Greenhouse Conditions Research Articles

Detoxifying bacterial genes for deoxynivalenol epimerization confer durable resistance to Fusarium head blight in wheat.

Fusarium head blight (FHB) and the presence of mycotoxin deoxynivalenol (DON) pose serious threats to wheat production and food safety worldwide. DON, as a virulence factor, is crucial for the spread of FHB pathogens on plants. However, germplasm resources that are naturally resistant to DON and DON-producing FHB pathogens are inadequate in plants. Here, detoxifying bacteria genes responsible for DON epimerization were used to enhance the resistance of wheat to mycotoxin DON and FHB pathogens. We characterized the complete pathway and molecular basis leading to the thorough detoxification of DON via epimerization through two sequential reactions in the detoxifying bacterium Devosia sp. D6-9. Epimerization efficiently eliminates the phytotoxicity of DON and neutralizes the effects of DON as a virulence factor. Notably, co-expressing of the genes encoding quinoprotein dehydrogenase (QDDH) for DON oxidation in the first reaction step, and aldo-keto reductase AKR13B2 for 3-keto-DON reduction in the second reaction step significantly reduced the accumulation of DON as virulence factor in wheat after the infection of pathogenic Fusarium, and accordingly conferred increased disease resistance to FHB by restricting the spread of pathogenic Fusarium in the transgenic plants. Stable and improved resistance was observed in greenhouse and field conditions over multiple generations. This successful approach presents a promising avenue for enhancing FHB resistance in crops and reducing mycotoxin contents in grains through detoxification of the virulence factor DON by exogenous resistance genes from microbes.

Deep learning-based detection of indicator species for monitoring biodiversity in semi-natural grasslands

Deep learning (DL) has huge potential to provide valuable insights into biodiversity changes in species-rich agricultural ecosystems such as semi-natural grasslands, helping to prioritize and plan conservation efforts. However, DL has been underexplored in grassland conservation efforts, hindered by data scarcity, intricate ecosystem interactions, and limited economic incentives. Here, we developed a DL-based object-detection model to identify indicator species, a group of vascular plant species that serve as surrogates for biodiversity assessment in high nature value (HNV) grasslands. We selected indicator species Armeria maritima, Campanula patula, Cirsium oleraceum, and Daucus carota. To overcome the hurdle of limited data, we grew indicator plants under controlled greenhouse conditions, generating a sufficient dataset for DL model training. The model was initially trained on this greenhouse dataset. Then, smaller datasets derived from an experimental grassland plot and natural grasslands were added to the training to facilitate the transition from greenhouse to field conditions. Our optimized model achieved remarkable average precision (AP) on test datasets, with 98.6 AP50 on greenhouse data, 98.2 AP50 on experimental grassland data, and 96.5 AP50 on semi-natural grassland data. Our findings highlight the innovative application of greenhouse-grown specimens for the in-situ identification of plants, bolstering biodiversity monitoring in grassland ecosystems. Furthermore, the study illuminates the promising role of DL techniques in conservation programs, particularly as a monitoring tool to support result-based agri-environment schemes.

Impact of microbial consortium of Rhizobium tropici and Rhizobium mayense on the growth of Phaseolus vulgaris L.

The main objectives of the present investigation was to characterize and recognize potential indigenous Rhizobium spp. associated with red clover nodules, as well as to evaluate the influence of prospective rhizobia inoculation (individual and consortia) on common bean plant growth. Total of 8 rhizobia like bacteria were isolated and were investigated for their specific PGP traits, production of hydrolytic enzymes. Results revealed, four isolates synthesize IAA (22.3 ± 1.45 to 88.6 ± 1.45 μg mL−1), three isolates solubilized phosphate (40.69 ± 1.25 to 216.3 ± 1.31 μg mL−1), three isolates solubilized potassium, produced siderophore, and showed chitinase production, two isolates possess ACC deaminase activity, one isolate was able to solubilize zinc, 5 isolates produced β- 1, 3-glucanase (0.38 ± 0.005 to 2.82 ± 0.011 % units) and four isolates produced cellulase. Two bacterial isolates found to exhibit most of the PGP activities, were selected and identified on the basis of phenotypic, biochemical tests and 16S rRNA sequencing, as Rhizobium tropici IHTF-1 and Rhizobium mayense IHTF-2. Interaction of these potential rhizobium strains individually and consortia with common bean plants under greenhouse conditions boosted root and shoot length, fresh and dry biomass compared to un-inoculated control plants. SEM study revealed that both the strains, IHTF-1 and IHTF-2 colonized common bean roots. These results imply that Rhizobium spp., identified in this work, can be used as bio-inoculants to increase common bean plant production in a sustainable way.

