Young Seedlings Research Articles

Comparative biochemical and transcriptome analysis provides insights into the regulatory mechanism of striped leaf albinism in arecanut (Areca catechu L.)

Frequent striped leaf albinism occurring in young seedlings leads to production loss of arecanut (Areca catechu L.) industry. Previous efforts has proved that this albinism phenotype was determined by genetic factors. However, the mechanism underlying albinism in arecanut remains unclear. In this study, to elucidate the regulatory mechanism of striped leaf albinism, comparison analysis was performed between leaves of normal and albinotic seedlings at physiological, biochemical and transcriptomic levels in arecanut. The albinotic leaves showed obvious degeneration in chloroplast, low chlorophyll content and reduced photosynthetic capacity. More than 5000 DEGs (differentially-expressed genes) was identified between normal and albinotic leaves. Among them, genes involved into the biosynthesis of chlorophyll, carotenoid and anthocyanin were significantly down-regulated in albinotic leaves. On the contrary, genes involved in leaf senescence and ABA (abscisic acid) synthesis were up-regulated in albinotic leaves. Unexpectedly, most genes involved in chloroplast development were up-regulated in albinotic leaves, indicating different regulatory mechanism of albinism in arecanut. Furthermore, transcription factor family genes, such as AP2/ERF-ERF (APETALA2/ethylene responsive factor), NAC (NAM/ATAF/CUC) and WRKY, were identified as DEGs between normal and albinotic leaves, which also indicated the senescence of albinotic leaves. The results indicated that the albinism mechanism of arecanut is different with those reported in other plants. Thus our data provides new insights into the mechanism underlying albinism. The genes related to albinism of arecanut identified in this study would be important targets for genetic modification or molecular markers development, which will be critical for improving the cultivation efficiency of this cash crop.

Nutrient Status of Tree Seedlings in a Site Recovering from a Landslide

The aim of the study was to investigate the effect of soil recovery after a landslide on the nutritional status of a young generation of Silver fir (Abies alba Mill.) and Silver birch (Betula pendula Roth.) trees. The study was carried out on the site of a landslide that took place in 2010 in the Gorlice Forest District (Southern Poland). Basic soil properties, macro, and microelements content and enzymatic activity were determined in the soil samples that were collected from across the landslide area, from locations distributed by a grid 10 × 10 m (18 points). Plant material samples, collected to indicate nutritional status, were also taken from each point. Results demonstrate that the nutritional status of emerging regeneration depends on soil acidification and soil organic matter content. The pH of the soils on the landslide determines the intensity of nutrient uptake by the young seedlings. The nutrition of young trees varied across the landslide zone, differing in terms of the soil’s organic matter content and its chemical properties. In comparison to the depletion zone, the accumulation zone proved to be substantially richer in soil organic matter, resulting in higher soil biochemical activity. The study demonstrates that Silver birch (Betula pendula Roth.) is improving nutrient cycling in areas disturbed by landslide.

Evaluating the integrative response of moringa leaf extract with synthetic growth promoting substances in maize under early spring conditions

The performance of spring maize is severely hampered by high temperature at reproductive phase, causing marked reduction in grain yield. Early sowing of spring maize can be a good adaptive approach however, due to low temperature causes adverse effect on germinating seeds and young seedlings, thus being detrimental to early planting. Exogenous application of natural and synthetic growth promoting substances may induce tolerance against temperature constraints. For this purpose, field experiment was conducted to explore the potential of moringa leaf extract (MLE, 3%), sorghum water extract (SWE, 10 ml L − 1), ascorbic acid (ASA, 50 mg L − 1), salicylic acid (SA, 50 mg L − 1) and hydrogen peroxide (H2O2, 2 µM) as priming agents on maize hybrid under early and optimum sowing dates. The performance of early planted maize crop was severely influenced by low temperature in comparison to optimum sown crop nevertheless exogenous application of growth promoting substances proved effective in improving stand establishment, phenotypic behavior, key physiological and biochemical attributes of maize crop. Low temperature persuaded inhibition in growth of maize was mainly ameliorated by seed priming with MLE + H2O2 and SWE + ASA. It can be concluded that application of growth promoting substances as priming agents proved to be the most successful strategy in conferring better thermotolerance at early sowing through improved antioxidant defense system and physiological mechanism of spring maize. Better crop performance with combined application of natural and synthetic growth enhancers was linked to improvement in crop stand establishment, better growth and development, dry matter partitioning and yield attributes.

