Root Zone Research Articles

Root productivity contributes to carbon storage and surface elevation adjustments in coastal wetlands

Abstract Background and aims Organic matter additions in coastal wetlands contribute to blue carbon sequestration and adjustment to sea-level rise through vertical substrate growth, with accurate modelling of these dynamics requiring information of root mass and volume additions across tidal gradients. This study aims to characterise the influence of vegetation zonation and tidal position on root mass and volume dynamics within substrates. Methods The root ingrowth technique was coupled with sediment cores to quantify below-ground root mass and volume production, standing stocks and turnover across two years to 90 cm depth at Kooweerup, Victoria, Australia. Results We indicate a complex non-linear relationship between fine root mass production and tidal position, influenced by variable vegetation structures across mangrove (442–3427 g m−2 yr−1), saltmarsh (540–860 g m−2 yr−1) and supratidal forest (599 g m−2 yr−1) zones. Fine root volume additions ranged from 274 to 4055 cm3 m−2 yr−1 across sampling locations. Root production was greatest for older mangroves and tidally defined optimal zones of production were evident for mangrove and saltmarsh. Live roots extended deeper than typically studied, reaching depths of 1.0 m in forested zones. Conclusion This information of root mass and volume additions across wetland live rooting zones can be used to improve highly parameterised models accounting for carbon sequestration and substrate vertical adjustment along intertidal gradients. We recommend that future studies measure root production across the entire active rooting zone or to 1 m depth to align with standard carbon accounting measurement depths.

SOME FEATURES OF LINEAR AND ANGULAR PARAMETERS OF THE EYE’S ANTERIOR SEGMENT IN PATIENTS WITH OCULAR HYPERTENSION AND GLAUCOMA

Purpose – detection of some features of the relationship between anterior segment structures in eyes with ocular hypertension and primary glaucoma using ultrasound biomicroscopy (UBM). Material and methods A total of 60 patients (60 eyes) aged 27-60 years (46.6±11.4) with ophthalmic hypertension (n=7) and primary glaucoma (n=53) (0-2 stages in accordance with Mills glaucoma classification) were examined. They were divided into 3 groups in accordance with the axial length (AL): 16 short (<23.0mm), 23 medium (23.0-24.5mm) and 11 long eyes (>24.5mm). Main linear (mm) and angular (°) parameters of the eye’s anterior segment were measured using UBM (Ellex Eye Cubed, 40 MHz, Ellex Inc., Australia). Results The anterior chamber depth in short eyes was measured as 2.11±0.05, in medium – 2.47±0.04, in long – 3.02±0.06, posterior chamber depth: 0.58 ± 0.04, 0.65 ± 0.03, 0.69 ± 0.05. Iris thickness in root zone was 0.34±0.02, 0.34±0.01, 0.33±0.03. Ciliary body thickness at 1 mm from scleral spur: 0.47±0.03, 0.55±0.04, 0.62±0.05, at 2 mm: 0.28±0.03, 0.33±0.02, 0.38±0.03 respectively. “Trabecula-iris” distances at 250 µm from the scleral spur was: 0.09±0.03, 0.12±0.03, 0.21±0.04, at 500 µm: 0.14±0.02, 0.18±0.03, 0.27±0.03. “Trabecula-ciliary processes” was 0.65±0.05, 0.87±0.04, 1.07±0.06, length of Zinn zonules – 0.33±0.05, 0.52±0.04, 0.71±0.06 respectively. Anterior chamber angle (at 12´) was 16.34±5.65, 22.49±3.85, 27.04±3.23, “sclera-iris” angle: 15.80±2.34, 19.56±1.12, 24.97±1.59, “sclera-ciliary processes” angle – 38.21±2.44, 48.69±2.97, 51.22±3.66. Almost all patients had a predominantly flat iris profile, in short eyes it was more convex and anterior positioned, in long eyes – a straight iris profile combined with predominant posterior position, but in several cases – a concave profile. Conclusion Anterior chamber depth in combination with different AL is the most important factor in spatial arrangement of the eye's anterior segment structure. In eyes with a short AL a shallow posterior chamber depth, adjoining the iris to trabecula and partial coverage of posterior chamber by ciliary processes were observed. There were some difficulties in visualizing Zinn zonules due to coverage by ciliary processes and their adjoining to the root zone of iris in medium and long eyes. A flat iris profile was found in all 3 groups of glaucoma patients, but in eyes with medium and high AL it was more convex. Key words: ultrasound biomicroscopy, glaucoma, ocular hypertension, biometry

