Journal of Phytopathology最新文献

Bacterial soft rots are amongst the most economically important diseases that cause significant yield losses in various crops. A clear identification of the causal agents is required to develop management strategies. In 2022 and 2023, after the widespread occurrence of soft rot disease in sugar beet fields in the Firuzan region, Hamedan Province, Iran, the current study was conducted to identify and characterize the causal agents. A total of 38 bacterial isolates were obtained from sugar beet plants with soft rot symptoms and subjected to biochemical and phenotypical characterization and pathogenicity tests on healthy slices from potato tubers and sugar beet taproots. Twelve isolates from this study along with the type strain Pectobacterium carotovorum ICMP 5702 were selected for subsequent screening by BOX-PCR. Six isolates were chosen for sequencing the 16SrRNA gene and phylogenetic analysis. In BLAST analyses, the pathogenic isolates S2, S9, S22, S11, S23 and 111 showed the highest similarity values (≥99%) with the reference sequences of Raoultella terrigena, Klebsiella michiganensis, Erwinia (Winslowiella) iniecta, Pantoea agglomerans and P. carotovorum, respectively. These isolates induced soft rot and maceration on plant materials from five species (bell pepper fruits, garlic cloves and slices from sugar beet taproot, potato tubers and carrot roots) 72 h after inoculation. In the greenhouse experiment, they caused soft rot symptoms in the taproots of 2-month-old sugar beet plants 3 weeks after inoculation. These soft rot agents had Gram-negative, catalase-positive and oxidase-negative reactions, grew under both aerobic and anaerobic conditions, tolerated and grew at 37°C and 5% NaCl. In general, the results of this research showed that in addition to Pectobacterium, four other genera from the order Enterobacterales including Erwinia, Pantoea, Klebsiella and Raoultella, are amongst the causes of soft rot in sugar beet in Firuzan region of Hamedan.

Anthracnose, caused by species in the Colletotrichum orbiculare complex, is a major foliar disease in open-field cucumber farming worldwide. This study aimed to develop and validate a standard area diagram (SAD) set to estimate the severity of anthracnose on cucumber leaves. For this purpose, a SAD set with nine levels of severity (1; 3; 5; 10; 20; 30; 40; 50 and 60%) is proposed. The SAD set was validated by 16 raters with no experience in evaluating plant diseases. Both accuracy and precision improved when the proposed SAD set was employed. The statistical parameters were bias coefficient factor-C_b (no SAD set = 0.891, with SAD set = 0.982); correlation coefficient-r (no SAD set = 0.851, with SAD set = 0.941); and Lin's concordance correlation coefficient-ρ_c (no SAD set = 0.755, with SAD set = 0.924). In addition, estimates were more reliable: intra-class correlation coefficient-ρ (no SAD set = 0.646, with SAD set = 0.887). The SAD set proposed here is a useful tool for improving visual assessments of anthracnose severity on cucumber leaves.

Sweet cherry (Prunus avium L.) is commonly affected by fruit rot, leading to reduction in yield and economic loss. In 2022, 144 symptomatic cherry fruit were randomly collected from 11 orchards in Yantai city. A total of 107 fungal strains were isolated and classified into eight species based on morphological and multi-locus phylogenetic analysis, including Alternaria alternata/tenuissima species complex (79.44%), Fusarium lateritium species complex (FLSC) (9.34%), F. verticillioides (2.80%), F. incarnatum (2.80%), F. proliferatum (1.87%), Diaporthe eres (1.87%), Botryosphaeria dothidea (0.94%), and Nothophoma quercina (0.94%), wherein A. alternata/tenuissima species complex was the most dominant genus. All fungal isolates showed aggressiveness on both wounded and unwounded cherry fruit, wherein D. eres exhibited the strongest virulence, and F. verticillioides had the lowest pathogenicity. This work systematically studied the fungal pathogens related to cherry fruit rot and first reported D. eres, B. dothidea, F. verticillioides, F. incarnatum, and N. quercina as the causal agents associated with cherry fruit rot in China. The results of this study will be helpful to get a better understanding about the causal agents of cherry fruit rot in China and provide a theoretical basis for the field control of this disease.

