Brown Spot Disease Research Articles

Isolation of Rhizospheric Bacteria from Soil and Their Antifungal Activity Against Helminthosporium oryzae the Causal Agent of Brown Spot of Rice

The brown spot of rice caused by Helminthosporium oryzae is a serious disease that affects the yield of rice crops. Brown spots of rice have been reported in almost all rice-growing countries. Therefore, the present study was to explore the management of brown spots of rice. through an antagonistic activity using rhizospheric bacteria. The method employed for soil sample collection was persuaded for bacterial isolation through the serial dilution plate technique. For the results of morphological characteristics of bacterial strain from soils of rice crop collected from Hyderabad. The results of the present study show that many colonies made by bacteria and which were consisted of different sizes, shapes, and colors. Whereas the results of the 15 isolates strains of rhizobacteria, only 06 bacterial strains IAP-1, IAP-2, IAP-04, IAP-09, IAP-12, and IAP-14 were found more effective in antagonizing H.oryzae, under in-vitro conditions. Antagonistic activity of rhizobacteria against H. organize showed significant inhibitory effects. The rhizobacteria showed the primordial result against against H. oryzae and will be helpful as a formulation not only for commercial purposes but also for beneficial biological control against the Brown spot of rice

Biological and Chemical Management Strategy to Control Brown Spot Disease in Rice Caused by Bipolaris oryzae

The main objective of this study was to assess the effectiveness of various fungicides in managing rice brown spot, a common fungal disease in India that can reduce crop yield and seed quality. During 2020-21 crop seasons, a research project was conducted in the experimental plot of the Department of Plant Pathology at the College of Agriculture in Rewa, Madhya Pradesh, India. Different treatments involving fungicide application at various rice growth stages were implemented. The results showed that all treatments involving fungicides significantly reduced the incidence of rice brown spot in-vitro condition and increased crop yield when compared to the control group. Among the fungicides, Difenoconazole 25% EC at a concentration of 200ppm proved to be highly effective in controlling the growth of the fungal mycelium. In in-vivo condition, the treatment involving T4, which includes seed treatment with the bio-control agent Trichoderma viride (10g/kg seeds), the application of Trichoderma viride (10g/l) at 15-20 days after transplanting, and the application of propiconazole (1g/l) at the booting exhibited the highest level of reduction in the incidence of brown spot disease, amounting to 13.6 per cent. The integrated management approach are very effective to control the brown spot disease in rice.

Using Deep Learning and Machine Learning: Real-Time Discernment and Diagnostics of Rice-Leaf Diseases in Bangladesh

Bangladesh is heavily reliant on rice production, but a staggering annual decline of 37% in rice output due to insufficient knowledge in recognizing and managing rice plant diseases has raised concerns. As a result, there is a pressing need for a system that can accurately identify and control rice plant diseases automatically. CNNs have demonstrated their effectiveness in detecting plant diseases, thanks to their exceptional image classification capabilities. Nevertheless, research on rice plant disease identification remains scarce. This study offers a comprehensive overview of rice plant ailments and explores DL techniques used for their detection. By evaluating the advantages and disadvantages of various systems found in the literature, the study aims to identify the most accurate means of detecting and controlling rice plant diseases using DL techniques. We present a real-time detection and diagnostic system for rice lead diseases that utilizes ML methods. This system is designed to identify three prevalent rice plant diseases, specially leaf smut, bacterial leaf blight and brown spot diseases. Clear images of affected rice leaves against a white background serve as input data for the system. To train the dataset, several ML algorithms were employed including KNN, Naive Bayes, J48 and Logistic Regression. Following the pre-processing stage, the decision tree algorithm demonstrated an accurateness of over 97% when claimed to test dataset. In conclusion, implementing an automated system that leverages ML techniques is vital for reducing the time and labor required for detecting and managing rice plant diseases. Such a system would contribute significantly to ensuring the healthy growth of rice plants in Bangladesh, ultimately boosting the nation’s rice production.