Gridded drought response assessment of winter wheat in Oklahoma using big data and AquaCrop-OS.

Winter wheat is the most dominant crop in Oklahoma and critically important to the economy of agricultural industry in this state and the region. However, weather anomalies such as droughts, which are frequent in Oklahoma, pose serious threats to winter wheat yield. This study was conducted to assess the effects of droughts on the simulated yield of dryland winter wheat (Ysd) in Oklahoma employing a gridded approach with the AquaCrop Open Source (AquaCrop-OS). Long-term (30-year) simulations showed that the average Ysd ranged from 0.9 to 7.1Mgha-1 across the 3281 grids of the Oklahoma winter wheat belt. At the climate division level, Ysd ranged from 2.9Mgha-1 in Panhandle to 5.5Mgha-1 in Central divisions. Fluctuation in Ysd generally agreed with the actual dryland yield measured at several research fields across the study area. However, the model tended to underestimate Ysd during certain drought events at some sites. The coefficient of variation (CV) for Ysd ranged from 0.1 to 1.6. Panhandle climate division had the largest CV, mainly due to inconsistency in growing season precipitation and temperature related stresses. In addition, grids with smaller total available water in the root zone, such as those with coarser textures near streams, had lower yields and larger CV. The strongest correlations between Ysd and drought indices (SPEI, Z-index, PDSI) existed in the months of March to May, when the crop is highly sensitive to water stress. Largest drought sensitivity of winter wheat, based on Ysd-drought index regression slopes, was estimated in West Central division for short to long-term droughts.

Estimating root zone soil moisture using the SMAR model and regression method at a headwater catchment with complex terrain

Estimating root zone soil moisture using the SMAR model and regression method at a headwater catchment with complex terrain

Impact of pulsed drip irrigation and organo-mineral N-fertilization on improving sandy soil properties and limon production

ABSTRACT The depletion of water resources has intensified with the evolving global climate change, leading to increased demands for water requirements in agricultural practices. In addressing these challenges, our consideration has centered on the implementation of environmentally friendly technologies. Lemon yields are diminishing due to the effects of severe climate change. To counter this decline, farmers resort to the application of nitrogen fertilizers in an attempt to boost yields. Nevertheless, the excessive use of nitrogen fertilizers has adverse effects on both plants and the environment. Therefore, two field experiments were carried out during the years 2021 and 2022 at the experimental farm (in the Nubaria region, Egypt) to examine the effects of two irrigation methods [conventional drip irrigation and pulse drip irrigation] and integrated nitrogen fertilization [five organo-mineral N fertilization rates OMN: OMN1 (100% mineral N + 0% organic N), OMN2 (75% MN + 25% ON), OMN3 (50% MN + 50% ON), OMN4 (25% MN + 75% ON), and OMN5 (0% MN + 100% ON)] on water productivity, lemon productivity, and fruit quality. In arid conditions, soil organic matter content, soil microorganisms activity, soil pH, water application efficiency, water stress inside the root zone, lemon productivity (LP), lemon water productivity (WPLemon), and lemon fruit quality were examined. The findings showed that the pulse drip irrigation approach improved LP, WPLemon, vitamin C, and lemon’s total soluble solids. The results also showed how integrated N-fertilization was important for increasing the proportion of organic component addition. Our findings suggested that applying pulsed drip irrigation coupled with integrating N-fertilization boosted water productivity, lemon productivity, and fruit quality. The highest outcomes were achieved when using pulse drip irrigation and 50% organic N + 50% mineral N-fertilizers.

