European Journal of Plant Pathology最新文献

Pyricularia oryzae is the causative agent of rice blast disease that affects rice yield. The use of chemical fungicides in disease management has generated concern for the environment. In this work, we have developed four agaronanofungicides; chitosan-hexaconazole (CHEN), chitosan-dazomet (CDEN), chitosan-hexaconazole-dazomet (CHDEN), and chitosan agronanofungicide (CEN), and evaluated their antifungal efficacy against P. oryzae. The antifungal effect of the agronanofungicides was studied (in-vitro and in-vivo) by the poisoned media technique, and glasshouse trials. The agronanofungicides significantly inhibited the growth of P. oryzae suppressing the mycelial and conidial growth. The ultrastructural investigations have shown mycelial breakage and damage of the cell membrane in chitosan-based agronanofungicide-treated cells. The results for the efficacy under glasshouse conditions showed that CHDEN was the most promising agronanofungicide in managing rice blast with disease severity index (19.80%), lesion length (1.63 cm), AUDPC (390.60 unit²), disease reduction (80.20%), and a protection index of 82.26%. The least effective fungicide was commercial ANV with a disease severity index of 45.60%, lesion length (3.83 cm), AUDPC (1205.75 unit²), disease reduction (54.40%), and a protection index (45.24%). The treatments of agronanofungicides have increased the yield significantly with CHDEN having 239.00 and the control 113.67 grains per panicle. Based on the harvest index, the CHDEN agronanofungicide treatment had a higher value (0.56) which is significantly different (p ≤ 0.05) while the control had 0.47. This work reveals the strong antifungal effect of CHDEN against P. oryzae and its role in increasing the rice yield.

Anthracnose of mango is one of the major postharvest diseases of mango fruit caused by members of the Colletotrichum gloeosporioides species complex such as Colletotrichum siamense. Crude extracts from dry trunk bark of four Cinnamomum species (C. burmanni, C. iners, C. loureiroi, and C. verum), a commercial cinnamon powder, cinnamaldehyde, eugenol, and cinnamon oil were assayed for their antifungal activity against Colletotrichum siamense. The crude extract of C. verum at 500 mg L⁻¹ showed the highest inhibition of mycelial growth. At a concentration above 10 g L⁻¹ cinnamaldehyde, eugenol, and cinnamon oil showed 100% mycelial inhibition. Using the microdilution assay, C. burmanni and C. verum crude extracts were effective against Colletotrichum siamense spore germination and showed a minimum inhibitory concentration (MIC) value of 625 mg L⁻¹ while the MIC value of cinnamaldehyde was 50 mg L⁻¹. The direct bioautography of the C. verum extract and the fractions obtained by column chromatography over silica gel against Cladosporium herbarum revealed clear inhibition zones on TLC plates. The treatment of Colletotrichum siamense spores with this active fraction led to severe membrane damage which was observed by scanning electron microscopy. Comparative HPLC analyses of the Cinnamomum extracts and the active fraction of C. verum, cinnamon power, and the cinnamaldehyde and eugenol as standards indicated cinnamaldehyde as the major compound. The C. verum fraction reduced disease severity and disease incidence on inoculated mango fruit. Moreover, uninoculated mango dipped into C. burmanni and C. verum extracts reduced the naturally occurring disease while total soluble solid, titratable acidity, and weight loss of dipped mango were insignificantly different from the untreated fruit control.

Sclerotinia sclerotiorum stands out as the most destructive pathogen affecting oilseed Brassica crops. Our study unveils the proteomic basis of a novel resistance mechanism, termed "Stem-Physical-Strength-Mediated-Resistance (SPSMR)," against S. sclerotiorum in Brassicaceae through a comparative proteomic analysis. Field assessments highlight significant differences in stem-physical strength attributes between the resistant (R) and susceptible (S) genotypes, emphasizing the importance of SPSMR. Field evaluation revealed that the resistant genotype S. alba SA1 demonstrates significantly (P ≤ 0.01) superior stem traits at various time points post-inoculation as compared to susceptible genotypes. Pearson's correlation analysis establishes significant associations between lesion length and stem attributes, with stem breaking strength emerging as a key contributor to resistance. Proteomic profiling at different infection stages reveals temporal dynamics, showcasing the resistant genotype's robust and adaptive defense response. KEGG enrichment analysis underscores the significance of phenylalanine metabolism and phenylpropanoid biosynthesis pathways. Differentially Expressed Proteins (DEPs) in resistant and susceptible genotypes revealed intricate expression profiles, particularly in lignin biosynthesis. Proteins associated with cell wall fortification, especially in the lignin biosynthetic pathway, exhibit nuanced expression profiles. Specific proteins, including phenylalanine ammonia-lyase, shikimate dehydrogenase, cinnamyl alcohol dehydrogenase 5, and peroxidase, show significantly higher expression in the resistant genotype across infection stages. Additionally, proteins involved in plant-pathogen, intracellular pH regulation, and antioxidant defense exhibit differential expression, contributing to a comprehensive understanding of the complex regulatory network during S. sclerotiorum infection. This research not only enhances our understanding of the molecular mechanisms underlying resistance but also underscores the varied strategies utilized by Brassicaceae to combat pathogenic intrusion, emphasizing the potential for developing resistant cultivars against S. sclerotiorum.

