Root Stem Research Articles

Expert System For Diagnosing Alzheimer's Using Certainty Factor Method

This expert system for diagnosing Alzheimer's disease is a computer-based stem system used as a tool to diagnose Alzheimer's disease based on a dynamic knowledge base. This knowledge base contains knowledge obtained from various sources including from the experience of experts who are proficient in their fields and also books related to diagnosis of Alzheimer's disease and then collected into a database system needed for making conclusions. In this system, the certainty factor method will be used using a forward chaining inference engine. The purpose of making this root stem p can be useful for many people and can know clearly about Alzheimer's disease from its symptoms and solutions, which will be displayed in the form of a website using PHP programming with MySQL database.

Phytophthora palmivora causes root and basal stem rot disease on macaw palm (Acrocomia aculeata) in Brazil

Macaw palm (Acrocomia aculeata Jacq.) is an oleaginous palm native to the American continent. It produces oil and has other important characteristics for the industry. In 2022, a severe disease causing basal stem rot, root rot, and plant mortality in a nursery and the field was detected on macaw palm plants in a farm, in João Pinheiro, Minas Gerais state, Brazil. From the rot symptomatic tissue of affected palms, two Phytophthora isolates were obtained by indirect isolation and were grown on PDA. Based on the morphological characteristics, particularly the coenocytic hyphae and papillate sporangia, the isolates were identified as Phytophthora palmivora. For phylogenetic analyses, the internal transcribed spacer (ITS) regions, β-tubulin gene (TUB), translation elongation factor 1-alpha gene (EF1-α), and two mitochondrial genes: cytochrome c oxidase subunit I (COXI) and cytochrome c oxidase subunit II (COXII), were amplified. Phylogenetic analyses confirmed that it is the species P. palmivora. Fulfillment of the Koch's postulates through pathogenicity test confirmed that P. palmivora was the causal agent of root rot and basal stem rot disease in macaw palm. This is the first report of this pathogen causing disease in macaw palms in Brazil.

Optimum Nitrogen, Phosphorous, and Potassium Fertilizer Application Increased Chrysanthemum Growth and Quality by Reinforcing the Soil Microbial Community and Nutrient Cycling Function

Nitrogen (N), phosphorus (P), and potassium (K) are three macronutrients that are crucial in plant growth and development. Deficiency or excess of any or all directly decreases crop yield and quality. There is increasing awareness of the importance of rhizosphere microorganisms in plant growth, nutrient transportation, and nutrient uptake. Little is known about the influence of N, P, and K as nutrients for the optimal production of Chrysanthemum morifolium. In this study, a field experiment was performed to investigate the effects of N, P, and K on the growth, nutrient use efficiency, microbial diversity, and composition of C. morifolium. Significant relationships were evident between N application rates, C. morifolium nutrient use, and plant growth. The N distribution in plant locations decreased in the order of leaf > stem > root; the distributions were closely related to rates of N application. Total P fluctuated slightly during growth. No significant differences were found between total P in the roots, stems, and leaves of C. morifolium vegetative organs. Principle component analysis revealed that combinations of N, P, and K influenced soil nutrient properties through their indirect impact on operational taxonomic units, Shannon index, and abundance of predominant bacterial taxa. Treatment with N, P, and K (600, 120, and 80 mg·plant−1, respectively) significantly improved plant growth and quality and contributed to the bacterial richness and diversity more than other concentrations of N, P, and K. At the flowering time, the plant height, leaf fresh weight, root dry weight, stem and leaf dry weight were increased 10.6%, 19.0%, 40.4%, 27% and 34.0%, respectively, when compared to the CK. The optimal concentrations of N, P, and K had a positive indirect influence on the available soil nutrient content and efficiency of nutrient use by plants by increasing the abundance of Proteobacteria, decreasing the abundance of Actinobacteria, and enhancing the potential functions of nitrogen metabolism pathways. N, P, and K fertilization concentrations of 600, 120, and 80 mg·plant−1 were optimal for C. morifolium cultivation, which could change environmental niches and drive the evolution of the soil microbial community and diversity. Shifts in the composition of soil microbes and functional metabolism pathways, such as ABC transporters, nitrogen metabolism, porphyrin, and the metabolism of chlorophyll II, glyoxylate, and dicarboxylate, greatly affected soil nutrient cycling, with potential feedback on C. morifolium nutrient use efficiency and growth. These results provide new insights into the efficient cultivation and management of C. morifolium.

BRIP1 and BRIP2 maintain root meristem by affecting auxin-mediated regulation.

