Leaf Midrib Research Articles

Mutation of rice SM1 enhances solid leaf midrib formation and increases methane emissions.

The leaf midrib system is essential for plant growth and development, facilitating nutrient transport, providing structural support, enabling gas exchange, and enhancing resilience to environmental stresses. However, the molecular mechanism regulating leaf midrib development is still unclear.In this study, we reported a rice solid midrib 1 (sm1) mutant, exhibiting solid leaf aerenchyma and abaxial rolling leaves due to abnormal development of parenchyma and bulliform cells. Map-based cloning revealed that SM1 encodes a litter zipper protein (ZPR). SM1 was mainly expressed in the sheaths and basal midrib and was associated with the nucleus. Further experiments indicated that SM1 can interact with OSHB1, preventing the formation of OSHB:OSHB dimers and subsequently repressing the expression of OSH1 involved in the regulation and maintenance of apical stem meristem formation. The sm1 mutant reduced long-distance oxygen transport ability from shoot to root. The impaired oxygen transport in the sm1 mutant may have contributed to the increase in methanogens and elevated methane emissions. Collectively, our findings revealed that the SM1-OSHB1-OSH1 modules regulate leaf aerenchyma development in rice. These modules not only enhance our understanding of the molecular mechanism of rice leaf aerenchyma development but also offer insights for reducing methane emissions through genetic modification.

‘Candidatus Liberibacter brunswickensis’ colonization has no effect to the early development of Solanum melongena

This study is the first to investigate the presence and movement of the novel Liberibacter species ‘Candidatus Liberibacter brunswickensis’ (CLbr) in eggplant, Solanum melongena. The psyllid, Acizzia solanicola can transmit CLbr to eggplant and CLbr can be acquired by CLbr-negative A. solanicola individuals from CLbr-positive eggplants. In planta, CLbr can replicate, move and persist. Investigation into the early development of eggplants showed that CLbr titres had increased at the inoculation site at 14 days post inoculation access period (DPIAP). CLbr had become systemic in the majority of plants tested by 28 DPIAP. The highest bacterial titres were recorded at 35 DPIAP in all samples of the inoculated leaf, the roots, stems and the midrib and petiole samples of the newest leaf (the top leaf). This finding strongly suggests that CLbr movement in planta follows the source to sink relationship as previously described for ‘Ca. Liberibacter asiaticus’ (CLas) and ‘Ca. Liberibacter solanacearum’ (CLso). No symptoms consistent with Liberibacter-associated diseases were noted for plants colonised by CLbr during this study, consistent with the hypothesis that CLbr does not cause disease of eggplant during the early stages of host colonisation. In addition, no significant differences in biomass were found between eggplant colonised with CLbr, compared to those that were exposed to CLbr-negative A. solanicola, and to control plants.

STUDY ON ANATOMICAL CHARACTERIZATIONOF EXOTIC SPECIES AMHERSTIA NOBILIS WALL

Amherstia nobilis, known as the Pride of Burma and colloquially referred to as Simshipa-vriksham, is a remarkable and rare tropical tree celebrated in Indian mythology, especially within the context of the epic Ramayana. Often dubbed the Queen of Flowering Trees. The species was named in honour of Lady Sarah Amherst, an early collector of Asian plants, and it stands as the sole representative of its genus. This study involves microscopic examination of various parts of the plant, revealing intricate details about its cellular structure, vascular arrangements, and overall morphology. Mature leaves of A. nobilis, for instance, have been analyzed micro-morphologically, with an average leaf area calculated. The leaves are characterized by numerous rubiaceous stomata, as hypostomatic. In the leaf midrib, the vascular area appears oval and vascular elements are U-shaped. The leaf lamina flanked by highly cutinized upper and lower epidermis layers. The palisade tissue is bi-layered, while the lower leaf lamina features loosely packed spongy layers with numerous vein bundles and large air spaces and contains starch grains. Histological examination of the rachis reveals an oval shape with a slightly thick-walled epidermis and hypodermis containing air cavities. The vascular region is well-differentiated withxylem elements in linear multiples. The secondary phloem elementspossess numerous prismatic crystals and patches of phloem fibers. In the mature stem, periderm formation, with a highly reduced cortical region containing chlorenchymatous cells. The vascular region comprises phloem tissues with patches of phloem fibers. The xylem is with large vessels arranged in linear multiples. The pith is highly reduced with included phloem elements. Wood anatomy reveals the vessels displaying paratracheal parenchyma distribution, appearing as aliform or eyelet type. The vessel elements are arranged in linear multiples, and the radial longitudinal section shows large vessel elements with bordered pits separated by end plates. The bark showed uni- and multi-seriate ray cells, long and narrow phloem parenchyma, and prismatic crystal deposits in phloem ray-parenchyma cells. The parenchyma cells are traversed by numerous phloem fibers, with starch granules deposited in phloem parenchyma. In conclusion, Amherstia nobilis, the Pride of Burma, exemplifies a unique combination of aesthetic appeal and complex anatomical structure, making it a subject of significant interest in botanical and horticultural research. Detailed histological and anatomical studies provide crucial insights into the species unique adaptations and structural features, underscoring the need for continued conservation efforts to protect this majestic and rare tropical tree.

