Successful use of woody species in reducing climatic and environmental risks of energy shortage and spreading pollution requires deeper understanding of the physiological functions controlling biomass productivity and phytoremediation efficiency. Targets in the breeding of energy willow include the size and the functionality of the root system. For the combination of polyploidy and heterosis, we have generated triploid hybrids (THs) of energy willow by crossing autotetraploid willow plants with leading cultivars (Tordis and Inger). These novel Salix genotypes (TH3/12, TH17/17, TH21/2) have provided a unique experimental material for characterization of Mid-Parent Heterosis (MPH) in various root traits. Using a root phenotyping platform, we detected heterosis (TH3/12: MPH 43.99%; TH21/2: MPH 26.93%) in the size of the root system in soil. Triploid heterosis was also recorded in the fresh root weights, but it was less pronounced (MPH%: 9.63-19.31). In agreement with root growth characteristics in soil, the TH3/12 hybrids showed considerable heterosis (MPH: 70.08%) under in vitro conditions. Confocal microscopy-based imaging and quantitative analysis of root parenchyma cells at the division-elongation transition zone showed increased average cell diameter as a sign of cellular heterosis in plants from TH17/17 and TH21/2 triploid lines. Analysis of the hormonal background revealed that the auxin level was seven times higher than the total cytokinin contents in root tips of parental Tordis plants. In triploid hybrids, the auxin-cytokinin ratios were considerably reduced in TH3/12 and TH17/17 roots. In particular, the contents of cytokinin precursor, such as isopentenyl adenosine monophosphate, were elevated in all three triploid hybrids. Heterosis was also recorded in the amounts of active gibberellin precursor, GA19, in roots of TH3/12 plants. The presented experimental findings highlight the physiological basics of triploid heterosis in energy willow roots.

Hungarian Centre of Excellence for Molecular Medicine Nonprofit Ltd 6728 Szeged Hungary

Institute of Experimental Botany Czech Academy of Sciences 165 02 Prague Czech Republic

Institute of Plant Biology HUN REN Biological Research Centre 6726 Szeged Hungary

Laboratory of Cellular Imaging HUN REN Biological Research Centre 6726 Szeged Hungary

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Clifton-Brown J., Harfouche A., Casler M.D., Dylan Jones H., Macalpine W.J., Murphy-Bokern D., Smart L.B., Adler A., Ashman C., Awty-Carroll D., et al. Breeding Progress and Preparedness for Mass-Scale Deployment of Perennial Lignocellulosic Biomass Crops Switchgrass, Miscanthus, Willow and Poplar. GCB Bioenergy. 2019;11:118–151. doi: 10.1111/gcbb.12566. PubMed DOI PMC

De Kam M.J., Vance Morey R., Tiffany D.G. Biomass Integrated Gasification Combined Cycle for Heat and Power at Ethanol Plants. Energy Convers. Manag. 2009;50:1682–1690. doi: 10.1016/j.enconman.2009.03.031. DOI

Dias G.M., Ayer N.W., Kariyapperuma K., Thevathasan N., Gordon A., Sidders D., Johannesson G.H. Life Cycle Assessment of Thermal Energy Production from Short-Rotation Willow Biomass in Southern Ontario, Canada. Appl. Energy. 2017;204:343–352. doi: 10.1016/j.apenergy.2017.07.051. DOI

Dey P., Pal P., Kevin J.D., Das D.B. Lignocellulosic Bioethanol Production: Prospects of Emerging Membrane Technologies to Improve the Process—A Critical Review. Rev. Chem. Eng. 2020;36:333–367. doi: 10.1515/revce-2018-0014. DOI

Gaykawad S.S., Zha Y., Punt P.J., van Groenestijn J.W., van der Wielen L.A.M., Straathof A.J.J. Pervaporation of Ethanol from Lignocellulosic Fermentation Broth. Bioresour. Technol. 2013;129:469–476. doi: 10.1016/j.biortech.2012.11.104. PubMed DOI

Ahmadi Moghaddam E., Ericsson N., Hansson P.A., Nordberg Å. Exploring the Potential for Biomethane Production by Willow Pyrolysis Using Life Cycle Assessment Methodology. Energy Sustain. Soc. 2019;9:6. doi: 10.1186/s13705-019-0189-0. DOI

