Biochemical and Gene Expression Analyses in Different Poplar Clones: The Selection Tools for Afforestation of Halomorphic Environments

Abstract

Halomorphic soils cover a significant area in the Vojvodina region and represent ecological and economic challenges for agricultural and forestry sectors. In this study, four economically important Serbian poplar clones were compared according to their biochemical and transcriptomic responses towards mild and severe salt stress to select the most tolerant clones for afforestation of halomorphic soils. Three prospective clones of Populus deltoides (Bora-B229, Antonije-182/81 and PE19/66) and one of hybrid genetic background P. nigraxP. deltoides, e.g., P. x euramericana (Pannonia-M1) were hydroponically subjected to NaCl as a salt stress agent in a concentration range from 150 mM to 450 mM. Plant responses were measured at different time periods in the leaves. Biochemical response of poplar clones to salt stress was estimated by tracking several parameters such as different radical scavenging capacities (estimated by DPPH, FRAP and ABTS assays), accumulation of total phenolic content and flavonoids. Furthermore, accumulation of two osmolytes, glycine betaine and proline, were quantified. The genetic difference of those clones has been already shown by single nucleotide polymorphisms (SNPs) but this paper emphasized their differences regarding biochemical and transcriptomic salt stress responses. Five candidate genes, two putative poplar homologues of GRAS family TFs (PtGRAS17 and PtGRAS16), PtDREB2 of DREB family TFs and two abiotic stress-inducible genes (PtP5SC1, PtSOS1), were examined for their expression profiles. Results show that most salt stress-responsive genes were induced in clones M1 and PE19/66, thus showing they can tolerate salt environments with high concentrations and could be efficient in phytoremediation of salt environments. Clone M1 and PE19/66 has ABA-dependent mechanisms expressing the PtP5CS1 gene while clone 182/81 could regulate the expression of the same gene by ABA-independent pathway. To improve salt tolerance in poplar, two putative GRAS/SCL TFs and PtDREB2 gene seem to be promising candidates for genetic engineering of salt-tolerant poplar clones.

Growth and Development of Short-Rotation Woody Crops for Rural and Urban Applications

“…Galović et al [4] used a forest health screening approach to test the variability among three hybrid poplar genotypes in their ability to tolerate salts in halomorphic soils such as those in the Vojvodina province in Serbia. The clones were hydroponically subjected to NaCl concentrations ranging from 150 to 450 mM, and biochemical responses were quantified in the leaves via estimation of radical scavenging capacities and accumulation of total phenolic content and flavonoids.…”

“…There are a total of 20 papers in the Special Issue representing 13 countries and four genera (Phalaris L., Populus L., Robinia L., Salix L.) (Figure 1; Table 1). In addition to the development and management of a Salix cultivar database [1], rural and urban applications represented in the Special Issue include: (a) forest buffers [2], (b) forest health screening [3,4], (c) phytoremediation [5][6][7], (d) short rotation coppice [8][9][10][11][12][13][14][15], (e) volume production [16][17][18], and (f) wastewater reuse [19,20] (Table 1). There were >130 genotypes from 27 genomic groups tested across all studies (Table 2), representing the importance of phyto-recurrent selection and other methods to choose clones for local and regional biomass production systems whose methodologies and approaches are relevant worldwide.…”

Responses to Drought Stress in Poplar: What Do We Know and What Can We Learn?

“…Drought avoidance strategies are particularly effective in trees, as they can generally rely on a high degree of phenotypic plasticity to adjust their morphological traits [ 18 , 19 , 20 ]. Tolerance mechanisms are aimed at maintaining biological functions under stress conditions; these encompass the accumulation of osmolytes (glycine betaine, proline, sugars) that help maintain water fluxes and cell turgor [ 21 , 22 ], the synthesis of molecules that exert a protective action on proteins and membranes as late embryogenesis abundant (LEA) proteins or proline, the expression of genes encoding ROS scavenging enzymes and aquaporins, channel proteins that contribute to water fluxes across membranes [ 23 , 24 ]. The deployment of avoidance and tolerance mechanisms is energetically costly and involves a trade-off between stress resilience and growth ( Figure 1 ).…”

In vitro culture initiation and regeneration of two highly productive clones of poplar

“…belong to the plants of the Salicaceae family, which are ecologically and economically important tree species. These fastgrowing trees are widely used for biofuel production, wood, pulp, and paper industries, environmental protection, and restoration of degraded soils (Gordon 2001;Pilipović et al 2019;Galović et al 2021). Poplars are also trees of great scientific importance due to ease of vegetative propagation, short rotation cycle, small genome size, and the ability to regenerate in vitro.…”