Journal of Phytopathology最新文献

Black Sigatoka disease is a significant threat to banana (Musa spp.) fruit yield and quality. For the control of the fungal pathogen, Pseudocercospora fijiensis, producers currently rely on fungicides such as Quinone outside Inhibitor (QoI). In this study, we examined the resistance status of P. fijiensis to QoI fungicides using 80 isolates from 24 localities in the main banana-producing areas of Mexico (Colima, Michoacán, Tabasco and Chiapas). Resistance was evaluated using the RFLP-PCR mutation assay on Cytochrome b gen (Cytb). The results showed the G143A mutation in three isolates from Chiapas, indicating a relatively low mutation frequency in the sampled areas, where additionally, a microplate bioassay confirmed the resistance to fungicides. We also evaluated the genetic structure and differentiation among the sampled populations, detecting differences between populations within each region and among all populations. Furthermore, our analysis revealed shared haplotypes between resistant populations in Chiapas and nonresistant populations in Michoacán. These findings provide valuable insight into the resistance status of P. fijiensis to QoI fungicides in Mexico and serve as foundation for the development of strategies to manage strobilurin resistance in the country. Overall, this study highlights the importance of monitoring and implementing effective management practices to mitigate the spread of resistant strains.

Agriculture confronts multifaceted challenges across the spectrum of crop production, with pest and disease management being a prominent concern. Timely diagnosis of crop diseases is imperative for mitigating production costs and curbing the adverse environmental impacts of chemical pesticides. In the present investigation, mobile phone-based foldscope microscopy (MBFM) was used to diagnose various field samples infected with fungal diseases of field and horticultural crops, and the same was validated with the normal microscope pictures and field symptoms. The MBFM was also used to diagnose seed-borne microflora associated with wheat and spores of commercial formulation of bioagents and validated. The MBFM utilises both symptoms and morphological structures of pathogen for in situ field diagnosis and hence advantages over the symptom-based mobile Apps. This study underscores the utility of foldscope microscope as a potent technique for plant pathologists and extension workers to enable real-time and in situ identification of diseases caused by fungal pathogens in various agricultural crops.

For millions of people worldwide, rice is one of the main food crops. Nevertheless, while being grown, rice is susceptible to many diseases. Most rice plant diseases are influenced by biotic and abiotic factors, including nematodes, viroids, fungus, viruses, bacteria, and other microorganisms, as well as temperature and other environmental factors. Thus, an automatic early classification of leaf disease is necessary to improve the rice yield. In this paper, for identifying and categorizing the rice leaf disease, a convolutional neural network (CNN) model is used, and the CNN is trained using the Remora Optimization Algorithm (ROA). A better classification outcome is attained by performing the segmentation process using K-means with the Fractional Tangential-Spherical Kernel (FTSK) algorithm. Furthermore, the developed Remora Optimization- Convolutional Neural Network (Remora-CNN) method achieved the optimal performance based on the testing accuracy, sensitivity and specificity of 0.925, 0.931, and 0.941 using the Rice Leaf Disease Image Samples Dataset.

The leaf rust (Puccinia triticina f. sp. tritici), stripe rust (Puccinia striiformis f. sp. tritici), and stem rust (Puccinia graminis f. sp. tritici) are major fungal constraints affecting wheat production worldwide. Identifying and deploying wheat varieties with diverse resistance are the best ways to manage all the rusts. Therefore, a continuous search goes on to identify diverse germplasm with effective rust resistance that expresses at different stages of plant growth (seedling and adult plant). A set of 22 rust resistant wheat genotypes and 4 checks (controls), viz., Avocet-Yr10, Avocet -Yr15, Agra Local, and respective positive checks were studied for characterising rust resistance genes using host–pathogen interactions complemented by molecular markers. Among 22 elite genotypes, 05 genotypes amplified 191 bp fragment with marker PSY1E1, confirmed the presence of gene Lr19/Sr25. These genotypes also expressed resistance to most virulent leaf rust pathotypes, 77-5 and 77-9 in host–pathogen interaction test (HPI). Seven genotypes showed the presence of Lr34/Yr18/Sr57/Pm38/Ltn1 in homozygous state, whereas G4 showed its presence in heterozygous condition. Among 22 genotypes, 16 genotypes possessed Yr10. Five genotypes (22.7%) exhibited two gene combinations, Lr19/Sr25, and Yr10 as revealed through the detection of 191 bp fragment with marker PSY1E1 and 260 bp fragment with co-dominantly inherited microsatellite marker Xpsp3000, respectively. All five genotypes (G2, G3, G8, G9, and G18) also expressed brown glumes controlled by the gene Rg1 tightly linked to Yr10 on the 1BS chromosome. Broad spectrum rust resistance present in these lines in good agronomic backgrounds could be used as potent genetic donors for diverse and durable rust resistance breeding programmes in wheat.

Ficus tikoua can be used as resources for fruit and herbal medicine inspiring large-scale planting in China. Nodular galls were found on the roots of the planted F. tikoua individuals in 2022. The mature females and egg masses of nematodes were extracted from the nodular galls, and microscopic examination suggested Meloidogyne infection. Molecular identification based on ITS, 18S rRNA sequences assigned the infecting species to Meloidogyne incognita, which was further demonstrated by the successful application of specific SCAR marker M. incognita in all samples. The pathogenicity of M. incognita was conducted on F. tikoua cutting seedlings based on Koch's postulates. This is the first report of M. incognita infection in F. tikoua in China.

