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    Topic review

    Arundo donax L.

    Subjects: Plant Sciences
    View times: 191
    Submitted by: Roberto PILU


    Arundo donax L., the giant reed—being a long-duration, low-cost, non-food energy crop able to grow in marginal lands—has emerged as a potential alternative to produce biomass for both energy production, with low carbon emissions, and industrial bioproducts.

    1. Introduction

    A. donax L. is a widespread species of unclear origin. This perennial grass grows spontaneously in temperate and tropical zones almost all over the world [1][2]. It can be found in ecosystems highly altered by anthropic activity and along riparian zones [3], where it often acts as an invasive weed reducing biodiversity [4], and brings an increased risk of wildfires and floods [5]. The roots can grow to 5 m in depth [1][6] and canes can reach 8–10 m in height and 3–4 cm in diameter (Figure 1). The leaves are flat, 5–8 cm wide and 30–100 cm long, inserted alternately in two ranks [1][7][8]. In southern Europe, new canes sprout continuously from rhizomes, starting in early March until August to November, when flowering takes place. Senescence follows in winter, with canes becoming yellow and generally losing leaves and inflorescences. Inflorescences are large plume-like panicles 30–100 cm long [7] that do not produce viable seeds [9][10][11][12][13].

    Figure 1. Crop field of A. donax L. for energy purposes in the third year of cultivation.

    Studies on A. donax L. sterility are often contradictory. In fact, this topic has yet to be clarified, since a drastic founder effect could explain this, rather than it being a consequence of defective chromosome pairing in aneuploid A. donax and A. micrantha Lam. [14]. At first glance, in A. donax, male and female gametogenesis fails right after meiosis. Following the megaspores’ mother cell formation at the tetrad stage, three chalazal megaspores degenerate, while one micropilar megaspore enlarges, develops a large nucleolus but no embryo sac, with the consequent proliferation of dysfunctional cells and the failure of ovule development. Pollen grains' cell walls usually collapse by autolysis, with the appearance of large numbers of vacuoles and variable numbers of nuclei and micronuclei. Despite this being the common result, the formation of a few viable pollen grains is reported with a frequency of 6.2% [14][15]. Meiosis occurs in less than 10% of microsporocytes, and no formation of exine occurs in the microsporangium [11]. A. donax sterility has been reported to be related to alterations in gametogenesis and fertilization and post-fertilization development [16]. A. donax sterility most likely has various causes that have led to its agamic propagation strategy. Reproduction is exclusively asexual and occurs through vegetative propagation [17][18] by fragmentation of rhizomes and cane fragments, which are dispersed by floods or by human activity [1][19].

    The worldwide spread of A. donax is related to several domestic and agricultural purposes such as the making of walking-sticks, baskets, mats, fishing rods, fences, plant stakes and musical instruments’ parts, especially the reeds for clarinets and saxophones [1][8][20][21]. A. donax is supposed to have spread from Asia, its native center, to America, passing through the Mediterranean area [15][22][23][24][25]. Other authors suggest that this plant originated in Mediterranean regions from native species [26]. At least four other species from the Arundo taxon are present in the Mediterranean area: A. plinii L., A. collina Ten., A. mediterranea, and A. micrantha Lam. [27][28]. Six lineages of A. donax are supposed to be distributed from Asia to the Mediterranean basin, with a putative area of origin in the Western and Southern edges of the Qinghai-Tibet Plateau [29]. The phylogenesis of A. donax is still debated, as the hypothesis that this species is polyploid or allopolyploid is shared by various authors based on its macroscopic traits, such as the great vegetative vigor and the absence of fertile seeds [12][13][30]. The literature data about the chromosome number of A. donax L. show some discrepancies, from an often-reported number of 108–110 chromosomes [12][30][31][32][33], to 84 chromosomes [13], or seed-producing cytotypes with 72 chromosomes, although this last result was published before the revised classification of the genus Arundo [28].