Fusarium incarnatum-equiseti species complex infects a wide variety of food crops. Six fungal isolates were isolated from rotted roots of Dolichos lablab (hyacinth bean), Trichosanthes dioica (pointed gourd), Momordica dioica (spiny gourd), Capsicum frutescens (chilli) and Pisum sativum (garden pea), and identified as Fusarium spp., belonging to Fusarium incarnatum-equiseti species complex (FIESC), through conidial morphology, sporodochia on carnation leaf agar medium and sequencing of nuclear ITS-rRNA and transcription elongation factor 1α gene. Multilocus phylogenetic analysis demonstrated their inclusion within the Incarnatum clade of FIESC. All of them were self-incompatible and failed to pair with other isolates. Vegetative incompatibility affected their pathogenicity and host specificity. The isolates secreted extracellular cell wall degrading enzymes cellulase (0.033 ± 0.002–0.403 ± 0.020 U.mL⁻¹), polygalacturonase (0.005 ± 0.0001–0.392 ± 0.010 U.mL⁻¹) and pectin-lyase (0.015 ± 0.001–0.407 ± 0.012 U.mL⁻¹) for direct penetration to root tissue. They also secreted toxic metabolites that inhibited germination of Cicer arietium (chickpea) and Pisum sativum (garden pea) seeds. The isolates exhibited complete pathogenicity on their original hosts (death due to root rotting, Disease Severity Index- 100%) but less pathogenicity in other non-host plants (yellowing of lower leaves without sign of root rot, Disease Severity Index- <20%). This study reported the production of plant cell wall degrading enzymes and toxic metabolites by some pathogens belonging to FIESC and three new hosts of the pathogen such as hyacinth bean, spiny gourd and garden pea, from the Indian subcontinent.

Wheat is one of the most significant food security crops in Ethiopia. However, the production and productivity of wheat is far below its potential due to many challenges. Wheat disease epidemics, typified by wheat rusts, are among the most important challenges, causing large-scale production losses that put farmers’ income and food security at risk. We analysed and presented the long-term and comprehensive wheat rust surveillance results to better understand the past rust disease occurrences, ultimately contributing to future wheat production and rust control strategies. A total of 1140 wheat fields have been surveyed from 2009 to 2021 throughout four administrative zones of the North Western Amhara region. We identified spatial and temporal trends in the distribution and status of wheat stem rust (Sr), yellow rust (Yr) and leaf rust (Lr) using a combination of different statistical tools and data-analysis methods. The results of the study indicated that 52.5%, 11.3% and 3.4% of the wheat fields were infected with yellow, stem and leaf rust, respectively. Even so, the distribution and intensity of wheat rust disease vary across locations, elevations and cultivated varieties. The associations between altitude and disease prevalence show a linear correlation. We also identified hotspots of yellow and stem rust, which will be used by the country's wheat rust disease early warning system. In order to reverse low varietal diversification in the farmer's field, it is necessary to work with all stakeholders involved in the wheat production sector in a better synergy.

Biologicals and fungicides were evaluated for the control of grey mould in detached fruit in semi-hydroponic strawberry cultivation. Bacillus subtilis (Serenade, Bio-Baci, Bio-Imune), B. amyloliquefaciens (No-Nema), B. pumilus, B. velezensis (Bombardeiro, BTP 11–19 and BTP 135–19) were compared to the fungicide fluazinam in detached fruit assays. After treatment, fruits were inoculated with 30 μL of a 10⁵ spores mL⁻¹ suspension and incubated in a growth chamber. The relative risk for symptom expression in the treatments in relation to the control was estimated by survival analysis. In the field experiment, Serenade, No-Nema, Bio-Imune, Bombardeiro and BTP 11–19, the fungus Clonostachys rosea, procymidone, boscalid, fluazinam, pyrimethanil and cyprodinil + fludioxonil were tested. Biological products were sprayed every 7 days and fungicides at intervals of 14 days. Disease incidence (field and postharvest) and yield were evaluated. In the detached fruit assay, the fungicide fluazinam, followed by the biological products No-Nema and Bio-Imune, reduced the relative risk for symptom expression. In the field, cyprodinil + fludioxonil was the most efficacious at harvest. However, no differences in yield were observed. In postharvest, all fungicides in addition to C. rosea, No-Nema and Bombardeiro reduced the incidence compared to the control during the main production peak (second), and cyprodinil + fludioxonil mixture was the most effective during the season. However, some biological products can be incorporated into an integrated management to reduce postharvest losses.