Xanthomonas oryzae pv. oryzae (Xoo) poses a major risk to worldwide rice cultivation due to its ability to cause bacterial blight (BB). Identifying the Xoo race patterns, and using resistant genes specific to a particular race is a promising strategy to develop varieties with durable resistance. In the present research, 300 Xoo isolates were confirmed and purified from 40 rice-producing areas of Bangladesh to determine the existing races/pathotypes of Xoo. The sensitive rice varieties IR24, BRRI dhan49, and Purbachi showed susceptible reactions against the tested isolates. Fourteen monogenic differentials and 18 pyramid lines were challenged against 300 isolates of Xoo. Bacterial blight resistance genes Xa1, Xa2, Xa3, Xa4, xa5, Xa7, xa8, Xa10, Xa11, xa13, Xa14, Xa21, Xa23, and Xa27 were found in each monogenic differential. By analyzing patterns of the reaction of 300 Xoo isolates on monogenic differentials, 13 pathotypes/races were determined. The effectiveness of the host plant R genes Xa4, xa5, Xa7, xa8, Xa10, xa13, Xa14, Xa21, and Xa27 against bacterial blight has been determined by analyzing frequency resistances and the responses of near isogenic and pyramid lines. Races 1, 3, and 6 were dominantly widespread across the country and were regarded as important races since they had the greatest number of isolates (25%, 23.33%, and 9.67% respectively). Race 2 was the most ubiquitous among the pathotypes, whereas Race 3 was the most virulent, having circumvented every evaluated resistance gene. The bacterial-blight resistant R genes Xa21 and Xa27 have shown resistance against eight and ten races out of thirteen different races, respectively (i.e., 54.7 and 44.3% of the isolates tested). In the evaluation of 50 pyramid lines against the 5 most virulent races, the combinations of Xa4, Xa7, xa13, and Xa21 or the combinations of Xa4, xa5, Xa7, xa13, and Xa21 genes were effective. At present, the suitable and effective R genes i.e., xa5, Xa7, xa8, xa13, Xa21, Xa23, and Xa27 could be utilized for the development of a durable BB-resistant variety in Bangladesh.

Lipopeptides (LPs) from B. tequilensis EA-CB0015 have antifungal activity against Fusarium species. Specifically, against F. oxysporum f. sp. cubense (Foc), the cause of Fusarium wilt of banana. Cinnamon (CN) extract is also known for its inhibitory activity against the Fusarium genus. The main goal of this research was to determine whether the effect of LPs and CN extract or their combination against a Foc isolate is related to an impairment of mitochondrial function. Our results show that biomass decreased by 74% (p < 0.0001) and 84% (p < 0.0001) when cultures were treated with 128 ppm LPs and 152.5 ppm CN extract, respectively. In parallel, we found a pronounced impairment of the bioenergetic response. That is, the routine oxygen consumption rate diminished by 55% (p = 0.0148) and 38% (p < 0.0001), respectively. Moreover, the ATP-linked respiratory rate decreased by 63% (p = 0.0461) and 44% (p = 0.0005), while the FCCP-simulated respiratory rate by 63% (p = 0.0255) and 45% (p = 0.0002). Therefore, our data suggest that the altered bioenergetic response observed in cultures of Foc treated with LPs or CN is mainly caused by an impairment of the activity of the respiratory complexes. On the other hand, biomass production was reduced by 80% (p < 0.0001) when cultures were treated with a mixture comprising only 10% LPs and 40% CN extract. Furthermore, ATP-linked and FCCP-stimulated respiratory rates decreased by 62% (p = 0.0024) and 68% (p < 0.0001), respectively under the same conditions. A potentially synergistic antifungal effect of cyclic LPs with a CN extract is suggested.

Graphical Abstract

Blast disease caused by the fungal pathogen Pyricularia oryzae is a serious disease affecting rice. The purpose of this study was to isolate, characterize, and identify chitinase-producing bacteria from the root-adhering soil and from the root surface and interior of two rice varieties, Khao Dawk Mali 105 (KDML105) and glutinous rice (RD6). In addition, their potential for promoting plant growth and inhibiting fungal pathogens was investigated in KDML105 rice seedlings. Among the 188 chitinase-producing bacteria screened, sixteen root-associated isolates showed plant growth-promoting traits and effectively inhibited P. oryzae in vitro. The plant growth-promoting activities included nitrogen fixation, phosphate solubilization, and indole acetic acid production. The effects of root-associated bacteria at 5 × 10⁹ CFU/isolate on the survival of rice plants challenged by spraying the leaves with a suspension of 10⁶ conidia of P. oryzae were investigated in vivo. Among the 16 tested isolates, colonization of KDML105 rice plants by the R-RD6-NP7 and R-RD6-NP19 isolates resulted in 86.67% to 83.33% and 98.33% to 96.67% survival of rice seedlings, respectively, at 7 to 45 days after fungal inoculation (DAI). In the pot–tray experiment, dead rice seedlings were first observed at 10 DAI, and at 30 DAI the survival of the R-RD6-NP7- and R-RD6-NP19-inoculated rice plants reached 97.67% and 99.33%, respectively. Spot inoculation of R-RD6-NP19 (identified as Kosakonia oryziphila) culture was performed on P. oryzae conidia on fresh rice leaves, and no symptoms of disease were observed. K. oryziphila NP19 is a root-associated and plant growth-promoting bacterium capable of colonizing rice plants and inhibiting rice blast fungal pathogens in the economical KDML105 rice variety. Therefore, this strain can be used as a bioinoculant to control rice blast disease in contaminated soils.