    Large-scale cultivation of A. donax was established between the 1930s and the 1960s in Northern Italy to produce the textile fiber Rayon, but after the Second World War, it became unsustainable due to the competition from petroleum-derived products [1][34]. Recently, the economic interest in this species has risen again and a considerable number of publications have dealt with different topics about this interesting crop: bioenergy, agronomy, invasiveness, and its use for phytoremediation [35]. The high yield in dry matter per hectare and the low inputs required for cultivation make A. donax a promising energy crop [8][36][37]. Chips and pellets for direct combustion are a practical solid fuel obtainable from A. donax [38], while other possibilities are gasification [39], second-generation bioethanol [40][41], and biogas for co-generation. For the last-named use, various experiments in northern Italy have promoted A. donax as an acceptable substitute of Zea mays L. in anaerobic digestion plants. Other potential benefits include biofuels [42][43], biocompounds for plastic polymers [44], green building technologies [45] and leaf protein concentrate as a feed ingredient [46].

    The capacity of A. donax to grow on marginal and abandoned lands makes this plant viable for cultivation on soil not suitable for traditional agriculture. Lands can be defined as marginal for different reasons, such as water scarcity, poor soil quality (e.g., high conductibility, low organic matter, etc.), and industrial pollution. On sandy loam soil (77% sand) with low organic matter content (1.2% organic matter) and low nutrients availability, the A. donax dry biomass yield was reported to be about 20 tha−1 [47]. This result was obtained with no irrigation, weeding or pest control. Taken together, these characteristics take this energy crop out of competition with food/feed cultures. Furthermore, A. donax has been classified as moderately salt tolerant with a 50% yield reduction at 11 dS m−1 salinity concentration [48]. Also, in this case, there is no competition with food-feed crops because, for these crops, the salinity concentrations determining 50% yield reduction are significantly lower, as in the case of corn (5.9 dS m−1) and rice (3.6 dS m−1) or similar as in the case of sugar cane (8–12 dS m−1). For sugar beets, it is reported a higher salt tolerance (15 dS m−1) but this culture requires a strong weeding control, irrigation and fertilization procedures.

    Marginal lands are growing worldwide due to anthropic activities, in fact secondary salinization affects 20% of irrigated land worldwide [49], and in Europe, the soil contaminated with heavy metals represent 6.24% (137,000 km2) of the total agricultural land [50]. This could mean an opportunity to cultivate energy crops environmental friendly such as A. donax in the near future.

    2. Genetic Engineering

    So far, to our knowledge, no transgenic A. donax plants with improved characteristics have been developed, possibly due to the limited regeneration of tissues and the absence of traits of interest well characterized at the molecular level. In any case, transient expression of GUS and GFP reporter genes is obtainable by an optimized particle bombardment protocol on Arundo donax callus cells. Important parameters to be taken into account include helium pressure, distance from stopping screen to target tissue, value of vacuum pressure, material and size of the microparticles, DNA concentration and number of bombardments. Higher efficiency in DNA transfer, resulting in 100–150 modification positive spots for explant, is achievable with cells bombarded twice at 1100 psi, with 9 cm target distance, 24 mm Hg vacuum pressure, 1 mm gold particle size, 1.5 µg DNA per bombardment, three days of pre-culture before the bombardment and six days of culture after bombardment. Bombardment with a GFP reporter gene resulted in higher expression than using GUS gene. The 35s promoter of CaMV can be used for the constructs, with hygromycin resistance to select modified cells [51]. Transformation of A. donax is also possible through protoplast manipulation. Starting from suspension culture, cell walls can be digested with a solution containing food-grade enzymes and 2–3 h incubation at 37 °C. The comparison among promoters highlighted that Ubi2 promoter from P. virgatum L. is a stronger promoter than CaMV 35S, with the second inducing low expression in A. donax. Trials with a different set-up of PEG-mediated transformation failed, while electroporation carried out at 130 V and 1000 μF resulted in a transformation efficiency of 3.3% ± 1.5% [52].

    The study of the A. donax genome is still a demanding research topic aimed at collecting knowledge needed for A. donax genetic improvement, since the lack of a high-quality reference genome sequence. A hybrid approach combining Illumina and long-read sequencing technologies, i.e., Pac Bio or Nanopore, could be used as previously reported for de novo sequencing in other crops [53][54]. In particular, the high-quality reference genome of Oryza longistaminata has been obtained incorporating Illumina and PacBio sequencing data [53], while the de novo genome sequence assembly of trifoliate yam (Dioscorea dumetorum) was the result of Illumina and Oxford Nanopore technologies [54].