Evaluation of Virgibacillus dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer against root-knot nematodes

Root-knot nematodes (RKNs) can result in severe losses to crop production and economies. Virgibacillus dokdonensis MCCC 1A00493, a deep-sea bacterium, has demonstrated potent antagonistic effects against Meloidogyne incognita in vitro. However, the control efficacy under greenhouse and field conditions remains unclear. In this study, we investigated the nematicidal effect of MCCC 1A00493 fermentation liquid and its synergism with black soldier fly (BSF) larval frass organic fertilizer both in greenhouse and field experiments. MCCC 1A00493 fermentation liquid demonstrated a significant control efficacy on RKNs both in greenhouse and field experiments, with the highest control efficacy reaching 68.97 % and 74.87 %, respectively. Meanwhile, the synergistic effects of MCCC 1A00493 and BSF larvae frass organic fertilizer was investigated by adding 10 % suspension (1 × 109 CFU/mL) of MCCC 1A00493 into 71.51 kg of chicken manure organic fertilizer produced by co-conversion of BSF larvae and Bacillus subtilis BSF-CL. It was noted that MCCC 1A00493 microbial organic fertilizer reduced disease incidence of RKNs significantly both in greenhouse and field experiments, with the root gall index decreasing by 51.75 % and 63.22 %, respectively. MCCC 1A00493 fermentation liquid and microbial organic fertilizer demonstrated a control efficacy on RKNs exceeded commercial nematicide avermectin and commercial bio-organic fertilizer, respectively. In addition, MCCC 1A00493 fermentation liquid and microbial organic fertilizer had positive effects on the growth of tomato plants. These findings confirmed that V.dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer have significant effect on RKNs and can be used as potential biocontrol preparations.

Potencial Simbiótico de Microrganismos do Solo na Promoção do Crescimento de Espécies Arbóreas da Mata Atlântica

The objective of this study was to evaluate the potential of topsoil obtained from a natural forest fragment in the Brazilian Atlantic Forest to serve as a source of symbiotic microorganisms capable of promoting the growth of native tree species in ecological restoration projects. In greenhouse conditions, 14 experiments in a completely randomized design were conducted in 1,700 cm³ pots filled with sterilized substrate. The effect of adding 80 g of topsoil, either in natura or sterilized, to the substrate was tested on the growth of 14 tree species. Plant height, stem diameter, mycorrhizal colonization and dry masses of shoot, roots, and nodules of tree species were measured. Applying the topsoil to the pots generally resulted in significant increases in height and stem diameter of seedlings compared to the control group during the four to six-month evaluation period. This effect was particularly greater in the nodulating species Plathymenia reticulata, Dalbergia nigra and Mimosa bimucronata, with increases in height and stem diameter of up to 328% and 484%, respectively. Forest topsoil also had a positive impact on the growth of shoot, roots, and nodules of the plants, significantly differing from the control groups. Only the plants that received the topsoil in natura exhibited mycorrhizal colonization and the formation of nodules in nitrogen-fixing species. These plants that established mycorrhizas and nodules presented higher concentrations of phosphorous and nitrogen in their biomass, respectively. Under controlled conditions, the use of forest topsoil proved to be a promising strategy for the introduction of microorganisms that can enhance the growth of tree species, thereby holding potential for implementation in nurseries and field settings.
 

