Brown Spot Disease Research Articles

First report of Phyllosticta capitalensis causing brown spot disease on guava fruits (Psidium guajava) in Mexico.

The guava (Psidium guajava L.) is a plant native to the tropical region of America. In Mexico, the area established with guava cultivation is 20,525 ha (SIAP 2021). Guava is commonly consumed as fresh fruit, being rich in nutrients such as vitamins and minerals (Murthy et al. 2020). During October 2020, in the municipality of Cocula (18.207835N, 99.670322W, 595 m above sea level), Guerrero, Mexico, severely infected immature guava fruits were observed. The incidence of disease in 150 sampled fruits was 12%. Were collected fifteen symptomatic fruits. The symptoms were circular to irregular dark brown spots that varied in size (0.5 to 2.5 cm). From symptomatic fruits, tissues were cut approximately 3 x 3 mm and disinfested with 1% NaOCl, washed three times with sterile distilled water, and transferred to PDA medium amended with streptomycin and tetracycline, and incubated at 28°C. Developing colonies were retransferred to new culture PDA medium, and purified by hyphal tip technique. Two representative isolates (PHYGUA7 and PHYGUA3) were selected for morphological and molecular characterization. After 15 days in PDA at 28°C in an incubator, colonies were flat, irregular, granular and greenish gray, pycnidia were black, granular, and grouped. The conidia were hyaline and ellipsoid, unicellular and smooth-walled, 7-11×5-6.5 μm (n=50), these characteristics were consistent with those described for the fungus Phyllosticta capitalensis (Wikee et al. 2013). Molecular identification was performed by partially sequencing the internal transcribed spacer gene (ITS), the actin gene (ACT), and the translation elongation factor 1-alpha (EF-1α) gene, using primers ITS1 and ITS4, ACT-512F/ ACT-783R, and EF1-728F/EF1-986R, respectively (White et al. 1990; Carbone and Kohn 1999). The resulting sequences were deposited in GenBank (PHYGUA7: OP810947, PHYGUA3: OP810948 for ITS, PHYGUA7: OP819845, PHYGUA3: OP819846 for ACT, and PHYGUA7: OP819847, PHYGUA3: OP819848 for EF-1α). Phylogenetic analysis using maximum likelihood concatenated sequences ITS, ACT and EF-1α with MEGA X, indicated that PHYGUA7 and PHYGUA3 isolated grouped with P. capitalensis (CPC 18848 type strain). For pathogenicity test of P. capitalensis, 15 healthy immature fruits in a field experiment in the fruits on the trees, and 15 healthy mature guava fruits (detached fruits) were superficially disinfected with 70% ethanol, wounded with a sterile toothpick, and inoculated at two equidistant points by inserting PHYGUA7 isolate mycelium. As a control treatment, 10 healthy immature fruits and 10 healthy mature fruits were only injured with a sterile toothpick. After 3 days symptoms were observed in mature fruits and numerous dark pycnidia developed, and seven days later symptoms were observed in immature fruits in all the points inoculated with the PHYGUA7 isolate, similar to the symptoms observed in the field. The control fruits remained asymptomatic. The fungus P. capitalensis was re-isolated from inoculated fruits, thus confirming Koch's postulates. In Mexico P. capitalensis has been reported in Mangifera indica, Epidendrum sp., and Schomburgkia tibicinis (Farr and Rossman, 2022). In Egypt and China P. capitalensis causes black spot on guava fruits (Arafat 2016; Liao et al. 2020). To our knowledge, this is the first report of P. capitalensis as the cause of brown spot on immature guava fruit in Mexico. This research provides relevant information to the design of disease management strategies.

Isolation and Characterization of Rice Blast and Brown Spot Disease in Different Regions of Tamil Nadu, India

Rice (Oryza sativa L.) is the most important staple food crop cultivated in almost every district of Tamil Nadu. Among the rice fungal diseases, rice blast caused by Pyricularia oryzae and brown spot caused by Bipolaris oryzae are considered to be most potent threats causing major yield losses in Tamil Nadu. The present study aims in identification and characterization of rice blast and brown spot pathogen from different rice growing regions of Tamil Nadu. Three isolates of blast pathogen and five isolates of brown spot pathogen were collected and characterized based on colony morphology and conidial characters. P. oryzae and B. oryzae was identified based on cultural and morphological characters. Molecular characterization of blast and brown spot isolates were done with universal ITS primers. Pathogenicity test was carried out for all the isolates of blast and brown spot and the isolate showing maximum disease incidence was found as virulent one. The present work of morphological and molecular characterization of blast and brown spot pathogen will therefore be helpful to identify and manage the disease effectively in Tamil Nadu.

Molecular analysis of broad-spectrum induced resistance in rice by the green leaf volatile Z-3-hexenyl acetate.