Phytohormone profile and CiFL1 expression in young seedlings of Cichorium intybus L. var sativum exposed to high temperature in relation to vernalization and de-vernalization processes

Cichorium intybus is a biennial plant species forming a taproot and a leaf rosette during the first year and which requires low temperature during vernalization to flower during the second year of its cycle. Heat stress, however, is known to induce premature flowering during the first year. The present work aims to compare the effect of heat treatment (38 °C during 3 days) and vernalization (4 °C during 6 weeks) on the phytohormonal profile and the expression of two chicory genes (CiFL1 and CiFT) homologous to the Arabidopsis flowering genes FLOWERING LOCUS C (FLC) and FLOWERING LOCUS T (FT). In Arabidopsis, FLC and FT code, respectively, for a repressor and an activator of flowering. Although CiFL1 was inhibited by vernalization, its expression was increased by heat treatment in both vernalized and non-vernalized seedlings while high temperature unexpectedly inhibited FT expression in vernalized seedlings. Vernalization induced a modification in the hormonal profile of C. intybus (cv. Melci) in a sense of a decrease in ethylene production, abscisic acid and total jasmonates content, while the level of salicylic and benzoic acids as well as polyamine spermidine increased. A limited effect on the gibberellins’ profile was observed. The subsequent impact of heat stress on phytohormone content was different in non-vernalized and vernalized seedlings, with a higher abscisic acid and jasmonates and a lower 1-aminocyclopropane-1-carboxylic acid concentration in the former than in the latter. These data are discussed in relation to the putative involvement of phytohormones in stress-induced flowering. It appears that heat stress implies different pathways than vernalization to hasten flowering process.

CONSTITUTIVELY PHOTOMORPHOGENIC1 promotes ABA-mediated inhibition of post-germination seedling establishment.

Under acute stress conditions, precocious seedling development may result in the premature death of young seedlings, before they switch to autotrophic growth. The phytohormone abscisic acid (ABA) inhibits seed germination and post-germination seedling establishment under unfavorable conditions. Various environmental signals interact with the ABA pathway to optimize these early developmental events under stress. Here, we show that light availability critically influences ABA sensitivity during early seedling development. In dark conditions, the ABA-mediated inhibition of post-germination seedling establishment is strongly enhanced. COP1, a central regulator of seedling development in the dark, is necessary for this enhanced post-germination ABA sensitivity in darkness. Despite their slower germination, cop1 seedlings establish faster than wild type in the presence of ABA in both light and dark. PHY and CRY photoreceptors that inhibit COP1 activity in light modulate ABA-mediated inhibition of seedling establishment in light. Genetically, COP1 acts downstream to ABI5, a key transcriptional regulator of ABA signaling, and does not influence the transcriptional and protein levels of ABI5 during the early post-germination stages. COP1 promotes post-germination growth arrest independent of the antagonistic interaction between ABA and cytokinin signaling pathways. COP1 facilitates the binding of ABI5 on its target promoters and the ABA-mediated upregulation of these target genes is reduced in cop1-4. Together, our results suggest that COP1 positively regulates ABA signaling to inhibit post-germination seedling establishment under stress.

Seed regeneration of sweet chestnut (Castanea sativa Miller) under different coppicing approaches

The management of Italian chestnut coppices has gradually been suspended after World War II, causing a widespread overaging of the concerned stands. In recent years, the renewed interest in coppice wood products increased the need of a solid knowledge on the most suitable restoration practices of overaged coppices.In this context, a key issue is assuring a qualitative and abundant seed regeneration of the chestnut tree (Castanea sativa Miller) in order to substitute overaged stools. Open questions still exist however on the role of the standards (trees released after coppicing) and, in particular, on their interaction with the post-coppicing establishment of seed regeneration.In order to clarify these aspects, we applied different coppicing systems in overaged chestnut coppices so as to create a gradient of residual coverage ranging from full coverage left (no intervention) to simple coppicing (all trees cut, no standards released). The impact of different treatments on chestnut regeneration has been then assessed through field surveys in the second and fifth year post-coppicing, respectively.Chestnut seed regeneration promptly and abundantly established to guarantee the replacement of dead stools also in the simple coppicing. The post-coppicing pulse of chestnut seed regeneration mostly originated from the existing annual seed bank and it was concentrated in the first two years after the intervention, whereas seed inputs by standards or by adult trees at the forest edge played a secondary or negligible role from the third post-coppicing year onwards. Thus, the presence of standards did not benefit regeneration. Rather, it displayed a marked depressive effect on the growth rate of young chestnut seedlings and, under significant shading conditions, enhanced the establishment of shade-tolerant tree species.From a silvicultural point of view, simple coppicing of overaged chestnut coppices represents a valuable management option combining a rapid establishment of natural seed regeneration of chestnut with the resprout and development of the most vigorous stools.