STUDY ON ANATOMICAL CHARACTERIZATIONOF RHINACANTHUS NASUTUS (L.) KURZ

Rhinacanthus nasutus (L.) Kurz, belonging to the family Acanthaceae, is an herbaceous shrub. This plant holds significant value in traditional medicine. The leaves of R. nasutus are commercially available as tea bags, marketed as a natural remedy for various ailments. However, the conservation status of R. nasutus necessitates appropriate protective measures to ensure its sustainability. Anatomical studies provide various histological layers, including the epidermis, cortex, vascular bundles, and pith. The leaves feature numerous diacytic stomata and hypostomatic nature. The leaf midrib exhibits a narrow epidermis with numerous glandular hairs. The medulla contains arc-shaped vascular bundles and lateral accessory bundles, with the stele comprising linear xylem elements towards the inner side and phloem elements on the outer region. Transfusion tracheids are present between the palisade and spongy cells, with tissues containing large quantities of oil droplets. The petiole shows a narrow epidermis with numerous glandular hairs. The vascular region features a V-shaped stele. The stem reveals the stelar region is extensive and the inner region is rich in developed xylem elements with linear multiple vessels. The medullary ray cells are narrow, and the pith region displays intruded primary xylem with thick-walled parenchyma cells. Wood anatomical analysis shows xylem parenchyma cells that are paratracheal. The vessel elements possessing perforation plates and transverse walls with bordered pits. Tracheids have a narrow lumen, and the lateral walls contain simple pits. The wood demonstrates multiseriate ray parenchyma and the bark consists of phloem rays and narrow fibers. In conclusion, R. nasutus exhibits a variety of histological and anatomical characteristics that support its traditional medicinal uses. The detailed anatomical studies contribute to understanding the plants structural adaptations and potential environmental interactions, thereby facilitating its identification and utilization in herbal medicine. The conservation of this species is critical to preserving its medicinal value and ensuring its availability for future research and therapeutic applications.

Utilizing Date Palm Leaf Biochar for Simultaneous Adsorption of Pb(II) and Iodine from Aqueous Solutions

This study addresses the environmental and health hazards posed by Pb(II) and iodine, two significant contaminants. The objective was to explore the adsorption of these substances from aqueous solutions using biochar derived from the leaf midribs of the date palm through a slow pyrolysis process. The pyrolysis was conducted in two stages within a vacuum furnace: initially at 300 °C for 1 h followed by overnight cooling, and then at 600 °C with a similar cooling process. The resulting biochar was characterized for its microstructural features and functional groups using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. It exhibited a porous structure with large numbers of pores (20 to 50 μm in size) and functional groups including O-H, C-H, and C=C, which are integral to its adsorption capabilities. For the adsorption studies, a 100 ppm Pb(II) ion solution was treated with varying amounts of biochar (20, 40, 60, and 80 mg) for 24 h. In parallel, iodine adsorption was tested, with biochar quantities ranging from 0.1 to 0.4 g/50 mL. Both treatments were followed by filtration and analysis using atomic absorption spectroscopy to determine the remaining concentrations of Pb(II) and iodine. The study also explored the effect of varying incubation periods (up to 30 h) on iodine adsorption. The results were significant; 100% adsorption of Pb(II) was achieved with the addition of 60 mg of biochar per 10 mL of solution. In contrast, for iodine, a maximum adsorption of 39.7% was observed with 30 mg or 40 mg of biochar per 50 mL. These findings demonstrate the potential of date palm-derived biochar as an effective and sustainable material for the removal of Pb(II) and iodine from contaminated water, offering valuable insights for environmental remediation strategies.

Leaf Anatomy Structure of Codiaeum variegatum (L.) Rumph. ex A. Juss Cultivars

Codiaeum variegatum (L.) Rumph. ex a. Juss is a common ornamental plant with a high variation of leaves shape and colour. This study aimed to analyze the leaves’ anatomy and the phenetic relationship between eight cultivars of C. variegatum which were defined by the differences in leaf morphology. The paraffin method prepared the transversal section of leaves, and anatomical characters were converted into binary data to calculate the similarity coefficient which was analyzed by Numerical Taxonomy System (NTSYS) 2.1 version. Leaves of eight cultivars of C. variegatum are varied in the anatomical structure of the primary vein and lamina. The eight cultivars of C. variegatum were clustered into four. The variations were found in 19 primary vein and lamina anatomy characteristics and the similarity coefficient is up to 0.59 between all cultivars. It can be concluded that the combination of leaf anatomical structures and midrib anatomical characters have notable taxonomic implications for future research.