Green leaf volatiles (GLVs), volatile organic compounds released by plants upon tissue damage, are key signaling molecules in plant immunity. The ability of exogenous GLV application to trigger an induced resistance (IR) phenotype against arthropod pests has been widely reported, but its effectiveness against plant pathogens is less well understood. In this study, we combined mRNA sequencing-based transcriptomics and phytohormone measurements with multispectral imaging-based precision phenotyping to gain insights into the molecular basis of Z-3-hexenyl acetate-induced resistance (Z-3-HAC-IR) in rice. Furthermore, we evaluated the efficacy of Z-3-HAC-IR against a panel of economically significant rice pathogens: Pyricularia oryzae, Rhizoctonia solani, Xanthomonas oryzae pv. oryzae, Cochliobolus miyabeanus, and Meloidogyne graminicola. Our data revealed rapid induction of jasmonate metabolism and systemic induction of plant immune responses upon Z-3-HAC exposure, as well as a transient allocation cost due to accelerated chlorophyll degradation and nutrient remobilization. Z-3-HAC-IR proved effective against all tested pathogens except for C. miyabeanus, including against the (hemi)biotrophs M. graminicola, X. oryzae pv. oryzae, and P. oryzae. The Z-3-HAC-IR phenotype was lost in the jasmonate (JA)-deficient hebiba mutant, which confirms the causal role of JA in Z-3-HAC-IR. Together, our results show that GLV exposure in rice induces broad-spectrum, JA-mediated disease resistance with limited allocation costs, and may thus be a promising alternative crop protection approach.

First Report of Nothophoma quercina Causing Brown Spot Disease on 'Huanghua' Pear (Pyrus pyrifolia Nakai) in China.

Pear (Pyrus L.) is an important fruit tree in China, which has the largest cultivation area and yield in the world (Jia et al. 2021). In June 2022, brown spot symptoms were observed on 'Huanghua' pear (Pyrus pyrifolia Nakai, cv. Huanghua) leaves in the germplasm garden of Anhui Agricultural University (High Tech Agricultural Garden), Anhui, Hefei, China. The disease incidence was approximately 40% according to the percentage of diseased leaves among 300 leaves (50 leaves each were obtained from 6 plants). Initially, small, brown, round to oval lesions appeared on the leaves, the spots were gray in the central, and surrounded by brown to black margins. These spots rapidly enlarged, eventually causing abnormal leaf defoliation. To isolate the brown spot pathogen, symptomatic leaves were harvested, washed with sterile water, surface-sterilized with 75% ethanol for 20 s, and washed 3-4 times with sterile water. Leaf fragments were placed onto PDA medium and incubated at 25°C for 7 days to obtain isolates. The colonies exhibited white to pale gray aerial mycelium and reached a diameter of 62 mm after 7 days of incubation. Conidiogenous cells were characterized as phialides, and exhibited a doliform to ampulliform shape. Conidia displayed various shapes and sizes, ranging from subglobose to oval or obtuse, with thin walls, aseptate hyphae, and a smooth surface. They measured 4.2-7.9 × 3.1-5.5 μm in diameter. These morphologies were similar to Nothophoma quercina as reported previously (Bai et al. 2016; Kazerooni et al. 2021). For molecular analysis, the internal transcribed spacers (ITS), beta-tubulin (TUB2), and actin (ACT) regions were amplified using the primers ITS1/ITS4, Bt2a/Bt2b, and ACT-512F/ACT-783R respectively. The sequences of ITS, TUB2, and ACT were deposited in GenBank (accession numbers: OP554217, OP595395, and OP595396, respectively). A nucleotide blast search revealed high homology with N. quercina sequences: MH635156 (ITS: 541/541, 100%), MW672036.1 (TUB2: 343/346, 99%), FJ426914.1 (ACT: 242/262, 92%). A phylogenetic tree was constructed with ITS, TUB2 and ACT sequences based on neighbor-joining method using MEGA-X software, which showed the highest similarity with N. quercina. To confirm the pathogenicity, the leaves of three healthy plants were sprayed with spore suspension (106 conidia/mL), whereas control leaves were prayed with sterile water. The inoculated plants were covered with plastic bags and cultured in a growth chamber (90% relative humidity) at 25°C. Typical disease symptoms appeared on the inoculated leaves after 7-10 days, whereas no symptoms were observed on the control leaves. The same pathogen was re-isolated from the diseased leaves, according with Koch's postulates. Therefore, based on morphological and phylogenetic tree analyses, we confirmed that the causal organism for brown spot disease was N. quercina fungus (Chen et al. 2015; Jiao et al. 2017). To our knowledge, this is the first report of brown spot disease caused by N. quercina on 'Huanghua' pear leaves in China.

