Candidate gene association studies implicate the detection of contributing single nucleotide polymorphism (SNP) for the target traits and have been recommended as a promising technique to anatomize the complex characters in plants. ERECTA gene in plants controls different physiological functions. In this study, we identified SNPs in 1.1 kb partial sequences of TaER-1 and TaER-2 of wheat (Triticum aestivum L.). Thirty-nine SNPs were identified in the coding regions of TaER-1 gene in 33 wheat genotypes, of which 20 SNPs caused non-synonymous mutations while 19 SNPs produced synonymous mutations; while 31 SNPs were located in the coding regions of TaER-2 gene in 26 genotypes, of which 18 SNPs caused non-synonymous mutations and 13 SNPs caused synonymous mutations. In addition, 32 SNPs in TaER-1 and 9 SNPs in TaER-2 were also identified in the non-coding regions. Moreover, the significant genetic associations of SNPs of TaER-1 and TaER-2 genes with carbon isotope discrimination, stomatal conductance, photosynthetic rate, transpiration rate, intrinsic water use efficiency (iWUE), leaf length, leaf width, stomatal density, epidermal cell density, and stomatal index were noted in wheat genotypes. This study confirms the importance of TaER-1 and TaER-2 genes which could improve iWUE of wheat by regulating leaf gas exchange and leaf structural traits. These identified SNPs may play a critical role in molecular breeding by means of marker-assisted selection.

The large application of nitrogen fertilizer will cause soil deterioration and pollute the environment. Reduction of nitrogen inputs and maintaining high yields are therefore essential to ensure a more sustainable agriculture. However, little information is available about rapeseed (Brassica napus L.) low nitrogen tolerance. We evaluated low nitrogen tolerance of 304 rapeseed accessions at seedling stage and performed a genome-wide association study to detect low nitrogen tolerance-related quantitative trait loci. A natural population comprising 304 B. napus inbred lines was genotyped with a Brassica 60K Illumina Infinium SNP array. Finally, 11 single-nucleotide polymorphisms were associated with 3 low nitrogen tolerance-related traits, which explained 5.79 - 7.57 % of the phenotypic variation. In addition, three possible candidate genes were located near the genetic region. Our results provide valuable information for understanding the genetic control of rapeseed low nitrogen tolerance at seedling stage and may facilitate a marker-based breeding for rapeseed low nitrogen tolerance.

Rapid and non-destructive assessment of water status is essential to enhance crop performance. This study aimed to evaluate photosynthetic performance and to monitor water status in cotton under field conditions. A two-year experiment was conducted with three irrigation regimes to measure the following parameters: photochemical reflectance index (PRI), structural independent pigment index (SIPI), water index (WI), solar-induced fluorescence (SIF; retrieved from reflectance by using Fraunhofer line-depth method), gas exchange, and chlorophyll fluorescence (CF). The results showed that PRI decreased > 30 % in moderate drought (MD) and >50 % in severe drought (SD), compared with control. PRI was found to be positively correlated with net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (T_r), actual quantum yield of photosystem II photochemistry (Φ_PSII), but a negatively correlated with nonphotochemical quenching (NPQ). Solar-induced fluorescence around 761 nm (SIF₇₆₁) had significant correlations with P_N, Φ_PSII, and NPQ, but not with maximal quantum yield of PS II photochemistry (F_v/F_m). The relationship between PRI and PN was stronger at the beginning of water stress (R² = 0.86) than for the all stress stages (R² = 0.54), indicating that PRI could be more effective for assessing PN of cotton at early water stress. PRI was better correlated with relative water content and photosynthetic parameters than SIPI and WI and so it could also be a good indicator to evaluate cotton water status.

The effects of silver nanoparticles (AgNPs), silver ions (Ag⁺), and polyvinylpyrrolidone (PVP) on mitosis and expression of a gene encoding cyclin-dependent kinase 2 (cdc2) in onion roots were compared. Three concentrations (5, 10, and 15 mg dm^-3) were employed in combination with three incubation times (3, 6, and 9 h). PVP enhanced mitotic index and cdc2 expression. Both silver forms decreased mitotic index and cdc2 expression. Genotoxicity of both silver forms were indicated by three major distinguishable classes of chromosome aberrations: spindle disturbances, clastogenic aberrations, and chromosome stickiness. Concerning Ag⁺ treatments, significant enhancements in occurrence of any chromosome aberration type was associated with significant decrease in mitotic index. On the other hand, disturbed spindle in AgNPs treatments was observed even in absence of significant reduction in mitotic index suggesting that AgNPs inhibit cellular events occurring during mitosis to proceed normally rather than starting of cell division.