Biochar from Date Palm Waste via Two-Step Pyrolysis: A Modified Approach for Cu (II) Removal from Aqueous Solutions

Heavy metals such as copper, often discharged from industrial processes and agricultural activities, pose significant environmental and health risks due to their toxicity, particularly in the soluble form of Cu (II). This study investigates the effectiveness of biochar produced from date palm leaf midrib waste via a two-step pyrolysis process, as a sustainable and economical adsorbent for removing Cu (II) from aqueous solutions The biochar was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. Adsorption experiments were conducted to evaluate the effects of pH, adsorbent dosage, contact time, and initial Cu (II) concentration. The maximum adsorption capacity was observed at pH 6, with a capacity of 70 mg/g. The adsorption data were best described by the pseudo-second-order kinetic model, indicating chemisorption as the primary mechanism. Thermodynamic studies indicated that the adsorption process was spontaneous and exothermic, with a Gibbs free energy change (ΔG) of −1.245 kJ/mol at 25 °C, enthalpy change (ΔH) of −15.71 kJ/mol, and entropy change (ΔS) of 48.36 J/mol·K. Reusability tests demonstrated that the biochar retained over 85% of its initial adsorption capacity after five cycles, with capacities of 60 mg/g in the first cycle, decreasing to 52 mg/g by the fifth cycle. This study highlights the potential of biochar derived from date palm waste as an efficient, sustainable adsorbent for the removal of Cu (II) from wastewater, contributing to both environmental management and waste valorization. Future research should focus on optimizing the biochar production process and exploring its application for the removal of other contaminants.

First Report of a 'Candidatus Phytoplasma sacchari'-Related Strain Associated with Yellowing and Decline of Silver Bluestem in Texas, U.S.A.

Silver bluestem [Bothriochloa laguroides (DC.) Herter] is a warm-season grass native to Texas. This perennial grass plays a crucial role in maintaining ecological balance and supporting wildlife in the region. In September 2022, while investigating the ecological impact of invasive grass species on a grassland located near Pipe Creek (TX), B. laguroides plants were observed showing symptoms that included yellowing of the blades and occasionally brown discoloration of the midveins and stems (Fig. S1). Disease incidence was estimated as 2% of silver bluestem plants in the 2 hectares surveyed. To investigate the possibility of a phytoplasma association with the symptoms, four symptomatic and four asymptomatic leaf samples were collected for further study. Total DNA was extracted from leaf midribs using a DNeasy Plant Mini Kit (Qiagen). The DNA extracts were tested using a phytoplasma-specific quantitative PCR assay (Hodgetts et al. 2009), which identified two out of the four symptomatic B. laguroides samples as positive for phytoplasmas. A semi-nested PCR assay for amplification of the 16S rRNA gene fragment was then performed on these samples with primers P1/16S-SR followed by P1A/16S-SR (Deng, and Hiruki 1991; Lee et al. 2004), and two additional housekeeping genes (tuf and secA) were amplified as previously described (Makarova et al. 2012; Hodgetts et al. 2008; Bekele et al. 2011). All amplicons of the expected size, 1.5 kb (16S rRNA), 0.4 kb (tuf) and 0.6 kb (secA), were purified and bi-directionally sequenced using primers from each gene second round PCR amplification. Analysis of the sequences derived from the three gene fragments revealed no variation between the two plant samples and confirmed they originated from a phytoplasma, termed strain TXSB-2 (Texas Silver Bluestem). Sequences from a single B. laguroides plant DNA extract were deposited in GenBank with accession numbers OR711913 (16S rRNA), OR709687 (tuf) and OR709688 (secA). A BLAST search of the 16S rRNA gene sequence from TXSB-2 against the NCBI nucleotide database, showed 99.58% sequence identity with an unclassified phytoplasma clone 139-1 from a leafhopper collected in Australia (MW281491) (Fig. S2). The partial nucleotide sequence of the tuf and secA genes showed 90.60% and 89.78% similarity, respectively, to the corresponding genes in 'Ca. P. sacchari' strain SCWL1 (CP115156) associated with sugarcane in China. The iPhyClassifier, an interactive online tool for phytoplasma identification and classification (Zhao et al. 2009), was used to determine the 'Candidatus Phytoplasma' species affiliation and group/subgroup classification status of this phytoplasma strain. The result showed that the TXSB-2 16S rDNA shared 98.94% sequence identity with that of the 'Ca. P. sacchari' reference strain (GenBank accession: MN889545), indicating TXSB-2 is a 'Ca. P. sacchari'-related strain. The result from virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA F2nR2 fragment revealed that TXSB-2 possessed a collective RFLP pattern that is distinct from the reference patterns of all established phytoplasma ribosomal subgroups and is proposed as the representative strain of a new subgroup designated as 16SrXI-H. 'Candidatus Phytoplasma sacchari' has been reported associated with sugarcane grassy shoot disease, which is considered among the most damaging diseases of sugarcane across parts of Southeast Asia and India (Kirdat et al. 2021). The same phytoplasma was recently confirmed infecting sorghum in India (Nithya et al. 2024). To our knowledge, this is the first report of a 'Ca. P. sacchari'-related strain infecting B. laguroides in the United States. Moreover, B. laguroides is a new host for strains related to 'Ca. P. sacchari'. Further investigation is required to elucidate the prevalence of this disease in the area, its natural vectors, and the potential consequences arising from this novel phytoplasma strain within its ecosystem in Texas.