Sweetgum Leaf Spot Image Segmentation and Grading Detection Based on an Improved DeeplabV3+ Network

Leaf spot disease and brown spot disease are common diseases affecting maple leaves. Accurate and efficient detection of these diseases is crucial for maintaining the photosynthetic efficiency and growth quality of maple leaves. However, existing segmentation methods for plant diseases often fail to accurately and rapidly detect disease areas on plant leaves. This paper presents a novel solution to accurately and efficiently detect common diseases in maple leaves. We propose a deep learning approach based on an enhanced version of DeepLabV3+ specifically designed for detecting common diseases in maple leaves. To construct the maple leaf spot dataset, we employed image annotation and data enhancement techniques. Our method incorporates the CBAM-FF module to fuse gradual features and deep features, enhancing the detection performance. Furthermore, we leverage the SANet attention mechanism to improve the feature extraction capabilities of the MobileNetV2 backbone network for spot features. The utilization of the focal loss function further enhances the detection accuracy of the affected areas. Experimental results demonstrate the effectiveness of our improved algorithm, achieving a mean intersection over union (MIoU) of 90.23% and a mean pixel accuracy (MPA) of 94.75%. Notably, our method outperforms traditional semantic segmentation methods commonly used for plant diseases, such as DeeplabV3+, Unet, Segnet, and others. The proposed approach significantly enhances the segmentation performance for detecting diseased spots on Liquidambar formosana leaves. Additionally, based on pixel statistics, the segmented lesion image is graded for accurate detection.

Antifungal Activity of Streptomyces hygroscopicus JY-22 against Alternaria alternata and Its Potential Application as a Biopesticide to Control Tobacco Brown Spot

Tobacco brown spot caused by Alternaria alternata is a devastating fungal disease endangering plant production. To effectively control brown spot disease, an antagonistic Actinomyces strain, Streptomyces hygroscopicus JY-22, was isolated from rhizospheric soil, which remarkably restrains the growth of phytopathogenic fungus Alternaria alternata. This antagonistic strain and its culture filtrate showed significant antifungal activity against Alternaria alternata. Firstly, the confrontation culture method of strains JY-22 and Alternaria alternata showed that Streptomyces hygroscopicus JY-22 had noticeable antifungal activity against Alternaria alternata, including inhibition of mycelial growth and mycelial morphological changes, compared with the control group. Furthermore, the culture filtrate of Streptomyces hygroscopicus JY-22 showed substantial inhibition of the mycelial growth and spore germination of Alternaria alternata in a dose-dependent manner. Additional studies revealed that these antifungal actions were mainly related to membrane-active mechanisms that increased membrane permeability and damaged the cell membrane, leading to changes in certain cytoplasmic properties, such as extracellular conductivity and ergosterol, MDA and soluble protein content. In detached-leaf and field experiments, foliar spraying with culture filtrate resulted in smaller lesions and a lower disease index than the control group. Taken together, these results suggest that Streptomyces hygroscopicus JY-22 and its culture filtrate have the potential to be a safe biopesticide for the bio-control of tobacco brown spot.

Influence of Fungicidal Seed Treatments against Pathogen Complex Found on Paddy Seed and Their Effects on Seedling Germination, Growth, and Plant Vigor

A paddy (Oryza sativa) seed treatment study was conducted by the Plant Pathology Department, GRDB, RRS, Burma to evaluate the effectiveness of eight fungicides [Amistar Xtra 28SC, Saaf 75 WP, Glory 75WG, Tridium 70WG, Antracol 70WP, Rodazim 50 SC, Carbendazim 50SC and Manzate Pro Stick TM], at varying rates, along with a healthy check and untreated control, on germination and seedling vigour of paddy, and identifying suitable fungicides to be used as pre-sowing seed treatment. Trials were carried out under laboratory, potted and field conditions. A completely randomized block (CRD) was used for the laboratory and pot trials and randomized complete block design (RCBD) was used for the field trials, with three replicates. These trials were conducted in both rice growing seasons (Spring and Autumn) in Guyana during 2020 and 2021. Dry seed examination and blotter test unearthed the presence of four dominant pathogenic genera (Curvularia lunata, Bipolaris oryzae, Pyricularia oryzae and Aspergillus spp). from the paddy seeds before being treated and in the untreated control. The results of the germination test during 2020 showed variability among treatments, percentage germination ranged from 61% in seeds treated with Amistar Xtra 28 SC 3.7ml/L to 91% in seeds treated with Saaf 75 WP 5.6g/L. While in 2021 the percentage germination ranged from 79% in seeds treated with Tridium 70 WG 4.3g/L to 95% in seed treated with Saaf 75 WP 5.6g/L. Results from the in vitro studies showed seeds treated with Saaf (3.1g/L and 5.6g/L), Manzate Pro Stick TM (3.7 g/L), Glory at 12.4g/L, Rodazim (at 3.7ml/L) and the healthy control produced seedlings with taller shoots, longer roots and ultimately the higher seedling vigour at 14 and 21 days after treatment as compared to other treatments and the untreated control. Similarly, under potted condition seed treated with Rodazim (1.2ml/L and 3.7ml/L), Saaf (5.6g/L) and Glory (7.4g/L and 12.4g/L) demonstrated SVI compared to the other treatments and the untreated control. Further, under field condition the three fungicides viz. Rodazim, Manzate and Glory found to be promising in previous trials were selected and evaluated against an untreated control. Data collected revealed no significant difference among any of the treatments for grain yield, number of tillers/m2, plant height, the weight per 1000 grain nor the number of unfilled grains per panicle. However, treatment with Manzate Pro Stick TM (3.7 g/L) produced the largest number of filled grains as compared to the other treatment and control. It is therefore recommended that farmers should employ seed treatment prior to sowing if do not have clean, certified disease free seeds and use the paddy seed treatment [Saaf (5.6g/L), Manzate Pro Stick TM (3.7 g/L), Glory at (12.4g/L), Rodazim (3.7ml/L)] as a method of controlling seed borne pathogens, enhancing germination, seedling vigour and ultimately improving productivity.