Determination of tomato leafminer: Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) damage on tomato using deep learning instance segmentation method

AbstractPests significantly negatively affect product yield and quality in agricultural production. Agricultural producers may not accurately identify pests and signs of pest damage. Thus, incorrect or excessive insecticides may be used. Excessive use of insecticides not only causes human health and environmental pollution, but also increases input costs. Therefore, early detection and diagnosis of pests is extremely important. In this study, the effectiveness of the instance segmentation method, a deep learning-based method, was investigated for the early detection of the damage caused by the T. absoluta pest in the leaf part of the tomato plant under greenhouse conditions. An original dataset was created by acquiring 800 healthy and damaged images under greenhouse conditions. The acquired images were labelled as bounding box and automatically converted to a mask label with the Segment Anything Model (SAM) model. The created dataset was trained with YOLOv8(n/s/m/l/x)-Seg models. As a result of the training, the box performance of the proposed YOLOv8l-Seg model was measured as 0.924 in the mAP0.5 metric. The YOLOv8l-Seg model mask values are, respectively: mAP0.5, mAP0.5–0.95, Precision, Recall showed the best performance with values of 0.935, 0.806, 0.956 and 0.859. Then, the YOLOv8l-Seg model, trained with different data input sizes, showed the best performance at 640 × 640 size and the lowest performance with a value of 0.699 in the mAP0.5 metric in the 80 × 80 size. The same dataset was trained with YOLOv7, YOLOv5l, YOLACT and Mask R-CNN instance segmentation models and performance comparisons were made with the YOLOv8l-Seg model. As a result, it was determined that the model that best detected T. absoluta damage in tomato plants was the YOLOv8l-Seg model. The Mask R-CNN model showed the lowest performance with a metric of 0.806 mAP0.5. The results obtained from this study revealed that the proposed model and method can be used effectively in detecting the damage caused by the T. absoluta pest.

Efficacy and residual toxicity of chitosan for Rhagoletis pomonella (Diptera: Tephritidae).

Chitosan is a naturally derived polymer that has significant potential for use as a bioinsecticide. Despite this, there is a lack of research as to the efficacy of chitosan for many insect pest species. The apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is one such pest for which chitosan toxicity has not been explored. In this study, the toxicity of chitosan for R. pomonella adults was tested via no-choice feeding assays. An aging trial was further used to test the mortality of flies provided dried chitosan-sucrose treatments (CST), which were aged for 0 or 3 days in greenhouse conditions. This study found that the CST is toxic for R. pomonella adults when ingested, leading to a significant increase in the rate of mortality compared to control groups. The use of dried chitosan, however, did not change the mortality of flies, suggesting this will not be an effective delivery mechanism. Effective biopesticide delivery systems have not been defined for chitosan use outside of a laboratory, indicating the need for further research testing delivery mechanisms. It is suggested that an effective method of delivery can be as a food-based bait in attract-and-kill traps, as chitosan must be ingested to kill flies. Forming a viscous solution, chitosan may be best suited to these lure systems.

The Detection of Crown Gall Disease in Kahramanmaraş and Surrounding Provinces

Aims: The aim of the study is to isolate the bacterial agent causing crown gall disease in Kahramanmaraş and its surrounding provinces, determine its prevalence in the region, and conduct its identification. 
 Material and methods: Between June and September of 2017-2019, strains obtained from the shoots and galls of vines showing symptoms of galls in vineyards in Kahramanmaraş, Adıyaman, Kilis, Gaziantep, and Şanlıurfa provinces were subjected to pathogenicity tests, classical, molecular, and MALDI-TOF MS identification.
 Results and Discussion: In this study, the prevalence of crown gall disease in 46 vineyards showing disease symptoms was determined as follows: Kahramanmaraş 76.47%, Adıyaman 75%, Gaziantep 50%, Kilis 33.33%, and Şanlıurfa 20%. From the 46 contaminated vineyards in the study area, 24 pathogenic of R. vitis strains were obtained. In the pathogenicity test conducted with R. vitis strains on the Hatun Parmağı grape variety under greenhouse conditions, the most virulent strains were determined based on the weights of the galls formed, and they were identified as CU52-3/2, CU39-11/5, and CU39-8/1. According to classical tests, 13 strains showed 100% similarity to R. vitis, while molecular characterization with R. vitis-specific primers revealed that 17 strains had the virA gene, 13 strains had the pehA gene, 10 strsains had the virF gene, and 6 strains had the octopine-type plasmid. Ten strains, representing the sample, were identicated as R. vitis through MALDI-TOF MS analysis. This study revealed the impact of pathogenic strains with different virulences on the same grape variety. In line with this, of control methods against highly virulent bacterial agents in reducing losses in plants can be investigated for their applicability in field and orchard areas in subsequent studies.
 Conclusions: Research on different grape varieties is essential to develop varieties that are resistant or tolerant to R. vitis, the pathogen causing this prevalent disease in Turkish viticulture.