Shrub leaf area and leaf vein trait trade-offs in response to the light environment in a vegetation transitional zone.

The leaf is an important site for energy acquisition and material transformation in plants. Leaf functional traits and their trade-off mechanisms reflect the resource utilisation efficiency and habitat adaptation strategies of plants, and contribute to our understanding of the mechanism by which the distribution pattern of plant populations in arid and semi-arid areas influences the evolution of vegetation structure and function. We selected two natural environments, the tree-shrub community canopy area and the shrub-grass community open area in the transition zone between the Qinghai-Tibet Plateau and the Loess Plateau. We studied the trade-off relationships of leaf area with leaf midvein diameter and leaf vein density in Cotoneaster multiflorus using the standardised major axis (SMA) method. The results show that the growth pattern of C. multiflorus , which has small leaves of high density and extremely small vein diameters, in the open area. The water use efficiency and net photosynthetic rate of plants in the open area were significantly greater than those of plants growing in the canopy area. The adaptability of C. multiflorus to environments with high light and low soil water content reflects its spatial colonisation potential in arid and semiarid mountains.

Optimized Nitrogen Application Rate Significantly Increases Total Economic Value and Quality of Flue-Cured Tobacco due to the Improvement of Superior Tobacco Yield

Summary With the improvement of irrigation and transportation infrastructures, single tobacco cultivation has been converted into tobacco–vegetable double cultivation in Yunnan Province. High residual nitrogen (N) levels in soil before tobacco transplanting induced by the excessive N input during the vegetable cultivation season resulted in a reduction of economic income and the quality of flue-cured tobacco. Therefore, the objective of this paper is to describe the optimization of N management and to provide a better understanding of the mechanism of optimal N application rate on the economic benefit and quality of tobacco. A field experiment with six N application rates (0, 45, 60, 75, 90, and 105 kg N ha−1) was carried out with a randomized block design in 2021 and 2022 in Yunnan Province. The economic value and yield, intrinsic chemical and processing quality, leaf growth rate and agronomic characters were determined. Compared with the currently recommended 105 kg N ha−1 rate, 75 kg N ha−1 significantly increased the total economic value and superior tobacco yields, improved the integrated grade of chemical compounds and resulted in leaf midrib proportions in an appropriate range. The total economic value positively correlated with the superior tobacco leaf yields (R2 = 0.91, p < 0.001), while not with medium and inferior leaf yield. The daily leaf growth rate in prosperous growth stage significantly correlated with the yield of superior tobacco and reached its maximum at a N rate of 75 kg N ha−1. The sum of N application rate and soil residual N before transplanting correlated with the total economic value (R2 = 0.66, p < 0.05) and superior leaf yield (R2 = 0.64, p < 0.05), respectively. Based on the amount of soil residual N before transplanting, the optimal N application rate was 66 kg N ha−1 which was 39 kg N ha−1 lower than the currently recommended N rate (105 kg N ha−1). Our results highlighted that the technical consultants and farmers should adjust the N application rate appropriately according to the residual N amount before transplanting and optimize the water and fertilizer management especially in the prosperous growth stage. An optimized N rate is not only of economic benefit and the improvement of quality of tobacco cultivation, but also environment friendly.

First Report of Phytophthora ramorum Causing Leaf Spots on Cornus capitata (Evergreen Dogwood) in United States.