Comprehensive Phenotypic Assessment of Rice Diseases in Cultivated Farms within Okpuitumo Community, Ikwo Local Government Area, Ebonyi State: Implications for Sustainable Rice Crop Management

Rice stands as a pivotal economic crop in Ebonyi State, particularly flourishing in Ikwo Local Government Area. However, the productivity of this vital crop faces significant challenges owing to pestilence and diseases. This study sought to employ advanced PLANTIX image analysis software to systematically screen rice farms suspected of disease infestations within Okpuitumo Community. The aim was to precisely identify prevalent diseases impacting the region's rice cultivation. Leveraging the iterative capabilities of the PLANTIX smartphone application, images of afflicted rice leaves were meticulously examined to identify specific disease types and quantify their severity. The study meticulously selected four villages—Anumocha, Odeligbo, Ettam, and Ogidiga—with three farms per village and five sampling points per farm, employing rigorous randomization protocols. The findings showcased a hierarchy of prevalent rice diseases within the community, highlighting the severity in the following descending order: Potassium deficiency (40%), Brown spot disease (38.33%), Magnesium deficiency (31.67%), Nitrogen deficiency (26.67%), Rice blast (6.67%), Zinc deficiency (5%), Bacterial blight (3.33%), Green horned caterpillar (1.67%), and Leaf scald (1.67%). Notably, the study underscored soil nutrient depletion and the prevalence of brown spot disease as primary impediments to rice cultivation in the area. Consequently, the study advocates for the implementation of robust soil nutrient restoration strategies alongside the development of brown spot disease-resistant or tolerant rice varieties that harmoniously align with the local agro-ecology. These interventions are imperative to safeguard the burgeoning population and the farming community against exacerbating food security crises and persistent poverty challenges

Identification of Pests, Diseases, and Nutrient Deficiencies in Rice (Oriza Sativa L.) Variety Sunggal

This study aims to identify pests, diseases and nutrient deficiencies in the Sunggal variety of rice (Oriza sativa L.). This research was conducted in June 2023. The research location was carried out in rice fields belonging to farmers in Sidorejo Hamlet, Polokarto District, Sukoharjo Regency. This research is descriptive qualitative by making direct observations or observations on rice fields, interviews and literature. The results showed that there were 7 pests that attacked this single variety rice plant, consisting of 5 pests from the insect class (insects), 1 from the mollusk class, and 1 from the aves class. Pests caused by insects (insects), namely: rice bug (Leptocorisa oryzae), ground bed bug (Scotinophara coarctata), white rice stem borer (Scirpophaga innotata Walker), armyworm (Spodoptera litura), grasshopper (Oxya servile). Caused by molluscs, namely the golden snail (Pomacea canaliculate) and caused by birds, namely sparrows (Lonchura sp). While there are 6 caused by diseases, namely caused by fungi/fungi there are 5 and caused by bacteria there is 1. Among those caused by fungi/fungus namely: brown leaf spot on rice (Helminthosporium oryzae), narrow brown leaf spot on rice (Cercospora oryzae), stem rot in rice (Sclerottium oryzae), rice leaf blight (Rhizotonia solani) and leaf blast (Pyricularia grisea). Caused by bacteria, namely bacterial leaf blight of rice (bacteria: Xanthomonas oryzae pv oryzae). Then lastly there is one that is caused by a lack of nutrients, namely: potassium deficiency.

Synthetic fungicides for controlling brown leaf spot of rice caused by Bipolaris oryzae

Rice (Oryzae sativa L.) is suffering from several biotic and abiotic factors. Among biotic factors, brown leaf spot of rice (BLS) is potentially devastating disease of rice causing the severe yield losses up to 100%. The current study was designed to evaluate most effective synthetic fungicides management strategy towards BLS disease. For this purpose, 12 fungicides were screened out under in vitro conditions and four most effective fungicides were further demonstrated against the targeted pathogen with three different concentrations (100, 150 and 150ppm) by using poisoned food technique. The results revealed that propiconazole and thiophanate methyl showed the strong inhibitory effect against B. oryzae followed by contaf plus and bavistin respectively. The promising fungicides (propiconazole and thiophanate methyl) under lab conditions were further evaluated in vivo against BLS disease by using 3 types of applications i.e. Pre-inoculation, Post-inoculation and after symptoms appearance. Findings showed that, Post-inoculation was found most effective as compared to other applications, furthermore combination of propiconazole and thiophanate methyl showed significant reduction in disease incidence percent as compared to solo applications. The reduction in disease incidence percent in all application methods suggested that these synthetic fungicides could be used against BLS of rice.

