Brown Leaf Spot Research Articles

Pathogenic variability among Curvularia species causing brown leaf spot disease of rice

Pathogenic variability among Curvularia species causing brown leaf spot disease of rice

Natural Defense: The Inhibitory Effects of Endophytic Bacillus and Xylaria sp. against Rice Pathogens

Aim: Endophytes living inside the plant tissues are known to play a crucial role in the physiology and developmental functioning of host plants. Rice is the major food crop that feeds half of the world population. But pest and diseases lead to drastic yield reduction in rice. Sustainable and eco-friendly disease management strategies are urgently needed to reduce the reliance on chemical pesticides and mitigate the environmental impact of intensive agriculture.The aim of the study was the selection of natural suppressors of the brown spot and sheath blight diseases in rice. In this study, three bacterial endophytes viz., Bacillus subtilis isolate PAL 11, B. altitudins isolate TSL-4 and B. altitudinis isolate KAM-11 and one endophytic fungal isolate Xylaria sp. isolate KTD-2 were tested for their potential to inhibit Bipolaris oryzae and Rhizoctonia solani under in vitro conditions. Methodology: In vitro evaluation of endophytes against two major rice pathogens viz., Rhizoctonia solani and Bipolaris oryzae causing sheath blight and brown leaf spot respectively were tested by dual culture technique. Results: All the tested bacterial and fungal endophytes significantly inhibited both the pathogens under in vitro conditions. Among the bacterial endophytes, B. subtilis isolate PAL-11 exhibited highest inhibition of both the pathogens. The mycelial inhibition of B. oryzae was 56.04 and 74.48 per cent respectively at 5 and 8 days after dual culturing whereas the inhibition of R. solani was 80.31 and 80.22 per cent respectively at 3 and 5 days after dual culturing. The fungal endophyte Xylaria sp. isolate KTD-2 exhibited 63.2 and 67.95 per cent inhibition of mycelial growth of B. oryzae at 5 and 8 days respectively after the pathogen inoculation. The mycelial growth of R. solani was also significantly inhibited (54.95 %) by the fungal endophyte at 5 days after pathogen inoculation. Conclusion: This research highlights the potential role of endophytes in sustainable agriculture and suggests that integrating beneficial microbes into rice disease management strategies could help enhance plant health, increase crop yields, and contribute to global food security.

Appraisal of antifungal potential of chemicals and plant extracts against brown leaf spot of soybean caused by Septoria glycine

Soybean is a legume crop originating in China. Its nutritional value, characterized by high-quality protein and unsaturated fats, makes it an excellent cholesterol-free diet option. Brown leaf spot of soybean, caused by Septoria glycine, is one of the most devastating diseases, resulting in significant yield losses. This study aimed to evaluate the effectiveness of new chemical fungicides (Topsin-M, Recado, Evito, Polyram-DF, and Curzate-M) at concentrations of 50, 100, and 150 ppm, and phyto-extracts (neem, clove, eucalyptus, ficus, and datura) at concentrations of 3, 5, and 7% against S. glycine under in vitro conditions. The most effective treatments from the in vitro tests were further investigated under greenhouse conditions using a completely randomized design with three replications per treatment. The results indicated that, among the fungicides, Topsin-M showed the lowest mycelial growth (3.5, 2.73, and 2.34 mm) at concentrations of 50, 100, and 150 ppm, respectively. Among the phyto-extracts, clove demonstrated the most effective results, with the least fungal growth (3.95 mm) at 7% concentration. Under greenhouse conditions, the best results were achieved with a combination of Topsin-M and clove, resulting in the lowest disease incidence (10.27%), followed by Topsin-M (17.65%) and clove (26.76%). This study suggests that new chemical fungicides and phyto-extracts can be effectively used as part of an integrated management strategy against brown leaf spot of soybean.