Perennial ryegrass (PRG; Lolium perenne) remains the backbone of grass swards in Northern Ireland due to its improved digestibility persistence, and ease of management compared with other grass species. However, innovative breeding approaches are needed that include positive environmental outcomes, as well as improved productivity in ruminants. The objective of this study was to evaluate the feasibility of root-trait screening and selection using the in situ coring method under commercial grass breeding field conditions. 108 root cores were sampled over a 2-year period from a field trial sown in autumn 2021. Root cores were washed, scanned, and analysed using the open-access root scanning platform Rhizovision. A seasonal effect was noted whereby significant differences were detected in October for root volume, network area, and surface area, but no significant differences for any root parameter were detected in April. No association was observed between root volume, network area, or surface area at the October sampling with either dry matter (DM) yield at the 4^th cut (October) or annual DM yield. These results suggest that this method may be useful for identifying improved germplasm in PRG for root characteristics; however, being comparatively labour and time intensive this method may not be practicable for large-scale breeding programmes.

The capacity of extracellular self-DNA (esDNA) to inhibit growth is getting more research attention as this could be explored for several purposes, including the development of specific bioherbicides. While the inhibitory effect has been studied in several dicotyledon species, little is known about the effects and subsequent signaling processes in monocots. Here, we measured the growth, counted the number of lateral and crown roots, determined greenness index, quantified the production of O₂^.- and H₂O₂, and determined the expressions of genes encoding antioxidant enzymes (SODs and CATs) in rice (Oryza sativa L.), a model plant of monocots. After 7 d of germination, rice roots were exposed to 0, 75, and 150 µg cm^-3 of esDNA. Inhibitory effect was found to be negatively correlated to esDNA concentration, as indicated by the length of primary roots. Interestingly, this negative effect was only observed in the directly exposed organ (root) but not in the length of shoot or fresh mass of the whole seedling. The percentage of greenness index of leaves and number of crown and lateral roots were also similar across treatments. However, esDNA exposure to root increased production of O₂^.- and H₂O₂ in the root. At the molecular level, the response was characterized by the decreased expression of the antioxidant genes SOD3, CATB, and CATC. These findings suggest that esDNA inhibits rice growth locally in, e.g. in treated roots, and the responses involve increased production of ROS and suppression of antioxidants. This study could be the basis for determining the combination of concentration and period of exposure that might significantly inhibit total growth of monocot weeds with a minimum effect on the crop.

The gene NCED1 encodes 9-cis-epoxycarotenoid dioxygenase, which catalyzes oxidative cleavage of 9-cis-epoxycarotenoids neoxanthin and violaxanthin to xanthoxin, a key step in the biosynthesis of abscisic acid in higher plants. In the present study, the complete NCED1 of 1 917 bp was cloned and characterized from rice (Oryza sativa L. cv. N22) as no earlier reports were available for its characterization from indica cultivar. The NCED1 had no intron and encoded a protein of 639 amino acids with a predicted molecular mass of 68.62 kD and pI of 6.07. The aliphatic index and grand average of hydropathicity were found to be 77.04 and -0.148, respectively. Multiple alignment analysis revealed that the sequence shared a high identity with the Oryza sativa japonica group (100 %) followed by Triticum aestivum (90 %), Hordeum vulgare (90 %), and Zea mays (89 %). The enzyme had a RPE65 domain of 476 amino acid residues. The RPE65 domain requires Fe(II) as a cofactor coordinated with 4 histidine residues and 3 glutamic acid residues. The phylogenic tree shows that NCED1 of japonica rice and NCED1 of indica rice were in the same group. They might have been evolved from a common ancestor. Analysis with a PSORT III tool shows that NCED is a chloroplastic protein. The real-time quantitative PCR and RNA-sequencing studies show that the expression of NCED1 was progressively reduced with increasing water stress, and a negative correlation between expression of OsNCED1 and severity of stress was established. Further, NCED1 expression negatively correlated with abscisic acid (ABA) accumulation under water stress whereas in some other species its expression increased along with ABA accumulation. This might be due to feedback inhibition of the ABA biosynthesis in rice.