Use of coal ash- and lignite-enriched compost to improve soil biological properties and reduce pineapple disease in Ultisols of Central Lampung

Ultisols used for pineapple cultivation are classified as suboptimal lands because of their low soil fertility. Application of compost enriched with other soil ameliorants, such as coal ash in the form of fly ash, bottom ash (FABA), and lignite, can be a good alternative to improve soil properties, including increasing the soil microbial and fauna populations, which play an important role in improving soil fertility and reducing the incidence of pineapple disease. The purpose of this study was to investigate the effects of FABA- and lignite-enriched compost on microbial and earthworm populations and the incidence of pineapple disease. FABA- and lignite-enriched compost at a dose of 50 tons/ha was applied using a spread-and-row technique in the pineapple plantation area in Central Lampung. The parameters observed included the microbial population (Pseudomonas, Bacillus, Actinomycetes, Trichoderma), functional microbial populations (nitrogen-fixing bacteria, phosphate-solubilizing microbes, siderophore producers), earthworm population, and incidence of pineapple diseases (marbling, brown spot, cork spot, and pink diseases). Generally, all treatments with FABA- and lignite-enriched compost showed better results than the control for all observed parameters. The treatment of FABA-enriched compost applied with a row technique was the best compared to other treatments because it tended to increase the population of Pseudomonas, Bacillus, Actinomycetes, and nitrogen-fixing bacteria, as well as earthworm abundance and biomass. In addition, in this treatment, there was no incidence of pineapple fruit disease. The abundance of earthworms and soil microbes, especially Pseudomonas was one of the factors which can create a healthier soil ecosystem to suppress the incidence of pineapple diseases.

Coniolariella gamsii Causes Poplar Leaf Spot Disease in Xinjiang, China

Populus laurifolia is one of the most valuable tree species in the world and an important silvicultural tree species in the Xinjiang Uygur Autonomous Region, China. In July 2017, an unreported brown leaf spot disease was observed on P. laurifolia in Altay City, Xinjiang. The causal agent of this leaf spot disease was isolated, and Koch’s postulates were performed to confirm its pathogenicity. Based on a morphological characterization and phylogenetic analyses, the causal organism was identified to be a fungal species, Coniolariella gamsii. The optimum mycelial growth conditions for C. gamsii are on PLPDA (Populus leaves potato dextrose agar) medium, at 28 °C, in the dark. The sporulation time when using PLPDA medium (12 days) is much less than that for PDA medium (25 days). Pathogenicity tests revealed that C. gamsii can also infect two other Populus species (P. bolleana and P. tomentosa). This is the first report of C. gamsii causing brown leaf spot disease on P. laurifolia, and the optimum culture and sporulation conditions have also been optimized for the first time. This study provides a theoretical basis for the diagnosis of this disease and the monitoring of the disease’s occurrence and epidemic status.

Rice resistance against Bipolaris oryzae infection is mediated by lower foliar potassium concentration

AbstractBrown spot, caused by Bipolaris oryzae, is a very important disease of rice. This study investigated the effect of potassium (K) on rice resistance to brown spot. The working hypothesis tested was that higher foliar K concentration could allow plants to respond more efficiently against fungal infection. Plants were grown in nutrient solution amended with three K rates (0.5, 1.0 and 2.5 mM) and noninoculated or inoculated with B. oryzae. The photosynthetic performance of plants, activities of defence and antioxidant enzymes and the concentrations of reactive oxygen species, phenolics and lignin were determined. Foliar K concentration was significantly higher by 38% and 91% for plants supplied with 1.0 and 2.5 mM K, respectively, compared to plants supplied with 0.5 mM K. Brown spot severity was significantly higher (≥20%) for plants supplied with 1.0 and 2.5 mM K than those supplied with 0.5 mM K (≤15%). Higher brown spot severity for plants supplied with 2.5 mM K resulted in changes in the photosynthetic apparatus, reduced chlorophyll a + b and carotenoids concentrations, and higher production of hydrogen peroxide and superoxide anion radical. In contrast, higher activities of defence and antioxidant enzymes and more production of phenolics for plants supplied with 0.5 mM K helped them to cope with B. oryzae infection more efficiently. In conclusion, rice resistance against brown spot was achieved by keeping a lower foliar K concentration linked to more active defence reactions, a robust antioxidative system and less damage to the photosynthetic apparatus.

