Journal of Phytopathology最新文献

Polygonatum cyrtonema, known as Huang Jing, is a traditional Chinese medicinal plant widely cultivated in China, especially in Hunan Province. From the summer of 2022 to 2024, a severe leaf blight outbreak was observed on P. cyrtonema. The representative isolate llw1 was obtained and exhibited morphological characteristics consistent with the genus Mycoleptodiscus. Multigene phylogenetic analysis revealed that llw1 clustered with M. terrestris and M. suttonii in a well-supported lineage (85/1.0 ML/PP) but formed a distinct branch within this clade. Morphologically, llw1 differs from M. terrestris by faster growth on PDA (≥ 90 mm vs. 50–56 mm in 5 days at room temperature), darker colony coloration (white to black vs. grey to green), slightly larger conidia (30.5 × 8.5 μm vs. 26 × 6.5 μm) and longer conidial appendages (15.0 μm vs. 12.5 μm). It also differs from M. suttonii by having shorter conidia (28–34 × 4.5–8.5 μm vs. 33–36 × 7–7.5 μm), shorter conidial appendages (15.0 μm vs. 19 μm) and darker colony coloration (white to black vs. white to pale yellow). Pathogenicity tests on P. cyrtonema reproduced the symptoms observed in the field and fulfilled Koch's postulates. Based on morphological, phylogenetic and ecological data, llw1 is proposed as Mycoleptodiscus polygonati sp. nov. This study also presents a revised phylogenetic framework for the M. terrestris species complex.

Phytophthora blight, caused by Phytophthora capsici, is a devastating disease that threatens pepper fruit production worldwide. PcPdeH, a high-affinity phosphodiesterase in the cAMP signalling pathway, is essential for P. capsici vegetative growth, the oxidative stress response and pathogenicity. To explore the regulatory role of PcPdeH in pathogenicity, we conducted a transcriptomic analysis comparing gene expression between the PcPdeH knockout mutant and wild-type strains during mycelial growth, 3 h post infection (hpi) and 12 hpi. The results demonstrated that disruption of PcPdeH significantly downregulated genes associated with hydrolase activity, carbohydrate metabolic processes, oxidoreductase activity and key metabolic pathways, including starch and sucrose metabolism, glycolysis, chloroalkane and chloroalkene degradation and fatty acid degradation. Functional enrichment analysis revealed that PcPdeH plays a regulatory role in metabolic adaptation and oxidative stress tolerance through the cAMP signalling pathway. These findings position PcPdeH as a central regulator within the cAMP signalling network of P. capsici, linking it to virulence-related processes and highlighting its potential as a target for disease management strategies.

Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (FON), is a major threat to watermelon (Citrullus lanatus) production worldwide. In this study, we characterised the biological properties of a highly virulent FON isolate and evaluated the resistance of 10 watermelon genotypes. Optimal growth of the pathogen occurred at 25°C and pH 7.0, and resistance levels among watermelon materials showed clear differentiation. Transcriptome analysis of a resistant (WX01) and a susceptible (WX07) genotype after FON inoculation revealed 2640 differentially expressed genes (DEGs). Functional enrichment indicated that DEGs were mainly involved in plant–pathogen interaction, hormone signal transduction, and phenylpropanoid biosynthesis. Notably, key genes associated with jasmonic acid (e.g., JAZ), salicylic acid (e.g., TGA), and auxin (e.g., GH3) signalling pathways exhibited significant expression differences between the two genotypes. qRT-PCR validation confirmed the transcriptomic results. Downregulation of JAZ and upregulation of TGA, GH3, and phenylpropanoid-related genes in WX01 suggest a coordinated defence response involving hormonal cross-talk and secondary metabolism. These findings provide new insights into the molecular basis of Fusarium wilt resistance in watermelon and identify candidate genes for breeding disease-resistant cultivars.

Cocos nucifera (coconut palm) is a vital tropical crop, but its productivity is increasingly threatened by leaf spot disease. Surveys in Penang and Kedah, Malaysia, revealed widespread leaf spot symptoms, prompting investigation into the causal agent. Eight fungal isolates from symptomatic leaves displayed morphological traits of Pestalotiopsis. Molecular analysis (ITS and tub2 sequences) and phylogenetic studies confirmed the pathogen as Pestalotiopsis parva. Pathogenicity tests reproduced symptoms and fulfilled Koch's postulates. This is the first report of P. parva causing leaf spot on C. nucifera in Malaysia, offering key insights for disease management in Malaysian plantations.