Pre-symptomatic leaf reflectance of Fusarium virguliforme infected soybean plants in greenhouse conditions

Sudden death syndrome (SDS) of soybean is caused by a soil-borne pathogen, Fusarium virguliforme. Prior to visible foliar symptoms, a destructive technique is usually carried out to diagnose root infection. The use of hyperspectral sensors for pre-symptomatic and non-destructive plant disease diagnosis has been on the rise. This study was designed to relate leaf spectral reflectance to F. virguliforme root infection in the absence of foliar symptoms. Soybean plants were grown under controlled greenhouse conditions. The plants’ spectral reflectance was measured weekly beginning at 21 days after transplanting (DAT) up until 42 DAT using a swing hyperspectral imaging system that is fixed on a gantry. Destructive root sampling confirmed F. virguliforme root infection using Real-time PCR. The most relevant wavelengths for discrimination were selected using the ReliefF algorithm. Three machine learning models [Partial least squares discriminant analysis (PLS-DA), support vector machine, and random forest] were evaluated for classification accuracy using the selected wavelengths. Relevant wavelengths for differentiating between the healthy and F. virguliforme infected plants were found in the visible and red-edge region from 500 to 750 nm, and the shortwave infrared region from 1400 to 2350 nm. In the absence of visible foliar symptoms, classification results showed over 79% mean F1-scores for all models. PLS-DA was able to differentiate healthy and F. virguliforme infected plants with a mean F1-score of 83.1 to 85.3% and a kappa statistic of 0.43 to 0.54. This work supports the use of hyperspectral remote sensing for early pre-symptomatic disease diagnosis under controlled environment.

Bioestimulante de algas melhora a tolerância à salinidade e a qualidade visual de espécies herbáceas ornamentais tropicais

ABSTRACT The use of biostimulants may mitigate the deleterious effects of salt stress on plant growth and physiological variables. Thus, the present study aimed to evaluate the growth, physiology, organic solutes, and visual characteristics of two tropical ornamental species (Celosia argentea and Catharanthus roseus) cultivated with brackish waters and treated with Ascophyllum nodosum extract. The experiment was performed in greenhouse conditions. The experimental design was a complete randomized block arranged in a split-plot scheme. The plots comprised three levels of electrical conductivity of the irrigation water (ECw - 0.5, 2.5, and 4.5 dS m-1), the subplots four concentrations of algae extract (0, 400, 800, and 1200 mg L-1), and the sub-subplots two tropical ornamental herbaceous species [C. argentea and C. roseus]. The salinity of the irrigation water negatively affects the morphological and physiological characteristics of the two species studied, mainly C. roseus. Irrigation with water up to 2.5 dS m-1 favored visual quality and increased the purchasing preference for C. argentea. The use of intermediate concentrations (400 mg L-1) of algae extract (A. nodosum) promoted partial mitigation of the effects of salt stress on biomass production and leaf gas exchange, especially for C. argentea, but these positive responses decreased or disappeared with the intensification of salt stress and the increase in algae extract concentration.

Morphological, molecular biology and pathological characterization of fungi causes root rot on grapevine