Effect of Trichoderma harzianum and Selected Botanicals on Brown Leaf Spot of Paddy (Oryza sativa L.) Caused by Helminthosporium oryzae (Breda de Haan)

Effect of Trichoderma harzianum and Selected Botanicals on Brown Leaf Spot of Paddy (Oryza sativa L.) Caused by Helminthosporium oryzae (Breda de Haan)

Effect of Different Media, Temperature, pH and Nitrogen Sources on Growth and Development of Helminthosporium oryzae Causing Brown Leaf Spot of Rice

Effect of Different Media, Temperature, pH and Nitrogen Sources on Growth and Development of Helminthosporium oryzae Causing Brown Leaf Spot of Rice

Screening of rice genotypes against brown leaf spot (Bipolaris oryzae) (Breda de Haan) shoemaker, under field and laboratory conditions at Banke, Nepal

A field experiment was carried out to screen 60 rice genotypes against brown leaf spot disease caused by Bipolaris oryzae with Sabitri as a resistant check and Mansuli as a susceptible check at Banke, Nepal. The field experiment was laid out in a randomized completed block design, and the seed infection screening was done in a laboratory with a completely randomized design. The disease assessment was done by calculating disease severity, the area under the disease progress curve (AUDPC), and the seed infection rate. The disease severity and AUDPC significantly varied for the tested genotypes. Based on the AUDPC and disease severity values, this study observed that one genotype was moderately resistant, 11 were susceptible, and 48 were highly susceptible. From our experiment, rice genotypes were primarily susceptible rather than resistant; thus, for the next-generation breeding program for brown leaf spot-resistant genotypes, more landraces should be screened from diverse environments of Nepal.

Search for sources of resistance to leaf diseases among present winter bread wheat varieties in the southern part of the Rostov region

The purpose of the current work was to search for sources of winter wheat varieties’ resistance to the most common pathogens of the area under artificial infectious backgrounds and recommend them for inclusion in the breeding process. The study was carried out on the experimental plots of the laboratory for plant immunity and protection of the FSBSI Agricultural Research Center “Donskoy” in 2021–2023. In order to expand the genetic diversity in immunity of newly developed varieties, it is necessary to use new sources of resistance. The objects of study were 78 winter wheat varieties from interstation variety testing, representing various breeding institutions in Russia and some foreign varieties. The study material was presented by the North Caucasian populations of pathogens of such wheat leaf diseases as powdery mildew, brown and yellow rust, and leaf spot (Septoria). Infectious backgrounds were formed according to generally accepted methods, using spore material of pathogens both stored and collected from crops in the previous year (types of rust) and collected from overwintered plants in the spring (powdery mildew, leaf spot). Weather conditions varied across the years of study (mainly in the autumn), but the damage to susceptible test varieties in the experiments was maximum. As a result of the study of the varieties on their resistance to one pathogen, there have been identified 23 varieties resistant to powdery mildew, 56 ones to leaf rust, 47 ones to yellow rust, 8 varieties to leaf spot. There has been given a characteristic of varieties according to various degree of resistance or susceptibility to each pathogen. On the resistance to two pathogens, there have been identified 17 varieties resistant to brown and yellow rust, 2 varieties resistant to brown rust and powdery mildew, 2 varieties resistant to yellow rust and powdery mildew, 1 variety resistant to brown rust and leaf spot. Ten varieties have shown resistance to no one pathogen, but they have had moderate resistance or moderate susceptibility to several other pathogens. 20 varieties were resistant to three diseases in various combinations, and 16 of them were resistant to brown, yellow rust, and powdery mildew. One variety ‘MV Nador’ from Hungary showed resistance to all 4 pathogens. All resistant varieties identified in the study can replenish the supply of winter wheat sources to the complex of leaf diseases for breeding purposes or be used in integrated crop protection against leaf diseases.

Network analyses predict major regulators of resistance to early blight disease complex in tomato

BackgroundEarly blight and brown leaf spot are often cited as the most problematic pathogens of tomato in many agricultural regions. Their causal agents are Alternaria spp., a genus of Ascomycota containing numerous necrotrophic pathogens. Breeding programs have yielded quantitatively resistant commercial cultivars, but fungicide application remains necessary to mitigate the yield losses. A major hindrance to resistance breeding is the complexity of the genetic determinants of resistance and susceptibility. In the absence of sufficiently resistant germplasm, we sequenced the transcriptomes of Heinz 1706 tomatoes treated with strongly virulent and weakly virulent isolates of Alternaria spp. 3 h post infection. We expanded existing functional gene annotations in tomato and using network statistics, we analyzed the transcriptional modules associated with defense and susceptibility.ResultsThe induced responses are very distinct. The weakly virulent isolate induced a defense response of calcium-signaling, hormone responses, and transcription factors. These defense-associated processes were found in a single transcriptional module alongside secondary metabolite biosynthesis genes, and other defense responses. Co-expression and gene regulatory networks independently predicted several D clade ethylene response factors to be early regulators of the defense transcriptional module, as well as other transcription factors both known and novel in pathogen defense, including several JA-associated genes. In contrast, the strongly virulent isolate elicited a much weaker response, and a separate transcriptional module bereft of hormone signaling.ConclusionsOur findings have predicted major defense regulators and several targets for downstream functional analyses. Combined with our improved gene functional annotation, they suggest that defense is achieved through induction of Alternaria-specific immune pathways, and susceptibility is mediated by modulating hormone responses. The implication of multiple specific clade D ethylene response factors and upregulation of JA-associated genes suggests that host defense in this pathosystem involves ethylene response factors to modulate jasmonic acid signaling.