    A parallel approach to identify putative target genes for A. donax genetic improvemt is the utilization of S. italica genome, the more related species that is actually sequenced. In fact, considering the lignin biosynthetic pathway genes, in particular PAL-like and CCoAMT-like genes, the high homology of four Mediterrean ecotypes of A. donax transcripts with S. italica L. [55] represent an important perspective for mining possible target sequences about this trait improvement by bioinformatics. A similar approach has been recently applied to isolate potential gene target to be used for genetic improvement of Miscantus × giganteus, a promising lignocellulosic biomass crop for biofuel production. Transcriptional analyses and phylogenetic and genome synteny analyses have allowed the identification of the major monolignol biosynthetic genes and the putative transcription factors regulating their expression [56] (Zeng et al. 2020).

    Different reviews have been published on genetic improvement of energy crops, but for the energy crops suitable for genetic transformation, such as swichgrass, important results in the improvement of energy production have been obtained by gene silencing [57][58] and CRISPR/CAS 9 (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR associated protein 9) [59] techniques. However, the data reported for A. donax are based on the results of agronomic studies with the aim of optimization of biomass quality.

    Currently, sequence databases and information on organs diversity and possible targets for improvement can be found in RNA-seq Illumina transcriptomics studies. Gene Ontology Analysis of metabolic differences among bud, culm, leaf and root tissues highlighted that the most variety can be found in the leaves, most notably for light, osmotic, salt and metal stress response, and for primary and secondary metabolites production [60]. About 40–45% of transcripts showed homologies with known sequences and functional annotations of Oryza sativa L., Triticum aestivum L. and mostly with S. bicolor L. and Z. mays L., most importantly for gene categories related to flowering time, plant height and structure, carbohydrates composition and vernalization response. CCoAMT-like genes deserve particular attention for their possible role in obtaining mutants with decreased content of lignin in culms [60]. The response of A. donax to low oxygen stress analyzed by a metabolomic approach [61] provided numerous insights required to target functional genes by transcriptomics.

    About the well-known A. donax tolerance to low soil quality, RNA-seq provided insights of the available defenses from adverse soil conditions. Considering the excess of Ni and Cu, doses of 25–100 mg/L activated the expression of a metal-uptake YSL-like gene and a macrophage protein which was NRAMP-like [62]. Adjustments in phytochelatin synthases expression could represent a reliable strategy to increase A. donax uptake of metalloid contaminants with the purpose of phytoremediation. With an RNA-seq methodology, three putative genes, AdPCS1-3 have been identified in A. donax. The expression of these three genes in response to CdSO4 stress was tissue specific, with AdPCS1 the most up-regulated compared with control. However, the production of Arabidopsis thaliana L. transgenic lines overexpressing these genes resulted in deleterious effects on growth, with necrotic effect, while the same strategy applied to yeast resulted in Cd-tolerant lines [63]. The responses to salt stress and salt tolerance are other important traits investigated by RNA-seq with improvement purposes. Different ecotypes exhibited a possible positive correlation of salt exposure with the expression of stress-induced transcription factors DREB2A-like and WRKY53-like, activation of detoxification processes and abscisic acid increase. Moreover, a fast response to salt stress, with overexpression of ion transporters and K+/Na+ homeostasis-related genes, such as SOS1-like, NHX1-like or KHT1-like, represents an effort to reduce the ionic stress, but was detrimental to the growth performance [64][65]. A RNASeq analysis [66] conducted under long-term salt stress allowed the identification of differentially expressed genes with a dose-dependent response. The analysis was performed on a total 38,559 DEGs (differentially expressed genes) and among them, 2086 were up-regulated and 1766 were down-regulated.

    In particular, it is reported the analysis of clusters related to salt sensory and signaling, hormone regulation, transcription factors, Reactive Oxygen Species (ROS) scavenging, osmolyte biosynthesis and biomass production. Several unigenes identified have the potential to be used to improve productivity and stress tolerance in A. donax. In particular, the silencing of the GTL1 gene (a homolog of Setaria italica trihelix transcription factor) acting as a negative regulator of water use efficiency could be a good target for NBT (new breeding techniques).