Phytophthora diversity was examined in eight forest and ornamental nurseries in the Czech Republic. A leaf baiting isolation technique and, in two nurseries, also Illumina DNA metabarcoding were used to reveal the diversity of Phytophthora in soil and irrigation water and compare the efficacy of both approaches. In total, baiting revealed the occurrence of 12 Phytophthora taxa in 59.4% of soil samples from seven (87.5%) nurseries. Additional baiting of compost was carried out in two nurseries and two Phytophthora species were recovered. Irrigation water was examined in three nurseries by baiting or by direct isolation from partially decomposed floating leaves collected from the water source, and two Phytophthora species were obtained. Illumina sequencing of soil and water samples was done in two and one nurseries, respectively. Phytophthora reads were identified as 45 Phytophthora taxa, 15 of them previously unknown taxa from Clades 6, 7, 8 and 9. Another 11 taxa belonged to known or undescribed species of the oomycete genera Globisporangium, Hyaloperonospora, Nothophytophthora, Peronospora and Plasmopara. Overall, with both techniques 50 Phytophthora taxa were detected with five taxa (P. taxon organica, P. plurivora, P. rosacearum, P. syringae and P. transitoria) being exclusively detected by baiting and 38 only by DNA metabarcoding. Particularly common records in DNA barcoding were P. cinnamomi and P. lateralis which were not isolated by baiting. Only seven species were detected by both techniques. It is recommended to use the combination of both techniques to determine true diversity of Phytophthora in managed or natural ecosystems and reveal the presence of rare or unknown Phytophthora taxa.

Grapevine (Vitis vinifera L.) is one of the most economically important and widely cultivated fruit crops worldwide. In the summers of 2018 and 2019, a new disease of grapevine was observed in vineyards of Bojnurd (North Khorasan province) and Gorgan (Golestan province) in Iran. The affected grapevines displayed cankerous lesions on the stems, sunken spots on the fruit, and irregular, dark-brown spots surrounded by a yellow halo on the leaves. A total of 40 infected samples yielded 45 bacterial isolates, which revealed two distinct groups: 18 isolates with creamy colonies and 27 isolates with yellow colonies. Based on the colony morphology, phenotypic and pathogenicity features, as well as analysis of 16S rRNA and housekeeping genes sequences the isolated strains were identified as Pseudomonas viridiflava and Pantoea agglomerans. To confirm the disease-causing ability of the isolates, grapevine seedlings and detached fruits were inoculated. The isolates reproduced the symptoms and were re-isolated from the inoculated plants, thus proving their pathogenicity. To the best of our knowledge, this is the first report worldwide of the occurrence of leaf and fruit spots and stem lesions of grapevine caused by P. viridiflava and P. agglomerans.

Disease management decision support systems (DSS) are typically prediction algorithms that help farmers assess the risk of an epidemic, to guide whether, and to what extent, fungicide treatment is needed. However, there is frequently little information presented to quantify the value of using the DSS, i.e. the likely increased profit or reduced impact to the environment, and the risks of failing to control the pest. Validation of DSS is often limited to a small number of sites and seasons, as extensive field testing is prohibitively expensive. It would therefore be beneficial to have a method to estimate the value of a DSS using existing data sets gathered for other purposes.

We present a theoretical framework for evaluating the value of DSS, and then describe how this can be applied in practice using four case studies of contrasting DSS under different data constraints. The four case studies include DSS that guide (i) the total dose of pesticide applied; (ii) the number of sprays required; (iii) the timing of the first fungicide application in a spray programme; and (iv) infection risk alerts. We demonstrate how our theoretical framework can be used to evaluate DSS, using existing field and literature data to infer the benefits and risks associated with their use. The limitations of using existing data are explored.

Colletotrichum coccodes is an important pathogen of potatoes. Recently, the closely related C. nigrum has been reported as an important pathogen of solanaceous crops but not as a pathogen of potato. This study confirms C. coccodes as the most prevalent Colletotrichum species infecting foliar and tuber tissue of potatoes in Australia and the USA. In addition, three isolates from the USA, previously identified as C. coccodes, were re-identified as C. nigrum. The gene loci TUB2, ACT, GAPDH, CHS-1 or HIS3 were all suitable for differentiating C. nigrum from C. coccodes. Australian and USA tuber and foliar isolates of C. coccodes and C. nigrum had similar pathogenicity on detached potato leaves. This is the first report of C. nigrum as a pathogen of potato. Moreover, the recently described C. dianense was revealed to be a synonym of C. nigrum.