Three wheat and two barley populations were studied in order to find loci responsible for dormancy and pre-harvest sprouting. A classical quantitative trait loci analysis was combined with an association mapping approach. Many quantitative trait loci and marker trait associations could be detected on all seven chromosome groups of wheat and on the chromosomes 2H, 3H, 5H, 6H, and 7H of barley. Especially, the known regions on chromosomes 3A and 4A for wheat and 5H for barley were confirmed. Putative functions could be found via a candidate homologues search and via expressed sequence tag annotation. On chromosome 3A, the viviparous1 gene is located which is associated to preharvest sprouting and dormancy. On chromosome 4A, a protein is detected which belongs to the aquaporin family. In barley, an association with the aleurain gene on chromosome 5H was found. The expression of aleurain is regulated by abscisic acid and gibberelic acid. An influence of both hormones on dormancy and pre-harvest sprouting is known. It can be concluded that dormancy and pre-harvest sprouting are very complex traits regulated by multigenes and/or quantitative trait loci.

Field study revealed that species diversity index of the community was 0.597. The data of interspecific association index of Alhagi graecorum and each of its associates, Chenopodium murale, Glinus lotoides and Malva parviflora, were 0.35, 0.41 and 0.33, respectively. Therefore, a net negative association and low diversity among the species were the main characters of the community. Laboratory experiments verified the role played by competition and allelopathy in this community organization. The bioassay results indicated that A. graecorum exhibited phytotoxic activity on the tested species. Accordingly, water-borne allelopathic compounds may be released from A. graecorum into the environment and suppress the growth of its associates where they were not able to compete with A. graecorum in the field, so the latter species become dominant.

Abiotic stresses strongly impair plant development and might impose detrimental effects particularly on seedlings. Irradiance and water deficit are relevant factors, which affect performance of young plants under controlled conditions. In our study, we investigated the influence of water shortage combined with different radiation sources - light emitting diodes (LED) and compact fluorescence lamps (CFL) - on physiological and biochemical parameters of young apple plants. Stress responses were assessed by fluorescence-based indices, while relative water, chlorophyll (Chl), and proline content served as reference parameters. The watering regime had a higher impact on biochemical indicators than the radiation sources. Lower Chl content was determined in plants grown under LED both in control and in water deficit plants. Nitrogen balance index and nitrogen balance index with red radiation excitation showed similar patterns regarding leaf Chl results in relation to the radiation source, being higher under CFL. In contrast, the flavonol index was higher in plants cultivated under LED. Stomatal conductance and maximal photochemical efficiency emphasised a radiation quality effect with higher values for CFL. In conclusion, fluorescence indices related to nitrogen status and flavonol content are promising parameters to sense physiological impairments under the given conditions. However, discrepancies compared to previous studies might be related to the different plant species, the nature of dehydration, and the measuring conditions.

Spermine (SPM) is involved in response to abiotic stress in plants, but the potential role of SPM in regulating senescence has not been well documented. Objectives of this study were to examine the effect of changes in endogenous polyamines (PAs) by SPM application on improving heat tolerance of creeping bentgrass (Agrostis stolonifera) and explore the SPM-regulated senescence associated with alterations of water and oxidative balance, photosynthesis, and heat shock proteins under heat stress. The results showed that persistent high temperature caused severe oxidative damage and significant decreases in chlorophyll (Chl) content, photosynthetic efficiency, and leaf water content leading to premature senescence in creeping bentgrass, as reflected by a significant upregulation of transcriptions of senescence-associated genes (AsSAG39, Ash36, and Asl20). The improvement of endogenous spermidine (SPD) and SPM content induced by SPM application could significantly alleviate heat stress damage to creeping bentgrass through maintaining higher Chl content, net photosynthetic rate, photochemical efficiency, and performance index on absorption basis, promoting osmotic adjustment ability and antioxidant enzyme (superoxid dismutase, catalase, peroxidase, and ascorbate peroxidase) activities to enhance the scavenging capacity of reactive oxygen species, and upregulating transcriptions of heat shock protein (HSP) genes (HSP90-5, HSP90.1-b1, HSP82, HSP70, HSP26.7, HSP17.8, and HSP12) helping to maintain normal synthesis and functions of proteins under high temperature stress, thereby delaying heat-induced leaf senescence. These findings reveal an important role of PAs in regulating senescence in perennial plants exposed to a high temperature environment.

Salicylic acid (SA) is an important plant hormone involved in the activation of defense responses against environmental stresses. However, there are still large of unsolved mysteries about how SA pretreatment affects the establishment of plant stress tolerance. In this study, application of SA at different concentrations and different times were conducted to investigate their effects on the response of Arabidopsis seedlings to salt stress. The pretreatment with 10 or 20 μM SA for more than 6 h promoted Arabidopsis seedlings resistance to salt stress. On the other hand, pretreatment with 200 μM SA reduced Arabidopsis resistance to salt stress and aggravated oxidative damage to the seedlings. At all concentrations used, SA pretreatment inhibited the total respiration and promoted reactive oxygen species (ROS) generation. However, the ROS content in 10 or 20 μM SA pretreated seedlings decreased to the basal level within 6 h and high activities of antioxidant enzymes and alternative oxidase were maintained. Notably, the SA-enhanced salt stress resistance was significantly impaired by blocking alternative oxidase (AOX) pathway. Our findings indicate that SA-mediated salt stress response is in a dose- and time-dependent manner and that the effects were related to the induction of AOX capacity and antioxidant system.

