Journal of Plant Pathology最新文献

Soft rot bacteria are important potato pathogens. Most of these bacteria were originally classified under the Erwinia genus, but are now identified as species of genera Pectobacterium and Dickeya. Studies have shown that genetic and phenotypic diversities of these pathogens vary across regions, and exploring such aspects in different potato-producing areas could provide insights into these bacteria’ ecology. In this study, 84 Taiwanese strains of potato-isolated soft rot bacteria were subjected to phylogenetic and phenotypic assays using the latest classification schemes. Preliminary testing with genus-specific primers suggested that all strains belonged to Pectobacterium. Multilocus sequence analysis divided them into four clades, each represented respectively by the type strain of P. brasiliense, P. carotovorum, P. versatile, and P. aroidearum. Among the species identified, P. brasiliense was found to be the most genetically diverse and prevalent. Phenotypic tests on representative strains of these species showed that all tested strains were able to grow at pH 5.5–10.0 and 16–37 °C. The ability to grow at pH 4.0–41 °C varied across strains, but the differences were unable to discriminate among species. Additional physiological assays were conducted, and while most assays did not allow reliable distinction among species, the indole production test was able to differentiate P. brasiliense strains from the other species. Inoculation of potato tubers revealed great intra-specific heterogeneity among maceration potentials of the tested strains. Interestingly, the maceration potentials of different Pectobacterium species responded differently to elevated temperature. The findings from this work contribute to a broader understanding of Pectobacterium strains affecting potatoes in Taiwan.

White rot, a major disease in sunflower cultivation caused by Sclerotinia sclerotiorum is difficult to control, with no completely resistant cultivars currently available. Different studies have shown that the application of benzothiadiazole (BTH) and arbuscular mycorrhizal fungi (AMF) can effectively control this disease. It has also been reported that both induced and genetically inherited resistance, elevated polyphenol oxidase (PPO) and peroxidase enzyme (POX) activities, and resistance-related genes expression. This study aimed to elucidate the biochemical and genetic responses of sunflower plants under white rot infection and different treatments by measuring the ROS-scavenging enzymes PPO and POX activities in healthy or infected sunflower plants, as well as identifying some defense genes. Sunflower cultivars with different levels of resistance to Sclerotinia sclerotiorum were used. Pregerminated seeds were soaked in an aqueous solution of BTH before being sown into trays and placed in a greenhouse. Before sowing, AMF was also applied to the substrate. Twenty-one-day-old plants were then inoculated with Sclerotinia sclerotiorum. Our results demonstrated that BTH and AMF induced some degree of systemic resistance in sunflower against white rot, especially combined. Even though the amount of pathogen detected in plants only varied between cultivars, not changing when inducers were applied, disease severity was reduced, demonstrating that treatments were effective against white rot. In addition, the activation of defense-related genes correlated well with the degree of resistance observed in plants. Therefore, our results provide insights for a better understanding of the mechanisms underlying induced-resistance to sunflower white rot infections.

Apple dimple fruit viroid (ADFVd) causes severe fruit disorder with significant economic losses in several apple cultivars. During 2020–2022, 137 leaf samples of apple trees showing round and depressed green spots, color dappling, scarring, and distortion of fruits, and others without symptoms, were collected in the west (Hamadan, Kermanshah, and Kurdistan provinces) and northwest (Ardabil, East, and West Azerbaijan provinces) of Iran. ADFVd was detected by RT-PCR in 72.3% of the tested samples, including a significant number showing no symptoms. Nine isolates were sequenced and showed minimal differences from each other and 75.9–100% nucleotide identities with ADFVd variants previously reported in GenBank. In phylogenetic analysis, Iranian isolates were placed in the cluster consisting of all ADFVd isolates originating from apples except those from Japan. The Iranian isolates were distinct from those reported in apples in China, Japan, Spain, Türkiye, and in fig in Italy, but were not differentiated from isolates in apples in Italy, showing that they probably have a common origin.