Kakuk B., Bagi Z., Rákhely G., Maróti G., Dudits D., Kovács K.L. Methane Production from Green and Woody Biomass Using Short Rotation Willow Genotypes for Bioenergy Generation. Bioresour. Technol. 2021;333:125223. doi: 10.1016/j.biortech.2021.125223. PubMed DOI

Tangahu B.V., Sheikh Abdullah S.R., Basri H., Idris M., Anuar N., Mukhlisin M. A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation. Int. J. Chem. Eng. 2011;2011:939161. doi: 10.1155/2011/939161. DOI

Capuana M. A Review of the Performance of Woody and Herbaceous Ornamental Plants for Phytoremediation in Urban Areas. Iforest-Biogeosci. For. 2020;13:139–151. doi: 10.3832/ifor3242-013. DOI

Hauptvogl M., Kotrla M., Prčík M., Pauková Ž., Kováčik M., Lošák T. Phytoremediation Potential of Fast-Growing Energy Plants: Challenges and Perspectives—A Review. Pol. J. Environ. Stud. 2020;29:505–516. doi: 10.15244/pjoes/101621. PubMed DOI

Marmiroli M., Pietrini F., Maestri E., Zacchini M., Marmiroli N., Massacci A. Growth, Physiological and Molecular Traits in Salicaceae Trees Investigated for Phytoremediation of Heavy Metals and Organics. Tree Physiol. 2011;31:1319–1334. doi: 10.1093/treephys/tpr090. PubMed DOI

Wani K.A., Sofi Z.M., Malik J.A., Wani J.A. Bioremediation and Biotechnology. Volume 2. Springer; Berlin/Heidelberg, Germany: 2020. Phytoremediation of Heavy Metals Using Salix (Willows) pp. 161–174.

Feng X., Xu S., Li J., Yang Y., Chen Q., Lyu H., Zhong C., He Z., Shi S. Molecular Adaptation to Salinity Fluctuation in Tropical Intertidal Environments of a Mangrove Tree Sonneratia Alba. BMC Plant Biol. 2020;20:178. doi: 10.1186/s12870-020-02395-3. PubMed DOI PMC

Hanley S.J., Karp A. Genetic Strategies for Dissecting Complex Traits in Biomass Willows (Salix spp.) Tree Physiol. 2014;34:1167–1180. doi: 10.1093/treephys/tpt089. PubMed DOI

Kulig B., Gacek E., Wojciechowski R., Oleksy A., Kołodziejczyk M., Szewczyk W., Klimek-Kopyra A. Biomass Yield and Energy Efficiency of Willow Depending on Cultivar, Harvesting Frequency and Planting Density. Plant Soil Environ. 2019;65:377–386. doi: 10.17221/594/2018-PSE. DOI

Isebrands J., Richardson J. Poplars and Willows: Trees for Society and the Environment. CABI; Wallingford, UK: 2014.

Suda Y., Argus G.W. Chromosome Numbers of Some North American Salix. Brittonia. 1968;20:191–197. doi: 10.2307/2805440. DOI

Serapiglia M.J., Gouker F.E., Smart L.B. Early Selection of Novel Triploid Hybrids of Shrub Willow with Improved Biomass Yield Relative to Diploids. BMC Plant Biol. 2014;14:74. doi: 10.1186/1471-2229-14-74. PubMed DOI PMC

Carlson C.H., Smart L.B. Heterosis for Biomass-Related Traits in Interspecific Triploid Hybrids of Willow (Salix spp.) Bioenergy Res. 2021;15:1042–1056. doi: 10.1007/s12155-021-10305-0. DOI

Cheng S., Zhu X., Liao T., Li Y., Yao P., Suo Y., Zhang P., Wang J., Kang X. Gene Expression Differences between High-Growth Populus Allotriploids and Their Diploid Parents. Forests. 2015;6:839. doi: 10.3390/f6030839. DOI

Tracy S.R., Nagel K.A., Postma J.A., Fassbender H., Wasson A., Watt M. Crop Improvement from Phenotyping Roots: Highlights Reveal Expanding Opportunities. Trends Plant Sci. 2020;25:105–118. doi: 10.1016/j.tplants.2019.10.015. PubMed DOI

Hund A., Reimer R., Stamp P., Walter A. Can We Improve Heterosis for Root Growth of Maize by Selecting Parental Inbred Lines with Different Temperature Behaviour? Philos. Trans. R. Soc. B Biol. Sci. 2012;367:1580–1588. doi: 10.1098/rstb.2011.0242. PubMed DOI PMC