INTERACTIVE IMPACT OF THE SPECTRAL COMPOSITION OF ADDITIONAL LIGHTING AND ROOT ZONE TEMPERATURE ON THE PRODUCTIVITY OF HYDROPONIC LETTUCE

Hydroponic lettuce production in greenhouses is becoming increasingly popular in Ukraine. However, there is a lack of research evaluating the impact of light spectra, root zone temperature, production systems, and lettuce varieties on yield. This study aims to determine the interactive effects of nighttime supplemental lighting, nutrient solution temperature, and production system on the growth and productivity of various lettuce varieties under suboptimal air temperatures typical for winter greenhouses. The study used three lighting regimes: no lighting (control), violet LEDs (spectrum R90:G0:B10), and warm white LEDs (spectrum R35:G42:B23). Two nutrient solution temperatures—12.6 °C (no heating) and 18.8 °C (with heating)—as well as two production systems—Nutrient Film Technique (NFT) and Constant Flood Table (CFT)—were applied for lettuce cultivation. Red and green lettuce varieties of four types were studied: leafy, heading, oakleaf, and romaine. The results showed that the absence of supplemental lighting and heating significantly reduced yield, while their combination positively influenced the dry mass of shoots. The highest productivity was achieved with the CFT system, especially when combined with violet LEDs, which had a higher red light component that stimulates plant growth. It was found that violet lighting significantly outperformed white LEDs, particularly when the nutrient solution was heated. The most sensitive lettuce varieties to root zone conditions and lighting were Adriana, Cedar, Red Sails, and Salvia. In particular, under violet LEDs, these varieties showed the highest productivity when the CFT system was used. This research suggests effective strategies for optimizing hydroponic lettuce cultivation in winter greenhouse conditions in Ukraine. The findings can be useful for farmers aiming to increase yield and product quality, as well as for optimizing costs under conditions of limited resources.

Effect of Nitrogen Fertilizer on the Rhizosphere and Endosphere Bacterial Communities of Rice at Different Growth Stages.

This study aimed to investigate the impact of nitrogen (N) fertilizer on bacterial community composition and diversity in the rhizosphere and endosphere of rice at different growth stages. Two treatments, N0 (no N application) and N1 (270 kg N ha-1), were implemented, with samples collected during the jointing, tasseling, and maturity stages. High-throughput sequencing was used to analyze the structure and composition of bacterial communities associated with Huaidao No. 5 (japonica conventional rice). The findings indicated that root zone location was the primary factor influencing the diversity and composition of rice root-associated bacterial communities. Further analysis revealed that nitrogen fertilizer primarily influenced rhizosphere bacterial diversity, while endosphere bacterial diversity was more significantly affected by growth stages. Rice recruited distinct beneficial bacteria in the rhizosphere and endosphere depending on the growth stage. Additionally, the relative abundance of functional genes related to nitrogen metabolism in root-associated bacteria was not significantly influenced by nitrogen application at 270 kg N ha-1. These findings offer valuable insights into how nitrogen fertilizer affects plant root bacterial communities across different growth stages.

Identification of WRKY transcription factors in Ipomoea pes-caprae and functional role of IpWRKY16 in sweet potato salt stress response