‘Sultanina’ leaves increase their trehalose content in response to grapevine brown leaf spot infection by regulating the pentose and glucuronate interchange pathway

Since the first discovery of grapevine brown leaf spot disease in Turpan, Xinjiang, China, in 2007, it has been a common occurrence in grapevine-growing regions. Grapevine brown leaf spot seriously decreases fruit yield and has become one of the most important leaf diseases in the Turpan region. However, thus far, there have been no reports on the evaluation of grapevine germplasm resources for resistance to brown leaf spot disease. In addition, the response mechanism of grapevine leaves to brown leaf spot infection has not been revealed. To better understand the resistance of grapevine germplasm resources to brown leaf spot disease, we first evaluated resistance in grapevine varieties. On this basis, the most susceptible variety ‘Sultanina’ was selected as the experimental material for this study. Transcriptome analysis and carbohydrate content analysis were performed on ‘Sultanina’ leaves with different levels of disease susceptibility. As the severity of the disease increased, the content of fructose gradually decreased, while the content of trehalose gradually increased. Transcriptome data revealed that differentially expressed genes were enriched in the pentose and glucuronate interchange pathway. These results suggest that the sugar trehalose may play an important role in the response of ‘Sultanina’ leaves to brown leaf spot infection. In addition, the pentose and glucuronate interchange pathway may be involved in the response mechanism of brown leaf spot disease. Our work provides new insights into the mechanism of the ‘Sultanina’ leaf response to brown leaf spot infection.

Phenotypic Variability in Resistance to Anthracnose, White, Brown, and Blight Leaf Spot in Cassava Germplasm.

Despite fungal diseases affecting the aerial parts of cassava (Manihot esculenta Crantz) and causing significant yield losses, there is a lack of comprehensive studies assessing resistance in the species' germplasm. This study aimed to evaluate the phenotypic diversity for resistance to anthracnose disease (CAD), blight leaf spot (BliLS), brown leaf spot (BLS), and white leaf spot (WLS) in cassava germplasm and to identify genotypes suitable for breeding purposes. A total of 837 genotypes were evaluated under field conditions across two production cycles (2021 and 2022). Artificial inoculations were carried out in the field, and data on yield and disease severity were collected using a standardized rating scale. The top 25 cassava genotypes were selected based on a selection index for disease resistance and agronomic traits. High environmental variability resulted in low heritabilities (h2) for CAD, WLS, and BLS (h2 = 0.42, 0.34, 0.29, respectively) and moderate heritability for BliLS (h2 = 0.51). While the range of data for disease resistance was narrow, it was considerably wider for yield traits. Cluster analysis revealed that increased yield traits and disease severity were associated with higher scores of the first and second discriminant functions, respectively. Thus, most clusters comprised genotypes with hybrid characteristics for both traits. Overall, there was a strong correlation among aerial diseases, particularly between BLS and BliLS (r = 0.96), while the correlation between CAD and other diseases ranged from r = 0.53 to 0.58. Yield traits showed no significant correlations with disease resistance. Although the mean selection differential for disease resistance was modest (between -2.31% and -3.61%), selection based on yield traits showed promising results, particularly for fresh root yield (82%), dry root yield (39%), shoot yield (49%), and plant vigor (26%). This study contributes to enhancing genetic gains for resistance to major aerial part diseases and improving yield traits in cassava breeding programs.

First Report of Alternaria alternata Causing Leaf Spot on Coffea arabica in China.