Liu Z., Liu X., Craft E.J., Yuan L., Cheng L., Mi G., Chen F. Physiological and Genetic Analysis for Maize Root Characters and Yield in Response to Low Phosphorus Stress. Breed Sci. 2018;68:268–277. doi: 10.1270/jsbbs.17083. PubMed DOI PMC

Ruiz M., Oustric J., Santini J., Morillon R. Synthetic Polyploidy in Grafted Crops. Front. Plant Sci. 2020;11:540894. doi: 10.3389/fpls.2020.540894. PubMed DOI PMC

Yao H., Gray A.D., Auger D.L., Birchler J.A. Genomic Dosage Effects on Heterosis in Triploid Maize. Proc. Natl. Acad. Sci. USA. 2013;110:2665–2669. doi: 10.1073/pnas.1221966110. PubMed DOI PMC

Hallahan B.F., Fernandez-Tendero E., Fort A., Ryder P., Dupouy G., Deletre M., Curley E., Brychkova G., Schulz B., Spillane C. Hybridity Has a Greater Effect than Paternal Genome Dosage on Heterosis in Sugar Beet (β vulgaris) BMC Plant Biol. 2018;18:120. doi: 10.1186/s12870-018-1338-x. PubMed DOI PMC

Das S.K., Sabhapondit S., Ahmed G., Das S. Biochemical Evaluation of Triploid Progenies of Diploid × Tetraploid Breeding Populations of Camellia for Genotypes Rich in Catechin and Caffeine. Biochem. Genet. 2013;51:358–376. doi: 10.1007/s10528-013-9569-x. PubMed DOI

Dudits D., Török K., Cseri A., Paul K., Nagy A.V., Nagy B., Sass L., Ferenc G., Vankova R., Dobrev P., et al. Response of Organ Structure and Physiology to Autotetraploidization in Early Development of Energy Willow Salix viminalis. Plant Physiol. 2016;170:1504–1523. doi: 10.1104/pp.15.01679. PubMed DOI PMC

Cseri A., Borbély P., Poór P., Fehér A., Sass L., Jancsó M., Penczi A., Rádi F., Gyuricza C., Digruber T., et al. Increased Adaptation of an Energy Willow Cultivar to Soil Salinity by Duplication of Its Genome Size. Biomass Bioenergy. 2020;140:105655. doi: 10.1016/j.biombioe.2020.105655. DOI

Dudits D., Cseri A., Török K., Sass L., Zombori Z., Ferenc G., Poór P., Borbély P., Czékus Z., Vankova R., et al. Triploid Hybrid Vigor in Above-Ground Growth and Methane Fermentation Efficiency of Energy Willow. Front. Plant Sci. 2022;13:770284. doi: 10.3389/fpls.2022.770284. PubMed DOI PMC

Schindelin J., Arganda-Carreras I., Frise E., Kaynig V., Longair M., Pietzsch T., Preibisch S., Rueden C., Saalfeld S., Schmid B., et al. Fiji: An Open-Source Platform for Biological-Image Analysis. Nat. Methods. 2012;9:676–682. doi: 10.1038/nmeth.2019. PubMed DOI PMC

Ivanov Dobrev P., Kamínek M. Fast and Efficient Separation of Cytokinins from Auxin and Abscisic Acid and Their Purification Using Mixed-Mode Solid-Phase Extraction. J. Chromatogr. A. 2002;950:21–29. doi: 10.1016/S0021-9673(02)00024-9. PubMed DOI

Dobrev P.I., Vankova R. Plant Salt Tolerance: Methods in Molecular Biology. Volume 913. Springer; Berlin/Heidelberg, Germany: 2012. Quantification of Abscisic Acid, Cytokinin, and Auxin Content in Salt-Stressed Plant Tissues. PubMed DOI

Zhang Y., Wang B., Qi S., Dong M., Wang Z., Li Y., Chen S., Li B., Zhang J. Ploidy and Hybridity Effects on Leaf Size, Cell Size and Related Genes Expression in Triploids, Diploids and Their Parents in Populus. Planta. 2019;249:635–646. doi: 10.1007/s00425-018-3029-0. PubMed DOI

Du K., Liao T., Ren Y., Geng X., Kang X. Molecular Mechanism of Vegetative Growth Advantage in Allotriploid Populus. Int. J. Mol. Sci. 2020;21:441. doi: 10.3390/ijms21020441. PubMed DOI PMC