Background Grapevine is subjected to attack by several of soilborne fungi causing root-rot diseases that lead to limit the production of grapevine. Objective This study aimed to investigate the morphological, molecular identification, and pathogenic potential of fungi that causes root-rot disease of grapevine in Egypt. Materials and methods Isolation of fungi causing root rot of grapevine plants from the samples of diseased roots of different cultivars, i.e., crimson, superior, and flame seedless. Identification according to characterizations of morphological, cultural, and molecular biology based on internal-transcribed spacer 1 (ITS1). Pathogenicity tests of fungal isolates on grapevine plants under greenhouse conditions. Root-rot incidence, disease severity, and plant growth characteristics were determined. Results and conclusion Isolation traits from affected grapevine trees with different grape varieties in Egypt’s El-Nobaria Province, El-Behira Governorate, yielded eighteen isolates of four fungal genera. Fusarium spp. was the most fungal genus highly frequent on all cultivars tested and colonization (100%) on root-rot tissue of superior and flame-seedless cultivars, then (75%) on Crimson cultivar. While Lasiodiplodia spp. was recorded with moderate frequency and high colonization (100%) on rotten tissue of Crimson cultivar followed by (75%) in both flame-seedless and superior cultivars. As opposed to that, fungi of Macrophomina phaseolina followed by Rhizoctonia solani had the least frequency and colonization percentage. Isolates of fungi were identified according to morphological characteristics, cultural, and molecular biology based on internal-transcribed spacer-1 (ITS1) sequencing and conserved in GenBank with accession numbers from (ON037457.1 to ON037474.1). Fungal isolates were varied for causes of root rot on grapevine plants and their reduction effect on the characteristics of growth of flame-seedless cultivar. Fusarium solani isolate (ON037462.1) was the most pathogenic isolate that caused (100%) of root rot, high disease severity, and highly significant reduced grapevine plant growth characteristics followed by isolates of Lasiodiplodia theobromae (ON037474.1). In this respect, a new isolate of fungal species was hosting grapevine plants, i.e., two isolates each of F. chlamydosporum, F. brachygibbosum, one isolate of F. ipomoeae, and one isolate of L. exigua are the new causal pathogens of root-rot disease on grapevine as the first report in Egypt.

Stem Cutting Propagation and Micropropagation of Northern Bayberry

Northern bayberry [Morella (formerly Myrica) pensylvanica] is an attractive, adaptable, semievergreen, northeastern North American native shrub that is sought for landscaping but difficult to propagate clonally. The impact of timing (June, July, or August) and concentration of indole-3-butyric acid [IBA (0, 2000, 4000 or 8000 ppm)] on propagation by stem cuttings was evaluated for genotypes of northern bayberry including the female cultivars Bobzam (Bobbee™) and UConn Compact and an unnamed male. Medium formulation and cytokinin type were evaluated for micropropagation of ‘Bobzam’ and ‘UConn Compact’. Stem cuttings of ‘Bobzam’ and ‘UConn Compact’ rooted poorly (at ≤55% and ≤20%, respectively) at all timings and concentrations of IBA; however, rooting success of ≥85% was achieved for the unnamed male genotype when cuttings were taken in June. Micropropagation of ‘Bobzam’ was successful using Woody Plant medium with 4 mg·L−1 zeatin and explants taken from shoots that had expanded 12 to 18 cm on containerized stock plants. Initiated explants of ‘Bobzam’ required eight subcultures before they began to produce shoots consistently at a 2× multiplication rate and eventually reached a 3× multiplication rate. Micropropagation attempts using Murashige and Skoog medium, the cytokinins 6-benzylaminopurine, meta-topolin, and thidiazuron, or the cultivar ‘UConn Compact’ were unsuccessful. Microshoots of ‘Bobzam’ rooted at ≥80% either by in vitro prerooting or ex vitro rooting directly in trays. Rooted microcuttings easily acclimated to greenhouse conditions and grew rapidly when potted to 1.04-L containers and then into 5.68-L containers. The micropropagation protocol developed for ‘Bobzam’ can be used by propagators to expand production of this popular female cultivar.

Spicing up oak forest restoration: a preliminary report of the protective use of chili peppers in direct seeding of acorns

Direct sowing of acorns is a technique for oak forest restoration, however, high seed predation by mammals can occur and cost‐effective alternatives to protect acorns are therefore required. The present study evaluated the protection provided by chili peppers (Capsicum annuum and Capsicum pubescens) to acorns of Quercus germana, an endangered endemic oak tree of the cloud forests. Greenhouse and field experiments were established to evaluate the effect of chili peppers on acorn removal, germination, and seedling emergence. These processes were related to the prevalent microhabitat characteristics where the acorns were introduced, and the fauna that consumed chili peppers and acorns was identified using camera traps. In the greenhouse trial, more seedlings emerged from acorns covered by fruits of C. pubescens (65.71 ± 8.14) and C. annuum (57.14 ± 8.49%) compared to unprotected acorns (31.43 ± 7.96%). Contrary to expectation, acorn removal in the field was greater using C. pubescens than the unprotected acorns, particularly in microsites with lower tree cover and higher grass dominance. Acorn removal was similar to chili pepper treatments. These results are explained by the camera trap records, which showed bird species consuming Capsicum fruits, thus exposing the acorns to subsequent removal and/or consumption by rodents. The studied Capsicum fruits had no negative effect on acorn germination and seedling emergence under greenhouse conditions, and future practices could, therefore, involve the use of different techniques to prevent the discovery of chili peppers by birds; for example, using green chili peppers for camouflage, or hiding them under litter or herbaceous vegetation.