First Report of Brown Spot Caused by Alternaria alternata on Potato (Solanum tuberosom L.) in Korea.

In June 2020, brown spot symptoms were observed in a commercial potato field located in Yeocheon, Gyeonggi Province, Korea. The symptoms were similar to those associated with early blight. Brown lesions on leaves were circular and expanded rapidly under high humidity and warm temperatures ranging 12°C at night to 30°C during daytime. Over 60% of potato (Solanum tuberosum L. cv. Superior) leaves showed the symptoms. For fungal isolation, infected leaf tissues (5 × 5 mm) from 14 infected samples were immersed in 70% ethanol for 1 min, rinsed three times in sterilized water, dried, placed on water agar amended with 100 ppm of streptomycin, and then incubated in the dark at 25°C. Hyphae emerging from the tissues were subcultured on V8-Juice agar (8% of V8-Juice, 1.5% agar, pH 7), and the obtaining cultures were subjected to single-spore isolation, resulting in 14 isolates (SYP-934~947). Three representative isolates, SYP-934 to SYP-936, were deposited in the Korean Agriculture Culture Collection (Accession Nos. KACC 410058 to KACC 410060). Conidia (n = 100) produced on the colony were brown, ellipsoid to ovoid with walls ornamented, 1 to 6 transverse and 0-3 vertical septa, and length × width of 20-45 × 7 to 24 μm (n = 100). Their morphological characteristics were consistent with Alternaria alternata (Simmons, 2007; van der Waals et al., 2011; Woundenberg et al. 2015). Sequences of the following loci in the 14 isolates were determined as described in Woundenberg et al. (2013 and 2014: the internal transcribed spacer (primer pairs VG9/ITS4, GenBank accession nos. OP581413-25), glyceraldehyde-3-phosphate dehydrogenase (gpd1/gpd2, OP588286-99), RNA polymerase second largest subunit (RPB2-5F2/fRPB2-7cR, OP588314-27), translation elongation factor 1-alpha (EF1-728F/EF1-986R, OP588300-13), Alternaria major allergen gene (Alt-For/Alt-Rev, OP588328-41), endopolygalacturonase (PG3/PG2b, OP588342-55), and an unknown gene region (OPA10-2R/OPA10-2L, OP588356-68). A neighbor-joining phylogenetic analysis based on the concatenated gene sequences, which was performed using the MEGA X program (Kumar et al., 2018), placed the 14 isolates in the clade containing A. alternata isolates. To test pathogenicity, one-month-old potato (S. tuberosum cv. Superior) plants grown in a 25°C growth chamber were sprayed with conidial suspensions (1×106 conidia/mL) prepared from 14-day-old cultures of three isolates (KACC 410058 to KACC 410060). Sterile distilled water was used as the control treatment. The inoculated pots were placed in a plastic box to maintain high humidity and incubated in the dark at 25°C for 2 days. The plants were transferred to a growth chamber (16h light with over 70% humidity at 25°C). Symptoms were first observed after 3 days post inoculation (dpi) with all three isolates, and severe brown spot symptoms were observed after 7 dpi. No symptom was observed in the control treatment. The pathogenicity assay was repeated at triplicate. Reisolated cultures from lesions were confirmed to be A. alternata based on their sequence at the rpb2 locus, thus fulfilling Koch's postulates. Alternaria alternata has been reported to cause brown spot and leaf blight on potato leaves in Israel (Dorby et al., 1984) and South Africa (van der Waals., et al. 2011). To our knowledge, this study is the first report of A. alternata causing brown spot disease in Korea.

First Report of Brown Leaf Spot Caused by Epicoccum tobaicum on Oat (Avena sativa) in Korea.

