First Report of Brown Leaf Spot of Rice Caused by <i>Bipolaris zeicola</i> in Pakistan

Foliar diseases of maize cause severe economic losses in India and around the world. The increasing severity of maize leaf blight (MLB) over the past ten years necessitates rigorous identification and characterization of MLB-causing pathogens from different maize production zones to ensure the success of resistance breeding programs and the selection of appropriate disease management strategies. Although Bipolaris maydis is the primary pathogen causing MLB in India, other related genera such as Curvularia, Drechslera, and Exserohilum, and a taxonomically distant genus, Alternaria, are known to infect maize in other countries. To investigate the diversity of pathogens associated with MLB in India, 350 symptomatic leaf samples were collected between 2016 and 2018, from 20 MLB hotspots in nine states representing six ecological zones where maize is grown in India. Twenty representative fungal isolates causing MLB symptoms were characterized based on cultural, pathogenic, and molecular variability. Internal Transcribed Spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene sequence-based phylogenies showed that the majority of isolates (13/20) were Bipolaris maydis. There were also two Curvularia papendorfii isolates, and one isolate each of Bipolaris zeicola, Curvularia siddiquii, Curvularia sporobolicola, an unknown Curvularia sp. isolate phylogenetically close to C. graminicola, and an Alternaria sp. isolate. The B. zeicola, the aforesaid four Curvularia species, and the Alternaria sp. are the first reports of these fungi causing MLB in India. Pathogenicity tests on maize plants showed that isolates identified as Curvularia spp. and Alternaria sp. generally caused more severe MLB symptoms than those identified as Bipolaris spp. The diversity of fungi causing MLB, types of lesions, and variation in disease severity by different isolates described in this study provide baseline information for further investigations on MLB disease distribution, diagnosis, and management in India.

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“…B. zeicola is also reported to be a pathogen of rice and maize in China [34] and a pathogen of rice in Pakistan [35].…”

Section: Discussionmentioning

confidence: 99%

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India

et al. 2021

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“…Brown spot (Bipolaris oryzae) is also a fungal disease, and it infects coleoptiles, leaves, leaf sheaths, panicle branches, glumes, and spikelets. Brown spot, caused by Bipolaris zeicola, is a major fatal disease in rice that can cause qualitative and quantitative crop Agriculture 2023, 13, 1264 2 of 17 damage [5][6][7]. Research indicates that bacterial brown spot in rice can reduce rice yields by up to 52% [8].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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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.

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First Report of Vascular Wilt on Peanut in Mexico Caused by Fusarium incarnatum

Romero-Arenas,

Andrade-Hoyos,

Silva-Rojas

et al. 2024

Plant Disease

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During the fall of 2020, wilt symptoms were presented in a commercial peanut field (Arachis hypogaea L.), variety 'CHAMPS' in Buenavista de Benito Juárez, México (18.460501 N, 98.627100 W). A peanut field was scout 80 days after planting, and plants presenting symptoms of root and crown rot, vascular chlorosis, and tissue death, were sampled. Disease incidence was estimated at 55% of the field. Isolations of the pathogen were made from stem and root tissues. These samples were disinfected by immersion in 1% sodium hypochlorite (NaClO) for 3 min and immersion in 70% ethanol for 1 min with 3 rinses with sterile distilled water. Subsequently, 0.5 cm fragments were removed and placed on media of potato dextrose agar (PDA) and Rose Bengal. Petri dishes were incubated in complete darkness at 26 °C for 7 days. Abundant aerial white mycelium was observed, which turned tan to brown and showed a slightly orange color on the back of the plate. Finally, pure cultures were obtained by single sporing (Aslam et al. 2020). Colonies identified as Fusarium spp. (Leslie and Summerell, 2006) were sub cultured on PDA agar media and Spezieller Nährstoffarmer (Pérez-Vázquez et al. 2022) to observe microscopic characteristics of ten isolates. Colonies of a representative strain (MA-PET-03) produced hyaline septate hyphae, macroconidia dorsoventrally curved, tapering towards both ends of 51–57 × 4.6–5.4 μm (n = 80) with most having 7 septa. Microconidia were unicellular, nonseptate, hyaline, and ovoid, 12.4–20.6 × 3.6–4.1 μm (n = 80). Chlamydospores were abundant and globose 5–11 μm diam (n = 80), intercalary, and solitary in short chains (Figure 1). The observed microscopic characteristics correspond to the description of Fusarium incarnatum (Khoa et al. 2006; Leslie and Summerell, 2006; Xia et al. 2019). The molecular analyses were done with genomic DNA extracted as previously reported by Pérez et al. (2022). A region from the translation elongation factor gene was PCR amplified using EF688/EF1251 primers (Alves et al. 2008) and from the calmodulin (CMDA) gene, using CALDF1 and CALDR1 primers (Noel et al. 2022). The corresponding PCR products were purified with the Gen Elute™ PCR Clean-Up Kit from Sigma-Aldrich Co. (St. Louis Mo. USA) and sequenced at Macrogen Inc. (Seoul, South Korea). The phylogenetic analysis was inferred using the Bayesian Inference method with 1 million generations, final standard deviation was 0.008516. The nucleotide substitution model for Calmodulin (CMDA) was GTR + G and for TEF1 GTR + I + G. This analysis showed that strain MA-PET-03 shared 100% identity (Figure 2) with F. incarnatum ex-type strain CBS 132.73 (CMDA: MN170342; TEF1: JMN1704761) from Pointed gourd (Trichosanthes dioica) in Malawi Africa. The sequences of strain MA-PET-03 were deposited in GenBank (CMDA: OQ679820; TEF1: OQ679821). The pathogenicity tests were carried out with a total of 20 peanut plants, variety 'CHAMPS', 18 days after having been sown in groups of five seeds in 250 g plastic pots, containing a sterilized mixture of Peatmoss and Agrellite (1:1 v./v), with four repetitions. The seeds were inoculated by immersion in 20 mL of spore suspension (106 conidia/mL) isolated from F. incarnatum for 10 min. The plants were maintained in a greenhouse (70% relative humidity and 28 °C) until the appearance of disease symptoms of. Likewise, 10 control plants were inoculated with sterile water. The experiment was repeated twice. The symptoms developed 15 days after inoculation, the plants presented symptoms of chlorosis, wilting of leaves, stems, and roots, a manifestation similar to that observed in the field, while the control plants remained healthy. F. incarnatum was consistently reisolated from inoculated stems and roots and identified by the microscopic characteristics described above. Peanut leaf blight and wilt disease caused by F. incarnatum has been reported in India (Thirumalaisamy et al. 2019). This first report emphasizes that this phytopathogen is a new threat for peanut producers in Mexico, which is why our finding suggests the need to seek new strategies for its control.

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First Report of Brown Leaf Spot of Rice Caused by Bipolaris zeicola in Pakistan

Cited by 6 publications

References 8 publications

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India

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

First Report of Vascular Wilt on Peanut in Mexico Caused by Fusarium incarnatum

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