BackgroundWRKY transcription factors are plant-specific and play essential roles in growth, development, and stress responses, including reactions to salt, drought, and cold. Despite their significance, the WRKY genes in the wild sweet potato ancestor, Ipomoea pes-caprae, remain unexplored.ResultsIn this study, 65 WRKY genes were identified in the I. pes-caprae transcriptomic data. A phylogenetic tree incorporating Arabidopsis thaliana and Ipomoea batatas revealed seven major groups, each characterized by conserved gene structural features. Transcriptome data of I. pes-caprae under salt stress conditions identified 17 highly expressed WRKY genes, whose promoter regions contain cis-acting elements associated with plant growth, stress responses, and hormone signaling. Further analysis revealed that the 17 IpWRKY genes exhibited differential expression patterns under various abiotic stresses, suggesting their potential roles in specific stress responses. The gene IpWRKY16 was significantly up-expressed under salt stress, drought, salicylic acid (SA), and abscisic acid (ABA) treatments. Subcellular localization analysis confirmed that IpWRKY16 is located in the nucleus. Under salt stress, IpWRKY16 overexpressing roots showed high activity in superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and low content in malondialdehyde (MDA). Using non-invasive micro-test technology (NMT), a significant efflux of Na+ was observed in the elongation zones of sweet potato adventitious roots that overexpressed IpWRKY16. Quantitative reverse transcription PCR (qRT-PCR) revealed that several ion transporter genes were responsive to IpWRKY16 expression, with IbSOS3, IbAHA4-1, and IbAHA4-2 showing the highest expression levels. We hypothesize that IpWRKY16 responds to salt stress by forming a complex regulatory network involving these key genes.ConclusionsThis study provides a foundational understanding of WRKY transcription factors in I. pes-caprae, offering insights into their potential role in enhancing salt-tolerance in sweet potato. Our findings contribute valuable genetic knowledge that could aid in the molecular breeding of stress-resilient sweet potato varieties.

ZmSPL12 Enhances Root Penetration and Elongation in Maize Under Compacted Soil Conditions by Responding to Ethylene Signaling.

Soil compaction poses a significant challenge in modern agriculture, as it constrains root development and hinders crop growth. The increasing evidence indicated that various phytohormones collaborate in distinct root zones to regulate root growth in compacted soils. However, the study of root development in maize under such conditions has been relatively limited. Here, we identified that the ZmSPL12 gene, belonging to the SPL transcription factor family, plays a crucial and positive role in regulating root development in the compacted soil. Specifically, the overexpression of ZmSPL12 resulted in significantly less inhibition of root growth than the wild-type plants when subjected to soil compaction. Histological analysis revealed that the capacity for root growth in compacted soil is closely associated with the development of the root cap. Further exploration demonstrated that ZmSPL12 modulates root growth through regulating ethylene signaling. Our findings underscored that ZmSPL12 expression level is induced by soil compaction and then enhances root penetration by regulating root cap and development, thereby enabling roots to thrive better in the compacted soil environment.

Diversity of arbuscular mycorrhizal fungi and Soil Physicochemical Parameters in Forest Species of the Abras de Mantequilla Wetland, Ecuador

Wetlands worldwide face increasing challenges due to human activities such as water extraction, deforestation, and overfishing. These ecosystems are crucial for biodiversity, water retention, and purification. In Ecuador, the “Abras de Mantequilla” wetland exemplifies these pressures. It serves as a vital site for studying the interactions between soil fertility and arbuscular mycorrhizal fungi (AMF) in forest ecosystems. The study focused on the soil fertility, particularly in relation to AMF in "Noah Morán" secondary forest within the Abras de Mantequilla wetland. The key role of AMF in improving soil fertility was highlighted. Soil samples were collected from the root zone of four forest tree species i.e., Guazuma ulmifolia, Albizia guachapele, Eugenia pustulescens, Cecropia peltate. The four investigated soil samples had marginal differences in the soil physicochemical properties. Number of AMF species were found in the four soils in the range of 16 to 39; Number of por Several AMF lowest por the lowest (16) and highest (39) AMF species were found in E. pustulescens and A. guachapele soils, respectively. AMF species ‘Akent’ was the most dominant (abundance #16) AMF species found in the soils of C. peltate. The ranges of Shannon_H and Simpson_1-D values were found to be 1.78-1.9 and 0.79-0.85, respectively. These insights are important to understanding soil-plant-microorganism interactions in promoting sustainable agricultural practices in the Abras de Mantequilla wetland.