Oat (Avena sativa) is one of the Korean winter crops, and oat consumption has been increasing because it is widely perceived as a superfood. Recently, various fungal diseases have been reported likely due to climate changes during the winter season in Korea (Choi et al., 2018; Kim, 2020). During the 2020-2021 winter to spring, we surveyed new fungal diseases among cereals, including oats, in the southern region of Korea. In April 2021, brown leaf spots on oat leaves were observed in Gangjin, Jeollanam-do, Korea. These brown spots were irregular circles, ranging from 2-7 mm in diameter. Samples from three infected leaves were surface sterilized by treating them with 70% ethanol for 1 min and 1% NaOCl for 1 min. The samples were subsequently rinsed at least twice with distilled water and dried with a sterile paper towel before being placed on 1.5% water agar supplemented with 100 ppm streptomycin. Hyphal tips derived from infected tissues after incubation at 25C for 7 days were transferred to a fresh potato dextrose agar (PDA). Three isolates, labeled as KJO-AN2-S1, KJO-AN2-S2 and KJO-AN2-S3, were obtained via single hyphal tip purification. Colonies on PDA were pigmented vermilion and subsequently turned to saffron color with irregular margins after 7 days. Conidia produced on PDA were golden to dark brown, globose to subglobose, solitary, and measured 15.5-21.5 μm in diameter (n=50). Cultural and morphological characteristics suggested that these isolates belong to Epicoccum species (Chen et al. 2017). For identification by sequencing, the ITS (MW691866-68), tub2 (MW691872-74), and rpb2 (MW691869-71) regions of three isolates were amplified using the primer pairs ITS5/ITS4 (White et al., 1990), Btub2Fd/ Btub4Rd (Woudengerg et al., 2009), and RPB2-5F2 (Sung et al., 2007)/fRPB2-7cR (Liu et al., 1999), respectively. A maximum likelihood phylogenetic analysis based on the concatenated ITS, tub2, and rpb2 sequences placed the three isolates within a clade comprising E. tobaicum CBS 384.36. A mycelial plug (5 mm diameter) was inoculated onto wounded and unwounded leaves of healthy 12-day-old oat (cv. Choyang) seedlings. The control leaves were inoculated with a sterile PDA plug. All inoculated and control plants were placed in a plastic box and incubated at 20℃ in darkness with 100% humidity. After 1 day, the inoculated mycelial plug or sterile PDA plug from plants was removed; the plants in plastic boxes were then transferred to a growth chamber set at 20℃ with 12 h light and 60-70% humidity. While brown spot lesions were observed in both unwounded and wounded leaves 7 days post-inoculation, both wounded and unwounded control leaves remained asymptomatic. The pathogen was recovered from all symptomatic leaf tissues but could not be isolated from control leaves. The re-isolated pathogen was identified as E. tobaicum through morphological characterization and sequence-based identification, fulfilling Koch's postulates. This study is the first to report a causal relationship between E. tobaicum and brown leaf spot disease of oat in Korea. Identification of this newly emerging fungal disease on oats will help prepare for effectively managing this disease.

Effect of rice rhizospheric Trichoderma spp and fungicide for the management of brown spot disease of rice

Brown spot of rice caused by Bipolaris oryzae is of worldwide occurrence and is known to cause substantial quantitative and qualitative losses in grain yield. This disease was responsible for the epic 'Great Bengal Famine' in 1942-1943, resulting in the death of 4 million people. Studies were carried out to evaluate the effect of rice rhizospheric Trichoderma spp and fungicide for the management of brown spot disease of rice. A total of 20 isolates of Trichoderma spp were isolated from rice rhizospheric soil and screened by dual culture method in which three isolates Ti20, Ti19 and Ti16 showing maximum inhibition of 67.86%, 64.29% and 60.71% were selected for further test. Six fungicides viz., Hexaconazole, Propiconazole, Carbendazim + Mancozeb, Metalaxyl + Mancozeb, Carbendazim and Copper oxychloride were evaluated against B. oryzae by poison food technique, out of which Propiconazole, Hexaconazole and Copper oxychloride were selected and further tested for their compatibility with the selected Trichoderma spp was done. The most efficient and compatible Trichoderma sp with fungicide i.e., (Ti19 + Hexaconazole 5% SC) were selected for managing the disease in pot experiment with different treatment combinations i.e., seed treatment, seedling dip and foliar spray. Results under pot experiment showed that, seed treatment with Ti19 and Hexaconazole 5% SC recorded lowest disease severity of 3.70%, 7.41% and 11.11% at tillering, booting and milking stages respectively, with significantly higher yield of 28.27 g/pot as compared to untreated control pots.

Effect of Nutrient Management and Weeds on Incidence of Fungal Diseases in Rice

High-input, modern agriculture uses large amounts of energy, water, fertilizers, and pesticides to produce high crop yields. One of the major bottlenecks of the modern agriculture in the tropics is substantial yield losses due to fungal diseases including rice blast, leaf spots and leaf scald. The aim of this study was to compare the incidence of fungal diseases in judicious nutrient management systems, including organic, integrated, and conventional, under different weed categories during dry season (May to September 2020) and wet season (November 2020 to March 2021). Rice disease incidence were collected for both seasons from 48-84 days after sowing. Additionally, disease incidences on grasses and sedges weeds were also calculated. Brown spot, narrow brown leaf spot, leaf scald, and rice blast incidences were substantial in wet season, while the disease incidences during dry season in 2020 were negligible. The disease incidences were significantly higher (P<0.05) in organic and conventional input systems compared to the integrated input system. Disease incidences of brown spot and leaf scald were found in the dry season. Higher disease incidences were recorded in the wet season than in the dry season. The incidences of the brown spot were higher on sedges than in grasses and vice versa were observed for narrow brown leaf spot disease. Leaf scald incidences were positively correlated with the significant nitrogen status of the rice crop. Disease incidence was low in integrated input system compared to conventional and organic input systems, while weeds were reported as alternative hosts. It can be concluded that the integrated nutrient management with recommended dosage of nitrogen application with proper weed management can lead to low disease incidents, hence is ecologically more sustainable.