    This entry is adapted from 10.3390/plants9111584


    1. Perdue, R.E. Arundo donax—Source of musical reeds and industrial cellulose. Econ. Bot. 1958, 12, 368–404.
    2. Faix, O.; Meier, D.; Beinhoff, O. Analysis of lignocelluloses and lignins from Arundo donax L. and Miscanthus sinensis Anderss., and hydroliquefaction of Miscanthus. Biomass 1989, 18, 109–126.
    3. Coffman, G.C.; Ambrose, R.F.; Rundel, P.W. Wildfire promotes dominance of invasive giant reed (Arundo donax) in riparian ecosystems. Biol. Invasions 2010, 12, 2723–2734.
    4. Osbrink, W.; A Goolsby, J.; Thomas, D.B.; Mejorado, A.; Showler, A.T.; de León, A.P. Higher Ant Diversity in Native Vegetation Than in Stands of the Invasive Arundo, Arundo donax L., Along the Rio Grande Basin in Texas, USA. Int. J. Insect Sci. 2017, 9, 1–9.
    5. Quinn, L.D.; Holt, J.S. Ecological correlates of invasion by Arundo donax in three southern California riparian habitats. Biol. Invasions 2007, 10, 591–601.
    6. Frandsen, P.R. Team Arundo: Interagency Cooperation to Control Giant Cane (Arundo donax). In Springer Series on Environmental Management; Springer Science and Business Media LLC: Berlin/Heidelberg, Germany, 1997; pp. 244–248.
    7. Tucker, G.C.; Gordon, C. The genera of Arundinoideae (Graminaeae) in Southeastern United States. J. Arnold Arboretum 1990, 71, 145–717.
    8. Pilu, R.; Manca, A.; Landoni, M. Arundo donax as an energy crop: Pros and cons of the utilization of this perennial plant. Maydica 2013, 58, 54–59.
    9. Bell, G. Ecology and Management of Arundo donax, and Approaches to Riparian Habitat Restoration in Southern California, Plant Invasions: Studies from North America and Europe; Brock, J.H., Wade, M., Pysek, P., Green, D., Eds.; Blackhuys Publishers: Leiden, The Netherlands, 1997; pp. 103–113.
    10. Di Tomaso, J.M.; Healey, E.A. Aquatic and riparian weeds of the west, University of California. Div. Agric. Nat. Res. 2003, 3421, 254–262.
    11. Balogh, E.; Herr, J.M.; Czakó, M.; Márton, L. Defective development of male and female gametophytes in Arundo donax L. (POACEAE). Biomass Bioenergy 2012, 45, 265–269.
    12. Bucci, A.; Cassani, E.; Landoni, M.; Cantaluppi, E.; Pilu, R. Analysis of chromosome number and speculations on the origin of Arundo donax L. (Giant Reed). Cytol. Genet. 2013, 47, 237–241.
    13. Haddadchi, A.; Gross, C.L.; Fatemi, M. The expansion of sterile Arundo donax (Poaceae) in southeastern Australia is accompanied by genotypic variation. Aquat. Bot. 2013, 104, 153–161.
    14. Hardion, L.; Verlaque, R.; Rosato, M.; A Rossello, J.; Vila, B. Impact of polyploidy on fertility variation of Mediterranean Arundo L. (Poaceae). Comptes Rendus Biol. 2015, 338, 298–306.
    15. Mariani, C.; Cabrini, R.; Danin, A.; Piffanelli, P.; Fricano, A.; Gomarasca, S.; di Candilo, M.; Grassi, F.; Soave, C. Origin, diffusion and reproduction of the giant reed (Arundo donax L.): A promising weedy energy crop. Ann. Appl. Biol. 2010, 157, 191–202.
    16. Makde, C.A.N. Reproductive Behavior of Arundo donax L. Int. J. Res. Biosci. Agric. Technol. 2014, II.
    17. Decruyenaere, J.G.; Holt, J.S. Seasonality of clonal propagation in giant reed. Weed Sci. 2001, 49, 760–767.