During a survey conducted in the 2021, 2022 and 2023 seasons, sunflower heads showing symptoms of dry rot were collected from 80 fields in the semi-arid Pampa region of Argentina. A total of 72% of the fields examined in 2021, 71% in 2022 and 63% in 2023 showed the presence of the disease. The highest incidence was recorded as 70% in 2021. Phomopsis head rot began as dry, brown spots on the back of the head, progressing to necrosis and twisting of adjacent leaves. Infected head tissue samples were surface sterilised, cultured on potato dextrose agar (PDA) and incubated at 25°C for 14 days. Diaporthe helianthi was identified based on cultural and morphological characteristics as well as molecular data. A phylogenetic analysis was performed. Internal transcribed spacer (ITS), translation elongation factor 1-α (ef1-α) and β-tubulin sequences were deposited in GenBank, showing the identity with the ex-type D. helianthi strain CBS 592.81. Pathogenicity experiments confirmed the presence of similar disease symptoms in inoculated sunflower heads, and D. helianthi was consistently reisolated from these organs. Our Koch's postulates testing results on heads constitute the first confirmed report that D. helianthi is the cause of Phomopsis head rot on sunflower in Argentina.

The occurrence of black pepper virus F (BPVF) was identified for the first time from India, and its complete genome sequence was determined using overlapping fragments obtained through reverse transcription polymerase chain reaction (RT-PCR). The RNA 1 and RNA 2 of the Indian isolate of BPVF (BPVF-IND) contained 6376 and 3340 nucleotides potentially coding for proteins of 230.7 kDa and 114 kDa respectively. Comparison of the RNA 1 sequence of BPVF-IND with that of BPVF from Brazil (BPVF- BR-PA) and China (BPVF- ZYP-1) revealed an identity of 95% and 90%, respectively, while RNA 2 showed an identity of 96% and 90%. The phylogenetic analysis of the Pro-Pol region of RNA 1 and coat protein region of RNA 2 revealed close clustering of all three BPVF isolates well separated from other species of the genus, Fabavirus. Diagnostics assays based on the RT-PCR and RT-recombinase polymerase amplification (RT-RPA) were developed for the sensitive detection of the virus that will help in the identification and propagation of virus-free black pepper plants.

Potato (Solanum tuberosum L.) is of great economic importance for Mauritius. During a disease survey carried out in a field in one of the major potato-growing regions of Mauritius, corky cracked lesions with halo and mycelial growth were observed on the skin surfaces of around 45% of tubers. The suspected fungus from the affected areas was isolated on amended potato dextrose agar and after 7 days, several fast-growing, pale brown Rhizoctonia-like colonies with a few sclerotia were observed. Additionally, microscopic analysis revealed some cells being multinucleate, forming hyphal branching at right angles with slight constriction together with septum near the branch base. Pathogenicity tests confirmed development of the same symptoms on potato tubers and the causal agent was reisolated successfully. Sequence analysis of the ITS region of representative isolate P114 amplified using ITS1F/ITS4 primers showed that it was identical to several isolates of multinucleate Rhizoctonia solani AG-4 HGI, and neighbour-joining phylogenetic analyses confirmed the identification. To our knowledge, this is the first report of R. solani AG-4 HGI-infecting potato tubers and causing corky cracks in Mauritius.

Cowpea (Vigna unguiculata), known for its high nutritional value, is one of the most important edible beans worldwide. In September 2023, a root rot disease was found in a greenhouse in Nanchang, Jiangxi Province, with symptoms of plant wilting. The isolates from the diseased samples were identified as Fusarium concentricum, F. fujikuroi and F. incarnatum based on morphological characteristics and phylogenetic analysis of four loci including the internal transcribed spacer region (rDNA-ITS), translation elongation factor 1-alpha (TEF1), beta-tubulin (TUB2) and calmodulin (CAM). The pathogenicity of the representative isolates was confirmed on asymptomatic cowpea seedlings. Although other Fusarium species, particularly F. oxysporum, have been previously reported as pathogens of cowpea, this study is the first to document F. concentricum, F. fujikuroi, and F. incarnatum as causative agents of cowpea root rot in China.

Fusarium basal rot (FBR), caused by Fusarium spp., is a significant threat to garlic production globally, including in Türkiye, where the unique Taşköprü garlic is highly valued. This study investigated the diversity and aggressiveness of 77 Fusarium isolates obtained from disease surveys of FBR in Taşköprü garlic and evaluated the yield and resistance of 20 garlic accessions, including 18 local landraces, the locally developed ‘Taşköprü 56’, and the commercial Chinese variety ‘ASCG’. Molecular identification using translation elongation factor 1-α (TEF1) and second largest RNA polymerase II B-subunit (RPB2) genes revealed F. oxysporum (67.5%) as the dominant species, followed by F. proliferatum (15.6%), F. solani (9.1%), F. redolens (5.2%) and F. clavum (2.6%), respectively. All isolates were pathogenic, but aggressiveness varied, with F. solani being the most aggressive, followed by F. redolens and F. oxysporum. While ‘ASCG’ exhibited the highest yield (3.15 ton/ha), it was highly susceptible to FBR (DSI = 97.50%). Conversely, the landrace ASTK2 displayed the highest resistance (DSI = 53.13%), but lower yield. Promisingly, several Taşköprü landraces, such as ASTK6 and ASTK13, demonstrated both moderate resistance and promising yield potential. Surprisingly, ‘Taşköprü 56’, despite being a locally developed variety, exhibited high susceptibility to FBR (DSI = 93.75%) and did not outperform many landraces in terms of yield. This study provides the first reports of F. redolens and F. clavum infecting garlic in Türkiye, and the first molecular characterisation of F. solani as a garlic pathogen in the country, highlighting the potential of local landraces for breeding FBR-resistant, high-yielding cultivars.