Dual effect of picolinic acid in the photosynthetic performance of rice plants infected by Bipolaris oryzae

AbstractBrown spot, caused by Bipolaris oryzae, is one of the most important diseases of rice. The non‐host toxin α‐picolinic acid (PA) has great potential to be used to enhance plant resistance against pathogen infection. The present study investigated the effect of spraying PA [0 (control), 1, 3, and 5 mg/mL] on the photosynthetic performance of rice plants (cultivar Metica‐1) infected or not with B. oryzae. Moreover, whether the PA treatment, especially at the highest concentration, could affect brown spot development was also evaluated. The chlorophyll a fluorescence parameters such as variable‐to‐maximum chlorophyll a fluorescence ratio (Fv/Fm), photochemical yield [Y(II)], yield for dissipation by down‐regulation [Y(NPQ)], the yield for non‐regulated dissipation [Y(NO)], and electron transport rate (ETR) as well as the concentration of photosynthetic pigments were determined. Based on the in vitro assay, PA inhibited mycelial growth of B. oryzae in a dose‐dependent manner and conidial germ tube length only decreased at 5 mg PA/mL. Conidia germination was not affected by the PA treatment. Necrotic lesions caused by PA were observed on leaves of non‐inoculated plants at 3 and 5 mg PA/mL. Symptoms of the brown spot were reduced on plants sprayed with 1 and 3 mg PA/mL compared to the control treatment. Brown spot lesions and those originating from PA toxicity overlapped for inoculated plants sprayed with 3 and 5 mg PA/mL. The photochemical performance of non‐inoculated plants was hampered by treatments with 3 and 5 mg PA/mL. Greater concentration of photosynthetic pigments and less impairment on the photosynthetic performance of inoculated plants sprayed with 1 mg PA/mL were noticed based on the values of Fv/Fm, Y(II), Y(NPQ), Y(NO), and ETR compared to inoculated plants non‐sprayed with PA. In conclusion, spraying rice plants with a low concentration of PA could decrease brown spot severity while preserving the photosynthetic capacity of the infected plants. The cellular damage generated by spraying the plants with the highest PA concentration did not favour the infection process of B. oryzae.

ResViT-Rice: A Deep Learning Model Combining Residual Module and Transformer Encoder for Accurate Detection of Rice Diseases

Rice is a staple food for over half of the global population, but it faces significant yield losses: up to 52% due to leaf blast disease and brown spot diseases, respectively. This study aimed at proposing a hybrid architecture, namely ResViT-Rice, by taking advantage of both CNN and transformer for accurate detection of leaf blast and brown spot diseases. We employed ResNet as the backbone network to establish a detection model and introduced the encoder component from the transformer architecture. The convolutional block attention module was also integrated to ResViT-Rice to further enhance the feature-extraction ability. We processed 1648 training and 104 testing images for two diseases and the healthy class. To verify the effectiveness of the proposed ResViT-Rice, we conducted comparative evaluation with popular deep learning models. The experimental result suggested that ResViT-Rice achieved promising results in the rice disease-detection task, with the highest accuracy reaching 0.9904. The corresponding precision, recall, and F1-score were all over 0.96, with an AUC of up to 0.9987, and the corresponding loss rate was 0.0042. In conclusion, the proposed ResViT-Rice can better extract features of different rice diseases, thereby providing a more accurate and robust classification output.

Research of segmentation recognition of small disease spots on apple leaves based on hybrid loss function and CBAM.