Cornus capitata Wall. ex Roxb. (evergreen dogwood) is a bushy evergreen tree or shrub native to East Asia grown for its showy creamy bracts in late spring followed by attractive red fruit. In Feb 2023, a sample of foliage with leaf spots and tip dieback from C. capitata 'Mountain Moon' was submitted from a Humboldt Co. nursery as part of a CDFA inspection program for Phytophthora ramorum. The leaf spots were medium to dark brown, irregularly shaped, and ranged from 5 to 8 mm in diameter. They were located primarily along the leaf midrib and covered up to 1/4 of the leaf surface. Six 6-mm-diameter leaf discs taken from the margins of brown lesions and tip dieback were plated on Phytophthora selective CMA-PARP (PARP) media (Jeffers and Martin 1986). After 6 to 10 days, colonies resembling P. ramorum, with coralloid coenocytic hyphae, chlamydospores, ellipsoidal semi-papillate and caducous sporangia, and a relatively slow growth rate were recovered. Abundant sporangia formed on agar singly or in clusters on sympodially branched sporangiophores (n = 50), varying in size from 35 to 60 μm × 20 to 30 μm (mean 45.6 × 24.8 μm) with a length/breadth ratio ranging from 1.3 to 2.3 (mean 1.8). Chlamydospores (n = 50) ranged from 35 to 62 μm in diameter (mean 51.9 μm) on 14-day-old PARP cultures. The internal transcribed spacer region (ITS) using primers ITS5/ITS4 (White et al. 1990; accession no. OR636225) and cytochrome oxidase subunit 1 region (cox1) using primers OomCox1Levup/Fm85mod (Robideau et al. 2011; OR635665) of one isolate (0254-32A) were amplified and sequenced. BLAST analysis showed 100% identity of both regions to P. ramorum ex-type strain (MG865581 and MH136973). Microsatellite loci placed the P. ramorum isolate in the NA2 clonal lineage (Goss et al, 2011). Pathogenicity of P. ramorum isolate 0254-32A was tested using five C. capitata plants (2.5-year-old, 28-cm-tall, 3.78-liter pot). Zoospore inoculum was produced as described in Blomquist et al. (2021). Above ground parts of each plant were sprayed with inoculum (15 ml, 1.3 × 105 zoospores/ml). Inoculated plants were incubated in a dew chamber in the dark at 23°C for 72 h and then placed in a 23±1°C growth chamber with a 12-h photoperiod. Five control plants were treated as above but with sterile water instead of the zoospore suspension. Two days after inoculation, brown spots were visible on leaves on all inoculated plants, initiating from where the drops of inoculum had persisted. After 3 days, brown lesions, from water drop- to majority of entire leaf-sized, were observed on approximately 75% of inoculated leaves. After 6 days, lesions expanded to the edges of leaves, causing leaf curling and defoliation. Lesions stopped expanding after 3 weeks, and by 4 weeks, most infected leaves had abscised, with no new infections observed. Phytophthora ramorum was consistently isolated from foliar lesions of inoculated plants on PARP. It was not isolated from leaf or stem tissues of control plants, which remained asymptomatic during the 4-week experiment period. Phytophthora ramorum was detected on C. capitata in the UK in 2015 (DEFRA 2015). To our knowledge, this is the first report of P. ramorum infecting C. capitata in the United States and the completion of Koch's postulates on any Cornus spp. Incidence on C. capitata in the California nursery was low. However, their proximity to other infected foliar hosts suggests Cornus spp. may present a potential risk for the spread of P. ramorum.

Morphology and chemical composition of Taiwan oil millet (Eccoilopus formosanus) epicuticular wax.

Taiwan oil millet has two types of epicuticular wax: platelet wax composed primarily of octacosanol and filament wax constituted essentially by the singular compound of octacosanoic acid. Taiwan oil millet (TOM-Eccoilopus formosanus) is an orphan crop cultivated by the Taiwan indigenous people. It has conspicuous white powder covering its leaf sheath indicating abundant epicuticular waxes, that may contribute to its resilience. Here, we characterized the epicuticular wax secretion in TOM leaf blade and leaf sheath using various microscopy techniques, as well as gas chromatography to determine its composition. Two kinds of waxes, platelet and filaments, were secreted in both the leaf blades and sheaths. The platelet wax is secreted ubiquitously by epidermal cells, whereas the filament wax is secreted by a specific cell called epidermal cork cells. The newly developed filament waxes were markedly re-synthesized by the epidermal cork cells through papillae protrusions on the external periclinal cell wall. Ultrastructural images of cork cell revealed the presence of cortical endoplasmic reticulum (ER) tubules along the periphery of plasma membrane (PM) and ER-PM contact sites (EPCS). The predominant wax component was a C28 primary alcohol in leaf blade, and a C28 free fatty acid in the leaf sheath, pseudopetiole and midrib. The wax morphology present in distinct plant organs corresponds to the specific chemical composition: platelet wax composed of alcohols exists mainly in the leaf blade, whereas filament wax constituted mainly by the singular compound C28 free fatty acids is present abundantly in leaf sheath. Our study clarifies the filament wax composition in relation to a previous study in sorghum. Both platelet and filament waxes comprise a protection barrier for TOM.

Morpho-biochemical characterization of a unique avocado (Persia americana Mill.) accession PA-026 (IC0644455)

A unique avocado accession PA-026 (IC0644455) bearing yellow colour fruits was identified and evaluated for morphological and biochemical parameters. The accessions PA-026 characterise as yellow coloured pulp, young shoots and leaf midribs, fruit weight (398.3 g), pulp weight (255.38 g), seed weight (92.35 g) and peel thickness (1.43 mm). The biochemical profiling showed that, it has high carotenoid content (7.17 mg/100 g), total phenols (102.24 mg GAE/100 g), FRAP activity (87.32 AEAC/100 g) and high β-carotene (3.85 μg/g) followed by α-carotene (1.03 μg/g), while, fatty acid profile showed presence of five fatty acids, among which oleic acid (52.11%) and palmitic acid (41.56%) were most dominant. In conclusion, avocado accession PA-026 was found unique with respect to yellow fruit, pulp colour, and high carotenoid content especially β-carotene, which could be used to improve the carotenoids content in avocado through breeding.