Effect of Plant Growth-Promoting Bacteria (PGPB) on the Development of Pea crop (Pisum sativum L.)

Microorganisms are of great importance in agriculture in terms of plant nutrients by reducing the need for chemical fertilization. In recent years, plant growth-promoting bacteria (PGPB) have been widely used as biological fertilizers (BF) in agriculture. This study was conducted to determine the effect of plant growth-promoting bacteria on the development of pea plants. Firstly the phosphate solubilization and nitrogen fixation potentials of the bacteria used in this study were determined. In the study, the effects of 4 different combinations, F1 [(Rhizobium sp. (FR-13) and Pseudomonas alcaligenes (FDG121)], F2 [(Pseudomonas fluorescens biotype F (FDG-7), Rhizobium sp. (FR-18) and Bacillus-megaterium-GC subgroup B(FDG-134)], F3 [Arthrobacter oxydans (FDG-72), Bacillus-megaterium-GC subgroup B (FDG-146), Rhizobium sp. (FR-11)] and F4 [Acinetobacter genospecies 9 (FDG-116), Brevibacillus agri (FDG-118), Methylobacterium zatmanii (FDG-123) and Bacillus-megaterium-GC subgroup A (FDG-153)] were investigated. Formulations made with bacteria that were found to be the best in terms of the properties specified among these strains were tested against pea plants under greenhouse conditions and their effects on the plant's total fresh and dry weight were investigated. The study was set up to have 3 replications. As a result of the statistical analysis made with the data obtained, the formulations used compared to the control; F2, F3 and F1 applications were important in total fresh weight, respectively, and F2 and F3 applications were important in total dry weight. As a result, these 3 formulations are especially effective on the yield of pea plants and can be used as potential biofertilizers.

The Effects of Liquid Biogas Digestate on Yield and Mineral Nutrition of Cucumber Growing in Greenhouse

This study aimed to investigate the effects of a liquid fraction of digestate obtained from different biogas plants on the growth and mineral nutrition of cucumber plants under greenhouse conditions. For this purpose, Liquid Biogas Digestates (LBD) obtained from two different plants (A-B) with different properties were applied to pots with 10 kg of soil in 5 different doses (0, 20, 40, 60, and 80 t ha-1) and the effects of the treatments were observed. As a result of the research, the highest yields increased 24.6% for digestate A in A5 (80 t ha-1) and 29% for digestate B in B3 (40 t ha-1) compared to control. While LBD contributed to the increase of N, Ca, Zn, Cu, and Mn concentrations in the leaf samples, it was observed that the dose increase did not have a linear effect on N, Ca, Zn, Cu, and Mn concentrations in the leaf samples. It is thought that liquid biogas wastes produced in biogas plants have positive effects on fruit yield, agricultural practices can be taken as the basis for the disposal of these wastes and the use of liquid biogas residues in soils by eliminating potential risks can provide significant benefits.

First report of Boeremia exigua causing spot blight on cowpea in China.