Identification technology of apple diseases is of great significance in improving production efficiency and quality. This paper has used apple Alternaria blotch and brown spot disease leaves as the research object and proposes a disease spot segmentation and disease identification method based on DFL-UNet+CBAM to address the problems of low recognition accuracy and poor performance of small spot segmentation in apple leaf disease recognition. The goal of this paper is to accurately prevent and control apple diseases, avoid fruit quality degradation and yield reduction, and reduce the resulting economic losses. DFL-UNet+CBAM model has employed a hybrid loss function of Dice Loss and Focal Loss as the loss function and added CBAM attention mechanism to both effective feature layers extracted by the backbone network and the results of the first upsampling, enhancing the model to rescale the inter-feature weighting relationships, enhance the channel features of leaf disease spots and suppressing the channel features of healthy parts of the leaf, and improving the network's ability to extract disease features while also increasing model robustness. In general, after training, the average loss rate of the improved model decreases from 0.063 to 0.008 under the premise of ensuring the accuracy of image segmentation. The smaller the loss value is, the better the model is. In the lesion segmentation and disease identification test, MIoU was 91.07%, MPA was 95.58%, F1 Score was 95.16%, MIoU index increased by 1.96%, predicted disease area and actual disease area overlap increased, MPA increased by 1.06%, predicted category correctness increased, F1 Score increased by 1.14%, the number of correctly identified lesion pixels increased, and the segmentation result was more accurate. Specifically, compared to the original U-Net model, the segmentation of Alternaria blotch disease, the MIoU value increased by 4.41%, the MPA value increased by 4.13%, the Precision increased by 1.49%, the Recall increased by 4.13%, and the F1 Score increased by 2.81%; in the segmentation of brown spots, MIoU values increased by 1.18%, MPA values by 0.6%, Precision by 0.78%, Recall by 0.6%, and F1 Score by 0.69%. The spot diameter of the Alternaria blotch disease is 0.2-0.3cm in the early stage, 0.5-0.6cm in the middle and late stages, and the spot diameter of the brown spot disease is 0.3-3cm. Obviously, brown spot spots are larger than Alternaria blotch spots. The segmentation performance of smaller disease spots has increased more noticeably, according to the quantitative analysis results, proving that the model's capacity to segment smaller disease spots has greatly improved. The findings demonstrate that for the detection of apple leaf diseases, the method suggested in this research has a greater recognition accuracy and better segmentation performance. The model in this paper can obtain more sophisticated semantic information in comparison to the traditional U-Net, further enhance the recognition accuracy and segmentation performance of apple leaf spots, and address the issues of low accuracy and low efficiency of conventional disease recognition methods as well as the challenging convergence of conventional deep convolutional networks.

Unraveling the role of effector proteins in Bipolaris oryzae infecting North East Indian rice cultivars through time-course transcriptomics analysis

Bipolaris oryzae, causing brown spot disease in rice, is one of the neglected diseases reducing rice productivity. Limited knowledge is available on the genetics of host-pathogen interaction. Here, we used time-course transcriptome sequencing to elucidate the differential transcriptional responses of the pathogen genes in two contradictory infection-responsive rice hosts. Evaluation of transcriptome data showed similar regulation of fungal genes within susceptible (1733) and resistant (1846) hosts at an early stage however, in the later stage, the number was significantly higher in susceptible (2877) compared to resistant (1955) hosts. GO enrichment terms for upregulated genes showed a similar pattern in both the hosts at an early stage, but in the later stage terms related to degradation of carbohydrates, carbohydrate transport, and pathogenesis are enriched extensively within the susceptible host. Likewise, similar expression responses were observed with the secretory and effector proteins. Plant pathogenic homologs genes such as those involved in appressorium and conidia formation, host cell wall degradative enzymes, etc. were reported to be highly upregulated within the susceptible host. This study predicts the successful establishment of B. oryzae BO1 in both the host surfaces at an early stage, while disease progression only occurs in the susceptible host in later stage.

Pentaketides and 5-p-Hydroxyphenyl-2-pyridone Derivative from the Culture Extract of a Marine Sponge-Associated Fungus Hamigera avellanea KUFA0732.

Five undescribed pentaketide derivatives, (R)-6,8-dihydroxy-4,5-dimethyl-3-methylidene-3,4-dihydro-1H-2-benzopyran-1-one (1), [(3S,4R)-3,8-dihydroxy-6-methoxy-4,5-dimethyl-1-oxo-3,4-dihydro-1H-isochromen-3-yl]methyl acetate (2), (R)-5, 7-dimethoxy-3-((S)-(1-hydroxyethyl)-3,4-dimethylisobenzofuran-1(3H)-one (4b), (S)-7-hydroxy-3-((S)-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran 1(3H)-one (5), and a p-hydroxyphenyl-2-pyridone derivative, avellaneanone (6), were isolated together with the previously reported (R)-3-acetyl-7-hydroxy-5-methoxy-3,4-dimethylisobenzofuran-1(3H)-one (3), (R)-7-hydroxy-3-((S)-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran-1(3H)-one (4a) and isosclerone (7), from the ethyl acetate extract of a culture of a marine sponge-derived fungus, Hamigera avellanea KUFA0732. The structures of the undescribed compounds were elucidated using 1D and 2D NMR, as well as high-resolution mass spectral analyses. The absolute configurations of the stereogenic carbons in 1, 4b, 5, and 6 were established by X-ray crystallographic analysis. The absolute configurations of C-3 and C-4 in 2 were determined by ROESY correlations and on the basis of their common biosynthetic origin with 1. The crude fungal extract and the isolated compounds 1, 3, 4b, 5, 6, and 7 were assayed for their growth inhibitory activity against various plant pathogenic fungi viz. Alternaria brassicicola, Bipolaris oryzae, Colletotrichum capsici, C. gloeosporiodes, Curvularia oryzae, Fusarium semitectum, Lasiodiplodia theobromae, Phytophthora palmivora, Pyricularia oryzae, Rhizoctonia oryzae and Sclerotium rolfsii.