Genome Sequence Resource of Alternaria alternata DZ Causing Tobacco Brown Spot

Alternaria alternata is an economically important pathogen that can cause severe plant diseases in various crops, such as citrus, pear, strawberry, and tobacco. Here, we report on the genome sequence of A. alternata DZ causing tobacco brown spot disease in most tobacco-producing areas. A total of 11 contigs, including 10 essential chromosomes and 1 mitochondria genome, were assembled by combining Oxford Nanopore and Illumina sequencing technologies. All 10 assembled chromosomes enabled detection of at least one of the telomeric terminal repeat sequences CCCTAA/TTAGGG. The assembled chromosomes were a total of 34.11 Mb in length with a GC content of 50.95%, whereas the mitochondrial genome was 50,595 bp in length with a GC content of 29.16%. We were unable to identify any evidence of conditionally dispensable chromosomes in the genome of A. alternata DZ, nor were we able to locate any ACT gene orthologs. This genome resource will provide valuable insights for comparative genomics research of the Alternaria genus and serve as a useful resource in investigations of plant-pathogen molecular interactions. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Improvement of the YOLOv5 Model in the Optimization of the Brown Spot Disease Recognition Algorithm of Kidney Bean

The kidney bean is an important cash crop whose growth and yield are severely affected by brown spot disease. Traditional target detection models cannot effectively screen out key features, resulting in model overfitting and weak generalization ability. In this study, a Bi-Directional Feature Pyramid Network (BiFPN) and Squeeze and Excitation (SE) module were added to a YOLOv5 model to improve the multi-scale feature fusion and key feature extraction abilities of the improved model. The results show that the BiFPN and SE modules show higher heat in the target location region and pay less attention to irrelevant environmental information in the non-target region. The detection Precision, Recall, and mean average Precision (mAP@0.5) of the improved YOLOv5 model are 94.7%, 88.2%, and 92.5%, respectively, which are 4.9% higher in Precision, 0.5% higher in Recall, and 25.6% higher in the mean average Precision compared to the original YOLOv5 model. Compared with the YOLOv5-SE, YOLOv5-BiFPN, FasterR-CNN, and EfficientDet models, detection Precision improved by 1.8%, 3.0%, 9.4%, and 9.5%, respectively. Moreover, the rate of missed and wrong detection in the improved YOLOv5 model is only 8.16%. Therefore, the YOLOv5-SE-BiFPN model can more effectively detect the brown spot area of kidney beans.

Influence of production situation on the incidence of brown spot of rice (Oryza sativa) caused by Bipolaris oryzae in the Philippines

AbstractBrown spot, caused by Bipolaris oryzae, is becoming more prevalent and important in the Philippines but risk assessment is limited. Surveys of 2186 farmers' fields were conducted in the major rice‐growing areas in the country from 2015 to 2018 to analyse the components of production situation (PS) that contribute to the area under the progress curve of brown spot incidence (aBS). Based on lasso regression, the components of PS that influence aBS, in decreasing order, are ecosystem (irrigated vs. rainfed), crop establishment method (direct seeding vs. transplanting), variety type (hybrid vs. inbred), rate of phosphorus fertilizer, rate of potassium fertilizer, application of organic fertilizer (with vs. without organic fertilizer) and frequency of fungicide application. Pairwise comparisons showed that aBS is positively associated with direct‐seeded rice, rainfed ecosystem, hybrid rice, moderate to high P and K rates and spraying of fungicide. Correspondence analysis and chi‐squared tests showed that the class with highest aBS is closely associated with the production situation characterized by rainfed ecosystem, direct‐seeded rice, fungicide application, moderate nitrogen and moderate to high phosphorus and potassium rates; and weather pattern (temperature, relative humidity, solar radiation, rainfall and wind speed) that occurs during the wet season. These results confirm previous studies showing that increased adoption of water‐saving technologies and direct seeding for adaptation and mitigation to climate change and reduction of agricultural labour, will most probably favour brown spot. Strategies to manage the disease under these production situations should be implemented in government programmes and considered in future research agendas.

Synergistic induction of phytoalexins in Nicotiana attenuata by jasmonate and ethylene signaling mediated by NaWRKY70.

Production of the phytoalexins scopoletin and scopolin is regulated by jasmonate (JA) and ethylene signaling in Nicotiana species in response to Alternaria alternata, the necrotrophic fungal pathogen that causes brown spot disease. However, how these two signaling pathways are coordinated to control this process remains unclear. In this study, we found that the levels of these two phytoalexins and transcripts of their key enzyme gene, feruloyl-CoA 6'-hydroxylase 1 (NaF6'H1), were synergistically induced in Nicotiana attenuata by co-treatment with methyl jasmonate (MeJA) and ethephon. By combination of RNA sequencing and virus-induced gene silencing, we identified a WRKY transcription factor, NaWRKY70, which had a similar expression pattern to NaF6'H1 and was responsible for A. alternata-induced NaF6'H1 expression. Further evidence from stable transformed plants with RNA interference, knock out and overexpression of NaWRKY70 demonstrated that it is a key player in the synergistic induction of phytoalexins and plant resistance to A. alternata. Electrophoretic mobility shift, chromatin immunoprecipitation-quantitative PCR, and dual-luciferase assays revealed that NaWRKY70 can bind directly to the NaF6'H1 promoter and activate its expression. Furthermore, the key regulator of the ethylene pathway, NaEIN3-like1, can directly bind to the NaWRKY70 promoter and activate its expression. Meanwhile, NaMYC2s, important JA pathway transcription factors, also indirectly regulate the expression of NaWRKY70 and NaF6'H1 to control scopoletin and scopolin production. Our data reveal that these phytoalexins are synergistically induced by JA and ethylene signaling during A. alternata infection, which is largely mediated by NaWRKY70, thus providing new insights into the defense responses against A. alternata in Nicotiana species.