Strong plastic responses in aerenchyma formation in F1 hybrids of Imperata cylindrica under different soil moisture conditions.

Hybrids can express traits plastically, enabling them to occupy environments that differ from parental environments. However, there is insufficient evidence demonstrating how phenotypic plasticity in specific traits mediates hybrid performance. Two parental ecotypes of Imperata cylindrica produce F1 hybrids. The E-type in wet habitats has larger internal aerenchyma than the C-type in dry habitats. This study evaluated relationships between habitat utilisation, aerenchyma plasticity, and growth of I. cylindrica accessions. We hypothesize that plasticity in expressing parental traits explains hybrid establishment in habitats with various soil moisture conditions. Aerenchyma formation was examined in the leaf midribs, rhizomes and roots of two parental ecotypes and their F1 hybrids in their natural habitats. In common garden experiments, we examined plastic aerenchyma formation in leaf midribs, rhizomes and roots of natural and artificial F1 hybrids and parental ecotypes and quantified vegetative growth performance. In the natural habitats where soil moisture content varied widely, the F1 hybrids showed larger variation in aerenchyma formation in rhizomes than their parental ecotypes. In the common garden experiments, F1 hybrids showed high plasticity of aerenchyma formation in rhizomes, and their growth was similar to that of C-type and E-type under drained and flooded conditions, respectively. The results demonstrate that F1 hybrids of I. cylindrica exhibit plasticity in aerenchyma development in response to varying local soil moisture content. This characteristic allows the hybrids to thrive in diverse soil moisture conditions.

First report of a 'Candidatus phytoplasma asteris' related strain (16SrI) associated with phyllody and witches'-broom symptom in Pisum sativum in Hisar, India.

Pea (Pisum sativum L.) is a leguminous vegetable crop, and India holds the fourth position in the production, primarily contributed by three major states: Uttar Pradesh, Madhya Pradesh, and Punjab (Anonymous, 2022). However, a survey conducted in February 2023 at the National Seed Corporation Farm (15 hectares) in Hisar, Haryana, revealed deformities in the growth of some pea plants. Approximately 10% of these plants exhibited a distinct bushy appearance, accompanied by phyllody and witches'-broom symptoms, characterized by deformed leaves and short internodes (Fig. 1). In response to these observed anomalies, a detailed molecular analysis was conducted at the Plant Pathology Laboratory, IARI, New Delhi. The investigation involved the collection of ten samples each from symptomatic and asymptomatic plants, and DNA was extracted from 100 mg leaf midribs using the CTAB method (Ahrens and Seemüller, 1992). The extracted DNA (100 ng/µl) along with one positive (Catharanthus roseus from glass house, 16SrII-D group) and one negative (without template DNA), served as a template for PCR reactions targeting the 16Sr RNA and secA genes. Universal primers P1/P7 and secAfor1/secArev3 were employed in the first round of PCR for the respective genes. Subsequently, the product from the 1st round was diluted and used as a template for the 2nd round of PCR with primers R16F2n/R16R2 for 16Sr RNA and secAfor2/secArev3 for the secA gene (Gundersen and Lee 1996; Deng and Hiruki 1991; Hodgetts et al. 2008). This nested-PCR approach yielded distinct bands, approximately 1.2 kb (16Sr RNA) and 480 bp (secA), from the DNA of all ten symptomatic plants and positive sample, while no bands were observed in any of the asymptomatic plants. The nested PCR products were sequenced by BBS labs (Barcode biosciences, Bengaluru). The 16Sr RNA gene sequences, showing 100% similarity, were submitted to NCBI as representative sequences (Acc. No. OQ690013, OQ690014, OQ709133, OQ709134). Similarly, secA gene sequences were submitted with Acc. Nos. OR604283-86. BLAST analysis revealed a maximum 99.76% identity with Onion yellows phytoplasma and 'Ca. P. asteris' reference strain for 16Sr RNA gene, and a maximum 100% identity with 'Elaeis guineensis' stunt phytoplasma for secA gene. The phylogenetic tree constructed using the 16S rRNA and secA gene sequences indicated that the pea phytoplasma strains of this study clustered with 'Ca. P. asteris' (16SrI-B) related strains (Fig 2a and 2b). Additionally, the 16S rRNA sequences from this study, when subjected to Virtual RFLP using iPhyclassifier (Zhao et al. 2009), exhibited a pattern (Fig. 3) matching the reference pattern of the 16S group I, subgroup B (GenBank accession: M30790), with a similarity coefficient of 1.0. Previously, Rao et al. (2021) reported several crops associated with the 16SrI ribosomal group, including eight sub-groups from India. However, this report represents the first instance of a phytoplasma 16SrI-B group associated with phyllody and witches'-broom symptoms in pea, both in India and globally. Considering the economic importance of pea as a vegetable crop, the observed disease incidence and affected area are significant. Urgent attention is required to conduct additional research and implement preventive measures to avert the potential outbreak of this disease in the near future.