    18. Ceotto, E.; di Candilo, M. Shoot cuttings propagation of giant reed (Arundo donax L.) in water and moist soil: The path forward? Biomass Bioenergy 2010, 34, 1614–1623.
    19. Boland, J.M. The importance of layering in the rapid spread of Arundo donax (Giant Reed). Madroño 2006, 53, 303–312.
    20. Hanson, H.C.; Zohary, M. Plant Life of Palestine, Israel, and Jordan. J. Range Manag. 1962, 15, 339.
    21. Arcidiacono, S.; Costa, R.; Marletta, G.; Pavone, P.; Napoli, M. Usi popolari delle piante selvatiche nel territorio di Villarosa (EN—Sicilia Centrale). Quad. Bot. Amb. Appl. 2010, 21, 95–118.
    22. Polunin, O.; Huxley, A. Flowers of the Mediterranean; Hogarth Press: London, UK, 1987.
    23. Lewandowski, I.; Scurlock, J.M.; Lindvall, E.; Christou, M. The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe. Biomass Bioenergy 2003, 25, 335–361.
    24. Ahmad, R.; Liow, P.-S.; Spencer, D.F.; Jasieniuk, M. Molecular evidence for a single genetic clone of invasive Arundo donax in the United States. Aquat. Bot. 2008, 88, 113–120.
    25. Hardion, L.; Verlaque, R.; Saltonstall, K.; Leriche, A.; Vila, B. Origin of the invasive Arundo donax (Poaceae): A trans-Asian expedition in herbaria. Ann. Bot. 2014, 114, 455–462.
    26. Zeven, A.C.; Wet, J.M.J. Dictionary of Cultivated Plants and Their Regions of Diversity; Hudoc: Wageningen, The Netherlands, 1982.
    27. Danin, A. Arundo (Gramineae) in the Mediterranean reconsidered. Willdenowia 2004, 34, 361.
    28. Hardion, L.; Verlaque, R.; Baumel, A.; Juin, M.; Vila, B. Revised systematics of Mediterranean Arundo (Poaceae) based on AFLP fingerprints and morphology. Taxon 2012, 61, 1217–1226.
    29. Zecca, G.; Tommasi, N.; Grassi, F. Multiple evolutionary lineages detected in giant reed (Arundo donax L.): Applied and evolutionary perspectives. Ann. Appl. Biol. 2020, 176, 285–295.
    30. Pizzolongo, P. Osservazioni cariologiche su Arundo donax e Arundo plinii. Annuali Bot. 1962, 27, 173–187.
    31. Hunter, A.W.S. A Karyosystematic investigation in Gramineae. Can. J. Res. 1934, 11, 213–241.
    32. Christopher, J.; Abraham, A. Studies on the Cytology and Phylogeny of South Indian Grasses. Cytolpgia 1971, 36, 579–594.
    33. Hardion, L.; Verlaque, R.; Fridlender, A.; Vila, B. Arundo. IAPT/IOPB chromosome data 11. Taxon 2011, 60, 1221.
    34. Facchini, P. La Canna Gentile per la Produzione della Cellulosa Nobile, l’impresa Agricolo Industriale di Torviscosa; Snia Viscosa: Milano, Italy, 1941.
    35. Jambor, A.; Török, Á. The Economics of Arundo donax—A Systematic Literature Review. Sustainability 2019, 11, 4225.
    36. Angelini, L.G.; Ceccarini, L.; Bonari, E. Biomass yield and energy balance of giant reed (Arundo donax L.) cropped in central Italy as related to different management practices. Eur. J. Agron. 2005, 22, 375–389.
    37. Angelini, L.G.; Ceccarini, L.; di Nasso, N.N.; Bonari, E. Comparison of Arundo donax L. and Miscanthus x giganteus in a long-term field experiment in Central Italy: Analysis of productive characteristics and energy balance. Biomass Bioenergy 2009, 33, 635–643.
    38. Dahl, J.; Obernberger, I. Evaluation of the combustion characteristics of four perennial energy crops (Arundo donax, Cynara cardanculus, Miscanthus x Giganteus and Panicum virgatum). In Proceedings of the 2nd World Conference on Biomass for Energy, Industry and Climate Protection, Rome, Italy, 10–14 May 2004.