<i>In vitro</i> assessment of bacterial endophytes for antagonistic activity against <i>Magnaporthe oryzae</i> and <i>Cochliobolus miyabeanus</i> in rice

Rice is the global staple food, contributing over half of the world’s agricultural production. Excessive fungicide use in rice farming poses environmental, fungicide resistance, and beneficial microbial disruption concerns, making biocontrol, particularly bacteria, a promising biocontrol agent due to their rapid growth, ease of handling, and robust colonization attributes. Endophytes are endosymbionts residing within host plants, playing a pivotal role in plant health without inciting any pathogenic effects. In this study, we investigated the antagonistic potential of four characterized bacterial endophytic strains, viz., Bacillus velezensis strains A6 and P42, B. pseudomycoides HP3d and Paenibacillus polymyxa PGSS-1 against major foliar rice pathogens viz., Magnaporthe oryzae and Cochliobolus miyabeanus. Against M. oryzae, all the endophytic strains exhibited significant per cent inhibition (50.00-66.67%) and the highest inhibition of 66.67% was achieved by B. pseudomycoides strain HP3d, while the lowest inhibition of 50 and 51.11% was by B. velezensis strain A6, P42, and P. polymyxa PGSS1, respectively. These endophytes outperformed the positive control, P. fluorescens which showed 44.44% inhibition. Similarly, against C. miyabeanus, 31.25-43.75% inhibition was recorded, of which B. velezensis strain A6 exhibited the highest inhibition (43.75%), while B. velezensis strain P42 showed the lowest (31.25%). Furthermore, a double Petri dish assay was conducted to evaluate the volatile compounds produced by these endophytes against the two rice pathogens. It was observed that the volatile compounds produced by B. pseudomycoides strain HP3d and P. polymyxa strain PGSS1 significantly and effectively inhibited the growth of M. oryzae by 88.89% when compared to P. fluorescens (50.00%), whereas B. velezensis strain A6 showed the lowest inhibition (33.33%). Against the brown spot pathogen, C. miyabeanus, the endophytes demonstrated inhibition ranging from 56.25-87.50%, with B. pseudomycoides strain HP3d and P. fluorescens achieving the highest inhibition (87.50%) and B. velezensis strain P42 showing the lowest (56.25%). These results highlight the significant and varied inhibitory effects of volatile compounds released by these endophytes against fungal pathogens of rice. Overall, our findings highlight the promising biocontrol potential of these endophytic strains under in vitro conditions with B. pseudomycoides strain HP3d and P. polymyxa PGSS1 showing exceptional efficacy and they can be deployed in the field for the management of foliar fungal pathogens in rice.

High-Quality Genome Resource of Nothophoma quercina Causing Brown Spot Disease in Pears

Brown spot, a serious disease caused by Nothophoma quercina, results in small, brown, round-to-oval lesions on the leaves and is a major concern in the pear industry. We previously reported a new pathogenic strain NqHH of Nothophoma quercina, which was isolated from ‘Huanghua’ pear ( Pyrus pyrifolia Nakai, cultivar Huanghua) leaves. However, genome information regarding this pathogen is limited. Herein, we detected the genome-wide sequence of the NqHH strain using the Illumina NovaSeq 6000 and PacBio Sequel Ⅱ systems. The genome of NqHH was estimated to be 35.3 Mb with an N50 length of 1.37 Mb, encoding for 11,659 predicted protein-coding genes. This genome sequence provides valuable information for the selection of pathogenic effectors and comparative genomics of brown spot disease in pears. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Knockout of CAFFEOYL-COA 3-O-METHYLTRANSFERASE 6/6L enhances the S/G ratio of lignin monomers and disease resistance in Nicotiana tabacum.