Effects of seedling age on the growth stage and yield formation of hydroponically grown long-mat rice seedlings

Understanding the characteristics of rice productivity is of great importance for achieving high yield formation. However, such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings (HLMS), which constitutes a new method of seedling cultivation. Field experiments were conducted to evaluate the effects of seedling age on the growth stage, photosynthesis characteristics, dry matter production, and yield of HLMS. A conventional japonica rice cultivar (Wuyunjing 24) and an indica hybrid rice cultivar (6 Liangyou 9368) were used as test materials. The results showed that the whole phase was shortened by 13–15 days for young seedlings (13-day-old) compared with old seedlings (27-day-old), which occurred because the growth process accelerated with the transplantation of young seedlings. As seedling age increased, the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage (MS). Compared with that of 27-day-old seedlings, the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71% for Wuyunjing 24 and by 3.78% for 6 Liangyou 9368 at the MS. Moreover, as seedling age increased, the leaf area index and photosynthetic potential decreased for both cultivars, and the photosynthetic rate markedly decreased at the heading stage (HS). With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014, the crop growth rate was higher for young seedlings than for old seedlings. Grain yield significantly decreased with seedling age, but no significant difference was detected between the 13- and 20-day-old seedlings for either cultivar. Therefore, equilibrious and high biological yield formation, vigorous growth in the late stages, and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings (13–20-day-old).

Efficient targeted mutagenesis in allotetraploid sweet basil by CRISPR/Cas9.

Sweet basil (Ocimum basilicum) is an economically important herb and its global production is threatened by basil downy mildew caused by the obligate biotrophic oomycete Peronospora belbahrii. Effective tools are required for functional understanding of its genes involved in synthesis of valuable secondary metabolites in essential oil and disease resistance, and breeding for varieties with improved traits. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 gene editing technology has revolutionized crop breeding and functional genomics. The applicability and efficacy of this genomic tool in the allotetraploid sweet basil were tested by editing a potential susceptibility (S) gene ObDMR1, the basil homolog of Arabidopsis DMR1 (Downy Mildew Resistant 1) whose mutations conferred nearly complete resistance against Arabidopsis downy mildew pathogen, Hyaloperonospora arabidopsidis. Two single guide RNAs targeting two different sites of the ObDMR1 coding sequence were designed. A total of 56 transgenic lines were obtained via Agrobacterium‐mediated stable transformation. Mutational analysis of 54 T0 transgenic lines identified 92.6% lines carrying mutations at target 1 site, while a very low mutation frequency was detected at target 2 site. Deep sequencing of six T0 lines revealed various mutations at target 1 site, with a complete knockout of all alleles in one line. ObDMR1 homozygous mutant plants with some being transgene free were identified from T1 segregating populations. T2 homozygous mutant plants with 1‐bp frameshift mutations exhibited a dwarf phenotype at young seedling stage. In summary, this study established a highly efficient CRISPR/Cas9‐mediated gene editing system for targeted mutagenesis in sweet basil. This system has the capacity to generate complete knockout mutants in this allotetraploid species at the first generation of transgenic plants and transgene‐free homozygous mutants in the second generation. The establishment of this system is expected to accelerate basil functional genomics and breeding.

Concentration-dependent physiological and transcriptional adaptations of wheat seedlings to ammonium.