Pea, Pisum sativum L. (2n = 14), is the third most important legume crop worldwide after common bean and chickpea. Pea production is severely affected by rust caused by Uromyces viciae-fabae. Lignification is one of the most important mechanisms playing a very significant role in plant disease resistance. In the present study, a total of 115 pea entries of the Australian germplasm together with four standard controls were observed for the presence of total lignin content (72 h) and its accumulation in relation to the different components of resistance. Out of all the test entries, one resistant entry ‘EC865975’ showed the maximum increase in total lignin content even more than the resistant check. It also exhibited a low AUDPC (the Area under the Disease Progress Curve) value of 292 and showed formation of smaller pustules measuring 0.7 mm in size with reduction in their number. Further, it was found that the total lignin content was highly negatively correlated (r = -0.796) with AUDPC. The higher accumulation of lignin content was found in resistant test entries over susceptible ones. The principal component analysis of the different parameters revealed that the total lignin content and AUDPC were only the parameters mostly contributing to the total phenotypic variation to the extent of 81.92% as they exhibited their Eigenvalue > 1. Further, the regression analysis considering the total lignin content as the independent variable and AUDPC, size and number of pustules, 100 seed weight and seed area as predictor variables revealed that the total lignin content caused 75.2% alteration in other predictor variables. Hence, the present study confirmed that the lignification can be used as a key biochemical parameter for screening of resistant sources from the various pea germplasms.

In an open-air market in southern Italy, we noticed ‘Lady finger’ banana fruit imported from Costa Rica showing a severe rot, whose symptoms consisted of necrotic peel lesions with variable shape and size. Fusarium sacchari and F. proliferatum were consistently isolated from symptomatic fruit. In pathogenicity tests on ‘Lady finger’ banana fruit, F. proliferatum was more virulent than F. sacchari. Quantitative Time-of-Flight Mass Spectrometric analysis of secondary metabolites produced by isolates of these two Fusarium species on three different matrices (banana peel, barley and maize kernels) identified 11 mycotoxins. Seven of them (Fusaproliferin, Fumonisins A₁, Fumonisins A₂ and Fumonisins B₁, Hydrolysed Fumonisin B₁, Fusarin C and Moniliformin) were detected in matrices contaminated by F. proliferatum isolates. Fumonisin A₁ was the prevalent mycotoxin in both maize kernels and banana peel, while Fumonisin A₂ prevailed in barley kernels. Similarly, seven mycotoxins (the cyclic hexadepsipeptides Enniatins B₂, B₃ and B₄, Fumonisins A₁ and B₂, Hydrolysed Fumonisin B₁ and Fusarin C) were detected in matrices contaminated by F. sacchari isolates, but they were only in part the same as those produced by F. proliferatum isolates. Fusarin C prevailed in all three matrices colonized by F. sacchari. Fumonisin A₁ was detected exclusively in maize kernels while Enniatins B₃ and B_4, Fumonisin B₂ and Hydrolysed Fumonisin B₁ were detected exclusively in barley kernels. Overall, F. proliferatum produced a higher amount of mycotoxins than F. sacchari. Moreover, in banana peel both species produced a lower number and amount of mycotoxins than in the other two matrices.

Wheat stem rust (Puccinia graminis f. sp. tritici) is the major threat to wheat production in Ethiopia due to the menace of high losses in grain yield and quality. A wheat stem rust survey was undertaken during the main cropping seasons (late October to early November) of 2015 and 2016 in the Horro Guduru Wollega highlands, western Ethiopia. The purposes of the survey were to assess the wheat stem rust distribution and disease intensity and determine its association with biophysical factors and cultivation practices. A total of 221 wheat fields in eight districts were assessed. Wheat stem rust was prevalent in both cropping seasons. The mean disease incidence ranged from 56.3 to 63.7%, while the disease severity mean ranged from 15.7 to 21.6%, respectively. Logistic regression was used to analyze the association of wheat stem rust with independent variables. Increased incidence (>50%) and severity (>5%) were strongly (P < 0.0001) associated with lower altitude (≤2400 m), susceptible varieties, broadcast sowing method, fungicide-unsprayed wheat fields, and wheat growth at flowering and milking stages. The survey indicates a highly prevalent wheat stem rust epidemic associated with biophysical factors and cultivation practices in the major wheat-growing districts. A combination of cultivation practices such as sowing wheat in rows, optimum fertilization, deployment of rust-resistant varieties, and effective fungicide application would be the most effective methods for managing wheat stem rust in the Horro Guduru Wollega highlands.