A non-invasive experiment for root zone monitoring using electrical resistivity imaging

A non-invasive experiment for root zone monitoring using electrical resistivity imaging

Salt Stress and its Implications in Vegetable Crops with Special Reference to the Cucurbitaceae Family

Salt stress is a significant abiotic factor that constrains agricultural productivity by impairing plant growth, particularly in arid and semi-arid regions. Vegetables, ranging from sensitive to moderately tolerant to salinity, experience adverse effects such as disruptions in seed germination, growth, flowering, and fruit development. Salinity hampers water uptake from the soil, as higher salt concentrations in the root zone increase the energy required by plants to absorb water. Sodium salts, in particular, interfere with the uptake of essential nutrients like nitrogen, phosphorus, and potassium, leading to nutritional imbalances. Furthermore, salinity induces oxidative and osmotic stress, ion toxicity, and hormonal disturbances, while also heightening plants‘ susceptibility to diseases. Crops in the Cucurbitaceae family, such as Cucumis sativus (cucumber) and Citrullus lanatus (watermelon), are known to exhibit diverse physiological and biochemical strategies to cope with salinity, including efficient ion transport regulation, osmolyte production, and antioxidant activity. Crops in the Cucurbitaceae family, such as Cucumis sativus (cucumber) and Citrullus lanatus (watermelon), exhibit diverse physiological strategies to cope with salinity. These traits are critical due to their economic significance in global agriculture. Understanding these mechanisms is crucial due to the economic significance of this family in global agriculture. This review examines the effects of salt stress on plant growth and development, explores tolerance mechanisms, and highlights the potential of crops from the Cucurbitaceae family to contribute to sustainable agricultural practices.

Microclimate Comparison Between Different Growth Forms at the Treeline Ecotone of Jiaozi Mountain, China

Climatic conditions strongly control the geographic distribution of treelines; long-term in situ climatic measurements at the treeline are still rare. While microclimatic differences between trees and shrubs at treeline ecotones are already well established and explained, supporting empirical data remain limited. In this study, we compared in situ microclimate measurements in the canopy, stem, and root zones of tree and shrub plots of Juniperus squamata Buch.-Ham. ex D.Don at the treeline ecotone of Jiaozi Mountain, Yunnan, China, in 2022. Although the shrubs experienced higher wind speeds compared to the trees at the treeline ecotone, the short stature of shrubs created warm stem and soil temperatures that are more suitable for plant growth and survival. Shrub distribution at higher elevations may be due to higher soil temperatures. The inability of shrubs to grow upright may be attributed to the fact that their canopy is limited by lower temperatures above the canopy during the frost season. This can provide new insights into the mechanisms of treeline formation.

In-Season Nitrogen Management in the Root Zone of Wheat in a Calcareous Soil Using the Response Index

ABSTRACT Excessive and inappropriate nitrogen (N) fertilizer applications on calcareous soils result in significant losses, necessitating a targeted approach for improved efficiency and yield. Field experiments were conducted over two seasons to develop a strategy for root-zone (RZ) N fertilization for wheat. In the first season, three methods of N fertilizer application were used: surface (SF), in the RZ at a depth of 10 cm (RZF10), and in the RZ at a depth of 20 cm (RZF20). The N fertilizer was applied in a range of 0–280 kg N ha−1. In the second season, another experiment was carried out to validate the results. The data showed that to achieve maximum yield levels, N fertilizer rates of 264 kg ha−1 for SF, 218 kg ha−1 for RZF10, and 183 kg ha−1 for RZF20 were required. The findings also revealed that relocating the application from the surface to depths of 10 and 20 cm resulted in an increase in recovery efficiency by 11.2% and 31.2%, respectively. A linear equation established the relationship between the response index at harvest (RI-Harvest) and the corrective N rate for RZF20. The in-season response index of the normalized difference vegetation index effectively predicted RI-Harvest, leading to the development of an empirical equation to predict the corrective N rate. The validation experiment demonstrated the effectiveness of the proposed strategy in adjusting N rates based on crop-specific needs. This approach allows growers to optimize profits by carefully applying N in the RZ, eliminating both excessive and inadequate use.

