Journal of Phytopathology最新文献

Foxtail millet (Setaria italica) an economically important crop globally, particularly in China. In 2021, a foxtail millet ear rot disease was first found in Chaoyang City, Liaoning Province, China. Symptomatic tissues were sampled, and the fungal isolate GZWB008 was identified as Curvularia geniculata based on morphological characteristics and ITS, GAPDH and RPB2 gene sequence analyses. Pathogenicity was confirmed by artificial inoculation, which produced symptoms consistent with those observed in the field. Koch's postulates were fulfilled by re-isolation of C. geniculata from inoculated symptomatic ears. This is the first report confirming C. geniculata as a causal agent of ear rot in foxtail millet, expanding knowledge of its host range and highlighting its potential threat to millet production.

Camellia sinensis and C. japonica plant leaves with spots were collected in Zhejiang Province, China. Three representative isolates resembling Nigrospora were selected for identification and pathogenicity test. Based on morphological characteristics and phylogenetic analyses of the partial regions of internal transcribed spacer (ITS), beta-tubulin (TUB2), and translation elongation factor 1-alpha (TEF) sequences, the isolates from C. japonica were identified as Nigrospora. oryzae and N. philosophiae-doctoris, while the one from C. sinensis as N. camelliae-sinensis. Inoculation of the isolates on healthy leaves showed symptoms similar to those observed in the field, and the fungi were reisolated from the lesions. To our knowledge, this represents the first report of leaf spot disease caused by Nigrospora species on C. japonica worldwide. The result further confirms that species residing the genus of Nigrospora act as causal agents of plant leaf spot disease, and their potential impact deserves further investigation.

The Prunus davidiana (Carrière) Franch. is an important tree species in Northwest China. However, fungal perforation caused by Wilsonomyces carpophilus can harm a variety of stone fruits, such as P. davidiana, seriously affecting the protection of germplasm resources and the cultivation of stone fruit in economic forests. In this study, the main pathogenic factors and host resistance strategies were explored by detecting the main cell wall-degrading enzymes, the activities of the resistant enzymes and substances produced by the host when W. carpophilus infects P. davidiana. In the present study, the pathogenicity of W. carpophilus (CFCC 71543) was determined on P. davidiana. The changes of six cell wall-degrading enzymes, including carboxymethyl cellulase (Cx), β-glucosidase, polymethylgalacturonase (PMG), polygalacturonase (PG), polygalacturonate trans-eliminase (PGTE) and pectin methyl trans-eliminase (PMTE), produced by different strains when they invaded the host were determined using 3,5-dinitrosalicylic acid and ultraviolet colorimetry. Additionally, the changes in phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), total phenol (TP), plant flavonoids, tannins and four other resistant substances were determined 2–16 days after inoculation. The results showed that the main cell wall-degrading enzyme of the strain (CFCC 71543) when infecting P. davidiana was PMG, with enzyme activity as high as 1548.456 U/g at 4 dpi, which was 3.988 times that of the control group. The level of five antioxidant enzymes and four resistant substances increased by varying degrees after infection by W. carpophilus. The main resistance enzyme of P. davidiana was POD, and POD activity reached 4184.889 U/g 8 days after inoculation, which was 4.074 times that of the control group. The main resistant substance was MDA, and the MDA content reached a peak of 217.63 nmol/g 8 days after inoculation, which was 2.376 times that in the control group. This is the first study to demonstrate that PMG is key in the infection of P. davidiana by W. carpophilus. The host produces five enzymes to resist infection by pathogenic bacteria, among which POD activity is the highest. Among the four resistant substances, MDA had strong resistance; the content of other resistant substances did not increase exponentially, and the resistance effect was not pronounced. These results provide a theoretical basis for an in-depth understanding of the pathogenic mechanism and are of great significance for the prevention and control of perforations.

Brinjal (Solanum melongena L.), an important solanaceous vegetable valued for its rich nutritional profile and potential health benefits, is widely cultivated in the tropical and subtropical regions of the world. Existing food and nutritional security concerns are exacerbated due to the rise in soil borne pathogens, a direct consequence of global warming, increasing the risk of crop diseases. Among these, Fusarium wilt, caused by multiple species of Fusarium, is very serious due to its severity and persistent nature. Traditional control measures, including cultural, biological and chemical approaches, have proven inadequate, highlighting the need for resistant cultivars. The current study focused on identifying fungal pathogen associated with brinjal wilt, by employing morpho-cultural identification, molecular characterisation by sequencing and DNA barcoding of internal transcribed spacer (ITS) and β-tubulin regions and pathogenicity assays of fungal isolate. Fusarium oxysporum f. sp. melongenae was identified as the pathogen associated with vascular wilt of brinjal. The study evaluated 90 diverse genotypes, including released varieties and local landraces of cultivated brinjal, and related wild Solanum sp. for resistance against Fusarium wilt by screening under field conditions. Confirmatory evaluation of disease reaction was done by screening under artificially inoculated conditions in pots. Percent disease incidence (PDI), area under disease progress curve (AUDPC) and area under disease progress stairs (AUDPS) were used to identify sources of resistance and understand disease progression patterns. Three genotypes namely Swarna Mani, S. sisymbriifolium and S. torvum were identified as highly resistant and seven genotypes namely G-17, Pink, CH-151, Sidhasar Local, Special Muktakeshi, H-183 and Pink Shiny Medium Long were found resistant to the disease under both field and pot conditions. Resistant genotypes exhibited distinct variations in disease progression patterns. The identified highly resistant and resistant genotypes hold significant potential for breeding programs aimed at enhancing crop resilience to the increasing threat posed by Fusarium species.