This study reveals that mutations in BRIP1/2 subunits of the BAS complex disrupt root meristem development by decreasing PIN genes expression, affecting auxin transport, and downregulating essential root genes PLT. Switch defective/sucrose non-fermentable (SWI/SNF) chromatin remodeling complexes play vital roles in plant development. BRAHMA-interacting proteins1 (BRIP1) and BRIP2 are subunits of BRAHMA (BRM)-associated SWI/SNF complex (BAS) in plants; however, their role and underlying regulatory mechanism in root development are still unknown. Here, we show that brip1 brip2 double mutants have a significantly shortened root meristem and an irregular arrangement in a portion of the root stem cell niche. The mutations in BRIP1 and BRIP2 cause decreased expression of the PIN-FORMED (PIN) genes, which in turn reduces the transport of auxin at the root tip, leading to the disruption of the accurate establishment of normal auxin concentration gradients in the stem cells. Chromatin immunoprecipitation (ChIP) experiments indicated that BRIP1 and BRIP2 directly bind to the PINs. Furthermore, we found a significant down-regulation in the expression of key root development genes, PLETHORA (PLT), in brip1 brip2. The brip1 brip2 plt1 plt2 quadruple mutations do not show further exacerbation in the short-root phenotype compared to plt1 plt2 double mutants. Using a dexamethasone (DEX)-inducible PLT2 transgenic line, we showed that acute overexpression of PLT2 partially rescues root meristem defects of brip1 brip2, suggesting that BRIP1 and BRIP2 act in part through the PLT1/2 pathway. Taken together, our results identify the critical role and the underlying mechanism of BRIP1/2 in maintaining the development of root meristem through the regulation of auxin output and expression of PLTs.

NnWOX1-1, NnWOX4-3, and NnWOX5-1 of lotus (Nelumbo nucifera Gaertn)promote root formation and enhance stress tolerance in transgenic Arabidopsis thaliana

BackgroundAdventitious roots (ARs) represent an important organ system for water and nutrient uptake in lotus plants because of degeneration of the principal root. The WUSCHEL-related homeobox (WOX) gene regulates plant development and growth by affecting the expression of several other genes. In this study, three WOX genes, NnWOX1-1, NnWOX4-3, and NnWOX5-1, were isolated and their functions were assessed in Arabidopsis plants.ResultsThe full lengths of NnWOX1-1, NnWOX4-3, and NnWOX5-1 were 1038, 645, and 558 bp, encoding 362, 214, and 185 amino acid residues, respectively. Phylogenetic analysis classified NnWOX1-1 and NnWOX4-3 encoding proteins into one group, and NnWOX5-1 and MnWOX5 encoding proteins exhibited strong genetic relationships. The three genes were induced by sucrose and indoleacetic acid (IAA) and exhibited organ-specific expression characteristics. In addition to improving root growth and salt tolerance, NnWOX1-1 and NnWOX4-3 promoted stem development in transgenic Arabidopsis plants. A total of 751, 594, and 541 genes, including 19, 19, and 13 respective genes related to ethylene and IAA metabolism and responses, were enhanced in NnWOX1-1, NnWOX4-3, and NnWOX5-1 transgenic plants, respectively. Further analysis showed that ethylene production rates in transgenic plants increased, whereas IAA, peroxidase, and lignin content did not significantly change. Exogenous application of ethephon on lotus seedlings promoted AR formation and dramatically increased the fresh and dry weights of the plants.ConclusionsNnWOX1-1, NnWOX4-3, and NnWOX5-1 influence root formation, stem development, and stress adaptation in transgenic Arabidopsis plants by affecting the transcription of multiple genes. Among these, changes in gene expression involving ethylene metabolism and responses likely critically affect the development of Arabidopsis plants. In addition, ethylene may represent an important factor affecting AR formation in lotus seedlings.

Temporal colonization of macadamia tree roots by Phytophthora cinnamomi based on a newly developed quantitative real‐time PCR assay

AbstractPhytophthora cinnamomi is an important soilborne pathogen causing root rot and stem cankers on macadamia in South Africa and other countries. It is unknown whether a temporal pattern exists in the colonization of macadamia tree roots by P. cinnamomi. To investigate this, three macadamia orchards were studied bimonthly for 2 years. The study also examined whether two types of feeder roots contained varying levels of P. cinnamomi DNA. A new sensitive P. cinnamomi‐specific quantitative real‐time PCR (qPCR) assay was used to conduct the assessments. Only symptomatic trees were studied in two of the orchards (ZC and ZD), while symptomatic and asymptomatic trees were assessed in the third orchard (ZA). In the ZC and ZD orchards, white non‐suberized feeder roots from a new root flush had higher levels of P. cinnamomi DNA than suberized feeder roots. In orchard ZD, autumn and winter yielded the highest P. cinnamomi root quantities in suberized roots. The symptomatic and asymptomatic trees in orchard ZA generally contained higher P. cinnamomi root quantities in winter than in summer. However, in orchard ZC, no significant temporal pattern was evident, although a trend was noticeable towards higher P. cinnamomi root colonization in autumn, winter and spring. Principal component analyses supported autumn and winter as the months yielding the highest P. cinnamomi root colonization levels. The study has contributed to a better understanding of the temporal nature of P. cinnamomi root colonization, and feeder root types that are optimal for qPCR quantifying the pathogen in macadamia.

