were further used in a short-term study where Cd (1 µ M ) was added and samples were collected 0, 15 and 30 min, 1, 3 and 24 h after start of treatment. PCs were analysed on high performance liquid chromatography (HPLC) using two different methods: post-column derivatization using Ellmans reagent and pre-derivatization with monobromobimane. Thlaspi caerulescens treated with Cd was used as internal PC standard. No PCs could be detected in Salix with either of the two methods in any of the treatments: different clones, metals, concentrations, plant parts or treatment time. The 16 thiol peaks shown were the same in both control and treated plants. Both HPLC methods showed PC peaks when Thlaspi was used but these peaks could not be associated with any of the 16 peaks. The amino acid composition of the 16 peaks was not the expected composition of that of PCs. Thus, Salix viminalis have no detectable levels of PCs, which in turn are not involved in heavy metal tolerance in Salix .     

Brittleness of twig bases in the genus Salix: fracture mechanics and ecological relevance

The twig bases within the genus Salix were investigated. Brittleness of twig bases as defined in the literature neither correlates with Young's modulus nor with growth strains, which were measured for S. alba, S. fragilis and S. x rubens. For the species S. alba, S. appendiculata, S. eleagnos, S. fragilis, S. purpurea, S. triandra, S. viminalis, and S. x rubens, fracture surfaces of broken twigs were investigated and semiquantitatively described in terms of 'relative roughness' (ratio of rough area of fracture surface over whole area of fracture surface). The relative roughness clearly corresponds with the classification into brittle and nonbrittle species given in the literature. An attempt was made to quantify brittleness with mechanical tests. The absolute values of stress and strain do not correlate with the brittleness of the twig bases as defined by the relative roughness. However, the 'index stress' (ratio of stress at yield over stress at fracture) or the 'index strain' (ratio of strain at yield over strain at fracture), correlate well with the relative roughness. The graphic analysis of index stress against index strain reveals a straight line on which the eight species are ordered according to their brittleness. Depending on growth form and habitat, brittle twig bases of willows may function ecologically as mechanical safety mechanisms and, additionally, as a propagation mechanism.     

Effects of varied nitrogen stress on growth and nutrition in three Salix clones

The ability of Salix aquatica Smith, S. fragilis L. and S. viminalis L. to absorb nitrogen at varied growth rates was investigated in nutrient solutions. The effects of five nitrogen addition rates on growth rates, nitrogen contents of the plants, nitrogen concentration of the media, and dry matter distribution between roots, stems and leaves, were studied.
These clones are highly efficient in absorbing nitrogen at low concentrations in the root medium, independent of growth rate. Strong linear regressions were found between any two of the three factors: relative rate of nitrogen supply (R_N), nitrogen content (plant), and relative growth rate (R). Dry matter production per unit nitrogen taken up and unit time (N-productivity) and per unit nitrogen taken up independent of time (N-efficiency) was closely correlated to the nitrogen status of the plant. Root development was favoured in the sub-optimum treatments, and leaf development in the optimum treatments. With regard to their ability to absorb nitrogen, these Salix clones appear satisfactory for efficient short rotation energy forestry.     

Genetic mapping of sex-linked markers in Salix viminalis L

A total of 88 selective primer combinations were screened using bulked males and females sampled from four families of Salix viminalis. A total of more than 1000 polymorphic fragments was obtained, of which only four cosegregated with sex. These four sex-linked markers were subsequently scored in individuals that were used for bulked sample preparation in additional individuals of the same families, and in individuals in other families. A pair of primers that amplified the sex-linked fragments was constructed from one of the sex-linked amplified fragment length polymorphism (AFLP) fragments. In hybridization of Southern blot filters with the sex-linked DNA fragments, the band was present in females and absent in males, but the opposite pattern of band segregation (a band found in males and no band in females) was never observed in either the AFLP or RFLP experiments. Two of the sex-linked markers were placed on a linkage map. They both map at the same location in a linkage group comprising other markers not segregating with sex. Our data suggest that a single locus governs the sex determination and that nonrecombining sex chromosomes are absent in S. viminalis. A close association was found between skewed sex ratio and segregation distortion at this locus.     

Melampsora rust species on biomass willows in central and north-eastern Germany

Melampsora willow rusts are the most important fungal pathogens in short rotation coppices of biomass willows. In the past, breeding programmes for rust resistant biomass willows concentrated on the distinction of races within the forma specialis Melampsora larici-epitea f. sp. larici-epitea typica that colonized Salix viminalis and related clones. In a new breeding program that is based on a wider range of willow species it is necessary to identify further Melampsora species and formae specialis that are pathogens of willow species other than S. viminalis. Therefore, three stock collections with Salix daphnoides, Salix purpurea, and other shrub willow species (including S. viminalis) species were sampled in north-eastern Germany. A fourth stock collection in central Germany contributed rusts of tree willows (Salix fragilis and Salix alba) and the large shrub Salix caprea. Out of 156 rust samples, 149 were successfully sequenced for ITS rDNA. A phylogenetic analysis combining Neighbour-Joining, Maximum-Likelihood and Bayesian analysis revealed six species: Melampsora ribesii-purpureae, Melampsora allii-salicis-albae, Melampsora sp. aff. allii-fragilis, Melampsora larici-pentandrae, Melampsora larici-caprearum, and Melampsora larici-epitea. The first four species were found exclusively on the expected hosts. Melampsora larici-caprearum had a wider host range comprising S. caprea and S. viminalis hybrids. Melampsora larici-epitea can be further differentiated into two formae speciales. The forma specialis larici-epitea typica (59 samples) colonized Salix viminalis clones, Salix purpurea, Salix×dasyclados, and Salix×aquatica. In contrast to this relatively broad host range, f. sp. larici-daphnoides (65 samples) was found exclusively on Salix daphnoides. With the distinction and identification of the rust species/formae speciales it is now possible to test for race-specific resistances in a more targeted manner within the determined pairings of rust and willow species.