Pseudocercospora puerariicola, a leaf spot fungus of Pueraria species, has been reported in East Asian countries, including Korea. Despite the ecological significance of this fungus, to date, no living cultures are present in Korea. The DNA nucleotide sequences of the internal transcribed spacer (ITS) region and the 28S rDNA gene (large subunit, LSU) of the fungus were deposited on GenBank database from Chinese, Laos, and Taiwanese isolates. However, these results were not sufficient to confirm pathogen identification to the species level. Therefore, we aimed to provide further information on this species based on the Korean isolates obtained from Pueraria montana var. lobata, adding more genetic locus to our study to support and affirm the identification of the fungus based on multi-loci analyses from Korean isolates. Nine samples were collected from different areas of Korea and deposited at the Korea University Herbarium, then used in this study. Three monoconidial isolates were obtained in 2022, and molecular phylogenetic analyses were performed using a combined multi-locus dataset of the ITS region, partial actin (actA), partial translation elongation factor 1-alpha (tef-1), and partial DNA-directed RNA polymerase II second largest subunit (rpb2) genes. The present study confirmed the presence of P. puerariicola in Korea as a causal agent of leaf spots on kudzu plants, providing the phylogenetic position of this fungus for the first time based on a multigene dataset and preserving three isolates in an authentic culture collection for future studies.

The widespread occurrence of fig cankers in the fig orchards of the central regions of Fars Province, Iran, prompted us to investigate the causative agents responsible for this decay. During this study we identified a newly emerged disease in fig trees, which we termed “Fig Black Necrosis”, in the commercially important fig cultivar Sabz. This disease is characterized by black wood necrosis under the bark of the infected fig branches. Our morpho-molecular investigation of fungal isolates from the infected fig trees exhibiting symptoms of black necrosis led to identifying the isolates as the basidiomycete, Butlerelfia eustacei, of the order Atheliales sensu lato. We conducted a comprehensive pathogenicity assessment on detached shoots and one-year-old saplings of eight distinct fig cultivars. The results revealed that B. eustacei could induce conspicuous brown lesions and wood discoloration. Moreover, our study demonstrated that this pathogen could cause wood necrosis and discoloration in detached shoots of 14 distinct tree species associated with various economically significant fruit, landscape, and ornamental trees growing alongside fig trees. In our survey, we clustered the inoculated fig cultivars based on six distinct pathogenicity characteristics using the principal component analysis approach. The results indicated that most fig cultivars, including all dried and most fresh figs, were moderately-susceptible to Fig Black Necrosis. The findings of this study provide insight into the newly emerged disease in fig orchards, aiming to better understand the causal agent and develop effective integrated management strategies against the disease.

Purple blotch disease incited by Alternaria porri is the major constraint in onion seed production, adversely affecting the quantity and quality of the seed. The indiscriminate and injudicious application of chemical pesticides has led to significant repercussions on both the environment and the overall well-being of living organisms, hence there is an urgent call for a transformative shift towards eco-friendly and sustainable approaches for combating the challenges posed by plant pathogens. In this context, the present study highlights the potency of formulated bio agents in enhancing seed vigour and suppressing onion purple blotch disease. Amongst the four bio agent formulations (Trichoderma harzianum 2.0% WP, Trichoderma viride 1.0% WP, Bacillus subtilis 1.50% LF and Pseudomonas fluorescens 1.75% WP) evaluated for priming impact on onion seedlings, Trichoderma harzianum 2.0% WP exhibited predominance in enhancing seed quality parameters with maximum seedling emergence (73.00 per cent), length (11.24 cm), dry weight (16.02 mg) and vigour indices I (818.63) and II (1168.61). This, in turn, led to maximum enhancement in total soluble sugars, total soluble phenolics, total chlorophyll content, polyphenol oxidase and peroxidase. All the investigated biochemical parameters revealed a positive correlation with vigour indices of seedlings. Trichoderma harzianum 2.0% WP (81.17 per cent) resulted in the maximum reduction in mycelial development of Alternaria porri. The potency of bio formulations under field conditions also exhibited supremacy of Trichoderma harzianum 2.0% WP with maximum disease management (23.08 per cent) representing AUDPC value (623.00), consequently leading to maximum increase in seed yield over control (5.61 per cent). Trichoderma harzianum 2.0% WP could be employed for long-term management of onion purple blotch.