Evaluation of the Physical Properties of Goatskins Tanned using Banana (Musa spp.) Leaf Midrib Tannins

Vegetable tannins have been studied over the years with an aim to reduce the pollution load caused by chrome tanning. Although mimosa tannins have been utilized commercially, they are expensive and not readily available. The purpose of this study was to assess the physical properties of leather tanned with banana leaf midribs tannins in order to determine their suitability as vegetable tannins. Selected banana leaf midrib samples were collected from Gikondi village in Mukurweini, Nyeri County, Kenya. They were shade-dried and ground into powder. The skins were processed conventionally using banana leaf midribs tannins of Musa sapientum Linn. and ‘Muraru’ (AA genome), with mimosa as a control. The physical properties of the resultant leathers were determined following the standard IUP methods. It was found that Musa sapenitum Linn, ‘Muraru’ (AA genome) and mimosa-tanned leathers had average shrinkage temperatures of 80.33 ± 0.74°C, 78.67 ± 0.47°C and 81.67 ± 0.94°C, respectively. The properties of the tanned leathers were compared with those of the control-tanned leather. Assessment of the physical properties indicated that the leathers met the minimum recommended values safe for Musa sapentium Linn-tanned leather, which failed at 30,000 flexes. These results indicate that banana leaf midribs can be used as an organic tanning agent source for production of leathers from goatskins.

Rhizoctonia solani AG1-IB, AG1-IC, and AG4-HGII cause bottom rot of field lettuce in Vermont.

Members of Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) species complex cause bottom rot on lettuce (Latuca sativa) and yield losses up to 70% (Subbarao et al. 2017). Severe symptoms include necrosis, stem rot, and/or discoloration especially on the leaf midrib. In Vermont, vegetable farms are small (0.5-30 acres) and grow lettuce concurrently with other vegetable crops in the same field but the AG(s) that causes the disease in Vermont has not been determined. Isolates (n = 157) were collected from 31 fields with reported history of bottom rot between July 10 and October 8, 2019, across Addison, Caledonia, Chittenden, Franklin, Lamoille, and Orleans counties. Isolates were collected from lettuce tissue or potato (Solanum tuberosum), a common rotation crop, or uncropped soil baited using radish (Raphanus sativus). Pieces of tissue (5-10 mm) were cut from the leading margin of lesions, surface disinfested with 0.1% NaClO for 1 min followed by 2 rinses with sterile water, blotted dry, and plated onto acidified 2% water agar (0.085% lactic acid, pH 4.8). After incubation for 48 to 72 h, mycelia resembling Rhizoctonia were examined for morphological characteristics including hyphal branching at ca. 90o angles, a septum near the branching point, multiple nuclei per cell, and lack of both clamp connections and conidia (Sneh et al. 1991). Colonies were white to dark brown, and some produced small sclerotia. Koch's postulates were performed by inoculating nine 8-week-old (9 leaf pairs) romaine lettuce plants (Johnny's Seeds, Winslow, ME, cv. Monte Carlo) per isolate. Isolates were grown on 2% potato dextrose agar for 1 week, from which a 5-mm agar plug was placed on the adaxial leaf surface at the base of a petiole. Plants were enclosed in a plastic bag to maintain high humidity and grown under a 16-hour photoperiod at 24 °C. Disease severity was rated 4 days after inoculation (0: healthy, 1: isolated lesions, 2: lesions across multiple petioles, and 3: systemic disease). Putative AG were determined by Sanger sequencing of the internal transcribed spacer (ITS) region using the ITS1F and ITS4B primer pair (758 bp) (Gardes and Bruns 1993). Contigs were assembled using CAP3 software (Huang and Madan 1999). Taxonomy was assigned to each OTU via the NCBI BLASTn database with criteria as 0.0 E and nucleotide match of at least 97%. Of the 10 isolates sequenced with sufficient coverage (735 to 784 bp alignment length) and definitive resolution (96.7 to 99.9% identity), 5 were putative AG 1-IB (Genbank Accession HG934430.1), 2 AG 1-IC (Genbank Accession AF354058.1), 2 AG 3 (Genbank Accession AF354064.1), and 1 AG 4-HGII (Genbank Accession AF354074.1). Fasta files and metadata are archived at 10.6084/m9.figshare.20301324, 10.6084/m9.figshare.20301375. Putative AG 1-IB was highly virulent on lettuce plants whether it originated from potato (mean 2.6) or lettuce (mean 1.3 to 3). AG 4-HGII and AG 1-IC isolated from lettuce and radish, respectively, were moderately severe (mean 1.4 to 2.2) on lettuce with identical symptoms. The two potato isolates (AG3) were not pathogenic on lettuce. Similarly, higher incidence of AG 1-IB is reported on lettuce in Quebec (Wallon et al. 2021), Ohio (Herr 1993), and Germany (Grosch et al. 2004). Because AG vary in their host range (Sneh et al. 1991), knowing the AG will inform management decisions such as crop rotation and weed control. This is the first report of the causal agent of bottom rot of lettuce or any AG of R. solani in Vermont.