Tree seedling shade tolerance arises from interactions with microbes and is mediated by functional traits

Shade tolerance is a central concept in forest ecology and strongly influences forest community dynamics. However, the plant traits and conditions conferring shade tolerance are yet to be resolved. We propose that shade tolerance is shaped not only by responses to light but also by a species’ defense and recovery functional traits, soil microbial communities, and interactions of these factors with light availability. We conducted a greenhouse experiment for three temperate species in the genus Acer that vary in shade tolerance. We grew newly germinated seedlings in two light levels (2% and 30% sun) and controlled additions of microbial filtrates using a wet-sieving technique. Microbial filtrate treatments included: <20 µm, likely dominated by pathogenic microbes; 40-250 µm, containing arbuscular mycorrhizal fungi (AMF); combination, including both filtrate sizes; and sterilized combination. We monitored survival for nine weeks and measured fine root AMF colonization, hypocotyl phenolics, stem lignin, and stem+root nonstructural carbohydrates (NSC) at three-week intervals. We found that differences in seedling survival between low and high light only occurred when microbes were present. AMF colonization, phenolics, and NSC generally increased with light. Phenolics were greater with <20 µm microbial filtrate, suggesting that soil-borne pathogens may induce phenolic production; and NSC was greater with 40-250 µm filtrate, suggesting that mycorrhizal fungi may induce NSC production. Across species, microbe treatments, and light availability, survival increased as phenolics and NSC increased. Therefore, shade tolerance may be explained by interactions among soil-borne microbes, seedling traits, and light availability, providing a more mechanistic and trait-based explanation of shade tolerance and thus forest community dynamics.

First Report of Diaporthe fruit rot and stem canker of hydroponic cucumber caused by Diaporthe sp. in the United States.

Multiple Diaporthe spp. cause root and fruit rots or stem lesions on Cucumis spp.: D. cucurbitae, D. melonis, D. longicolla (syn. D. eres), D. pterocarpi, D. sclerotioides, D. sojae, and D. ueckerae (Broge et al. 2020; Fukada et al. 2018; Udayanga et al. 2012, 2015). From May-August 2021, cucumbers (Cucumis sativus) 'Katrina' and 'Alcazar' were grown in a 24-plant, commercial Bato bucket system with rockwool blocks on a perlite substrate in a research greenhouse in Wooster, Ohio. At maturity, plants collapsed rapidly from stem lesions without foliar chlorosis (25% of 'Katrina' and 17% of 'Alcazar'). Lesions were 7.5 to 15 cm in length, tan to golden-brown with black pycnidia and located 5 to 15 cm above the crown. Stems shredded easily with vascular discoloration around the lesion. Two identical fungal strains were isolated on ½ acidified potato dextrose agar (APDA) following surface disinfestation with 0.6% sodium hypochlorite for 30 s and sterile water rinse. Fungal cultures were floccose, white to tan mycelia with pycnidia. Oblong, elliptical, biguttulate, aseptate alpha conidia were observed with mean dimensions: 8.0 µm (5.2-9.8 µm) by 3.1 µm (2.5-3.8 µm) on ½ APDA and 9.8 µm (6.6-12.4 µm) by 3.0 µm (1.9-5.3 µm) on petioles. On prune extract agar, beta conidia mean dimensions were: 19.7 µm (12.0-27.7 µm) by 1.2 µm (0.8-1.8 µm). Fungal DNA was amplified and sequenced bidirectionally with ITS (ITS4/ITS5), CAL (CAL228F/737R), HIS (CYLH3F/H3-1B), TEF1 (EF1-728f/EF1-986R), and TUB2 (Bt1a/Bt1b) primers (Carbone and Kohn 1999; Glass and Donaldson 1995) (GenBank: OP265712-13, OP288460-65, OQ418506-07). Based on a maximum likelihood phylogenetic tree of concatenated genes, this novel Diaporthe sp., most closely related to D. stewartii, has not been reported on Cucumis spp. Strains were deposited in the USDA-ARS Culture Collection (NRRL# 64461-62). Koch's postulates were conducted in a greenhouse with mean day temperature of 25°C and 12 hr supplemental lighting. One-month old cucumbers 'Katrina,' grown in rockwool cubes (5 plants per isolate) and potting mix (6 plants per isolate), were inoculated with a one-week-old culture of either strain. The second true leaf was cut and a pipette tip containing an inoculated plug of ½ APDA was placed on the remaining petiole (Mathew et al. 2018). Non-inoculated ½ APDA was used for controls. Plants were tarped for 24 hours to increase humidity and pipette tips removed after one week. After two weeks, petioles were shrunken, tan to golden brown with pycnidia. After 3-4 weeks, stem lesions matching those above were observed on inoculated plants, and plants collapsed. For fruit rot, three Beit Alpha cucumbers were rinsed with tap water, dried, a 5 mm plug was removed from the fruit and replaced with a 5 mm plug of one-week-old fungus on ½ APDA. After 3 days, fruits were water soaked and soft. For root rot, two plates of one-week-old cultures were macerated in 500 mL of sterile water and mixed with 1500 mL of vermiculite. Two seeds of cucumber 'Katrina' were planted into three reps of each isolate and control. All control seeds germinated, but all inoculated seeds experienced pre- or post-emergence damping off. No symptoms were ever observed on any controls. Fungi were isolated from all inoculated tissues as described above. Based on morphology, Diaporthe sp. was isolated from all inoculated plants but never from controls. This Diaporthe sp. may be a new constraint to hydroponic cucumber production, but incidence needs to be determined globally.