With the extensive utilization of graphene nanomaterials, they inevitably enter our environment. The potential phytotoxicity and environmental impact of graphene oxide (GO) have recently attracted much attention. We designed the experiment based on seed germination, seedling morphology, physio-biochemical properties, and antioxidant enzyme activities of five rice genotypes (9311, MH63, R527, K866, and Nipponbare) under six concentrations of GO (0, 5, 10, 50, 100, and 150 mg dm^-3). We studied the effects of different concentrations of GO on germination index (GI), shoot length (SL) and root length (RL), adventitious root number, shoot and root fresh masses, root/shoot ratio, chlorophyll (Chl) content, malondialdehyde content, and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Graphene oxide treatments significantly enhanced seed germination and root growth and inhibited shoot growth of all genotypes. Furthermore, we found a significant genotype-dependent response to GO treatments. According to the relative increment trend of GI, SL, and RL, root/shoot ratio, antioxidant enzyme activities (CAT, POD, and SOD), and Chl content, 'R527' showed more tolerance to GO treatments than the other four genotypes. The 'MH63' and 'K866' were more sensitive than 'Nipponbare' and '9311'. It indicates that the GO-tolerant genotype might avoid free radicals damage from GO by increased antioxidant enzyme activities. Moreover, we should consider the genotype differences when evaluating the potential phytotoxicity of GO and environmental risk to ecosystems.

Heat stress is one of the most crucial factors affecting crop growth and productivity worldwide. So, searching for a potent eco-friendly heat stress alleviator is the main issue nowadays. The current study was conducted to assess the ameliorative effects of 1.5 mM potassium silicate (K₂SiO₃, further only Si) or 1.66 mM silicon dioxide nanoparticles (SiNPs) on wheat (Triticum aestivum L.) seedlings exposed to heat stress (45 °C, 4 h). The observations show that Si or SiNPs treatments significantly restored the heat stress-provoked ultrastructural distortions of cellular organelles, particularly chloroplasts and the nucleus. Further, both Si and SiNPs enhanced the photosynthetic capacity as revealed by increments in the photochemical efficiency of photosystem II and the performance index as well as the content of photosynthetic pigments. A reduction in malondialdehyde accumulation in Si and SiNPs treated plants was positively related to their membrane stability index. The reverse transcription PCR analysis showed that Si treatment but not SiNP treatment stimulated the overexpressions of both Triticum aestivum plasma membrane intrinsic protein (TaPIP1) and Triticum aestivum nodulin 26-like intrinsic protein (TaNIP2) aquaporin genes parallelly with an improvement in the relative water content. This investigation reveals that Si was more effective than SiNPs in restoring the heat stress injuries. To the best of our knowledge, this is the first investigation exploring the effects of Si and SiNPs in improving thermotolerance of wheat seedlings.

Salt stress is one of the most important stresses that affect coastal vegetation. A halophyte Carex pumila plays a crucial role in the maintenance of fragile ecosystems in coastal areas. Thus, understanding the mechanism of C. pumila responses to salt stress is a prerequisite for the conservation and utilization of this species. After treatment with 200, 300, 400, 500 mM NaCl for 60 h, C. pumila leaves displayed a decline in the relative water content and an increase in salt injury index. Osmolyte accumulation, as a function of osmotic adjustment, and antioxidant enzyme activities were maintained under salinity, even at a high NaCl concentration. High NaCl concentrations severely affected the photosystem II, the JIP-test indicated a significant decrease in performance indexes and quantum efficiencies and an increase in phenomenological fluxes. Metabolic analyses showed the changes of 39 metabolites, including 16 kinds of organic acids, 9 kinds of amino acids, 9 kinds of sugars, 3 kinds of sugar alcohols, and 2 amines. The identified metabolites were mainly involved in the glycolysis, pentose phosphate pathway, and tricarboxylic acids cycle.

