Journal of Phytopathology最新文献

Rhizome rot poses a significant threat to ginger cultivation, caused by a complex interaction of pathogens such as Pythium aphanidermatum, Fusarium oxysporum, Ralstonia solanacearum, Sclerotium rolfsii and Meloidogyne incognita. The pathogens were individually inoculated at 75, 105 and 135 days after planting (DAP), as well as in various combinations, to evaluate disease severity and symptom development. Results revealed that R. solanacearum exhibited the highest disease severity and fastest symptom development across all stages of inoculation, followed by P. aphanidermatum, F. oxysporum, S. rolfsii and M. incognita. The combined inoculation of pathogens significantly increased disease incidence and rhizome rot compared to individual inoculations, indicating synergistic interactions among the pathogens. Sequential inoculation experiments demonstrated that pre-infection by M. incognita exacerbated disease severity, highlighting the role of nematodes in predisposing plants to secondary infections.

Banana cultivation has great socio-economic importance in the Cariri region (state of Ceará), Brazil. This study aimed to monitor the severity of anthracnose (caused by Colletotrichum musae) in bananas (cv. Prata) collected at three postharvest processing steps (dehanding, first washing and second washing) in packinghouses of four producing companies (A, B, C and D) in the wet (February–May) and dry (September–December) seasons of production in 2019. Averaged across packing companies and processing stages, disease severity was higher in the wet season (42.4%) than in the dry season (19.6%), but disease variability, expressed by the coefficient of variation, was higher in the dry season. In most cases, there were significant (p ≤ 0.05) differences among processing stages within each packinghouse and season, but the stage with the highest disease severity was not consistent. In other words, there was no predictable change in disease severity from dehanding to first and second washing. It was impossible to identify a single pattern in the severity of anthracnose in banana fruits collected from different companies and stages of postharvest processing, and this may be associated with the management adopted in each production area.

Chrysanthemum Fusarium wilt (CFW) is a devastating soil-borne disease affecting the cut chrysanthemum industry globally. In Vietnam, this disease has been occurring silently and is posing a risk of epidemic outbreaks in the southern provinces, especially Lam Dong. Results from a survey in 2023 showed that stunted growth, curved and small stems, dried-rot roots, leaf drooping and green or yellow wilting of plants after transplanting or at their flower bud initiation were common symptoms observed across the main chrysanthemum-growing farms in Lam Dong. The occurrence of CFW was recorded in relation with the host cultivar, irrigation method and fungicide-spraying regime. Among the cultivars grown in Lam Dong, ‘Doa cu’ was the most susceptible to CFW. The use of sprinkler irrigation and infrequent application of fungicides were attributed to increase both disease incidence and severity. Thirty fungal isolates obtained from diseased plants were identified as Fusarium oxysporum and F. falciforme based on morphological features and molecular analysis of ITS and TEF-1α genes. The detection frequency of these two species was almost equal, which shows their balanced role in the occurrence of CFW in Lam Dong. In-planta pathogenicity assays of Fusarium isolates against plantlets grown from cuttings and invitro propagation showed a variation in pathogenicity and a specialisation of isolates for these planting materials. These results suggest that the profiles of population and aggressiveness of Fusarium isolates diverged with the type of planting material, and between the stock and the commercial farms.

Synthetic fungicides are used to control anthracnose caused by Colletotrichum gloeosporioides; however, their frequent application increases the risk of pathogen resistance, environmental damage, and health concerns. It has been reported that caprylic acid (CA) inhibits the in vitro development of C. gloeosporioides; however, its antifungal mechanism and in vivo antifungal potential are still unknown. Therefore, the present work aims to analyse the effect of a CA-enriched sub-fraction (CAES) extracted from Vitex mollis fruit on the fungal microstructure by confocal fluorescence microscopy and morphometric analysis. Moreover, the effect of CAES on anthracnose development and quality parameters in papaya fruit was evaluated. The confocal microscopy images confirmed that CAES damaged the cell wall of conidia, given their decreased width. The increased fluorescence intensity in the CAES and CA-treated mycelium suggested they were attached to the plasma membrane. These treatments produced structural alterations of the vacuoles and septa in mycelium, while in the fungicide thiabendazole (TBZ) treatment, apoptotic bodies appeared. CAES at 1.0 g L⁻¹ had the best effect against anthracnose incidence and severity in papaya fruit, whereas TBZ was only effective on anthracnose severity. None of the applied treatments affected the fruit quality parameters. Therefore, CAES may be develop as an effective option to suppress anthracnose on papaya fruit.

Melon holds significant economic importance for Brazilian agribusiness. It exhibits high polymorphism and genetic variability, yet knowledge regarding its genetic diversity and response to root diseases remains limited. Therefore, this study aimed to assess the genetic diversity and response of melon plant accessions to Monosporascus cannonballus. Two trials were conducted involving 29 melon accessions and a commercial hybrid of the yellow melon plant, Natal RZ. In the first trial, the accessions and the commercial hybrid were grown in the field under a randomised complete block design with three replications. They were evaluated for fruit-related descriptors: number of fruits per plant (NFP), average fruit weight, shape index, pulp thickness, pulp firmness (PF) and total soluble solids (TSS). Standardised Euclidean distances were calculated on the basis of the results, and the accessions were grouped using the UPGMA method. In the second trial, the melon plant accessions and commercial hybrid were cultivated in a greenhouse under a completely randomised design with 12 replications. For inoculation, wheat grains infested with M. cannonballus isolate CMM-2429 were used. Evaluations were conducted 60 days after transplanting, assessing the incidence and severity of the disease, and biometric variables. The study revealed genetic variability among the evaluated accessions for fruit descriptors and response to M. cannonballus. Most divergent accessions were A16, A53, NZR, A28, A51 and A44, with divergence primarily observed in NFP, PF and TSS. Promising accessions for breeding programmes aimed at resistance to M. cannonballus included A01, A04, A25, A27 (moderately resistant) and A26 (highly resistant to the pathogen).