The root-knot nematode Meloidogyne javanica is a significant pathogen that causes substantial yield losses in tomato plants. Moroccan farmers generally lack knowledge regarding the density of this pathogen, which can trigger visible and localised symptoms. Additionally, regional studies that establish damage thresholds for this issue are scarce. This study investigated the damage threshold of M. javanica on tomato plants using nine initial population densities (Pi) of second-stage juveniles (J2s): 0, 0.5, 1, 2, 4, 8, 16, 32 and 64 J2s (g dry soil)⁻¹. Aboveground growth (plant height and fresh and dry shoot weight) and belowground growth (root length and diameter) were assessed after 90 days. The plant growth parameters were significantly reduced at higher inoculum densities. The Seinhorst model fitting revealed the highest minimum relative yield (m) for shoot fresh weight (m = 0.761 ± 0.012) and the lowest for root diameter (m = 0.509 ± 0.026). The tolerance limit (T) varied, with the highest shoot dry weight (T = 1.657 ± 0.329 J2s (g soil)⁻¹) and lowest root diameter (T = 0.095 ± 0.019 J2s (g soil)⁻¹). The production of eggs by M. javanica increased significantly with increasing initial population density, rising from 211 ± 64 eggs (g roots)⁻¹ at 0.5 J2s (g soil)⁻¹ to 3735 ± 380 eggs (g roots)⁻¹ at 64 J2s (g soil)⁻¹, representing a 17.7-fold increase. Tomato plants exhibited the maximum galling index at lower nematode densities. Symptoms began at densities as low as 0.095 J2 (g soil)⁻¹, with severity increasing with nematode density. Given the severe damage caused at low densities, Moroccan farmers must adopt early detection and effective management strategies.

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a major bacterial disease affecting rice, wheat, triticale and Brassica crops. It was recently confirmed in Senegal with high incidence in rice fields. However, the precise Xoc strains responsible for the recent outbreaks remains unknown, and the sources of resistance to the growing disease pressure have yet to be identified. In this study, we tested the pathogenicity of Xoc strains collected from a 2023 epidemic in Senegal on Senegalese rice varieties and on near isogenic lines (NILs) specifically developed for a sister pathovar, Xanthomonas oryzae pv. oryzae (Xoo). We identified both local varieties and NILs resistant to 80% of the strains. However, neither NILs nor local varieties were resistant to S52-4-4, suggesting a significant mutation in this particular strain that poses a serious threat to rice production in Senegal. Comparative genomic and phylogenetic analysis revealed a close evolutionary relationship between S52-4-4 and pathogenic strains BLS256 and CFBP2286 from the Philippines and Malaysia respectively. Moreover, the detection of an equivalent number of TAL effectors in both S52-4-4 and BLS256 provided further evidence that both strains have a shared common ancestry. These findings, together with the available genomic sequence and characterisation of S52-4-4 in this study are useful for studying Xoc populations in Senegal and other countries. Nonetheless, S52-4-4 adaptation to all local cultivars grown in Senegal requires a prompt management response.

Branch cankers were detected on peach orchards in Puebla, Mexico. Based on morphology, cultural features and molecular analysis, the causal agent was identified as Pallidophorina paarla. Koch's postulates were fulfilled by pathogenicity tests carried out on peach trees. To our knowledge, this is the first report of P. paarla causing branch cankers of peach in Mexico.