Nicotiana tabacum is an important economic crop, which is widely planted in the world. Lignin is very important for maintaining the physiological and stress-resistant functions of tobacco. However, higher lignin content will produce lignin gas, which is not conducive to the formation of tobacco quality. To date, how to precisely fine-tune lignin content or composition remains unclear. Here, we annotated and screened 14 CCoAOMTs in Nicotiana tabacum and obtained homozygous double mutants of CCoAOMT6 and CCoAOMT6L through CRSIPR/Cas9 technology. The phenotype showed that the double mutants have better growth than the wild type whereas the S/G ratio increased and the total sugar decreased. Resistance against the pathogen test and the extract inhibition test showed that the transgenic tobacco has stronger resistance to tobacco bacterial wilt and brown spot disease, which are infected by Ralstonia solanacearum and Alternaria alternata, respectively. The combined analysis of metabolome and transcriptome in the leaves and roots suggested that the changes of phenylpropane and terpene metabolism are mainly responsible for these phenotypes. Furthermore, the molecular docking indicated that the upregulated metabolites, such as soyasaponin Bb, improve the disease resistance due to highly stable binding with tyrosyl-tRNA synthetase targets in Ralstonia solanacearum and Alternaria alternata. CAFFEOYL-COA 3-O-METHYLTRANSFERASE 6/6L can regulate the S/G ratio of lignin monomers and may affect tobacco bacterial wilt and brown spot disease resistance by disturbing phenylpropane and terpene metabolism in leaves and roots of Nicotiana tabacum, such as soyasaponin Bb.

Role of Bacillus spp. Plant Growth Promoting Properties in Mitigating Biotic and Abiotic Stresses in Lowland Rice (Oryza sativa L.).

The ability of microorganisms to promote plant growth and mitigate abiotic and biotic stresses makes them an interesting tool for sustainable agriculture. Numerous studies aim to identify new, promising bacteria isolates. Traditional culture-based methods, which focus on selecting microorganisms with plant-growth-promoting traits, such as hormone production, nutrient solubilization, and antifungal properties, are widely used. This study aims to investigate the role of plant-growth-promoting properties in bacteria-mediated stress mitigation and the suitability of traditional culture-based methods as a screening tool for the identification of beneficial bacteria. To this end, we tested three endophytic Bacillus isolates, which have previously been shown to affect tolerance against iron toxicity in lowland rice, (a) for their effect on the resistance against brown spot disease, and (b) for plant-growth-promoting traits using common culture-based methods. Both B. pumilus isolates inhibited fungal growth in vitro and reduced brown spot disease in two of three rice cultivars in planta, although they tested negative for all plant-growth-promoting traits. While B. megaterium was negative for ACC deaminase activity and nutrient solubilization, it exhibited auxin production. Nevertheless, B. megaterium did not suppress brown spot disease in any of the three rice cultivars. This study shows that bacteria do not necessarily have to possess classical plant-growth-promoting properties in order to be beneficial to plants, and it emphasizes the limitation of common culture-based methods in effectively identifying beneficial bacteria. Moreover, our results highlight the significance of the interaction between bacteria and plant cultivars in determining the beneficial effects of Bacillus spp. on plants under biotic or abiotic stresses.

English

Narrow brown leaf spot disease of rice caused by fungus Cercospora oryzae Miyake emerged as potential threat to rice crop in previous few years worldwide and can cause more than 40% yield loss. The disease symptoms were noted on various commercially important rice varieties in the rice growing districts of Punjab province of Pakistan. Hence, the studies were planned to assess the effects of Propiconazole fungicide application timings and different rice varieties on the severity of narrow brown leaf spot (NBLS) disease of rice to develop an accurate management strategy for the disease. The Propiconazole fungicide was tested at three various growth phases (early booting, late booting, and soft dough) of four rice varieties against the percent severity of the NBLS disease The experiments were designed under strip-plot (crisscross) design with four replications at research area of Plant Pathology Department, University of Agriculture Faisalabad. Analysis of variance has demonstrated that the main and interactive effects of fungicide applications and rice varieties were found significant. The main effects of years were found non-significant but their interactions with fungicide application timings and rice varieties were significant. Fungicide applications at soft dough and late booting phases of rice variety B-515 were found least effective to reduce the disease severity, respectively. Fungicide application at early booting of rice variety PK-1121 was found most effective by reducing the maximum percent diseases severity (47.25%) compared to control. It is concluded that, to minimize hazardous effects of chemicals on the environment by practicing multiple sprays at inappropriate growth phases of rice crop, fungicides must be applied during the early and late booting phases of rice varieties on mildly resistance, susceptible and highly susceptible rice varieties to reduce NBLS disease severity and to enhance the rice production and quality

First Report of Leaf Blotch Caused by Phyllosticta capitalensis on Daphne odora in China.