Yunnan Province is the major region for coffee (Coffea arabica) cultivation in China, contributing to over 98% of the national yield and total production value (Ma et al. 2022). In May 2023, brown spot symptoms were observed only on the leaves of coffee plants in a field located in Baoshan City (98°52'37.988400"E, 24°58'17.673600"N), Yunnan Province. Notably, brown and irregularly shaped spots initially started on the leaf bases. The spots enlarged and developed concentric rings with dark brown margins, which are often surrounded by yellow halos. Finally, the necrotic spots spread across the entire leaf and caused the leaf to curl and fall off. The incidence of the disease was approximately 3% of the coffee plants (n = 600). The symptomatic leaves collected from 10 plants were sectioned (5 × 5 mm), subjected to surface sterilization with 70% ethanol for 40 s, rinsed with sterile distilled water, air-dried, and transferred to potato dextrose agar (PDA). Fungi with grayish-white, cotton-like aerial mycelia grew after 7 days at 28°C. The older mycelia of these isolates displayed dark gray pigmentation. Single conidia were cultivated on PDA, and 15 morphologically similar monosporic isolates were ultimately obtained. Microscopic observation revealed that these isolates produced branched, septate, transparent and amber mycelium. Brown, elliptical or pear-shaped conidia with 2 to 4 transversal septa and 0 to 3 longitudinal septa, measuring 9.6 to 33.3 long × 6.0 to 15.0 μm wide (n = 30), were observed on potato carrot agar (PCA). Molecular identification of multiple genes, such as ITS (Schoch et al. 2012), RPB2 (O'Donnell et al. 2010) and GAPDH (Berbee et al. 1999), indicated consistent 100% identity among these isolates. Sequences of the representative isolates CFSY1-CFSY5 were deposited in GenBank (acc. nos.: OR351112, PP188577, PP188578, PP294863, PP294864, OR509742, PP215341-PP215344, OR509740 and PP239378-PP239381), revealing 98.35% - 100% homology with distinct Alternaria alternata strains previously deposited in GenBank (acc. nos.: PP110780, MN649031 and OR485338). The multigene phylogenetic analysis positioned isolates CFSY1-CFSY5 within a distinct cluster, alongside diverse A. alternata isolates. Based on morphological and molecular characterizations, the pathogen was identified as A. alternata. To verify its pathogenicity, a conidial suspension (1×106 conidia/mL) of isolate CFSY1 was sprayed on six leaves of three healthy one-year-old C. arabica seedlings. Subsequently, the inoculated seedlings were covered with plastic bags and placed in a growth chamber under controlled conditions (a 14 h daylight period and a 10 h dark period at 28°C). The experiment was repeated three times. After 20 days, typical brown spot symptoms analogous to those originally observed in the field appeared on the leaves in all inoculated plants. Reisolation, morphology identification and DNA sequencing substantiated Koch's postulates. In contrast, control plants treated with sterilized water remained asymptomatic, and no pathogen was reisolated from them. Significantly, A. alternata has been previously reported as the causal agent for leaf spot disease in a diverse variety of woody plant species in China, including Prunus avium (Ahmad et al. 2020), Magnolia grandiflora (Liu et al. 2019) and citrus (Wang et al. 2010). This study represents the first report of brown leaf spot caused by A. alternata specifically on C. arabica in China, enriching the contents of fungal pathogens under Chinese coffee cultivation conditions.

First Report of Leaf Spot of Pineapple (Ananas comosus (L.) Merr Caused by Neoscytalidium dimidiatum in Malaysia.