Survival tactics of an endangered species Withania coagulans (Stocks) Dunal to arid environments.

Withania coagulans is a valuable medicinal plant with high demand, but its wild growth and local usage pose a threat to its natural habitat. This study aims to understand the plant's growth, anatomy, and physiology in different environmental conditions to aid in conservation and re-vegetation efforts. Fifteen differently adapted populations of Withania coagulans were collected from diverse ecological regions, viz., (i) along the roadside, (ii) hilly areas, (iii) barren land, and (iv) wasteland to unravel the adaptive mechanisms that are responsible for their ecological success across heterogenic environments of Punjab, Pakistan. The roadside populations had high values of photosynthetic pigments, total soluble proteins, root endodermis thickness, stem and leaf cortical thickness, and its cell area. The populations growing in hilly areas showed better growth performance such as vigorous growth and biomass production. Additionally, there was enhanced accumulation of organic osmolytes (glycine betaine and proline), chlorophyll content (chl a/b), and enlarged epidermal cells, cortical cells, vascular bundles, metaxylem vessels, and phloem region in roots. In case of stem area, epidermal thickness, cortical thickness, vascular bundle, and pith area showed improved growth. However, the barren land population showed significant increase in carotenoid contents, vascular bundle area, and metaxylem area in roots, and xylem vessels and phloem area in stems and leaves. The wasteland population surpassed the rest of the populations in having greater root dry weight, higher shoot ionic contents, increased root area, thick cortical, and vascular bundle area in roots. Likewise, cortical thickness and its cell area, and pith area in stems, whereas large vascular bundles, phloem region, and high stomatal density were recorded in leaves. Subsequently, natural populations showed the utmost behavior related to tissue organization and physiology in response to varied environmental conditions that would increase the distribution and survival of species.

The cold-induced factor CBF3 mediates root stem cell activity, regeneration, and developmental responses to cold

Plant growth and development involve the specification and regeneration of stem cell niches (SCNs). Although plants are exposed to disparate environmental conditions, how environmental cues affect developmental programs and stem cells is not well understood. Root stem cells are accommodated in meristems in SCNs around the quiescent center (QC), which maintains their activity. Using a combination of genetics and confocal microscopy to trace morphological defects and correlate them with changes in gene expression and protein levels, we show that the cold-induced transcription factor (TF) C-REPEAT BINDING FACTOR 3 (CBF3), which has previously been associated with cold acclimation, regulates root development, stem cell activity, and regeneration. CBF3 is integrated into the SHORT-ROOT (SHR) regulatory network, forming a feedback loop that maintains SHR expression. CBF3 is primarily expressed in the root endodermis, whereas the CBF3 protein is localized to other meristematic tissues, including root SCNs. Complementation of cbf3-1 using a wild-type CBF3 gene and a CBF3 fusion with reduced mobility show that CBF3 movement capacity is required for SCN patterning and regulates root growth. Notably, cold induces CBF3, affecting QC activity. Furthermore, exposure to moderate cold around 10°C–12°C promotes root regeneration and QC respecification in a CBF3-dependent manner during the recuperation period. By contrast, CBF3 does not appear to regulate stem cell survival, which has been associated with recuperation from more acute cold (∼4°C). We propose a role for CBF3 in mediating the molecular interrelationships among the cold response, stem cell activity, and development.