Long-Term Application of an Oil Residue Organic Fertilizer Improved Soil Physical Properties in the Root Zone of Jujube Trees

Organic fertilizers have been widely applied in Chinese agriculture. Soil aggregate composition and pore size distribution indicate the effects of fertilizer practices on soil quality. While the effects of the long-term application of organic fertilizers on total soil pore space have been reported, few studies have examined the distribution of connected pore spaces (of critical importance for solute transport in the soil). Soil physical and chemical properties influence plant growth and soil processes. We compared the effects of organic fertilizer application (10 years, 5 years, and no application) on soil connectivity pore structures and physicochemical properties within the root zone (20–40 cm depth) around date palms through CT scanning or core samples. Specifically, when the number of years of organic fertilizer application increased, the proportion of 2–0.25 mm particle size aggregates in the soil increased, and soil connectivity pore structure became more complex and stable, with higher connectivity, pore numbers, and numbers of pore throats. The connectivity of particles of the 0–300 μm size class of pores increased and the proportion of the 500–1000 μm class of pore throats increased. Soil organic matter and enzyme activity were significantly related to soil pore structure characteristics. In conclusion, the application of organic fertilizer improved soil pore structures, and the effects became more pronounced with the increased duration of application. These results provide theoretical and practical support for the application of organic fertilizer to improve soil structures in arid areas, and the findings have significant implications for sustainable agriculture in arid and semi-arid regions.

Simulating water and salt changes in the root zone of salt-alkali fragrant pear and the selection of the optimal surface drip irrigation mode.

Faced with the increasingly serious problem of water scarcity, developing precise irrigation strategies for crops in saline alkali land can effectively reduce the negative effects of low water resource utilization. Using a model to simulate the dynamic changes in soil water and salt environment in the root zone of fragrant pear trees in saline alkali land, and verifying them from a production practice perspective with comprehensive benefits as the goal, can optimize the irrigation amount and irrigation technology elements of saline alkali fruit trees, broaden the comprehensive evaluation perspective of decision-makers, and have important significance for improving the yield and production efficiency of forestry and fruit industry in arid and semi-arid areas worldwide. In this study, a two-year field experiment based on three irrigation levels (3000, 3750, and 4500 m3·ha-1) and four emitter discharge rates (1, 2, 3, and 4 L·h-1) was conducted in Xinjiang, China. The root zone soil water content (SWC) and soil salinity content (SSC) dynamics were simulated during the fertility period of fragrant pear using the numerical model HYDRUS-2D and field data. The results showed that the R2, root mean squared error (RMSE), and Nash-Sutcliffe efficiency coefficient (NSE) of the HYDRUS-2D simulated soil water content (SWC) (soil salinity content SSC) reached 0.89-0.97 (0.91-0.97), 0.02-0.16 cm3·cm-3 (0.22-1.54 g·kg-1), and 0.76-0.95 (0.68-0.96), respectively, indicating the strong performance of the model. A positive correlation was observed between the irrigation amount and soil infiltration depth. Moderately increasing irrigation amount could effectively leach soil salinity at a depth of 80-100 cm and maintain a water and salt environment in the main root zone of 0-80 cm, benefiting the growth and development of the main root system of fragrant pear, as well as the yield and quality of above-ground fruits. The irrigation amount and emitter discharge were optimized and quantified based on multi-objective optimization methods, normalization processing, and spatial analysis methods to maximize yield, fruit weight, soluble solids, and net profits. When the yield, fruit weight, soluble solids, and net profits simultaneously reached 90% of their maximum value, the irrigation amount and emitter discharge ranges were 4274-4297 m3·ha-1 and 3.79-3.88 L·h-1, respectively. Our study provides new insights into regulating soil water and salt environmental factors in the saline fragrant pear root zone and assessing the impact of soil water and salt management under precision irrigation strategies, and profoundly influences decision-making for irrigation of forest fruits in saline arid zones based on a production practice perspective.