Aplikasi Pestisida Nabati dan Trichokompos terhadap Penyakit Bercak Daun (Cercospora oryzae) pada Padi Beras Merah di Lahan Basah

Cultivation of brown rice (Oryza nivara L.) in wetlands continues to expand because its consumers continue to increase. This study aims to determine the ability of Trichocompost and a solution of botanical pesticides from kalakai, babadotan and purun tikus in controlling brown spot disease caused by the fungus Cercospora oryzae on brown rice plants in wetlands. Based on the results of observations, the application of trichocompost and purunrat solution was able to reduce the incidence of leaf spot disease from 95.1% in controls to 76.5%. The results of disease intensity showed that the application of trichocompost and kalakai solution was able to reduce disease intensity from 19.55% in controls to 14.10%. The application of trichocompost and babadotan solution increased the number of grains of rice from 216.60 grains in the control to 243.20 grains. The application of Trichocompost and kalakai solution increased the weight of 100 grains from 1.79 g to 2.10 g. The application of only trichocompost, Trichocompost and kalakai solution, trichocompost and babadotan solution, and trichocompost and purunrat solution have the same ability to reduce the incidence and intensity of Cercospora disease. All treatments tested were unable to increase plant height growth.

Deciphering of seed Health of common food grains (wheat, rice) of North Eastern UP and Gurgaon Haryana, India

The stored random samples of food seeds of wheat and rice (60 samples) were purchased from places of Eastern UP and Gurgaon district Haryana. Its moisture contents were estimated. The Mycological investigations of wheat seeds revealed presence of a total number of 16 fungal species viz., Alternaria alternata, Aspergillus candidus, Aspergillus flavus, A. niger, A. ochraceous, A. phoenicis, A. tamari, A. terreus, A. sydowi, Fusarium moniliforme, F. oxysporum F. solani, P. glabrum, Rhizopus nigricans, Trichoderma viride and Trichothecium roseum. While mycological analysis of rice seeds showed presence of 15 fungal species viz., Alternaria padwickii, A. oryzae, Curvularia lunata, Fusarium moniliforme, Aspergillus clavatus, A. flavus, A. niger, Cladosporium sp., Nigrospora oryzae, Alternaria tenuissima, Chaetomium globosum, F. solani, Microascus cirrosus, Helminthosporium oryzae, Pyricularia grisea. It also projected variation in presence of fungal species in blotter and agar plate method of analysis. In wheat Blotter method of analysis showed 16 fungal species while agar plate depicted 13 fungal species. In rice Agar plate method depicted presence of 15 fungal species while blotter method shows presence of 12 fungal species. The insect analysis revealed that wheat samples were infected with Tribolium castaneum. While rice seeds sample showed presence of insect Sitophilus oryzae. The investigations revealed that Aspergillus flavus, A. niger, Sitophilus oryzae and Tribolium castaneum caused reduction in seed weight loss, seed germination, carbohydrate and protein contents of common food grains (wheat, rice). It also revealed that randomly selected A. flavus isolate 1 of wheat showed higher potential of aflatoxin B1 production (1392.940 μg/l) while rice isolate 2 showed 1231.117 μg/l production.

Nickel enhances rice resistance against Bipolaris oryzae infection

Nickel enhances rice resistance against Bipolaris oryzae infection

Transcriptome profiling uncovers the involvement of CmXyn1, a glycosyl hydrolase 11, in Cochliobolus miyabeanus pathogenicity

Necrotrophic pathogen Cochliobolus miyabeanus (C. miyabeanus) causes rice brown leaf spot disease and drastically affects the yield and quality of rice grains. However, the molecular mechanism of rice-C. miyabeanus remains poorly understood due to the limited research conducted on this pathosystem. To elucidate the molecular mechanism of rice-C. miyabeanus, a transcriptome analysis was conducted from in vitro and in planta grown C. miyabeanus. This analysis led to the identification of a total of 24,060 genes of which 426 in vitro and 57 in planta expressed genes were predicted to encode for secretory proteins. As these 57 genes were specifically expressed in planta and were predicted to be secretory in nature, these were consider as putative effectors, highlighting their possible roles in the fungal pathogenicity. Notably, among these putative effectors, CmXyn1 which encodes a glycosyl hydrolase 11 displayed the highest expression level under in planta conditions and was thus selected for further functional characterization. Interestingly, the extracellular expression of CmXyn1 transiently induced cell death in Nicotiana benthamiana leaves, while intracellular expression was comparatively lesser effective. In addition, transcriptome analysis on rice leaves during C. miyabeanus infection and comparing it to the rice leaf transcriptome data obtained during hemibiotrophic pathogen Magnaporthe oryzae infection led to the discovery of 18 receptors/receptor-like kinases that were commonly expressed in response to both pathogens, indicating their key roles in rice defense response. Taken together, our findings provide new insights into rice-C. miyabeanus interaction as well as the unique and common defense responses of rice against hemibiotroph and necrotroph model systems.