Daphne odora Thunb. an evergreen shrub with scented flowers, is used for ornamental purposes but it also has medicinal benefits (Otsuki, et al. 2020). In August 2021, leaf blotch symptoms were observed on roughly 20% of leaves of D. odora var. marginata plants in Fenghuangzhou Citizen Park, Nanchang city (28°41'48.12″ N, 115°52'40.47″ E), Jiangxi Province, China. Brown lesions first appeared on the edges of leaves, which eventually dried and died (Fig. 1A). For fungal isolation, 12 symptomatic leaves were randomly collected, the edges between diseased area and healthy area were cut into small pieces (4×4 mm), surface-sterilized by dipping in 70% ethanol for 10 s and 1% sodium hypochlorite for 30 s, and then rinsed three times with sterile distilled water. Leaf pieces were then plated on potato dextrose agar (PDA) and incubated at 28 ℃ for 3-4 days. A total of 10 isolates were recovered from the diseased leaves. The pure colonies of all fungal isolates had similar characteristics, and three isolates were randomly selected (JFRL 03-249, JFRL 03-250 and JFRL 03-251) for further study. Colonies of this fungus were gray and uneven, with a granular surface, and irregular white edges, finally turning black on PDA (Fig. 1B, C). Pycnidia were black, globose and 54-222 μm in diameter (Fig. 1D). Conidia were hyaline, single-celled, and nearly elliptical, which ranged from 7 to 13 × 5 to 7 μm (n=40) (Fig. 1E). These morphological characteristics were consistent with those described for the fungus Phyllosticta spp. (Wikee et al. 2013a). To confirm the fungal identity, the internal transcribed spacer (ITS) region, actin (ACT), translation elongation factor 1-alpha (TEF1-a), glyceradehyde-3-phosphate dehydrogenase (GPD) and RNA polymerase II second largest subunit (RPB2) genes were amplified using primers ITS5/ITS4, ACT-512F/ACT-783R, EF-728F/EF2, Gpd1-LM/Gpd2-LM and RPB2-5F2 /fRPB2-7cR, respectively (Wikee et al. 2013b). The sequences of the selected isolates were 100% identical. Hence, sequences of one representative isolate JFRL 03-250 were deposited in GenBank (OP854673, ITS; OP867004, ACT; OP867007, TEF1-a; OP867010, GPD; and OQ559562, RPB2). BLAST search analysis in GenBank showed 100% similarity with those of P. capitalensis (GenBank accession nos. ITS, MH183391; ACT, KY855662; TEF1-a, KM816635; GPD, OM640050 and RPB2, KY855820). From a phylogenetic perspective, a maximum likelihood phylogenetic tree was constructed by using IQtree V1.5.6 based on multiple sequences (ITS, ACT, TEF1-a, GPD and RPB2) (Nguyen et al. 2015), and the cluster analysis resulted the representative isolate JFRL 03-250 within a clade comprising Phyllosticta capitalensis (Fig. 2). Based on morphological and molecular characters, the isolate was identified as P. capitalensis. To confirm pathogenicity and fulfill Koch's postulates, 6 healthy potted plants were inoculated with 1× 106 conidia/ml suspension of isolate JFRL 03-250 by spraying on the leaves, whereas 6 plants were sprayed with sterile distilled water to serve as control. All potted plants were incubated at 28°C, 80% relative humidity and 12-h light/12-h dark alternating conditions in a climate cabinet. After 15 days, similar symptoms were observed in the inoculated leaves as in the field (Fig. 1F), whereas control leaves remained asymptomatic (Fig. 1G) and P. capitalensis was successfully re-isolated from the symptomatic leaves. Previously, P. capitalensis has been reported to cause brown leaf spot disease of various host plants around the world (Wikee et al. 2013b). However, to our knowledge, this is the first report of brown leaf spot caused by P. capitalensis on D. odora in China.

First report of Calonectria pseudopteridis causing brown spot on Eriocaulon buergerianum in Zhejiang province, China.