In June 2017, severe leaf spots symptoms were observed by growers on pineapple leaves of Josapine variety in in Alor Pongsu (5°01'60.00" N, 100°34' 59.99" E), Perak,northwest of Peninsular Malaysia. The early infection stage shows that several brown spots could be observed, which then would merge to form large brown to creamy white lesions that cover all the leaf surface. This infection finally caused the plant to die after a while. Disease observations conducted from 2018 - 2023 showed that 10-15% incidences of the disease were observed in several pineapple farms located in Johor, Kedah, and Sarawak. The aim of this study to confirm the causal pathogen of the disease by performing isolation, pathogenicity testing, and identification of the primary causal pathogen from 20 samples of infected leaves collected from Alor Pongsu. The leaf tissues between infected and healthy were cut into small pieces (0.5 cm 0.5 cm), and surface sterilized with 1% sodium hypochlorite for 30 seconds, followed by 70% ethanol for 30 seconds, and rinsed thrice with sterilized water before placing on Potato Dextrose Agar (PDA). The PDA plates were incubated at room temperature (28 ± 2℃) in natural light. After five days of incubation, the potential causal pathogen was purified using a single conidial isolation technique for morphological and molecular characterizations. All 32 isolates displayed similar phenotypes. Based on morphological observation on PDA, the colonies were initially white of aerial mycelia but gradually darkened as the culture aged. Microscopic features of the 14-day-old fungal culture showed that the mycelia were branched with 0- 1 septa, pigmented, and brown. Arthroconidia were ellipsoid to ovoid or round shaped, hyaline, with rounded apex, truncate base, and occurring singly or in chains averaging 9 ± 3 × 5 ± 2 μm (n = 20). Based on the morphological characteristics, the fungal isolates were tentatively identified as Neoscytalidium species. A representative isolate of Neoscytalidium coded as UiTMPMD2 was further identified through PCR implication of the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers and BLAST homology search as Neoscytalidium dimidiatum (Penz.) Crous & Slippers based on 100% similarity (575 bp out of 575 bp) to a reference sequence (accession no. KU204558.1). The sequence was deposited in Gen Bank (accession no. OR366479) with reference sequence code of INBio:30A. Pathogenicity tests were performed on 10 whole plants of Josapine pineapple (4 months old) using a leaf inoculating method (Wu et al. 2022) in a glasshouse (25-32°C) and repeated twice. Four mature leaves per each plant were wounded at two points and inoculated with mycelium PDA plugs from 7-days-old cultures of N. dimidiatum. Control plants were wounded in the same manner but inoculated with sterilized PDA plugs. Seven days post inoculation, leaf spot symptoms were observed on treated plants with the pathogen, while the control plants remained symptomless. Pathogen was successfully reisolated from brown leaf spot symptoms in which the cultural and morphological characteristics were identical to those of the originals. Neoscytalidium dimidiatum has a wide range of hosts and it has been reported in Malaysia to cause stem canker on pitahaya (Mohd et al. 2003; Khoo et al. 2023 ) and fruit rot of guava (Ismail et al. 2021). To the best of our knowledge this is the first report of N. dimidiatum causing leaf spots on pineapples in Malaysia. This report establishes a foundation for further study ofN. dimidiatum that can effectively address the disease in pineapple.

Evaluation of the control efficacy of antagonistic bacteria from V-Ti magnetite mine tailings on kiwifruit brown spots in pot and field experiments.

Seemingly barren heavy-metal-polluted vanadium (V) and titanium (Ti) magnetite mine tailings contain various functional microbes, yet it is unclear whether this includes microbial resources relevant to the biological control of plant diseases. Kiwifruit brown leaf spot disease, caused by Corynespora cassiicola, can seriously reduce kiwifruit yield. To discover effective control measures for kiwifruit leaf spot, 18 bacteria strains among 136 tailing-isolated bacteria from V-Ti magnetite mine tailings were identified as inhibiting C. cassiicola by the confrontation plate method, indicating that antagonistic bacteria surviving in the V-Ti magnetite mine tailings were present at a low level. The 18 antagonistic strains could be divided into two BOX-A1R clusters. The 13 representative strains that were selected for phylogenetic tree construction based on their 16S rRNA sequences belonged to the Bacillus genus. Five predominant strains exhibited different toxin-production times and intensities, with four of them initiating toxin production at 32 h. Among them, Bacillus sp. KT-10 displayed the highest bacteriostatic rate (100%), with a 37.5% growth inhibition rate and an antagonistic band of 3.2 cm against C. cassiicola. Bacillus sp. KT10 also showed a significant inhibitory effect against the expansion speed of kiwifruit brown spots in the pot. The relative control effect was 78.48 and 83.89% at 7 days after the first and last spraying of KT-10 dilution, respectively, confirming a good effect of KT-10 on kiwifruit brown leaf spots in the field. This study demonstrated for the first time that there are some antagonistic bacteria to pathogenic C. cassiicola in V-Ti magnetite mine tailings, and Bacillus sp. KT10 was found to have a good control effect on kiwifruit brown leaf spots in pots and fields, which provided an effective biological control measurement for kiwifruit brown leaf spots.