The fungus Trichoderma spp., commonly isolated from soil, rhizosphere, and as an endophyte in different plant tissues, displays greater antagonistic potential against different types of pathogens. This study aimed to select isolates of Trichoderma spp. from common bean and soybean fields in Minas Gerais State, Brazil, to evaluate their antagonism against Sclerotinia sclerotiorum. Forty-eight isolates of Trichoderma spp. (30 rhizospheric, 11 epiphytic, four endophytic, and three from crop debris) were used in this study. Based on the sequencing of ITS, TEF1-α, and RPB2 regions, these isolates were classified in eight species of Trichoderma as follows: T. harzianum (29 isolates), T. koningiopsis (five isolates), T. hamatum (four isolates), T. atroviride (four isolates), T. asperelloides (two isolates), T. longibrachiatum (two isolates), T. asperellum (one isolate), and T. neokoningii (one isolate). Eight isolates completely inhibited mycelial growth of S. sclerotiorum in the pairing culture test in vitro. Twenty-four isolates displayed the greatest ability to parasitise sclerotia in soil with efficiency ranging from 79% to 99%. In water-agar medium, 31 isolates inhibited myceliogenic germination of sclerotia from 78% to 100%, while seven isolates inhibited the carpogenic germination of sclerotia by more than 85%. Eight isolates affected the colonisation of detached leaflets of common bean and soybean plants by hyphae of S. sclerotiorum. The isolates UN34 and IM2 of T. harzianum were the most promising. The isolate UN34 reduced fungal survival and both myceliogenic and carpogenic germinations of sclerotia, while the colonisation of leaflets and stems of common bean and soybean plants by S. sclerotiorum was greatly lower by the IM2 isolate. In conclusion, the isolates of Trichoderma spp. obtained in this study displayed great potential for use for the biocontrol of S. sclerotiorum.

Plant diseases have always been a problem because they can significantly decrease both the quality and quantity of crops. Diseases, pests, and weeds present major challenges in crop cultivation, leading to substantial crop damage and posing significant risks to the economy and food security. Plant diseases pose a significant threat to the quality and yield of agricultural products. Prompt and reliable detection and identification of these diseases are crucial for ensuring sustainable agriculture and food security. Preventing ailments and providing guidance to farmers is crucial to enhancing the yield on a large scale. Manual feature extraction is the most expensive approach used in earlier plant disease detection methods. Additionally, many of the real-time applications face issues with cost complexity, misclassification, and overfitting. Hence, an effective model called Xception-Deep Kronecker Network (Xception-DKN) is proposed for severity disease classification utilising hyperspectral leaf image. Initially, the hyperspectral leaf image is pre-processed. Then, the selection of the band phase is performed utilising Fractional Water Wheel Plant Dingo Optimizer (FWWPDO), that is the incorporation of Dingo Optimizer (DOX), Fractional Calculus (FC), and Water Wheel Plant Algorithm (WWPA). Outputs from the selection bands are forwarded into the leaf segmentation phase that is carried out using Black Hole Entropic Fuzzy Clustering (BHEFC). Next, using a majority voting approach, a fusion of bands is performed. Then, fused band output as well as individual leaf segmentation outcome is exposed into the Feature Extraction (FE) stage for extracting the features, including Weber Local Descriptors (WLDs) and Local Binary Patterns (LBPs). Thereafter, disease recognition is executed on leaves by utilising a Deep Conval Neural Network (deep CNN) for normal and abnormal cases. Nevertheless, Deep CNN hyperparameters are fine-tuned utilising FWWPDO, which is developed by integrating the Water Wheel Plant Dingo Optimizer (WWPDO) and Fractional Concept (FC). Thereafter, severity level classification is performed using the proposed Xception-DKN into low, moderate and severe cases. Xception-DKN is the combined form of Xception and Deep Kronecker Network (DKN), where the layers are adjusted by Taylor concepts. The Xception-DKN has achieved the highest accuracy of 92.204%, true positive rate (TPR) of 94.011%, and true negative rate (TNR) of 91.210%.

Wounds are crucial entry points for infection by Ceratocystis spp. Consequently, tool disinfestation is a crucial practice in disease management, especially for host crops such as kiwifruit, teak, mango and cacao, which require cultural practices that cause wounds, such as pruning and thinning. Although conventional sanitisers, such as sodium hypochlorite, are recommended for controlling Ceratocystis wilt, their effectiveness on tools lacks scientific validation. Additionally, there is no consensus on the optimal exposure time and active ingredient concentration for effective disinfestation. Our study confirmed that C. fimbriata can be mechanically spread from diseased to healthy plants via pruning shears. We then evaluated the effectiveness of conventional sanitisers and hot water (80°C) for the disinfestation of pruning shears and scalpels on kiwifruit plants. Firstly, in vitro comparisons revealed that ammonium chloride solution and hot water effectively inhibited the mycelial growth of the fungus. Furthermore, immersing tools in hot water (80°C for 15 s) was the only effective disinfestation method, while sodium hypochlorite and other conventional sanitisers failed to eliminate the pathogen at the dosages and exposure times tested. Based on these findings, a revision of disinfestation protocols for Ceratocystis wilt is recommended, with further studies needed to evaluate different concentrations and exposure times. In conclusion, hot water is an effective alternative to conventional sanitisers in preventing the mechanical spread of the pathogen.