Melatonin (N-acetyl-5-methoxytryptamine) is an essential molecule which regulates plant growth and development and alleviates the damaging effects of abiotic stresses. To evaluate the important functions of melatonin in response to salinity stress, the effects of exogenous melatonin on the antioxidant system and growth of tomato (Solanum lycopersicum L.) under 150 mM NaCl stress were investigated. The application of 100 μM melatonin compensated the growth inhibition caused by salt-stress. Melatonin treated seedlings had an increased fresh and dry masses of shoots and roots. The application of 1 - 200 µM melatonin notably enhanced the relative chlorophyll content (SPAD index), root characteristics, and gas exchange in tomato seedlings subjected to salt stress compared to seedlings treated with salt stress alone. Moreover, melatonin pretreatment minimized accumulation of reactive oxygen species and improved activities of antioxidative enzymes including catalase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase.

Gibberellic acid (GA) is a natural plant growth regulator (PGR) which stimulates germination, vegetative growth, flowering, and fruit formation. However, when high concentrations of GA are used, it inhibits plant growth and development and causes abnormalities in the plant tissue. In our study, we determined the effects of different concentrations of GA on Allium cepa L. var. cepa roots. Increasing concentrations of GA (50 - 5 000 mg dm^-3) were used in A. cepa root growth inhibition tests. Further, random amplified polymorphic DNA technique was used for determination of possible genotoxic effects of 600 - 1200 mg dm^-3 GA on A. cepa root tips. Our findings show cytotoxic and genotoxic effects of these concentrations of GA and indicate that the difference among control and treatment groups were statistically significant.

γ-Aminobutyric acid (GABA) regulates plant tolerance to abiotic stresses; however, a transcriptomic change and key stress-related genes induced by GABA have not been investigated in plants during a prolonged period of salt stress. Roots of creeping bentgrass (Agrostis stolonifera) cv. Penncross were pretreated with or without 0.5 mM GABA solution for 2 days and then subjected to salt stress for 20 days (150 mM NaCl solution for 3 d, 200 mM NaCl for another 3 d, and 250 mM NaCl for 14 d) in controlled growth chambers. The application of GABA significantly increased GABA content in roots and alleviated a salt-stress induced decrease in GABA content in leaves. This was associated with a significant increase in salt tolerance as demonstrated by a significantly higher leaf relative water content, photochemical efficiency, performance index on absorption basis, and lower electrolyte leakage in GABA-pretreated plants as compared to untreated plants under salt stress. Transcriptomic analysis found that GABA-induced salt tolerance was closely associated with saccharide, amino acid, and lipid metabolism. The GABA upregulated key differentially expressed genes including cytochrome P450 (CYP450), zinc transporter 29 (ZTP29), alpha-amylase 3 (AMY3), 3-ketoacyl-CoA synthase 6 (KCS6), aldehyde oxidase (AO), acetyl-CoA carboxylase 1 (ACC1), and magnesium-chelatase (Mg-CHT) involved in zinc homeostasis, starch degradation, and the biosynthesis of wax, fatty acid, chlorophyll, and abscisic acid, which could contribute to GABA-regulated salt tolerance. Current findings prove that GABA application is an efficient approach to enhance salt tolerance of creeping bentgrass during a prolonged period of salt stress and also provide valuable information to better understand key candidate genes and regulatory pathways of GABA-induced salt tolerance in plants.

In plants, calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) regulate Ca2+ signalling and so responses to biotic and abiotic stresses. However, the details of specific CIPKs functions in various stress responses are poorly understood. Here, we report roles of dicot and monocot CIPK2 genes in response to salinity and heavy metals. Arabidopsis thaliana AtCIPK2 was found to be universally expressed in different tissues and organs and furthermore induced by salinity. Overexpression of AtCIPK2 or Tibetan Plateau wild barley (Hordeum spontaneum) HsCIPK2 in Arabidopsis alleviated toxic effects of NaCl and mercury on seed germination and root growth. Similarly, reduced toxic effects of copper and cadmium on seed germination, but not on root growth, were observed in these transgenic lines. Live-cell fluorescence imaging analysis revealed that HsCIPK2 was predominantly distributed in the cytoplasm and nucleus and weakly localized at the plasma membrane (PM), but its PM association was rapidly enhanced upon exposure to high salinity and mercury. These results suggest an involvement of CIPK2 in plant tolerance to salinity and mercury and provide a new insight into physiological functions of CIPKs in plant response to heavy metals.