Transcriptional activation by WRKY23 and derepression by removal of bHLH041 coordinately establish callus pluripotency in Arabidopsis regeneration.

Induction of the pluripotent cell mass termed callus from detached organs or tissues is an initial step in typical in vitro plant regeneration, during which auxin-induced ectopic activation of root stem cell factors is required for subsequent de novo shoot regeneration. While Arabidopsis (Arabidopsis thaliana) AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19 and their downstream transcription factors LATERAL ORGAN BOUNDARIES DOMAIN (LBD) are known to play key roles in directing callus formation, the molecules responsible for activation of root stem cell factors and thus establishment of callus pluripotency are unclear. Here, we identified Arabidopsis WRKY23 and BASIC HELIX-LOOP-HELIX 041 (bHLH041) as a transcriptional activator and repressor, respectively, of root stem cell factors during establishment of auxin-induced callus pluripotency. We show that auxin-induced WRKY23 downstream of ARF7 and ARF19 directly activates the transcription of PLETHORA 3 (PLT3) and PLT7 and thus that of the downstream genes PLT1, PLT2, and WUSCHEL-RELATED HOMEOBOX 5 (WOX5), while LBD-induced removal of bHLH041 derepresses the transcription of PLT1, PLT2, and WOX5. We provide evidence that transcriptional activation by WRKY23 and loss of bHLH041-imposed repression act synergistically in conferring shoot-regenerating capability on callus cells. Our findings thus disclose a transcriptional mechanism underlying auxin-induced cellular reprogramming, which, together with previous studies, outlines the molecular framework of auxin-induced pluripotent callus formation for in vitro plant regeneration programs.

Delayed rooting hormone application and stem cutting collection time improved Flacourtia indica rooting ability and root growth

Flacourtia indica (Burm.f.) Merr. is an important fruit and medicinal tree in Southern Africa. Efforts to achieve early fruiting have failed with juvenile propagules (planting materials) such as seed. Assessing rooting ability of mature (fruit bearing) F. indica stem cuttings is vital to attaining early fruiting, or precocious fruiting, which reduces the long juvenile phase experienced by many woody fruit trees when propagated from seeds (juvenile planting materials). The objectives of this study were to assess responses of mature stem cuttings to different application times of rooting hormone (Seradix® No. 2) and collection times of stem cuttings, and also to identify important pheno-phases in the yearly tree growth cycle of F. indica. A significantly higher rooting percentage (p < 0.001) was obtained with delayed Seradix® No. 2 application than with immediate application. Stem cuttings collected at flowering and leaf fall seasons were responsive to Seradix® No. 2 application, but all stem cuttings collected at fruiting time failed to produce roots. For stem cuttings collected during flowering time, immediate Seradix® application resulted in significantly (p = 0.0482) more roots than in stem cuttings subjected to delayed Seradix® application. The failure to produce roots of cuttings collected at fruiting time could be due to low sugars (carbohydrates) in the stem cuttings. The study concluded that the best time to collect stem cuttings from mature F. indica trees for rooting is either at flowering or leaf fall stages and that delayed Seradix® No. 2 application improves rooting of stem cuttings from mature F. indica trees.

Preserving root stem cell functionality under low oxygen stress: the role of nitric oxide and phytoglobins.

The preservation of quiescent center stem cell integrity in hypoxic roots by phytoglobins is exercised through their ability to scavenge nitric oxide and attenuate its effects on auxin transport and cell degradation. Under low oxygen stress, the retention or induction of phytoglobin expression maintains cell viability while loss or lack of induction of phytoglobin leads to cell degradation. Plants have evolved unique attributes to ensure survival in the environment in which they must exist. Common among the attributes is the ability to maintain stem cells in a quiescent (or low proliferation) state in unfriendly environments. From the seed embryo to meristematic regions of the plant, quiescent stem cells exist to regenerate the organism when environmental conditions are suitable to allow plant survival. Frequently, plants dispose of mature cells or organs in the process of acclimating to the stresses to ensure survival of meristems, the stem cells of which are capable of regenerating cells and organs that have been sacrificed, a feature not generally available to mammals. Most of the research on plant stress responses has dealt with how mature cells respond because of the difficulty of specifically examining plant meristem responses to stress. This raises the question as to whether quiescent stem cells behave in a similar fashion to mature cells in their response to stress and what factors within these critical cells determine whether they survive or degrade when exposed to environmental stress. This review attempts to examine this question with respect to the quiescent center (QC) stem cells of the root apical meristem. Emphasis is put on how varying levels of nitric oxide, influenced by the expression of phytoglobins, affect QC response to hypoxic stress.