Conventional wheat production utilizes fertilizers of various nitrogen forms. Sole ammonium nutrition has been shown to improve grain quality, despite the potential toxic effects of ammonium at elevated concentrations. We therefore investigated the responses of young seedlings of winter wheat to different nitrogen sources (NH4 NO3 = NN, NH4 Cl = NNH4 + and KNO3 = NNO3 - ). Growth with ammonium-nitrate was superior. However, an elevated concentration of sole ammonium caused severe toxicity symptoms and significant decreases in biomass accumulation. We addressed the molecular background of the ammonium uptake by gathering an overview of the ammonium transporter (AMT) of wheat (Triticum aestivum) and characterized the putative high-affinity TaAMT1 transporters. TaAMT1;1 and TaAMT1;2 were both active in yeast and Xenopus laevis oocytes and showed saturating high-affinity ammonium transport characteristics. Interestingly, nitrogen starvation, as well as ammonium resupply to starved seedlings triggered an increase in the expression of the TaAMT1s. The presence of nitrate seamlessly repressed their expression. We conclude that wheat showed the ability to respond robustly to sole ammonium supply by adopting distinct physiological and transcriptional responses.

Novel insight at the Effect of Cold Atmospheric Pressure Plasma on the Activity of Enzymes Essential for the Germination of Pea (Pisum sativum L. cv. Prophet) Seeds

Great attention is currently being paid to the application of non-thermal plasma in agriculture. Seed germination is the first and critical time in the life cycle of each plant. Cold atmospheric pressure plasma (CAPP) generated by Diffuse Coplanar Surface Barrier Discharge, working at atmospheric pressure in ambient air, oxygen or nitrogen atmosphere in different time applications (60, 180, 300 s) was used to investigate its influence on early stages of germination processes in pea (Pisum sativum L. cv. Prophet). For evaluation of physiological parameters germination, the imbibition rate, percentage of germination, germination potential, germination index, seeds and seedlings vitality index, and seedlings length index were determined. In this work, also CAPP influence on dehydrogenases and lytic enzymes (amylase, glucanase and protease) as well as genotoxic effects were studied. Infrared spectra of pea seeds surface demonstrate that reactive oxygen and nitrogen species as well as UV radiation produced in plasma cause oxidation of lipids and polysaccharides on the surface of samples and lead to increase of wettability related to increased imbibition which can accelerate germination. A significant positive effect had mainly CAPP generated in air and nitrogen atmosphere at treatment time of 60 s on the studied germination and growth parameters and overall activation of lytic enzymes in pea seeds compared to untreated control. Increased concentrations of radicals in young 3-day old seedlings and activation of antioxidant enzymes suggest that low plasma doses act as low stress, which paradoxically has a stimulating effect on germination, growth and development of seedlings.

Expression profiles of four BES1/BZR1 homologous genes encoding bHLH transcription factors in Arabidopsis.

Arabidopsis bHLH-type transcription factors—BRASSINOSTEROID INSENSITIVE 1-EMS-SUPPRESSOR 1 (BES1) and BRASSINAZOLE RESISTANT 1 (BZR1)—play key roles in brassinosteroid (BR) signaling. By contrast, the functions of the other four BES1/BZR1 homologs (BEH1–4) remain unknown. Here, we describe the detailed expression profiles of the BES1/BZR1 family genes. Their expressions were distinct regarding growth-stage dependence and organ specificity but exhibited some overlaps as well. Furthermore, their mRNA levels mostly remained unchanged responding to seven non-BR phytohormones. However, BEH1 and BEH2 were downregulated by brassinolide, suggesting a close association with the BR function. Additionally, BEH4 was ubiquitously expressed throughout the life of the plant but displayed some expression preference. For instance, BEH4 expression was limited to guard cells and the adjacent pavement cells in the leaf epidermis and was induced during growth progression in very young seedlings, suggesting that BEH4 is specifically regulated in certain contexts, although it is almost constitutively controlled.

EFFECT OF DIFFERENT CROP ESTABLISHMENT METHODS ON RICE (ORYZA SATIVA L.) GROWTH, PRODUCTIVITY AND PROFITABILITY- A REVIEW