    39. Jeguirim, M.; Trouvé, G. Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis. Bioresour. Technol. 2009, 100, 4026–4031.
    40. Jeon, Y.J.; Xun, Z.; Rogers, P.L. Comparative evaluations of cellulosic raw materials for second generation bioethanol production. Lett. Appl. Microbiol. 2010, 51, 518–524.
    41. Adani, F.; Papa, G.; Schievano, A.; Cardinale, G.; D’Imporzano, G.; Tambone, F. Nanoscale Structure of the Cell Wall Protecting Cellulose from Enzyme Attack. Environ. Sci. Technol. 2011, 45, 1107–1113.
    42. Galletti, A.M.R.; Antonetti, C.; Ribechini, E.; Colombini, M.P.; di Nasso, N.N.; Bonari, E. From giant reed to levulinic acid and gamma-valerolactone: A high yield catalytic route to valeric biofuels. Appl. Energy 2013, 102, 157–162.
    43. Corno, L.; Pilu, R.; Adani, F. Arundo donax L.: A non-food crop for bioenergy and bio-compound production. Biotechnol. Adv. 2014, 32, 1535–1549.
    44. Fiore, V.; Scalici, T.; Valenza, A. Characterization of a new natural fiber from Arundo donax L. as potential reinforcement of polymer composites. Carbohydr. Polym. 2014, 106, 77–83.
    45. Carneiro, P.; Jerónimo, A.; Silva, V.; Cartaxo, F.; Faria, P. Improving Building Technologies with a Sustainable Strategy. Proc. Soc. Behav. Sci. 2016, 216, 829–840.
    46. Carlsson, R. Trends for future applications of wet fractionation of green crops. In Proceedings of the Commission of the European Communities Forage Protein Conservation and Utilization Seminar, Dublin, Ireland, 15–18 September 1982.
    47. Di Nasso, N.; Roncucci, N.; Bonari, E. Seasonal dynamics of aboveground and belowgrownd biomass and nutrient accumulation and remobilization in giant reed (Arundo donax L.): A three-year study on marginal land. Bioenergy Res. 2013, 6, 725–736.
    48. Nackley, L.L.; Kim, S.-H. A salt on the bioenergy and biological invasions debate: Salinity tolerance of the invasive biomass feed stock Arundo donax. GCB Bioenergy 2014, 7, 752–762.
    49. Mayak, S.; Tirosh, T.; Glick, B.R. Plant growth-promoting bacteria confer resistance in tomato plants to salt stress. Plant Physiol. Biochem. 2004, 42, 565–572.
    50. Tóth, G.; Hermann, T.; da Silva, M.; Montanarella, L. Heavy metals in agricultural soils of the European Union with implications for food safety. Environ. Int. 2016, 88, 299–309.
    51. Dhir, S.; Knowles, K.; Pagan, C.L.; Mann, J.; Dhir, S. Optimization and transformation of Arundo donax L. using particle bombardment. Afr. J. Biotechnol. 2010, 9, 6460–6469.
    52. Pigna, G.; Dhillon, T.; Dlugosz, E.M.; Yuan, J.S.; Gorman, C.; Morandini, P.; Lenaghan, S.C.; Stewart, C.N. Methods for suspension culture, protoplast extraction, and transformation of high-biomass yielding perennial grass Arundo donax. Biotechnol. J. 2016, 11, 1657–1666.
    53. Li, W.; Li, K.; Zhang, Q.; Zhu, T.; Zhang, Y.; Shi, C.; Liu, Y.; Xia, E.; Jiang, J.; Shi, C. Improved hybrid de novo assembly and annotation of African wild rice, Oriza longistaminata, from Illumina and PacBio sequencing reads. Plant Genome 2020, 13, e20001.