SEC14-like condensate phase transitions at plasma membranes regulate root growth in Arabidopsis.

Protein function can be modulated by phase transitions in their material properties, which can range from liquid- to solid-like; yet, the mechanisms that drive these transitions and whether they are important for physiology are still unknown. In the model plant Arabidopsis, we show that developmental robustness is reinforced by phase transitions of the plasma membrane-bound lipid-binding protein SEC14-like. Using imaging, genetics, and in vitro reconstitution experiments, we show that SEC14-like undergoes liquid-like phase separation in the root stem cells. Outside the stem cell niche, SEC14-like associates with the caspase-like protease separase and conserved microtubule motors at unique polar plasma membrane interfaces. In these interfaces, SEC14-like undergoes processing by separase, which promotes its liquid-to-solid transition. This transition is important for root development, as lines expressing an uncleavable SEC14-like variant or mutants of separase and associated microtubule motors show similar developmental phenotypes. Furthermore, the processed and solidified but not the liquid form of SEC14-like interacts with and regulates the polarity of the auxin efflux carrier PINFORMED2. This work demonstrates that robust development can involve liquid-to-solid transitions mediated by proteolysis at unique plasma membrane interfaces.

First report of Phytopythium vexans causing root rot on Macadamia integrifolia in China.

Soil-borne plant-pathogenic Phytopythium spp. can cause root rot and damping off on important plant species, resulting in serious economic loss. A survey in October 2021 identified soil-borne diseases occurring on Macadamia integrifolia in Yunnan Province, China. Microbes were isolated from necrotic roots of 23 trees with root rot symptoms by growing on cornmeal-based oomycete-selective 3P (Haas 1964) and P5APR (Jeffers and Martin, 1986) media at 24ºC in the dark for 7 days. Of the 56 single-hyphal isolates obtained, 18 were morphologically similar to Phytopythium vexans (van der Plaats-Niterink 1981; de Cock et al. 2015). Isolates LC04 and LC051 were selected for molecular analyses. The internal transcribed spacer (ITS) region and the cytochrome c oxidase subunit II (CoxII) gene were PCR-amplified using universal primers ITS1/ITS4 (White et al. 1990) and oomycete-specific primers Cox2-F/Cox2-RC4 (Choi et al. 2015), respectively. The PCR products were sequenced with the amplification primers and sequences were lodged in Genbank (Accession no. OM346742, OM415989 for ITS, OM453644, OM453643 for CoxII for isolates LC04 and LC051, respectively). The top BLAST hit in the Genbank nr database for all four sequences was Phytopythium vexans (>99% identity). A maximum-likelihood phylogenetic tree was constructed with analogous concatenated ITS and CoxII sequences from either type or voucher specimens of 13 Phytopythium species in the same phylogenetic clade as P. vexans (Table 1; Bala et. al 2010). Isolates LC04 and LC051 grouped most closely to P. vexans, with LC051 basal and sister to LC04 and P. vexans voucher specimen CBS119.80 with 100% support (Fig. 1). Millet seed inoculated with agar pieces colonized by P. vexans LC04 and LC51 was used to fulfill Koch's postulates (Li et al. 2015) in a completely randomized experimental design. Four 6-month-old M. integrifolia var. Keaau (660) seedlings were transplanted into pasteurized commercial potting mix containing 0.5% (w/w) inoculum. Plants were grown in free draining pots and watered once a day. At 14 days post-inoculation, roots were discolored compared to control plants inoculated with millet seed mixed with agar plugs lacking P. vexans (Fig. 2). By 30 days post-inoculation, infected roots were discolored with obvious decay and reduction in root system size. Control plants were symptomless. P. vexans was successfully re-isolated from two lesioned roots from each plant. The infection experiment was done twice, demonstrating that P. vexans LC04 and LC51 caused root disease on M. integrifolia. P. vexans causes root rot, damping-off, crown rot, stem rot or patch canker on economically important trees in many parts of the world, including seven plant species in China (Farr and Rossman 2022). This is the first report of pathogenic P. vexans on M. integrifolia in China. Reports of pathogenic P. vexans on multiple hosts in several parts of the world suggest it should be considered a quarantine risk and included in risk mitigation or pest management plans that include other species of Phytopythium, or species of Pythium or Phytophthora, to which P. vexans has many similarities (de Cock et al. 2015).