Rice is the staple food crop for more than half of the world’s population though it is cultivated in only 11% of the world’s cultivable land. It is a good source of energy, vitamins, minerals, amino-acids, anti-oxidants etc. Rice is commonly grown by transplanting seedling into the puddled soil, which is labour, water-, energy-intensive and is becoming less reliable to the resource-poor farmers. Also, repeated puddling deteriorates soil quality thus farmers are shifting the puddled transplanting method (TPR) to direct seeding method (DSR) as this method has emerged as feasible alternative establishment method to deal with the water and labour shortages. Though DSR method of rice cultivation suffers from lower grain yield compared to traditional transplanting method, the grain yield can be increased through proper weed control and crop management practices. Farmers can be benefitted by the less cost, higher yield, lower drudgery of transplanting and the quick maturity of DSR as they can plant succeeding crops early. System of Rice Intensification (SRI), a method emerged from Madagascar uses single and young seedlings at wider spacing and is one of the water-saving rice production technology which yield is nearly twice to that of conventional transplanting method. Recent studies and experiment should focus on the optimization of management practices for each method to improve rice growth and narrow the yield gap between them along with with the reduction of inputs (water and labour) costs. The main aim of this review article is to provide comparisions between different rice planting methods on the growth parameters, productivity and economics. Moreover, this article presents the different statistical relationship between the crop establishment methods of rice and its growth, productivity and economics.

Effects of nitrogen fertilization on removal kinetics of thiocyanate (SCN−) in rice seedlings

Thiocyanate (SCN−) is frequently detected in the environmental matrix due to various industrial activities such as the coking wastewater and gold mining operations, thus posing a potential threat to living organisms. In the present study, we conducted a hydroponic experiment to investigate the effects of ammonium (NH4+) and nitrate (NO3−) fertilization on uptake kinetics of SCN− by rice seedlings. Inhibition rate (IR) of relative growth was used as a response endpoint to quantify the adverse effect of SCN− exposure to rice seedlings. Uptake kinetics of SCN− by rice seedlings was estimated by Michaelis–Menten equation using MATLAB 2018b. The results showed that the IR values of SCN-treated young seedlings fed with NO3− at 57.4 mg/L (30%) were higher than that at 15.24 mg NH4+/L (30%). However, the IR value of SCN-treated seedlings fed with NH4+ at 35.56 (70%) and 50.8 mg/L (100%) were higher than those of 122.43 (70%) and 174.9 mg NO3−/L (100%). A linear uptake mode for SCN− uptake was observed in the N starvation treatment, whereas exponential curves for SCN− uptake were observed in other N fertilization treatments. The calculated Michaelis–Menten kinetics (i.e., Vmax and Km) for SCN− uptake by rice seedlings fed with NO3− were higher than those of NH4+ addition. In conclusion, NH4+ fertilization resulted in more negative impact on the uptake of SCN− by rice seedlings than NO3− treatments, thus mitigating the phytotoxicity of SCN− to rice seedlings.

Adaptive strategy of allohexaploid wheat to long-term salinity stress

BackgroundMost studies of crop salinity tolerance are conducted under short-term stress condition within one growth stage. Understanding of the mechanisms of crop response to long-term salinity stress (LSS) is valuable for achieving the improvement of crop salinity tolerance. In the current study, we exposed allohexaploid wheat seeds to LSS conditions from germination stage to young seedling stage for 30 days. To elucidate the adaptive strategy of allohexaploid wheat to LSS, we analyzed chloroplast ultrastructure, leaf anatomy, transcriptomic profiling and concentrations of plant hormones and organic compatible solutes, comparing stressed and control plants.ResultsTranscriptomic profiling and biochemical analysis showed that energy partitioning between general metabolism maintenance and stress response may be crucial for survival of allohexaploid wheat under LSS. Under LSS, wheat appeared to shift energy from general maintenance to stress response through stimulating the abscisic acid (ABA) pathway and suppressing gibberellin and jasmonic acid pathways in the leaf. We further distinguished the expression status of the A, B, and D homeologs of any gene triad, and also surveyed the effects of LSS on homeolog expression bias for salinity-tolerant triads. We found that LSS had similar effects on expression of the three homeologs for most salinity-tolerant triads. However, in some of these triads, LSS induced different effects on the expression of the three homeologs.ConclusionsThe shift of the energy from general maintenance to stress response may be important for wheat LSS tolerance. LSS influences homeolog expression bias of salinity-tolerant triads.

Seed Transmission of Tomato Leaf Curl New Delhi Virus from Zucchini Squash in Italy.

Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus affecting tomato cultivation on the Indian subcontinent. Recently, however, a new strain of the virus, named ToLCNDV-ES, has spread to Mediterranean countries such as Spain, Italy, and Tunisia, and occurred in Cucurbita crops, causing economic damage. Although ToLCNDV is spread by the sweet potato whitefly (Bemisia tabaci), like other begomoviruses, it has not been clear how ToLCNDV suddenly spread from the Indian subcontinent to the Mediterranean region. In 2017, ToLCNDV was diagnosed in young seedlings germinated naturally from fruits fallen in the prior year on a farm located in Giugliano in Campania, Naples, Italy, suggesting a possible role of the seeds in vertical transmission of the virus. Because sweet potato whiteflies were widespread naturally in that region, it was necessary to verify that in an artificial insect vector-free condition. Seeds were harvested from two ToLCNDV-infected zucchini squash cultivars in Naples in 2017 and 2018 to examine whether ToLCNDV can be transmitted from zucchini squash seeds to young plants. Viral DNA was amplified from these seeds and 1- to 3-week-old seedlings germinated from them with a ToLCNDV-specific primer set. According to PCR results, viral contamination was confirmed from all harvested seeds and dissemination was proven from 61.36% of tested seedling samples. Mechanical transmission from seed-borne virus-infected seedlings to healthy zucchini squash plants was also succesful, demonstrating that seedlings from ToLCNDV-infected seeds did act as inoculum. This is the first report demonstrating that ToLCNDV is a seed-transmissible virus in zucchini squash plants in Italy.

Arp2/3 Complex Is Required for Auxin-Driven Cell Expansion Through Regulation of Auxin Transporter Homeostasis.

The Arp2/3 complex is an actin nucleator shown to be required throughout plant morphogenesis, contributing to processes such as cell expansion, tissue differentiation or cell wall assembly. A recent publication demonstrated that plants lacking functional Arp2/3 complex also present defects in auxin distribution and transport. This work shows that Arp2/3 complex subunits are predominantly expressed in the provasculature, although other plant tissues also show promoter activity (e.g., cotyledons, apical meristems, or root tip). Moreover, auxin can trigger subunit expression, indicating a role of this phytohormone in mediating the complex activity. Further investigation of the functional interaction between Arp2/3 complex and auxin signaling also reveals their cooperation in determining pavement cell shape, presumably through the role of Arp2/3 complex in the correct auxin carrier trafficking. Young seedlings of arpc5 mutants show increased auxin-triggered proteasomal degradation of DII-VENUS and altered PIN3 distribution, with higher levels of the protein in the vacuole. Closer observation of vacuolar morphology revealed the presence of a more fragmented vacuolar compartment when Arp2/3 function is abolished, hinting a generalized role of Arp2/3 complex in endomembrane function and protein trafficking.

Occurrence and pathogenicity of Enterobacter sp. causing sprout decay and seedling stunting of upland cotton (Gossypium hirsutum L.)

AbstractA new sprout decay and seedling stunting disease of unknown aetiology in upland cotton (Gossypium hirsutum L.) affecting nearly 5%–10% of young seedlings was noticed in vertisols of central Vidarbha (Maharashtra state, India) in July of 2017. The bacterium was consistently isolated from diseased seedlings and identified with a polyphasic method of characterization, including morphological, physiological, biochemical and 16S rRNA gene sequence analysis. The bacterium strain CICR‐MGMG1 was isolated from diseased plants identified as Enterobacter sp. Inoculation of healthy cotton seed with an axenic culture of strain CICR‐MGMG1 isolated from diseased young seedling reproduced disease symptoms of yellowing, stunting and deformed growth similar to the symptoms reported from infected field condition. The strain CICR‐MGMG1 was consistently isolated from both diseased seedlings and stunted plants. Thus, the pathogenicity test of Koch's postulates was confirmed with the bacterium Enterobacter sp. strain CICR‐MGMG1 as the causal organism of sprout decay and seedling stunting. To the best of our knowledge, this is the first record of Enterobacter sp. causing sprouts decay and seedling stunting of cotton.

Arbuscular Mycorrhizal Fungi Inoculation as a Climate Adaptation Strategy for Establishment of Swietenia macrophylla King. Seedlings