Cloning and transformation of CStr1 antibiotic gene from Streptomyces roseus for the management of brown leaf spot in rice incited by Helminthosporium oryzae

Rice seeds when treated with Streptomyces sp. showed significant increases in per cent germination, root length, shoot length and seedling vigour. Among the twenty isolates of Streptomyces sp. tested, the isolate CStr 1 was the most effective in promoting plant growth. The Streptomyces sp. isolate Str1 recorded a vigour index of 518.40. In the present investigation, out of the twenty rhizospheric actinomycetes isolates, all isolates were confirmed as Streptomyces at the genus level based on the PCR amplification of the DNA using genus specific primers which yielded an amplicon size of 620 bp. The partial sequence of DNA of seven isolates from rice rhizosphere showed 99-100 per cent similarity to Streptomyces sp in the NCBI database. The isolate Str 1 showed 100 per cent identity to S. roseus respectively in the NCBI database. Western blot analysis of leaf samples from rice plants showed that barley chitinase antiserum was able to recognize a protein with sizes of 42 kDa. The antibiotics identified as 4H-1-Benzopyran-4-one, 2-(3,4-dihydroxyphenyl)-6,8-di-?-D-glucopyranosyl-5,7-dihydroxy- (CAS) with molecular formula C27H30O16.. KEYWORDS :Antibiotic gene, chitinase, Helminthosporium oryzae, Streptomyces roseus, western blotting Rice

Utilization of Antagonistic Bacteria for Managing Potato Brown Leaf Spot Caused by Alternaria tenuissima and Plant-Associated Biochemical Changes During Disease Development

Utilization of Antagonistic Bacteria for Managing Potato Brown Leaf Spot Caused by Alternaria tenuissima and Plant-Associated Biochemical Changes During Disease Development

Cultivating Resilience: Disease Resistance Screening of Buckwheat (Fagopyrum spp.) Genotypes in India's Semi-tropical Belt

Buckwheat (Fagopyrum spp.) is a major pseudo cereal, the comprehensive exploration of buckwheat genotypes in the semi-tropical climatic region of India, reveals significant genetic variability among the genotypes for a range of biometrical features, underlining the potential for genetic improvement in this crop. Notably, traits such as days to maturity, and economic yield demonstrate substantial genetic potential for enhancement through targeted breeding programs, exhibiting relatively high genetic advancement values, indicating their potential for effective improvement through breeding programs. Disease resistance, as assessed by the percentage disease index (PDI) of chlorotic leaf spot and brown leaf spot, also reveals noteworthy scope for improvement, crucial for sustaining buckwheat cultivation in disease-prone regions. A correlation analysis uncovers intricate relationships between agronomic traits and disease parameters, with the observed positive correlation between plant height (PH) and economic yield (EY) suggesting that taller buckwheat plants may have a slight advantage in terms of yield, and the negative correlation between test weight (TW) and disease severity, both for chlorotic leaf spot (PDI CL) and brown leaf spot (PDI BL), underscores the potential for selecting genotypes with higher test weights as a means to enhance disease resistance. Identification of genotypes with low disease susceptibility offers promising avenues for disease-resistant buckwheat cultivation. Understanding the genetic parameters and disease dynamics presented in this study would be proved invaluable in developing resilient buckwheat varieties, ensuring food security, and promoting sustainable agriculture in the region opening doors to effective disease management strategies and improved crop productivity in buckwheat cultivation.

Isolation and Identification of Alternaria alternata from Potato Plants Affected by Leaf Spot Disease in Korea: Selection of Effective Fungicides.

Brown leaf spot disease caused by Alternaria spp. is among the most common diseases of potato crops. Typical brown spot symptoms were observed in commercial potato-cultivation areas of northern Korea from June to August 2020-2021. In total, 68 isolates were collected, and based on sequence analysis of the internal transcribed spacer (ITS) region, the collected isolates were identified as Alternaria spp. (80.9%). Phylogenetic analysis revealed that a majority of these isolates clustered within a clade that included A. alternata. Additionally, the ITS region and rpb2 yielded the most informative sequences for the identification of A. alternata. Pathogenicity tests confirmed that the collected pathogens elicited symptoms identical to those observed in the field. In pathogenicity tests performed on seven commercial cultivars, the pathogens exhibited strong virulence in both wound and non-wound inoculations. Among the cultivars tested, Arirang-1ho, Arirang-2ho, and Golden Ball were resistant to the pathogens. Furthermore, among the fungicides tested in vitro, mancozeb and difenoconazole were found to be effective for inhibiting mycelial growth. In summary, our findings suggest that A. alternata plays a critical role in leaf disease in potato-growing regions and emphasise the necessity of continuous monitoring and management to protect against this disease in Korea.