Liu Z., Jiang J., Ren A., Xu X., Zhang H., Zhao T., Jiang X., Sun Y., Li J., Yang H. Heterosis and Combining Ability Analysis of Fruit Yield, Early Maturity, and Quality in Tomato. Agronomy. 2021;11:807. doi: 10.3390/agronomy11040807. DOI

Alarcon M.V., Salguero J. Transition Zone Cells Reach G2 Phase before Initiating Elongation in Maize Root Apex. Biol. Open. 2017;6:909–913. doi: 10.1242/bio.025015. PubMed DOI PMC

Perilli S., Di Mambro R., Sabatini S. Growth and Development of the Root Apical Meristem. Curr. Opin. Plant Biol. 2012;15:17–23. doi: 10.1016/j.pbi.2011.10.006. PubMed DOI

Pavlikova E., Rood S.B. Cellular basis of heterosis for leaf area in maize. Can. J. Plant Sci. 1987;67:99–104. doi: 10.4141/cjps87-011. DOI

Saini S., Sharma I., Kaur N., Pati P.K. Auxin: A Master Regulator in Plant Root Development. Plant Cell Rep. 2013;32:741–757. doi: 10.1007/s00299-013-1430-5. PubMed DOI

Korasick D.A., Enders T.A., Strader L.C. Auxin Biosynthesis and Storage Forms. J. Exp. Bot. 2013;64:2541–2555. doi: 10.1093/jxb/ert080. PubMed DOI PMC

Noah A.M., Casanova-Sáez R., Ango R.E.M., Antoniadi I., Karady M., Novák O., Niemenak N., Ljung K. Dynamics of Auxin and Cytokinin Metabolism during Early Root and Hypocotyl Growth in Theobroma Cacao. Plants. 2021;10:967. doi: 10.3390/plants10050967. PubMed DOI PMC

Su Y.H., Liu Y.B., Zhang X.S. Auxin-Cytokinin Interaction Regulates Meristem Development. Mol. Plant. 2011;4:616–625. doi: 10.1093/mp/ssr007. PubMed DOI PMC

Chapman E.J., Estelle M. Mechanism of Auxin-Regulated Gene Expression in Plants. Annu. Rev. Genet. 2009;43:265–285. doi: 10.1146/annurev-genet-102108-134148. PubMed DOI

Dello Ioio R., Nakamura K., Moubayidin L., Perilli S., Taniguchi M., Morita M.T., Aoyama T., Costantino P., Sabatini S. A Genetic Framework for the Control of Cell Division and Differentiation in the Root Meristem. Science. 2008;322:1380–1384. doi: 10.1126/science.1164147. PubMed DOI

Takei K., Sakakibara H., Taniguchi M., Sugiyama T. Nitrogen-Dependent Accumulation of Cytokinins in Root and the Translocation to Leaf: Implication of Cytokinin Species That Induces Gene Expression of Maize Response Regulator. Plant Cell Physiol. 2001;42:85–93. doi: 10.1093/pcp/pce009. PubMed DOI

Barker R., Fernandez Garcia M.N., Powers S.J., Vaughan S., Bennett M.J., Phillips A.L., Thomas S.G., Hedden P. Mapping Sites of Gibberellin Biosynthesis in the Arabidopsis Root Tip. New Phytol. 2021;229:1521–1534. doi: 10.1111/nph.16967. PubMed DOI

Li X., Chen L., Forde B.G., Davies W.J. The Biphasic Root Growth Response to Abscisic Acid in Arabidopsis Involves Interaction with Ethylene and Auxin Signalling Pathways. Front. Plant Sci. 2017;8:1493. doi: 10.3389/fpls.2017.01493. PubMed DOI PMC

Pasternak T., Groot E.P., Kazantsev F.V., Teale W., Omelyanchuk N., Kovrizhnykh V., Palme K., Mironova V.V. Salicylic Acid Affects Root Meristem Patterning via Auxin Distribution in a Concentration-Dependent Manner. Plant Physiol. 2019;180:1725–1739. doi: 10.1104/pp.19.00130. PubMed DOI PMC

Xu P., Zhao P.X., Cai X.T., Mao J.L., Miao Z.Q., Xiang C. Bin Integration of Jasmonic Acid and Ethylene into Auxin Signaling in Root Development. Front. Plant Sci. 2020;11:271. doi: 10.3389/fpls.2020.00271. PubMed DOI PMC