Research Highlights: Drought stress significantly decreased the performance of seedlings in the nursery. Seedlings inoculated with Claroideoglomus etunicatum is recommended to produce superior planting stock of mahogany seedlings with better drought resistance in the nursery. Background and Objectives: With numerous intense droughts across tropical regions due to climate change, it is crucial to understand effects of drought stress on tree seedlings to improve crop management practices and avoid failures on large scale planting. Swietenia macrophylla, a commercial timber species in India, is poorly studied in relation to its management including physiological responses to various environmental stresses. Arbuscular mycorrhizal fungi (AMF) is known to improve performance of tree seedlings under drought conditions and produce quality planting stock in nursery. This study aims to understand the responses of mahogany seedlings under different levels of drought stress when inoculated with three types of AMF, namely Funneliformis mosseae, Claroideoglomus etunicatum, and Rhizophagus intraradices. Materials and Methods: The experiment is conducted in pot culture using a factorial completely randomized design. Different irrigation regimes were applied at 100, 80, 60, and 40 percentage of weekly cumulative evapotranspiration. The seedlings were tested for biometric, physiological, and mycorrhizal parameters periodically. Results: Physiological attributes such as rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, and water potential were found to be higher in the daily irrigated (control) seedlings. Performance of the seedlings were poorest in the least irrigated treatment. It was apparent that inoculated seedlings performed better than the non-inoculated ones. Conclusions: Among the three different AMF species used, C. etunicatum was found to be the most beneficial and suitable for the young mahogany seedlings. These seedlings also recorded higher root colonization percentage and total spore count in the rhizosphere soils. Seedlings inoculated with C. etunicatum showed positive influence on rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, relative growth rate (RGR) and water potential of seedlings.

Mild cadmium stress induces auxin synthesis and accumulation, while severe cadmium stress causes its rapid depletion in barley root tip

The aim of this study was to investigate the effect of 4-phenoxyphenylboronic acid (PPBo), an effective inhibitor of YUCCA enzyme on mild, moderate and severe Cd stress-induced responses in the root tips of young barley seedlings. While mild and moderate Cd stresses increased, severe Cd stress decreased the root IAA level. PPBo post-treatment strongly inhibited the Cd-induced IAA accumulation without affecting the Cd level in roots and mitigated the mild Cd stress-induced root growth inhibition, root swelling and lipoxygenase and glutathione peroxidase activity. In addition, PPBo reduced the H2O2 and NO generation under mild but had no effect under severe Cd stress, indicating that both H2O2 and NO act downstream of IAA in root responses to mild Cd stress. In turn, moderate or severe Cd stress strongly reduced the expression of IAA synthesis and cell cycle genes in the barley root tip. Therefore, we can conclude that IAA accumulation in the barley root tips is a distinctive feature of mild and moderate Cd stresses, which is involved in both root growth reorientation and defense response activation. PPBo completely reversed this Cd-induced IAA accumulation and stress responses, indicating that Cd induces IAA synthesis via indole-3-pyruvic acid biosynthesis pathway. On the contrary, severe Cd stress reduced IAA level was coupled with high ROS in the root tips and root growth arrest.

Transcriptome profiling of mild-salt responses in Lycium ruthenicum early seedlings to reveal salinity-adaptive strategies

The traditional Chinese desert shrub Lycium ruthenicum is widely distributed in arid environments such as north-west China, exhibiting ideal salt tolerance to cope with soil desertification, salinity, and alkalinity. However, the salt-tolerance mechanism of L. ruthenicum, especially of its young seedlings at early vegetative stages, remains largely unknown. In the present study, we collected whole-seedling samples from Lycium ruthenicum at a-pair-leaf stage with and without a mild salt (75 mM sodium chloride) treatment, and then performed transcriptome profiling to compare their gene expression patterns. The de novo assembly achieved 94,651 unigenes with 55,156 annotated. Among them, 199 differentially expressed genes (DEGs) were identified between salt-treated seedlings and control, with 41 up-regulated and 158 down-regulated. These DEGs were highly enriched into gene ontology (GO) classifications ‘metabolic process’ and ‘catalytic activity’, into Clusters of Orthologous Groups (COG) function classifications ‘translation, ribosomal structure and biogenesis’ and ‘energy production and conversion’, and into Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways ‘ribosome’ and ‘oxidative phosphorylation’. Specifically, genes involved in energy metabolism (oxidative phosphorylation) and related energy-consuming metabolisms, including ribosome-associated biogenesis and biosynthesis of organic nitrogen-derived compatible solutes (i.e., arginine and proline), were generally down-regulated. Specific genes involved in abscisic acid (ABA) biosynthesis and signaling pathway were simultaneously up-regulated. Changes in the transcript levels of salt-responsive DEGs selected from the transcriptomic profiling were further validated by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. Based on these results, salinity-adaptive strategies for the L. ruthenicum early seedlings are discussed.