Application of humic acid increases the economic value and yield of superior tobacco as well as improves the chemical and processing quality

AbstractThe overuse of nitrogen (N) fertilizer in the vegetable growing season leads to a high amount of soil residual N and a decrease of resistance to tobacco disease in the vegetable–tobacco continuous cultivation system, which will seriously threaten the sustainable development of tobacco production. Humic acid (HA) rich in bioactive substances and microelements may enhance leaf growth rate and improve the quality of tobacco. A two‐factor randomized block experiment was carried out over 2 years to evaluate the effects of additional applying HA (0 and 150 L ha−1) combined with three N rates (0, 60, and 90 kg N ha−1) on tobacco growth, economic value, chemical, and processing quality. Applying HA significantly increased the tobacco economic value by 5%–28%. The superior tobacco yields positively correlated with the economic value (R2 = 0.88), which was the key factor determining the increase of the economic value. The application of HA decreased the disease severity and increased the microelement uptake and the daily leaf growth rate in the prosperous growing stage which was positively correlated with the superior tobacco yield. Applying HA significantly improved the chemical quality and reduced the leaf midrib proportion. At the N rate of 60 kg N ha−1, HA showed the best effect of improving quality and increasing income. Our results demonstrated that the addition of HA can significantly improve the economic value and the chemical and processing quality of tobacco. The best effect can be achieved by adjusting the N rate appropriately according to the amount of soil residual N before transplanting tobacco seedlings.

Potential functions of the shared bacterial taxa in the citrus leaf midribs determine the symptoms of Huanglongbing.

Citrus is a globally important fruit tree whose microbiome plays a vital role in its growth, adaptability, and resistance to stress. With the high throughput sequencing of 16S rRNA genes, this study focused on analyzing the bacterial community, especially in the leaf midribs, of healthy and Huanglongbing (HLB)-infected plants. We firstly identified the shared bacterial taxa in the midribs of both healthy and HLB-infected plants, and then analyzed their functions. Results showed that the shared bacterial taxa in midribs belonged to 62 genera, with approximately 1/3 of which modified in the infected samples. Furthermore, 366 metabolic pathways, 5851 proteins, and 1833 enzymes in the shared taxa were predicted. Among these, three metabolic pathways and one protein showed significant importance in HLB infection. With the random forest method, six genera were identified to be significantly important for HLB infection. Notably, four of these genera were also among the significantly different shared taxa. Further functional characterization of these four genera revealed that Pseudomonas and Erwinia likely contributed to plant defense against HLB, while Streptomyces might have implications for plant defense against HLB or the pathogenicity of Candidatus Liberibacter asiaticus (CLas). Overall, our study highlights that the functions of the shared taxa in leaf midribs are distinguished between healthy and HLB-infected plants, and these microbiome-based findings can contribute to the management and protection of citrus crops against CLas.

A potential candidate gene associated with the angles of the ear leaf and the second leaf above the ear leaf in maize

BackgroundLeaf angle is a key trait for maize plant architecture that plays a significant role in its morphological development, and ultimately impacting maize grain yield. Although many studies have been conducted on the association and localization of genes regulating leaf angle in maize, most of the candidate genes identified are associated with the regulation of ligule-ear development and phytohormone pathways, and only a few candidate genes have been reported to enhance the mechanical strength of leaf midrib and vascular tissues.ResultsTo address this gap, we conducted a genome-wide association study (GWAS) using the leaf angle phenotype and genotyping-by-sequencing data generated from three recombinant inbred line (RIL) populations of maize. Through GWAS analysis, we identified 156 SNPs significantly associated with the leaf angle trait and detected a total of 68 candidate genes located within 10 kb upstream and downstream of these individual SNPs. Among these candidate genes, Zm00001d045408, located on chromosome 9 emerged as a key gene controlling the angles of both the ear leaf and the second leaf above the ear leaf. Notably, this new gene’s homolog in Arabidopsis promotes cell division and vascular tissue development. Further analysis revealed that a SNP transversion (G/T) at 7.536 kb downstream of the candidate gene Zm00001d045408 may have caused a reduction in leaf angles of the ear and the second leaf above the ear leaf. Our analysis of the 10 kb region downstream of this candidate gene revealed a 4.337 kb solo long-terminal reverse transcription transposon (solo LTR), located 3.112 kb downstream of Zm00001d045408, with the SNP located 87 bp upstream of the solo LTR.ConclusionsIn summary, we have identified a novel candidate gene, Zm00001d045408 and a solo LTR that are associated with the angles of both the ear leaf and the second leaf above the ear leaf. The future research holds great potential in exploring the precise role of newly identified candidate gene in leaf angle regulation. Functional characterization of this gene can help in gaining deeper insights into the complex genetic pathways underlying maize plant architecture.