Cowpea or black-eyed pea [Vigna unguiculata (L.) Walp.] is a dual-purpose leguminous crop grown for food and fodder. In September 2022, cowpea plants exhibiting symptoms of a leaf spot and blight were observed in Renda Town located in Jingning County of Gansu Province, China, with the disease incidence in individual cowpea fields as high as 100%. Diseased leaves showed variable-sized, nearly circular brown blotches, large blotches with dark brown margins, and the adaxial surfaces of blotches had small black dots and whorls (Fig. 1). Multiple isolates with consistent colony characteristics were obtained from cowpea leaves with typical symptoms. The isolates were transferred to fresh potato dextrose agar medium (PDA) and then purified by transferring hyphal tips to PDA. Three isolates, JNJD-1, JNJD-2, and JNJD-3, were selected for subsequent identification and pathogenicity determination. After eight days at 25℃ on PDA, the colonies appeared irregular, aerial mycelium dense, cottony, atrovirens to olive brown, with white hyphae on the undulate margin (Fig. 2A and B). The pycnidia were globose to sub-globose, brown to dark brown, with 70-110 μm diameters. Single celled hyaline conidia were ellipsoidal to oblong with obtuse ends, and measured 6.6-9.3 × 2.8-4.1 μm (x̄ = 7.8 × 3.5 μm, n = 50) (Fig. 2C). Morphological characteristics are similar to the description of the genus Boeremia (Aveskamp et al, 2010). Primer pairs ITS1/ITS4, LR0R/LR5, fRPB2-5F2/fRPB2-7cR, and TUB2FD/TUB4RD were used to amplify portions of the ITS, LSU, RPB2, and TUB genes, respectively (Chen et al, 2015). The obtained sequences (Accession numbers: PP033662 to PP033664 for ITS, PP033667 to PP033669 for LSU, PP035531 to PP035533 for RPB2, and PP035534 to PP035536 for TUB) were 97% identical to that of a B. exigua strain CBS 431.74 (accession no. FJ427001, EU754183, GU371780, and FJ427112) (Table 1). The constructed maximum likelihood tree indicated close relationships between three isolates and B. exigua, which clustered together (Fig. 3). Cowpea plants (cultivar Junlintianxia) at the three-leaf stage were inoculated by spraying a spore suspension (1×106 conidia/ml) of JNJD-1, JNJD-2, and JNJD-3 until run off and incubated at greenhouse conditions (25°C and 12 h light). Inoculations with sterile water were used as a control and each treatment was repeated 3 times with five plants per replicate. Small brown spots appeared on the infected leaves at 2 dpi, followed by the appearance of large blotches, with dark brown at the margin and grayish-white in the center at 5 dpi (Fig. 4A). These lesions gradually increase and coalesce, causing leaf chlorosis and finally defoliation in serious cases. Disease incidence in inoculated cowpea plants treated with the isolates JNJD-1, JNJD-2, and JNJD-3 reached almost 100%. In contrast, control plants developed no symptoms (Fig. 4B). The pathogens were re-isolated from the inoculated leaves and identified as B. exigua using morphological and molecular analysis, whereas no fungus was isolated from control leaves. The experiment was repeated once under the same conditions, yielding similar results. B. exigua has a broad host range, infecting 19 families and 31 genera of plant species, and causing leaf spots, leaf blight, and tuber rot (Lan and Duan 2022). To our knowledge, this is the first report of the pathogen B. exigua causing spot blight on cowpeas. It has been reported that B. exigua infects leguminous crops from multiple genera, such as field pea, soybean, white clover, and Dumasia villosa (Liu et al, 2023). This study further enriches the host range of this pathogen and the pathogen species of cowpea leaf diseases.

Bio-Inoculation of Tomato (Solanum lycopersicum L.) and Jalapeño Pepper (Capsicum annuum L.) with Enterobacter sp. DBA51 Increases Growth and Yields under Open-Field Conditions

The rhizobacterium Enterobacter sp. DBA51 (DBA51), isolated from the semi-desert in Coahuila, Mexico, was previously found to increase the vegetative growth of tomato and tobacco plants cultivated under greenhouse conditions. The present report describes the results obtained from two independent open-field experiments performed with tomato and jalapeño pepper commercial crops inoculated with DBA51. Additionally, plants inoculated with Bacillus subtilis LPM1 (LPM1) and uninoculated plants were included as positive and negative controls, respectively. DBA51 and LPM1 significantly promoted growth at vegetative stages in the tomato plants; this effect was evident in the stem diameter (DBA51 with p < 0.0001 and LPM1 with p < 0.0001) and height (DBA51 with p < 0.0001 and LPM1 with p < 0.0001) of the tomato plants. However, no differences were detected in the jalapeño pepper plants. Additionally, DBA51 and LPM1 treatments increased tomato fruit production by 80% and 31%, respectively, compared to uninoculated plants. A similar increase in yield was recorded in DBA51- and LPM1-treated jalapeño pepper plants, which was 75% and 56% higher than uninoculated controls, respectively. These results strongly recommend the potential use of DBA51 as a biofertilizer in horticultural crops.