Industrial clove waste (ICW), a plant-based byproduct of the clove processing industry, contains various chemical compounds with potential antifungal, insect-repellent and antimicrobial properties. The chemical composition of industrial clove waste was analysed using GC-MS, which revealed benzyl benzoate as the major constituent (96.30%). Water-soluble formulations were prepared by mixing industrial clove waste with different adjuvants. Among these, three formulations—ICW (50%) + Tween 80 (30%) + water (20%), ICW (60%) + Tween 80 (20%) + water (20%) and ICW (70%) + Tween 80 (10%) + water (20%) were found to be water-soluble. The ICW 50% water-soluble formulation met the WHO specifications for pesticide emulsifiable concentrate formulations in terms of physical parameters and was selected for further studies. Phytotoxicity tests revealed no adverse effects on the vegetative and flowering flush of mango plants. Field trials showed that the 1.0% concentration of the ICW 50% formulation significantly reduced powdery mildew severity to 10.40%, with a disease reduction of 79.36% over the control. At 0.5% concentration, it recorded 11.20% disease severity and 77.77% disease reduction. Pre-harvest sprays of ICW 50% formulation at 1.0% and 0.5% concentrations resulted in post-harvest anthracnose incidence levels of 3.75% and 5.00%, with reductions of 88.46% and 84.61% over the control, respectively. Likewise, fruit dip treatments at 1.0% and 0.5% recorded 2.50% and 3.75% post-harvest anthracnose incidence, achieving 92.30% and 88.46% reduction over the control, respectively.

Tomato (Solanum lycopersicum), a globally significant crop, is highly susceptible to bacterial speck disease caused by Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). In this paper, we studied the effect of plant growth-promoting bacteria (PGPB) Bacillus subtilis MGMM36 and Bacillus velezensis MGMM30 on tomato resistance to Pst DC3000 under greenhouse conditions. Seed pre-treatment with either B. subtilis or B. velezensis improved plant viability (60% and 50% survival, respectively, compared to 25% in plants infected with Pst DC3000 alone) and mitigated pathogen-induced damage. B. subtilis provided stronger protection compared to B. velezensis: plants treated with B. subtilis showed a 20% reduction in shoot length (SL), a 10% reduction in root length (RL) and a 15% reduction in leaf area (LA) compared to the control. However, plants treated with B. velezensis exhibited a 30% decrease in SL, a 25% decrease in RL and a 22% decrease in LA. Furthermore, in infected plants grown from seeds previously treated with PGPB, no increase in CAT (SICAT), SOD (SISOD) and PTO gene expression was observed, in contrast to untreated plants. Both B. subtilis and B. velezensis increased the expression of the PR1 gene, restoring it to levels found in uninfected control plants. These findings underscore the potential of two strains of Bacillus spp. as sustainable biological agents to enhance disease resistance and promote tomato growth, with the aim of practical application for pesticide reduction and environmental protection.

The increasing occurrence of virus disease in cowpea raises concerns about the emergence of new or expanding viral threats in the production of vegetable and pulse crops. During the summer of 2022, plants showing veinal necrosis disease on cowpea were observed at the experimental farm of the Indian Agricultural Research Institute (IARI), New Delhi. To elucidate the natural occurrence of groundnut bud necrosis virus (GBNV) associated with vein necrosis disease in cowpea, this study employed biological and molecular approaches, including the characterization and in silico prediction of structural and functional features of the N and NSs proteins, as well as subcellular localization studies in both natural and experimental host systems. Mechanical transmission successfully reproduced the typical disease as observed in the field on cowpea plants (cv. Pusa Komal). Molecular diagnosis using RT-PCR indicated the presence of GBNV in the diseased plant samples. Cloning and sequencing of the near-complete small RNA segment of GBNV revealed 98.9% nucleotide and > 99% amino acid identity in the nucleocapsid (N) gene, and 98% nucleotide and 99% amino acid identity for the non-structural silencing suppressor (NSs) gene, compared to known GBNV isolates. Phylogenetic analysis further placed the associated virus strain within the major clade of GBNV in plants. Further, the N and NSs proteins were successfully transiently expressed in plant and found localized in the cytoplasm of cowpea and Nicotiana benthamiana, the natural and experimental host of the virus respectively. The experimental reproduction of the disease and characterization of the N and NSs genes of the virus associated with pathogenesis revealed the association of the GBNV strain in the occurrence of veinal necrosis of cowpea. For the first time, functional motifs within the N and NSs genes were comprehensively predicted through bioinformatic analyses and their subcellular localization was examined in both natural and experimental hosts using confocal microscopy.