Neoscytalidium dimidiatum is an asexual, opportunistic and necrotrophic pathogen that causes the devastating stem canker disease of dragon fruit species (Selenicereus spp.). Despite this, information about its intraspecific diversity remains lacking. Examination of the morphological variations of 40 N. dimidiatum isolates hosted by S. megalanthus, S. monacanthus and S. undatus from eight allopatric regions in the Philippines detected three distinct morphotypes. Sequencing of three partial gene markers (ITS, ACT and TUB2) of representative isolates revealed low intraspecific genetic diversity of the pathogen from the three hosts. Phylogenetic analysis of internal transcribed spacer (ITS) sequences of the isolates in this study and worldwide collections of the phytopathogen in the GenBank database infers similar founding populations and the possible specificity of the dragon fruit-infecting N. dimidiatum. Pathogenicity and aggressiveness assay of the isolates on detached stems of dragon fruit did not detect host specificity to S. monacanthus and S. undatus. However, some isolates (i.g., MBDF0802A, MBDF0808B, MBDF0339A and MBDF0007A) significantly had shorter latent period to the stems of S. undatus than S. monacanthus. A higher aggressiveness component of lesion size development on S. undatus stems by isolates from S. monacanthus was recorded suggesting a possible directional selection of highly aggressive N. dimidiatum in this host. This is the first population study on the phenotypic traits and the genetic structure of N. dimidiatum. Valuable inputs for further study of the pathogen are provided, which may help inform the design of management options for stem canker disease of dragon fruit.

bZIP transcription factors play a crucial role in regulating various physiological processes in phytopathogens. Ustilaginoidea virens is known to possess 28 bZIP transcription factors; however, their biological functions remain unexplored. In this study, the function of UvbZIP14 in U. virens was investigated. The expression levels of UvbZIP14 were found to be up-regulated after rice inoculation with U. virens. The knockout mutants and complemented strains of UvbZIP14 were generated and characterised. The knockout mutants display increased growth and decreased conidiation. Compared with the wild-type strain, the knockout mutants exhibit reduced sensitivity to NaCl and sorbitol but increased sensitivity to CFW. There was no significant difference in the number of false smut balls in rice between the knockout and wild-type strains. These results findings highlight the significant role of UvbZIP14 in regulating vegetative growth, conidiation and tolerance to abiotic stress in U. virens.

Streptomyces saraceticus strain 31 (SS31) exhibits antagonistic activities against a variety of phytopathogenic bacteria, fungi and nematodes. In our effort to integrate SS31 into an effective pest management programme for controlling plant pathogens, we assessed the toxicities of 74 pesticides commonly employed in agricultural production on SS31 using paper disc assays. Most of the test insecticides, acaricides, nematicides and plant growth regulators showed no antagonistic effects towards SS31. However, all six tested herbicides, glyphosate, paraquat, glufosinate-ammonium, quizalofop-ethyl, pendimthalin and butralin exerted strong inhibitory effects on SS31. Among the 42 tested fungicides, half of them, including acid amides, strobilurins, carbamates, antibiotics and morphine displayed no detrimental effects on SS31. Notably, copper-based fungicides demonstrated high toxicity to SS31. Although chlorothalonil and thiophanate methyl + streptomycin displayed inhibitory effects on SS31, applying these pesticides with SS31 in pot tests resulted in a lower Meloidogyne incognita galling index compared with the mock control under greenhouse conditions. Additionally, applying SS31 with carbofuran or ethoprop effectively controlled M. incognita. These findings can provide strategies to refine application timing and enhance the beneficial effects of SS31.

Persimmon (Diospyros kaki) is an important fruit crop that is widely cultivated in China, and its production is severely affected by anthracnose. Endophytic bacterial communities play an important role in the establishment of plant diseases, although little is known about these endophytes in persimmon plants. Fangshan persimmon is well known for its excellent quality in Zhejiang Province, China. The present study demonstrated that the Colletotrichum complex was the causal agent of anthracnose in persimmon in Zhejiang. High-throughput sequencing revealed that bacterial communities in Fangshan persimmon twigs were dominated by the phyla Proteobacteria, Actinobacteriota, Firmicutes and Bacteroidota. Persimmon twigs infected with Colletotrichum showed obvious shifts in the endophytic bacterial communities, and these shifts in slight infections varied from those in severe infections. For slight infections, the genera Pseudomonas and Burkholderia–Caballeronia–Paraburkholderia were significantly more abundant in slightly symptomatic twigs than in healthy twigs, whereas the genera 1174-901-12, Methylocella and Streptococcus exhibited the opposite trend. In severe infections, the genera Curtobacterium, Pseudomonas and Kineococcus were significantly more abundant in severely symptomatic twigs than in healthy twigs, whereas the genera 1174-901-12, Lactobacillus and Amnibacterium exhibited opposite trends. The genera Pseudomonas and Curtobacterium showed the strongest positive correlation with anthracnose. This is the first report of endophytic bacterial communities associated with persimmon plants and their interaction with anthracnose disease, and these findings are important for developing biocontrol strategies for persimmon anthracnose.