Fusarium head blight caused by the hemibiotrophic fungus Fusarium graminearum is one of the most devastating diseases of wheat which reduces both grain yield and quality. To better understand mechanism underlying wheat resistance to this pathogen, the expressions of five candidate genes encoding phenylalanine ammonia-lyase (PAL), glucanase-2 (Gl 2), class IV chitinase (Cht-4), cytochrome P₄₅₀ (CYP₎, and pleiotropic drug resistance (PDR) following spike inoculation with F. graminearum was compared in susceptible cv. Falat and resistant cv. Sumai3 at three time points (48, 96, 144 h after inoculation). Real-time quantitative PCR analysis indicated earlier and greater inductions of PAL, Glu-2, and Cht-4 in spikes of 'Sumai3' as compared to 'Falat' in response to F. graminearum inoculation. The expression of CYP in the resistant 'Sumai3' was about three times higher than in 'Falat' at 144 h after pathogen inoculation. Moreover, soil drench application of sodium salicylate (SA) one day before pathogen inoculation drastically curtailed pathogen infection in both the cultivars. Furthermore, SA treatment caused an induction of these genes in spikes of the susceptible cultivar to show a similar pattern as in the resistant one when inoculated with F. graminearum. Proteomics analysis of F. graminearum treated spikes 96 h after inoculation confirmed an increase of Glu and Cht spot volume in 'Sumai3' whereas a decrease in 'Falat'. The SA treatment also caused significant increases in Glu and Cht spot volumes in both the cultivars. Our findings show an association between SA improvement of wheat defense against F. graminearum infection and induction of genes encoding proteins involved in pathogen response (Glu-2, Cht-4), secondary metabolite biosyntheses (PAL), and xenobiotic detoxification (CYP and PDR).

Root rot caused by Fusarium solani, is one of the most severe diseases in pepper (Capsicum annuum L.). Grafting has been attempted as an effective means to control the disease, but little is known about the disease resistance mechanism in grafted pepper. Therefore, we investigated the changes of biomass, cell structure, and the secondary metabolism in roots of control (non-grafted pepper) and grafted peppers using cvs. Weishi and Buyeding as rootstocks and the cv. Xinfeng 2 as a scion. After a manual inoculation, less F. solani invaded grafted pepper roots and consequently less serious injury to the root cell ultra-structure compared with the control was found. The roots of grafted pepper infected with F. solani exhibited greater biomass production and root activity than the roots of infected controls. Grafting led to an increased content of salicylic acid, benzoic acid, vanillin, lignin, and polyamines, as well as activities of phenylalanine ammonia lyase, polyphenoloxidase, and peroxidase. These results suggest that grafting improved the resistance of peppers to root rot.

Wild rice genotypes are rich in genetic diversity. This has potential to improve agronomic rice by allele mining for superior traits. Late embryogenesis abundant (LEA) proteins are often associated with desiccation tolerance and stress signalling. In the present study, a group 3 LEA gene, Wsi18 from the wild rice Oryza nivara was expressed under its own inducible promoter element in stress susceptible cultivated indica rice (cv. IR20). The resulting transgenic plants cultivated in a greenhouse showed enhanced tolerance to soil water deficit. Transgenic plants had higher grain yield, plant survival rate, and shoot relative water content compared to wild type (WT) IR20. Cell membrane stability index, proline and soluble sugar content were also greater in transgenic than WT plants under water stress. These results demonstrate the potential for improving SWS tolerance in agronomically important rice cultivar by incorporating Wsi18 gene from a wild rice O. nivara.

Frost tolerance of ten Bulgarian winter wheat (Triticum aestivum L.) cultivars (Milena, Pobeda, Sadovo-1, Enola, Kristal, Laska, Svilena, Russalka, No301 and Lozen) and five foreign cultivars (Mironovskaya 808, Bezostaya-1, Rannaya-12, Skorospelka-35 and Chinese Spring) was studied in two experimental seasons following natural cold acclimation and in one experiment carried out in controlled acclimation conditions. Considerable intercultivar variability in plant survival was observed after freezing at -21 °C following sufficient cold acclimation, or at -18 °C following insufficient or controlled acclimation. In seven cultivars, the effects of chromosome 5A on frost tolerance were investigated in their F₂ hybrids with chromosome 5A monosomic lines of cultivars with high, intermediate and low frost tolerance. The effects of chromosome 5A depended on the stress severity and the genetic background of the hybrids and varied even in cultivars of similar frost tolerance and vernalization requirements. Effects of other chromosomes besides 5A on frost tolerance were assumed. The analysis of six microsatellite loci located in the interval from centromere to Vrn-1 on of chromosomes 5AL, 5BL and 5DL showed that the major loci determining frost tolerance in Bulgarian winter wheats were Fr-A2 on chromosome 5AL, and, to a lesser extent, Fr-B1 on chromosome 5BL. A strong association of the 176 bp allele at locus wmc327 tightly linked to Fr-A2 with the elevated frost tolerance of cvs. Milena, Pobeda, Sadovo-1, Mironovskaya-808 and Bezostaya-1 was revealed. Relatively weaker association between frost tolerance and the presence of the 172 bp allele at locus Xgwm639 tightly linked to Fr-B1 was also observed.