INVESTIGATE THE IMPACT OF ZINC OXIDE NANOPARTICLES UNDER LEAD TOXICITY ON CHILLI (CAPSICUM ANNUUM L)

Capsicum annuum L is a commercially significant and valuable crop throughout the world. Weather variations and other stresses can significantly affect the growth and productivity of plants and limit crop productivity. One of the biggest stresses is lead poisoning since it hinders agricultural output and growth. Plants undergo biochemical, physiological, and morphological alterations in response to lead toxicity. As a result, the use of nanoparticles as an emerging method can significantly increase crop productivity. In this study, Kiar plants were employed to synthesize zinc oxide nanoparticles. Seed priming was performed using various applications of ZnO-NPs solution. In a field experiment, chilli plants were cultivated with various concentrations of lead acetate. Two different concentrations (250mg L-1 and 500mg L-1) were administered into the root zone. The following measurements were made after the ZnO nanoparticle supplementation: total chlorophyll content, carotenoids, peroxidase, catalase, flavonoids, and total phenolics content. Root and shoot length, fresh root weight and shoot weight, and dry root weight and shoot weight were all included in the morphological study. Nonetheless, the most noteworthy outcomes, proving that the concentration of ZnO-NPs affected chilli plants, was obtained upon applying the particles at a 150 ppm concentration. In comparison to untreated plants, the outcomes demonstrated that all plants treated with ZnO nanoparticles performed better when under stress.

First Report of Crown and Root Rot on Eastern Redbud (Cercis canadensis) Caused by Calonectria cylindrospora in Tennessee.

Eastern redbuds (Cercis canadensis) are the important trees in Tennessee nurseries, known for their vibrant spring blooms, and heart-shaped foliage (Kidwell-Slak and Pooler 2018). In May 2023, container-grown eastern redbuds exhibited crown and root rot symptoms. Disease incidence was 50% of 100 plants and severity was 40% for the affected root area. Symptoms appeared as sunken lesions localized around the crown region, while the roots showed dark brown to black discoloration. To isolate the causal agent, tissues from the symptomatic crown and roots were excised and surface sterilized with 1% sodium hypochlorite for 1 minute, followed by 70% ethanol for 30 seconds, and washed twice with sterile water. About 0.3 mm2 sections of the diseased tissues were placed on potato dextrose agar (PDA) and malt extract agar (MEA) and incubated at 25°C under 12 hours light/dark conditions. Colonies appeared orange to red-brown after 4 to 6 days on both PDA and MEA. Microscopic observations were conducted using two weeks old cultures grown on MEA. The conidiogenous apparatus (avg. 90 μm × 60 μm, n=50) consisted of penicillate conidiophore-bearing branches. The septate stipe extension (avg. 145 μm × 6 μm, n=50) terminated in a sphaeropedunculate vesicle (avg. 10 μm, n=50). The uniseptate macroconidia (avg. 45 μm × 4.5 μm, n=50) were hyaline, cylindrical, rounded at both ends and straight. The observed morphological traits aligned with Calonectria cylindrospora described by Liu et al. (2020). Pathogen identity was confirmed by sequencing specific genetic markers amplified from genomic DNA extracted using DNeasy PowerLyzer Microbial Kit from 7-day-old pure cultures. The primer pairs ITS1/ITS4 (White et al. 1990), T1F/T222 (O'Donnell et al. 2000), and EF1/EF2 (Carbone and Kohn 1999) were used to amplify and sequence the ribosomal internal transcribed spacer (ITS), and nuclear beta-tubulin (TUB) and translation elongation factors 1-α (EF1-α) genetic markers, respectively. The sequences of the three isolates were 99.8, 100, and 100% identical to C. cylindrospora (CBS 136425, CBS 30978, and CBS 119670) in the NCBI database, respectively. Phylogenetic analysis of concatenated sequences of ITS, TUB, and EF1-α of C. cylindrospora and other closely related taxa (Liu et al. 2020) retrieved from GenBank confirmed the identity of the pathogen as C. cylindrospora (Fig. 1). The sequences of three isolates (FBG5441, FBG5751, and FBG5752) were deposited in GenBank with accession numbers PQ482527, PQ482528, and PQ482529 (ITS), PQ493360, PQ493361, and PQ493362 (TUB), and PQ493363, PQ493364, PQ493365 (EF1-α), respectively. Three isolates were used to inoculate 1-year-old container-grown (1-gal) healthy eastern redbud plants. Conidial suspension (1.0 × 105 conidia/mL) was prepared for each isolate by using 14-day-old fungal cultures grown on MEA and was applied directly to the crown of the redbud, with an additional volume poured at the root zone for absorption (200 ml per plant) while sterile water was used as control. There were six replications for each isolate and control. Six weeks post-inoculation, the inoculated plants showed crown and root rot symptoms, while the controls remained healthy. Fungal isolates identical to the original in morphology and DNA sequences were recovered from inoculated plants. C. cylindrospora is recognized as a pathogen of ornamental plants (Aiello et al. 2022). To our knowledge, this is the first report of C. cylindrospora causing crown and root rot in redbud in Tennessee. Identifying this pathogen as the causal agent is important for developing effective and timely management strategies.