The phyllody severity in sesame crop ranged from 9% to 20% under field conditions, and the maximum was recorded in Thiruvannamalai district of Tamil Nadu, India. The observed morphological characters of the transmitting insect vector Orosius albicinctus were light ochraceous colour with irregular striations and dark brown with black mottling. The infected sesame samples were subjected to PCR amplification by using universal primer pair P1/P6, followed by nested PCR using R16F2n/R16R2 primers, which amplified ~1.25 kb, which was also occurred in the Parthenium weed plant. Further, BLAST analysis showed that the sequences were aligned with the 16SrII-B group phytoplasma consisting of Candidatus Phytoplasma aurantifolia (94.87%), sesame phyllody (97.97%), Blainvillea acmella phytoplasma (97.70%) and Mollugo disticha phyllody phytoplasma (98.28%). Since there is no adorus impact despite the vast host range, polyphagous insect vectors, lack of environmentally acceptable effective insecticide, and unavailability of resistant sources, management of phyllody disease has been attempted with biotic inducers (salicylic acid [SA], methyl jasmonate [MeJA] and beta amino butyric acid [BABA]) individually (50, 100 and 150 ppm) and in combination. Among the inducers tested in vitro, SA 50 ppm showed a higher vigour index (1401) in the seed infiltration method of seed treatment, further confirmed in blotter paper technique. The same treatment showed a high germination percentage (86%) with more shoot length on the 60th day (67.0 cm) and five branches/plant under glasshouse experiment. In addition, SA 50/100 ppm increased the phenolic activity and plant defence enzymes; hence it has been further test verified at two different field locations, and the results revealed that seed infiltration treatment with SA 50/100 ppm, followed by foliar application of SA (50/100 ppm) at 30, 45 and 60 DAS, was shown to be effective by recording lesser disease severity compared to control (42.2%). Also, salicylic acid treatment showed higher germination (87.6%), more capsules/plant, thereby incorporation of inducers like salicylic acid in the integrated disease management will serve as a viable and sustainable management option.

Berkeleyomyces, a globally spread genus of soil-borne fungi comprising B. basicola and B. rouxiae, causes black root rot in over 170 plant species including the ornamental shrub Ilex crenata. These two species are morphologically indistinguishable and were previously grouped under Thielaviopsis basicola. Historical records did not account for hidden species diversity, including pathogenic diversity on specific host plant species such as lettuce. The first objective of this study was to determine whether strains of both Berkeleyomyces species affect I. crenata, as this knowledge could influence the selection of isolates for resistance breeding. We collected 33 isolates from I. crenata plants in gardens, parks and nurseries in Flanders (Belgium) and the Netherlands, and characterised this Berkeleyomyces collection to species and subspecies level using Genotyping-by-Sequencing (GBS). Most I. crenata isolates belonged to two near-clonal groups within B. basicola. Virulence testing revealed that B. basicola and B. rouxiae could incite similar disease levels in I. crenata, with smaller differences in virulence related to the host of origin. Our second objective was to develop novel qPCR assays, allowing fast species identification and quantification of both Berkeleyomyces species. We developed two sets of species-specific qPCR assays: one set on the 60S locus (with sensitivity down to 100 fg DNA), and another set on the rDNA ITS locus (with sensitivity down to 10 fg DNA), which can be run in duplex format. The qPCR assays were successfully used to quantify the pathogen. They show potential for use in other hosts as well as in epidemiological studies.