Biological Control of Pseudomonas syringae in Tomato Using Filtrates and Extracts Produced by Alternaria leptinellae

Endophytic fungi offer promising alternatives for sustainable plant disease management strategies, often through the production of bioactive secondary metabolites. This study investigated the biocontrol potential of filtrates and extracts, produced under controlled conditions, from Alternaria leptinellae E138 against Pseudomonas syringae in tomato plants under greenhouse conditions. To understand the main mechanisms involved in biocontrol, the direct inhibition of bacterial growth and disruption of quorum sensing activity caused by metabolites were studied in vitro, as well as indirect mechanisms, such as their capacity to produce phytohormone-like substances, nutrient mobilization, and antioxidant activity, which can enhance plant growth and fitness. Moreover, a mass spectrometry analysis was used to tentatively identify the secondary metabolites present in the extract with antimicrobial properties, which could explain the biocontrol effects observed. Mycopriming assays, involving the direct treatment of tomato seeds with the fungal A. leptinellae E138 extracts, produced increased germination rates and seedling vigor in tomato seeds. As another treatment, postemergence application of the extracts in greenhouse conditions significantly improved plant health and resulted in a 41% decrease in disease severity. Overall, this study underscores the potential of A. leptinellae E138 extract as a plant growth promoter with biocontrol capabilities, offering promising avenues for sustainable plant disease management.

Characterizing the pathogenicity and mycotoxin production capacity of Fusarium spp. causing root rot of Angelica sinensis in China.

Root rot is a very destructive soil-borne disease, which severely affects the quality and yield of Angelica sinensis in major planting areas of Gansu Province, China. Twelve Fusarium strains were identified from root rot tissue and infected soil in the field, by comparing each isolate strain internal transcriptional spacer, translation elongation factor 1-α sequence and RNA polymerase second largest subunit gene (RPB2) with the sequences of known fungal species in the NCBI database. Of these isolates, four were F. acuminatum, followed by three F. solani, two F. oxysporum, and one each of F. equiseti, F. redolens, and F. avenaceum. Under greenhouse conditions, pathogenicity testing experiment was carried out using five strains: two F. acuminatum, one F. solani, one F. oxysporum, and one F. equiseti. Among them, the incidence of F. acuminatum-induced root rot on A. sinensis was 100%; hence, it was the most aggressive. Liquid chromatography was used to show that F. acuminatum was capable of producing neosolaniol (NEO), deoxynivalenol (DON), and T-2 toxins. Of these, the level of NEO produced by F. acuminatum was high, compared with the other two toxins. By isolating Fusarium spp. and characterizing their toxin-producing capacity, this work provides a new information for effectively preventing and controlling A. sinensis root rot in the field, as well as improving the quality of its medicinal materials. Keywords: Angelica sinensis, Fusarium spp., mycotoxins, pathogenicity tests, root rot disease.

Explicating Botanical Bactericides as an Intervention Tool towards Citrus Canker

Recent research efforts were made to investigate botanical bactericides as an intervention tool for citrus canker. Five botanical extracts (Eruca vesicaria, Eucalyptus globulus, Trigonella foenum-graecum, Nigella sativa, and Citrullus colocynthis) were evaluated at three different concentrations (0.25%, 0.5%, and 0.75%) against Xanthomonas citri pv. citri under in vitro conditions. Among all treatments, two effective plant extracts, alone and in combinations, were assessed at three different time points (7 days, 14 days, 21 days) under greenhouse conditions. In vitro and greenhouse experiments were conducted under a Completely Randomized Design. Results showed that C. colocynthis expressed the maximum inhibition zone (3.22 mm), followed by N. sativa (2.82 mm), T. foenum-graecum (2.68 mm), E. globulus (1.64 mm), and E. vesicaria (1.31 mm) compared to the control. Effective extracts of C. colocynthis and N. sativa were assessed under greenhouse conditions, both alone and in combination, against citrus canker. The minimum disease incidence (18.74%) was exhibited by the combination of C. colocynthis and N. sativa, followed by C. colocynthis (22.59%) and N. sativa (23.27%) compared to the control. Based on these findings, it is recommended that the application of botanical extracts is a reliable strategy for managing citrus canker.