The long non-coding RNA LINDA restrains cellular collapse following DNA damage in Arabidopsis thaliana.

The genomic integrity of every organism is endangered by various intrinsic and extrinsic stresses. To maintain genomic integrity, a sophisticated DNA damage response (DDR) network is activated rapidly after DNA damage. Notably, the fundamental DDR mechanisms are conserved in eukaryotes. However, knowledge about many regulatory aspects of the plant DDR is still limited. Important, yet little understood, regulatory factors of the DDR are the long non-coding RNAs (lncRNAs). In humans, 13 lncRNAs functioning in DDR have been characterized to date, whereas no such lncRNAs have been characterized in plants yet. By meta-analysis, we identified the putative long intergenic non-coding RNA induced by DNA damage (LINDA) that responds strongly to various DNA double-strand break-inducing treatments, but not to replication stress induced by mitomycin C. After DNA damage, LINDA is rapidly induced in an ATM- and SOG1-dependent manner. Intriguingly, the transcriptional response of LINDA to DNA damage is similar to that of its flanking hypothetical protein-encoding gene. Phylogenetic analysis of putative Brassicales and Malvales LINDA homologs indicates that LINDA lncRNAs originate from duplication of a flanking small protein-encoding gene followed by pseudogenization. We demonstrate that LINDA is not only needed for the regulation of this flanking gene but also fine-tuning of the DDR after the occurrence of DNA double-strand breaks. Moreover, Δlinda mutant root stem cells are unable to recover from DNA damage, most likely due to hyper-induced cell death.

First Report of Charcoal Rot Caused by Macrophomina phaseolina on Hemp (Cannabis sativa) in Missouri.

Charcoal rot, caused by Macrophomina phaseolina, is abundantly present in the soil and has been reported as pathogenic to both soybean and corn, as well as numerous other hosts, including hemp grown for fiber, grain, and cannabinoids (Casano et al. 2018; Su et al. 2001). Hemp (Cannabis sativa) production in Missouri was a relatively new addition to the 2021 growing season. Charcoal rot was reported in Reynolds, Knox, and Boone counties in Missouri from commercial and experimental fields. One of the fields in question experienced heavy disease pressure and had an uneven stand loss, but the total loss was estimated at approximately 60% of the field and was attributed to charcoal rot. Charcoal rot signs and symptoms, microsclerotia on the lower stem and root tissue, wilting and stem discoloration, were observed on a majority of the hemp plants received at the University of Missouri Plant Diagnostic Clinic in July and late Fall of 2021, including samples from Bradford Research Farm in Boone County and Greenley Research Center in Knox County. Root and crown tissue from the hemp plants from the Greenley Research Center were cultured onto acidified potato dextrose agar (APDA). Macrophomina phaseolina and other fungi grew from the plated tissue after about three days of incubation at room temperature. Macrophomina phaseolina was confirmed based on the presence of melanized hyphae and microsclerotia (Siddique et al. 2021). The microsclerotia were black, round to ovoid shaped and ranged from about 34-87 µm (average 64 µm) in length and 32-134 µm (average 65 µm) in width (n = 44). A single-hyphae isolation from a putative M. phaseolina isolate was conducted to obtain a pure culture. The M. phaseolina culture from the Greenley Research Center was used to complete Koch's postulates of charcoal rot on four hemp cultivars. Sterilized toothpicks were added to pure cultures of M. phaseolina on APDA and incubated at room temperature for one week to allow for colonization and for use in greenhouse inoculation. Four hemp cultivars (Katani, Grandi, CFX-2, and CRS-1) were grown in a sterilized silt loam for three weeks in a greenhouse. About four plants per cultivar were grown for inoculation and one plant per cultivar was used as a control. The plants were inoculated with the M. phaseolina colonized toothpicks that were gently rubbed onto stem tissue and subsequently inserted into the soil at the stem. For six weeks, the plants were kept in greenhouse conditions of 25°C with a 12-hour light and dark cycle and were watered when soil appeared dry. Plants were kept in a loosely sealed container constructed from wood and vinyl sheeting to minimize cross contamination with other plants grown in the same greenhouse. Plants were monitored weekly for charcoal rot symptoms. Symptoms that resembled charcoal rot, wilting and microsclerotia on the lower stem, were present on inoculated plants after about four weeks and symptoms were not present on the control plants. Isolates resembling M. phaseolina in culture were recovered from symptomatic plants; therefore, Koch's postulates were successfully fulfilled and the fungus was recovered from the inoculated plants. DNA was extracted from the pure cultures of both the initial isolate and the isolate obtained from Koch's postulates using GeneJet Plant Genomic DNA Purification Kit (Thermo Scientific, California, USA) and the internal transcribed spacer (ITS) region of ribosomal DNA including ITS1, 5.8S, and ITS4 regions were amplified using universal primers ITS1 and ITS4 (White et al. 1990). The ITS region was sequenced and compared to reference sequences in GenBank by BLAST analysis. Recovered isolates (GenBank accession no. OQ455934.1) showed closest sequence similarity (100%) to M. phaseolina accession number GU046909.1. Little is known about the life cycle, growth conditions, and possible inoculum buildup in the soil in hemp in Missouri. In addition, M. phaseolina is a known pathogen of corn and soybean and effective management strategies are challenging for these crops as well due to the broad host range of the pathogen. Cultural management practices, such as crop rotations to reduce inoculum in the soil and closely monitoring for symptoms, may help reduce the severity of this disease.