Eriocaulon buergerianum is a traditional Chinese herb, used to treat eye diseases. In July 2020, a severe brown spot disease occurred on E. buergerianuim in Yongjia county (120°19'E, 27°58'N), Zhejiang province, China. Seventy-three plants from a survey of about 150 plants showed brown leaf spots. The spots were yellowish-brown to brown, and primarily affected leaves. As the disease progressed, the spots expanded, and fused. Sixty of the 150 plants wilted (Fig. 1 A-D). Diseased tissues were surface-sterilized in 75% ethanol (30 s), rinsed three times with sterile distilled water, air-dried (5 min), placed on potato dextrose agar (PDA) at 26°C (12-h light/dark cycle), and cultured for 4 days. Hyphal tip technique was used to obtain five isolates, which were transferred to malt extract agar (MEA), oatmeal agar (OA), and PDA. After seven days of growth at 26°C, the colonies had light, yellowish-brown centers with gray-white edges; the reverse sides had reddish- to yellowish-brown centers. Seven-day-old colonies grown on oatmeal agar (OA) produced a sparse aerial mycelium with yellowish-brown centers, and light yellowish-brown centers on the reverse side. Seven-day-old colonies grown on PDA exhibited yellowish-brown, floccose, aerial mycelia with reddish-brown to yellowish-brown pigment on the back (Fig. 1 E-G). The colonies also produced microsclerotia on OA and PDA media. On carnation leaf agar (CLA) and water agar (WA), only macroconidia were produced. Macroconidiophores comprised a stipe bearing penicillate, fertile branches, and a clavate vesicle. Macroconidia were cylindrical, rounded at both ends, colorless, hyaline, 1- to 2-septate, but mainly one, and 71.86 to 96.11 µm (mean = 82.27 µm, n = 50) × 4.13 to 5.21 µm (mean = 4.63 µm, n = 50) (Fig. 1 H-K). Morphological characteristics of the isolate on CLA or WA medium were similar to the Calonectria petridis species complex (Alfenas et al. 2015; Liu et al. 2020). The actin (Act), calmodulin (Cal), internal transcribed spacer (ITS), Histone3 (His3), a fragment of the large subunit nuclear ribosomal DNA (LSU), RNA polymerase II subunit 2 (Rpb2), translation elongation factor 1α (Tef1), and β-tubulin 2 (Tub2) genes were sequenced. The sequences were deposited in GenBank as: His3: Not detected; Act, OM933603, MZ770831, OM933604-OM933606; Cal, OM933607, MZ770832, OM933608-OM933610; ITS, OM955624, MZ720794, OM955625-OM955627; LSU, OM955640, MZ720792, OM955641-OM955643; Rpb2, OM933615, MZ770834, OM933616-OM933618; Tef1, OM933611, MZ770833, OM933612-OM933614; and Tub2, OM933619, MZ770835, OM933620-OM933622. Sequences of the Act, Cal, ITS, LSU, Rpb2, and Tef1 genes of these strains show a 99% match to the ex-type strain Ca. pteridis CBS111793 and Ca. pseudopteridis CBS163.28 (Act, GQ280494, MT335112; Cal, GQ267413, MT335347; ITS, GQ280616, MT359808; LSU, GQ280738, MT359568; Rpb2, KY653438, MT412640; Tef1, FJ918563, MT412878). The Tub2 sequences showed 99% identity with sequences of the ex-holotype Ca. pteridis CBS111793 (Tub2, DQ190578) (Alfenas et al. 2015; Liu et al. 2020; Lombard et al. 2016). Phylogenetic analysis showed that these strains and Ca. pseudopteridis CBS163.28 were clustered in a high-support bootstrap value clade (bootstrap = 85) (Fig. 2). In August 2020, healthy E. buergerianum plants in the blooming-fruiting stage were used to test the pathogenicity of the isolates. The mycelium of isolate GJC3 was cultured on CLA medium at 26°C (12-h light/dark cycle) for ten days. Eight healthy plants were inoculated by spraying with a conidial suspension (10 mL of 1 × 105 conidia/mL). Another eight plants were sprayed with sterilized water 10 mL of sterilized water as controls. The experiment was repeated three times. Pathogenicity tests were performed in the greenhouse (60% relative humidity, 28 to 20°C day/night, temperature range, and natural sunlight). After 15 days, inoculated plants showed yellowish-brown to brown spots and withering of the leaves, whereas the control plants remained healthy (Fig. 1 L-N). Ca. pseudopteridis was reisolated from the inoculated plants, and its morphology and gene sequences were similar to the original isolate GJC3. Ca. pseudopteridis was not isolated from the control plants. Morphological characteristics, molecular data and pathogenicity test identified these organisms as Ca. pseudopteridis. This report provides a basis for further research on biology and management of this disease.