Flash Drought Teleconnection With the Large‐Scale Climate Drivers in the Homogeneous Rainfall Regions of India

ABSTRACTFlash drought events can be characterised by the quick depletion of crop root zone soil moisture (rapid intensification) and hence can be termed as agricultural flash droughts. These events can have devastating impacts, such as increasing the risk of agricultural yield loss, heatwaves and increased wildfire risk, which further have cascading impacts on the socio‐economic conditions. The regional hotspots of flash droughts are analysed for winter, pre‐monsoon, monsoon and post‐monsoon seasons over India from 1981 to 2020. We assess the impact of the El Niño‐Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the flash drought frequency (FDF: number of flash drought events). The causal connection of the FDF with the ENSO and IOD is analysed using the PCMCI (Peter and Clark's algorithm combined with the Momentary Conditional Independence) algorithm. The monsoon season (June–September) is found to be more prone to flash droughts with higher spatial/regional average values of total per pixel FDF during the 40‐year period over the Central Northeast (~54) and West Central (~41) regions. It is observed that the fraction of the total number of flash droughts during the El Niño years (38.8%) is higher as compared with that in La Niña years (25.7%). It is also found that the co‐occurrence of positive/negative IOD with the El Niño phase can alter the seasonal fraction of FDF over India, highlighting the high complexity in the ENSO–IOD interactions. The causal analysis shows that only the Southern Peninsula and West Central regions have significant direct and lagged causal links of average per pixel FDF with IOD. Whereas, similar (direct and lagged) causal connections are observed between the ENSO and IOD. This study reveals that flash droughts and their teleconnections vary greatly among the seasons and regions in India, limiting its accurate predictions and increasing the risk to agricultural communities.

Effect of biological additives to a putting green with low plant‐available phosphorus

AbstractThe use of phosphorus fertilizers on managed turf has become discouraged, if not restricted, in many places because of the risk of pollution of surface waters posed by excessive phosphorus application. Therefore, nontraditional options to increase phosphorus availability to turf are worthy of investigation. The objectives of this study were to evaluate the effect of additions of arbuscular mycorrhizal fungi and an N‐fixing bacterium, Methylobacterium symbioticum, on the nutritional status of a mature bentgrass putting green on a sand root zone with low plant‐available phosphorus status. The biological amendments were added at various intervals after aerification, and turfgrass responses were recorded over two field seasons. Mycorrhizae did not result in increased turfgrass visual quality, clipping yield, or clipping P content. Additions of the N‐fixing bacterium resulted in increased mid‐season clipping N content and increased visual turfgrass quality, but the overall effect was relatively small. It appears that applications of M. symbioticum to turfgrass hold promise for improving nutrient use efficiency and visual turfgrass quality and deserve future exploration.