Biocontrol of cucumber Fusarium wilt by Trichoderma asperellum FJ035 dependent on antagonism and spatiotemporal competition with Fusarium oxysporum

Fusarium wilt is one of the major constraints of cucumber production worldwide and is difficult to control in production. This study selected a strain of Trichoderma asperellum FJ035 with a good antagonistic effect against Fusarium oxysporum f. sp. cucumerinum Owen (FOC) by plate confrontation test and secondary metabolites (volatile substances and non-volatile substances) antagonism tests. T. asperellum FJ035 inhibited spore germination of FOC and improved the germination potential of cucumber seeds. The spatiotemporal competition dynamics of T. sperellum FJ035 green fluorescence-labeled strain and FOC red fluorescence-labeled strain in the cucumber rhizosphere were monitored under a laser confocal microscope. The results showed that the vitality of FOC in the cucumber rhizosphere exceeded that of T. asperellum FJ035, but T. asperellum FJ035 exerted some inhibitory effects on FOC. When inoculation of T. asperellum FJ035 24 h before inoculation of FOC could significantly reduce the accumulation of FOC on the roots of cucumber, corresponding to the highest control efficiency against cucumber Fusarium wilt were 69.79% and 75.96% under hydroponic and potted conditions, respectively. T. asperellum FJ035 also significantly improved the root length, plant height, stem thickness, fresh weight, and area index of the first true leaves of cucumber seedlings, and effectively mitigating the adverse effects of FOC on cucumber growth.

Drought stress amelioration in tomato (Solanum lycopersicum L.) seedlings by biostimulant as regenerative agent.

Drought adversely affects many physiological and biochemical events of crops. This research was conducted to investigate the possible effects of biostimulants containing plant growth-promoting rhizobacteria (PGPR) on plant growth parameters, chlorophyll content, membrane permeability (MP), leaf relative water content (LRWC), hydrogen peroxide (H2O2), proline, malondialdehyde (MDA), hormone content, and antioxidant enzymes (catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD)) activity of tomato (Solanum lycopersicum L.) seedlings under different irrigation levels. This study was carried out under controlled greenhouse conditions with two irrigation levels (D0: 100% of field capacity and D1: 50% of field capacity) and three biostimulant doses (B0: 0, B1: 4 L ha-1, and B2: 6 L ha-1). The results of the study show that drought stress negatively influenced the growth and physiological characteristics of tomato seedlings while biostimulant applications ameliorated these parameters. Water deficit conditions (50% of field capacity) caused decrease in indole acetic acid (IAA), gibberellic acid (GA), salicylic acid (SA), cytokine, zeatin, and jasmonic acid content of tomato seedlings by ratios of 83%, 93%, 82%, 89%, 50%, and 57%, respectively, and shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, plant height, stem diameter, and leaf area decreased by 43%, 19%, 39%, 29%, 20%, 18%, and 50%, respectively, compared to the control (B0D0). In addition, 21%, 16%, 21%, and 17% reductions occurred in LRWC, chlorophyll a, chlorophyll b, and total chlorophyll contents with drought compared to the control, respectively. Biostimulant applications restored the plant growth, and the most effective dose was 4 L ha-1 under drought condition. Amendment of biostimulant into the soil also enhanced organic matter and the total N, P, Ca, and Cu content of the experiment soil. In conclusion, 4 L ha-1 biostimulant amendment might be a promising approach to mitigate the adverse effects of drought stress on tomato.

The breathless niche: unrevealing the metabolic landscape of root stem cells under hypoxia stress.

The breathless niche: unrevealing the metabolic landscape of root stem cells under hypoxia stress.