We examined the dynamics of phenolic compounds (PheCs) and carotenoids (Cars) in the leaves of wild type (WT) spring barley (Hordeum vulgare L.) and its mutant lacking chlorophyll b Chlorina f2 (Clo f2) grown from seeds at high irradiance (8 d at 1 000 μmol m^-2 s^-1; HI) during 9 d of acclimation to low irradiance (50 μmol m^-2 s^-1; LI). Our results show that a leaf epidermal flavonoid UV-shielding index remained rather constant after transfer of plants from HIto LIconditions and that it was significantly lower in Clo f2 compared to WTplants. This suggests that HIpretreated plants can be well protected against excessive UVfor at least 9 d, as supported also by the constant absorbance of leaf PheCs extracts in the UV-A region (at 335 nm). In contrast, absorbance in the UV-B region (at 270 nm) was reduced, particularly during the initial days of LItreatment, indicating specific changes in PheC profile. High-performance liquid chromatography of soluble PheCs revealed stable content of the major PheC saponarin during LIacclimation, whereas luteolin and feruloylquinic acid content decreased, particularly in WTplants. We also observed a pronounced decrease in Car relative content, particularly a reduction in the xanthophyll cycle pigments (violaxanthin, antheraxanthin, and zeaxanthin, VAZ) pool and diminution of their de-epoxidation state (DEPS) in dark-adapted leaves. As both VAZ and DEPS were higher in HI-acclimated Clo f2 plants than they were in WTplants, the presence of a significant VAZ pool within the lipid phase of thylakoid membrane is indicated. That can contribute to antioxidant capacity particularly in Clo f2 plants. We can therefore conclude that there is a tendency to retain the PheCs responsible for UVshielding during LIacclimation. Meanwhile, the accumulation of both PheCs and zeaxanthin serving as effective antioxidants is considerably downregulated within 9 d.

The aim of this study was to identify single nucleotide polymorphism (SNP) markers genetically linked to root elongation rate (RER) in sugar beet (Beta vulgaris L.). A population of 244 F₃ individuals, obtained from the cross between lines L01 (a low RER) and L18 (a high RER), was phenotyped by measuring RER of 11-d-old seedlings grown in a hydroponic culture. Two DNA bulks of 50 F₃ individuals with extreme phenotypes were used for bulk segregant analysis by restriction-associated DNA sequencing. A total of 20 376 SNPs were identified. Single nucleotide polymorphisms were filtered to reduce the number of the false positive and mapped on candidate chromosomal regions of the B. vulgaris reference genome. One of the total of SNPs selected, SNP10139, was strongly linked to RER (P < 0.01). The pattern of association between the SNP10139 genotype and RER was also evaluated on a breeding line panel comprising 40 low and 40 high RER individuals with different allele frequencies between groups (P < 0.01). The SNP10139 sequence was mapped on the B. vulgaris peptide transporter (PTR) gene, a carrier that influences root elongation in Arabidopsis thaliana. Our results suggest that SNP10139 influence RER in sugar beet, and sequence information can be used in marker-assisted selection programs.

Nitric oxide (NO) is an important molecule involved in the perception of stress induced by toxic compounds such as arsenic (As). The present study investigated the role of NO applied as sodium nitroprusside (SNP) in cell signalling and the ability of NO to attenuate the toxic effects of As (in the form of sodium arsenate) in water hyacinth (Eichhornia crassipes). Water hyacinth plants were collected and assigned to one of the following treatments: control; 100 μM SNP; 20 μM As; or 20 μM As + 100 μM SNP. The plants remained under these conditions for 0, 4, 12, and 24 h. After each time interval, the plants were collected and As absorption, production of reactive oxygen species (ROS), integrity of membranes, and antioxidant enzyme activities were evaluated. The plants were able to absorb and accumulate large amounts of As, even after only four hours of exposure to the pollutant. The absorption and bioaccumulation factor of As was even greater when plants were exposed to both As and SNP. The accumulation of As triggered increases in ROS production and cell membrane damage. In the presence of SNP, the tolerance index to As increased and damage was mitigated. Therefore, from the present work, it was possible to conclude that exogenous NO influenced the ability of plants to tolerate As; this finding has implications for phytoremediation in areas contaminated by As.