    54. Siadjeu, C.; Pucker, B.; Viehover, P.; Albach, D.; Weisshaar, B. High contiguity de novo genome sequence assembly of trifoliate yam (Discorea dumetorum) using long read sequencing. Genes 2020, 11, 274.
    55. Evangelistella, C.; Valentini, A.; Ludovisi, R.; Firrincieli, A.; Fabbrini, F.; Scalabrin, S.; Cattonaro, F.; Morgante, M.; Mugnozza, G.S.; Keurentjes, J.J.B.; et al. De novo assembly, functional annotation, and analysis of the giant reed (Arundo donax L.) leaf transcriptome provide tools for the development of a biofuel feedstock. Biotechnol. Biofuels 2017, 10, 138.
    56. Zeng, X.; Sheng, J.; Zhu, F.; Wei, T.; Zhao, L.; Hu, X.; Zheng, X.; Zhou, F.; Hu, Z.; Diao, Y.; et al. Genetic, transcriptional, and regulatory landscape of monolignol biosynthesis pathway in Miscantus x giganteus. Biotechnol. Biofuels 2020, 13, 179
    57. Fu, C.; Xiao, X.; Xi, Y.; Ge, Y.; Chen, F.; Bouton, J.; Dixon, R.A.; Wang, Z.-Y. Downregulation of Cinnamyl Alcohol Dehydrogenase (CAD) Leads to Improved Saccharification Efficiency in Switchgrass. BioEnergy Res. 2011, 4, 153–164.
    58. Xu, B.; Escamilla-Treviño, L.L.; Sathitsuksanoh, N.; Shen, Z.; Shen, H.; Zhang, Y.-H.P.; Dixon, R.A.; Zhao, B. Silencing of 4-coumarate:coenzyme A ligase in switchgrass leads to reduced lignin content and improved fermentable sugar yields for biofuel production. New Phytol. 2011, 192, 611–625.
    59. Park, J.-J.; Yoo, C.G.; Flanagan, A.; Pu, Y.; Debnath, S.; Geun, Y.C.; Ragauskas, A.J.; Wang, Z.-Y. Defined tetra-allelic gene disruption of the 4-coumarate:coenzyme A ligase 1 (Pv4CL1) gene by CRISPR/Cas9 in switchgrass results in lignin reduction and improved sugar release. Biotechnol. Biofuels 2017, 10, 1–11.
    60. Sablok, G.; Fu, Y.; Bobbio, V.; Laura, M.; Rotino, G.L.; Bagnaresi, P.; Allavena, A.; Velikova, V.; Viola, R.; Loreto, F.; et al. Fuelling genetic and metabolic exploration of C 3 bioenergy crops through the first reference transcriptome of A rundo donax L. Plant Biotechnol. J. 2014, 12, 554–567.
    61. Scartazza, A.; Vita, F.; Alpi, A.; Guglielminetti, L. Arundo donax L. response to low oxygen stress. Environ. Exp. Bot. 2015, 111, 147–154.
    62. Shaheen, S.; Ahmad, R.; Mahmood, Q.; Pervez, A.; Shah, M.M.; Hafeez, F. Gene expression and biochemical response of giant reed under Ni and Cu stress. Int. J. Phytoremediat. 2019, 21, 1474–1485.
    63. Shiliang, H.; Stragliati, L.; Bellini, E.; Ricci, A.; Saba, A.; di Toppi, L.S.; Varotto, C. Evolution and functional differentiation of recently diverged phytochelatin synthase genes from Arundo donax L. J. Exp. Bot. 2019, 70, 5391–5405.
    64. Docimo, T.; de Stefano, R.; de Palma, M.; Cappetta, E.; Villano, C.; Aversano, R.; Tucci, M. Transcriptional, metabolic and DNA methylation changes underpinning the response of Arundo donax ecotypes to NaCl excess. Planta 2019, 251.
    65. Sicilia, A.; Santoro, D.F.; Testa, G.; Cosentino, S.L.; Piero, A.R.L. Transcriptional response of giant reed (Arundo donax L.) low ecotype to long-term salt stress by unigene-based RNAseq. Phytochemistry 2020, 177, 112436.
    66. Sicilia, A.; Testa, G.; Santoro, D.F.; Cosentino, S.L.; Piero, A.R.L. RNASeq analysis of giant cane reveals the leaf transcriptome dynamics under long-term salt stress. BMC Plant Biol. 2019, 19, 1–24.