A virus discovery investigation using high-throughput sequencing in sugarcane samples from Ethiopia revealed the presence of sugarcane mild mosaic virus (SCMMV, genus Ampelovirus) and sugarcane umbra-like virus (SULV, genus Umbravirus). The genome sequences of two isolates of SCMMV and one SULV were determined. The sequences of the two SCMMV isolates were 13,005 nucleotides in length and showed ~73.5% nucleotide identity along the genome and ~90.2, 96.8, and 90.4% amino acid sequence identity among each other in the RdRp, CP, and HSP70h, respectively. Isolate SCMMV ET2 showed a close relationship to group A isolates from Colombia, the USA, and the Philippines, with amino acid sequence identity of the predicted virus proteins in the range of 94–98.9%. Conversely, SCMMV ET1 shared a closer relationship with group B isolates from Colombia, Ivory Coast, and Argentina, exhibiting a 93–99% amino acid sequence identity. The complete genome sequence of SULV, comprising 3041 nucleotides, exhibited the highest identity with its counterpart from South Africa (MN868593). These findings contribute to expanding our understanding of the viral diversity within the sugarcane crop in Ethiopia.

Soybean is frequently affected by pathogenic fungi, which are usually managed by chemicals. Foliar sprays with biological agents have been introduced as new allies to reduce plant diseases. This study verified foliar sprays of Bacillus subtilis-based product applied for three consecutive cropping seasons associated or not with chemical fungicides to control Asian rust (Phakopsora pachyrhizi) and the effect of B. subtilis-produced metabolites against pathogenic fungi and on soybean growth. Field treatments were as follows: (i) Foliar application of B. subtilis-based product, followed by chemical sprays; (ii) chemical management alone; (iii) B. subtilis-based product alone, and (iv) control treatment with water sprays. In the three years, B. subtilis-based product alone or followed by chemicals reduced at least 75% the Asian rust severity, similar to chemical management. Moreover, soybean grain yield increased when B. subtilis-based product was followed by chemicals. Cell-free filtrates and volatile organic compounds (VOCs) from B. subtilis isolate or from the formulated bioproduct were tested against fungi pathogens Fusarium cf. incarnatum/equiseti and Macrophomina phaseolina. All filtrates and VOCs emission reduced more than 40% the mycelial growth of both fungi. Also, the filtrates stimulated the soybean growth at a rate similar to the bioproduct, indicating the potential of the B. subtilis compounds to control fungi pathogens and promote plant growth. Therefore, the B. subtilis-based product showed a satisfactory protection and yield increment for soybean and B. subtilis-produced metabolites antagonized pathogenic fungi and stimulated the soybean plant growth.

Bean scab caused by Elsinoë phaseoli is a major challenge to common bean cultivation in Kenya. However, knowledge about its epidemiology and management is limited. This study conducted three experiments in Kakamega, Kenya, evaluating scab inoculum sources and control options. The first experiment evaluated three different inoculum sources over two seasons; bean crop residue caused the highest scab incidence in both the 2021 (62.1%) and 2022 (81.1%) seasons. The second experiment assessed the effect of rotation history on scab over three seasons. Scab incidence consistently surpassed 90% within the first 30 days after planting in half-yearly rotated fields across all seasons, while the disease was absent after planting in fields with no recent history of legumes. Fields rotated out of legumes consistently had the highest grain yield, averaging 1.5 t ha⁻¹ over the seasons. Additionally, the rotation land treatment displayed significantly more pods per plant during the 2021 (9.7), 2022a (9.8), and 2022b (12.5) seasons. In the third experiment, the impact of five fungicides and four cropping systems on bean scab was investigated over two seasons. Neither fungicide treatments nor cropping systems had an effect on bean scab incidence even when only severe symptoms were considered. Carbendazim had the highest yield (1.9 t ha⁻¹) outperforming the unsprayed control only in the 2022 season while none of the other fungicides outperformed the control treatment in yield parameters in either season. This study emphasizes the challenge of managing bean scab without proper crop rotation and underscores the role of crop residue as a critical inoculum source.

Root-knot nematodes, particularly, Meloidogyne incognita, are among the most destructive endoparasitic nematodes, infecting a diverse range of plant hosts. Nematode-trapping fungi are known for their potential application as biological control agents against plant parasitic nematodes. In the present study, the nematode-trapping fungus Arthrobotrys thaumasia was isolated from the rhizosphere soil of tomato plants in the West Mediterranean Region of Türkiye. Two hundred and twenty-three tomato plant rhizosphere soil samples yielded six nematode-trapping fungal isolates, giving an occurrence frequency of 2.69%. Using morphology and molecular marker sequences (ITS and β-tubulin loci), the species of the fungi was confirmed to be A. thaumasia. In vitro, A. thaumasia reduced second-stage juveniles of M. incognita by 77.5% (isolate I-Y4-2) and 72.5% (isolate B-G5-1). This is the first report on the isolation and characterization of the nematode-trapping fungus A. thaumasia from Türkiye. Two isolates of A. thaumasia (I-Y4-2 and B-G5-1) appear to be promising biological control agents that may be utilized for controlling M. incognita-caused root-knot diseases.