We investigated whether changes in abscisic acid (ABA) content in leaves of Mikania micrantha infected by the holoparasite Cuscuta campestris at five growth stages, influenced the host stomatal conductance (g_s), transpiration rate (E) and net photosynthetic rate (P_N). C. campestris infection caused a negative effect on g_s, E and P_N of the host plants. ABA content in host leaves infected by C. campestris was significantly lower at 6 d after parasitization (DAP) and significantly higher at 13 and 33 DAP, relative to uninfected controls. In the parasite, ABA content was lowest at 13 DAP and then sharply increased to the maximum at 26 DAP. Moreover, the ABA content in the parasite was always lower than in the infected host leaves. The results suggest that an increase in host ABA concentration contributes to reduced host g_s, E and P_N in the holoparasitic C. campestris - M. micrantha association.

Plant cell lines represent useful models in plant cell biology. They allow simple analysis of the effects of various factors including modulated gene expression at cellular and subcellular levels. The tobacco BY-2 cell line is a favoured model due to its high proliferation rate, capability of effective synchronization, and accessibility to transformation. A relatively high uniformity of BY-2 cultures allows morphological phenotyping and assessment of growth parameters like mitotic index, viability, or cell density. Here we review already published and newly introduced optimized guidelines to carry out reliable, reproducible and efficient characterization of BY-2 cultures from suggestions of appropriate methods to acquire primary data, proper statistical treatment, and biological interpretation. The presented experimental data demonstrate the extent of natural variability and the effect of initial cell density on various cell culture features. Supportive equations allow to estimate some derived phenotypic parameters like cell cycle duration or fresh biomass of the culture and to determine the size of data sets for reliable documentation of a certain phenotypic change. The optimized protocols and accompanying discussion of weak points of different approaches should serve as practical guide for both beginners and experienced researchers working on BY-2 cells.

In many polar and alpine ecosystems, lichens of genus Umbilicaria represent dominant species forming community structure. Photosynthetic and spectral properties of the lichens may change rapidly according to an actual hydration status of their thalli. In this study, we investigated responses of photochemical reflectance index (PRI), normalized difference vegetation index (NDVI), effective quantum yield of photosynthetic efficiency of photosystem (PS) II (Φ_PSII), and several photosynthetic parameters derived from fast induction kinetics of chlorophyll fluorescence (OJIP) to controlled dehydration. We used U. arctica and U. hyperborea collected close to Nuuk, Greenland. In both the species, PRI showed a curvilinear increase with dehydration, i.e., a decreasing water potential (Ψ_w). The increase was apparent within Ψ_w range of 0 to -10 MPa. The PRI increase was less pronounced in U. arctica than in U. hyperborea. NDVI decreased with a progressive thallus dehydration in both the species, however, throughout Ψ_w range of 0 to -30 MPa, U. hyperborea had lower NDVI values than U. arctica. The relationship between Φ_PSII and Ψ_w resulted in a typical S curve. A critical Ψ_w at which photosynthetic processes were fully inhibited was -30 MPa in both the species, however, species-specific differences in the S curve shape were found. Analyses of photosynthetic parameters derived from OJIPs revealed that the absorption of radiation energy and a trapping rate increased with dehydration in active reaction centres of PS II, the number of which decreased with a more pronounced lichen thallus dehydration. It is concluded that U. arctica and U. hyperborea possess effective physiological mechanisms to maintain an effective photosynthesis when partly dehydrated (the Ψ_w range of 0 to -15 MPa). In spite of similar ecological niches that these two lichens occupy in nature, their spectral and photosynthetic properties differred.

Drought stress presents a considerable threat to the global crop production. As a dominant source of vegetarian diet, cereals and grain-legumes remain crucial to meeting the growing dietary demands worldwide. Therefore, breeding cultivars of these staple crops with enhanced drought tolerance stands to be one of the most sustainable solutions to enhance food production in changing climate. Given the context, a more focused survey of environment-defined germplasm sets is imperative to comprehend such adaptive traits. In parallel, uncovering the genetic architecture and the molecular networks that collectively contribute towards drought tolerance is urgently required through rationally combining large-scale genomics, proteomics, and metabolomics data. Also, attention needs to be directed to reasonably quantify the epistatic as well as environmental influences, thereby warranting deployment of analyses like metaquantitative trait loci (QTL) that encompass multiple environments and diverse genetic backgrounds. Further, innovative techniques like genomic selection (GS) and genome wide association study (GWAS) would help to capture the quantitative variation underlying drought tolerance. Equally importantly, integration of physiological traits-based techniques with ever-evolving 'omics' technologies and the new-generation phenotyping platforms will be of immense importance in advancing our existing knowledge about the genetically-complex and poorly-understood phenomena, such as plant drought response, and a deeper understanding would likely to provide a great impetus to the progress of crop breeding for drought tolerance.