Impact of different chemical fungicides on brown leaf spot of rice caused by Bipolaris oryzae and on yield under field condition

Impact of different chemical fungicides on brown leaf spot of rice caused by Bipolaris oryzae and on yield under field condition

First Report of Epicoccum nigrum Causing Brown Leaf Spot of Sweet Cherry (Prunus avium) in China

Sweet cherry (Prunus avium L.) has become an important economic fruit in China, mainly produced in Shandong Province. In recent years, the planting area of Aba Prefecture in Sichuan Province has increased. In June 2022, sweet cherry brown leaf spot was found in a cherry plantation (100ha) in Wenchuan County (30°54′50.21″N, 103°24′49.10″E), with an incidence of 50 - 70%. The symptoms appeared as brown circular spots on the leaf, gradually expanding until multiple lesions coalesced to form large irregular brown spots; eventually entire leaves were killed. To isolate the causal pathogens, 10 diseased trees were randomly selected from an orchard, one diseased leaf was taken from each tree, and samples (4×4 mm2) were cut from the border between diseased and healthy tissues of 10 diseased leaves, surface sterilized with 75% ethanol for 30 sec, washed three times with sterilized water, dried on sterilized filter paper and placed on potato dextrose agar (PDA). After 5d at 25℃, five morphologically similar colonies were obtained, colony appears yellow fluffy and released a large amount of red-orangepigment. Microscopy revealed circular to ovoid, verrucose, and multicellular conidia measuring 20×25 μm diameter (n = 30) were produced on the mycelia. The morphological characteristics were consistent with the description of Epicoccum nigrum (Lima et al 2011). To further identify the strains, the internal transcribed spacer (ITS), β-tubulin, and RNA polymerase second largest subunit (RPB2) gene regions were amplified with ITS1/ITS4 , Bt2a/Bt2b, and 5f2/7cr (White et al. 1990; Glass and Donaldson 1995; Sung et al. 2007), respectively. BLAST analysis revealed that the ITS, β-tubulin, and RPB2 sequences were 99.2%, 100% and 99.6% homologous, with those of E. nigrum (KU204750.1, OL782123.1, and MW602294.1), respectively. The sequences of the five isolates were identical; and those of representative strain TY3 were deposited in GenBank (ITS, OP410968; β-tubulin, OR502448; RPB2, OP484927). Maximum likelihood phylogenetic analyses were performed for the combined data set with ITS , β-tubulin and RPB2 using MEGA6 under the Tamura–Nei model (Tamura et al. 1993). Isolate TY3 clustered with E. nigrum type strain CBS 505.85. The pathogenicity of TY3 was tested on 10 sweet cherry trees aged 3 years (there were about 50 leaves per plant). Five plants were sprayed with 50 mL of spore suspension (1×105 spores/mL), while the controls (Five plants) were sprayed with 50 mL of sterile water. All plants were in closed plastic bags to maintain high humidity, placed in a greenhouse, and incubated at 25℃with a 12-h photoperiod. Twelve days after inoculation, 35% of the inoculated leaves showed lesions; that were consistent with those observed in the field, and the control group was asymptomatic. To confirm Koch´s postulates, two isolates were taken from the margins of leaf lesions and both were confirmed to be E. nigrum based on morphological observations and molecular identification using ITS β-tubulin, and RPB2 sequences. This is the first report of brown leaf spot caused by E. nigrum on P. avium in China. This discovery needs to be considered in developing and implementing disease management programs in sweet cherry production.

Comparative analysis of paddy leaf diseases sensing with a hybrid convolutional neural network model

The major food in south India is Paddy. Early detection of leaf disease can increase the production of crops. In the agricultural field, farmers can control the spreading of leaf disease with the help of the modeling of automated disease classification. In comparison to the manual approach to paddy leaf infection detection via visual examination, automated identification of rice illnesses using an image of the paddy leaf may be advantageous. Deep learning, a highly well-liked and effective machine learning method, has recently demonstrated considerable promise in the categorization task of images. In this work, Contrast Limited Adaptive Histogram Equalization (CLAHE) pre-processes the augmented images of paddy leaves. The Gray level co-occurrence metrics (GLCM) model then extracts the features from an image of the pre-processed paddy leaves. The five disease classes of paddy leaves were finally identified using the hybrid CNN model as follows: Bacterial Leaf Blight (BLB), Sheath Rot (SR), Narrow Brown Leaf Spot (NBLS), Brown Spot (BS) and Leaf Smut (LS). MATLAB platforms handle implementation works. While compared to the previous approaches, the proposed model reveals the superiority of paddy leaves classification.