Journal of Plant Pathology最新文献

Climate change is driving the emergence of novel tree diseases at the global scale, requiring new approaches for the formal confirmation of the pathogenicity of novel pathogens on novel hosts. At the same time, predictive models need to account for the possible effect of environmental changes and of abiotic stressors on disease severity for all diseases. By wound-inoculating Botryosphaeria dothidea on potted California coast live oaks and Cryptostroma corticale on potted silver maples, simultaneously in well-watered and in water-deprived conditions, I show that drought conditions increase the severity of disease symptoms. I also show that, by including a water-stressed treatment, I can formally prove pathogenicity and fulfill Koch’s postulates for putative pathogens that could not be confirmed in the absence of the stressor. Additionally, I show that the inclusion of data obtained in water stress conditions increases the differentiation between symptoms caused by fungal infection vs. symptoms caused by wound trauma, thus reducing the possible effect of outliers, a significant problem affecting many trials for fulfilling Koch’s postulates conducted with a limited number of replicates. The availability of comparable datasets in the presence and the absence of an abiotic stressor allows for the calculation of an Environmental Disease Component Index. Positive values of the index indicate a significant role of environmental change in disease progression and identify those pathogens that must be modeled factoring in climatic stressors. I suggest that this index may be extremely valuable for identifying pathogens likely to become emergent as climate changes.

The study investigated early blight, a major fungal disease affecting tomatoes, across two distinct agroclimatic zones in India, resulting in a collection of 90 Alternaria isolates. Morpho-cultural characterization grouped these isolates into 11 putative clusters, which were subjected to further analysis. Pathogenicity tests revealed that all 11 isolates were pathogenic on the Pusa-Ruby tomato cultivar. Molecular analysis, specifically comparing nucleotide sequences of the ß-tubulin (ß-tub), cytochrome-B (cyt-B) and Alternaria major allergen gene (Alt a1) using the MycoCosm and NCBI databases, identified these isolates as Alternaria alternata. The phylogenetic tree, constructed via the Maximum-Likelihood method using the Alt a1 gene, demonstrated that all 11 isolates clustered with A. alternata, Sector—Alternaria, alongside reference strains from the NCBI database. Additionally, Alt a1 showed the capability to differentiate sub-groups within Sect.—Alternaria, indicating its intraspecific discriminatory potential. In conclusion, the study confirms the widespread presence of pathogenic A. alternata on tomatoes and highlights the importance of marker gene, Alt a1 in discerning the identity of Alternaria species.

Rust diseases are a major concern in legume production worldwide causing heavy losses especially in developing countries that depend on grain legumes as staple food. Fungal species from Uromyces, Phakopsora and Puccinia genera are the main causal agents of the various legume rust diseases. They induce up to 100% yield losses on susceptible cultivars and are emerging as a substantial threat to global food security. Developing durable resistance to rust has thus become a critical breeding objective alongside efforts to improve cultural and disease management practices. This review specifically focuses on the recent advances in understanding and enhancing genetic rust resistance across diverse legume crops. Key topics covered include: (i) the diversity and host range of the rust species affecting legumes; (ii) the disease management strategies from cultural practices to chemical control; (iii) the available screening methods for identifying new sources of resistance; (iv) the genetic basis of resistance, encompassing both major resistance genes and quantitative trait loci; (v) insights into gene regulation and effector molecules leading to legume-rust interactions; and (vi) emerging genomic-assisted breeding techniques that can accelerate the development of durable rust resistance in legumes. Overall, this review highlights the progress made to date and the remaining challenges in sustainably managing rust diseases across diverse legume crops through integrated approaches spanning pathogen biology, advanced phenotyping, genetic resistance, and molecular breeding.

The development of environmentally friendly control methods to mitigate the severe damages caused by Phytophthora cinnamomi in the Mediterranean climate-type ecosystems is essential. In this way, crop waste and by-products which represent between 13 and 65% of agriculture production, are a rich source of bioactive compounds with antifungal and biocide activity. The main objective of this work was to determine the biocide activity against P. cinnamomi of three organic extracts. These extracts enriched in bioactive compounds come from residues of asparagus (Asp) and olive crops (Oliv and OH, from fruits and leaves respectively). They were evaluated at two doses (0.15 and 0.10%) on the mycelial growth and sporangial production of P. cinnamomi by in vitro experiments. Mycelial growth and sporangial production were significant reduced from the three plant extracts at the two doses tested, reaching a total inhibition with Asp at both doses. In general, no phytotoxicity symptoms were observed on seed germination and plant development, except for a plant yield reduction in the substrate treated with Oliv and Asp at the highest dose. In experiments performed in artificially infested soil, Asp induced a reduction of chlamydospores viability greater than 75% compared to unamended soil. Additionally, in planta experiments showed a significant reduction in plant mortality in substrate amended with OH. These results suggest that soil application of Asp and OH can limit P. cinnamomi infectivity and survival, setting the first steps to develop a sustainable method to control the root disease based on agricultural waste circular economy.

During the screening of lettuce (Lactuca sativa L.) samples from the United Kingdom in 2015 using high throughput sequencing (HTS) technology, the genome of a novel virus was identified in a plant showing symptoms of stunting and yellowing. The virus genome consisted of two RNA molecules; an RNA1 of 6001 nt encoding a polyprotein with protein cofactor, helicase, protease and RNA-dependent RNA polymerase motifs and an RNA2 of 6553 nt encoding a polyprotein with viral movement and coat protein motifs. Independently, in 2018, an analysis of ribodepleted total RNA from a dandelion (Taraxacum officinale L.) displaying leaf malformation and puckering revealed a complex infection involving a secovirus related to the UK lettuce virus. Moreover, a small survey confirmed the presence of the secovirus in environmental dandelion samples in Slovakia. Detailed analysis of these sequences suggests they all belonged to the same putative species, a member of the subgenus Stramovirus, genus Sadwavirus, family Secoviridae named lettuce secovirus 1 with the tentative Latin binomial Sadwavirus lactucae.

Sclerotinia stem rot (SSR), caused by the necrotrophic fungal pathogen Sclerotinia sclerotiorum, is a severe disease of broadleaf crops including canola/rapeseed (Brassica napus), leading to significant yield loss in conducive years. Replication of field conditions is challenging in variety disease resistance screening with testing required under a wide range of environmental conditions and at different plant growth stages. We investigated the role of thermal time in disease progression using three sowing times in the growing season, with six commonly grown Australian varieties of canola inoculated with four diverse West Australian isolates of S. sclerotiorum at 30% flowering. Area Under the Disease Progression Stairs (AUDPS), sclerotia production and weight, and seed production were measured. Time of sowing was found to be a crucial factor in explaining differences in AUDPS, stem width, seed production and sclerotia number according to the analysis of variance (P < 0.05), influencing isolate aggressiveness and disease progression. Linear mixed-effect models, regression decision tree models and principal components analysis were also conducted to determine the importance of a range of variables being included in variety screening for resistance. For all these analyses, both thermal time from sowing to 30% flowering when plants were inoculated, as well as thermal time over the 28-day inoculation period, in both canola and S. sclerotiorum, were important in explaining the variation. The study concludes by recommending that thermal time should be included in future SSR prediction risk models.

The study aimed to evaluate the effectiveness of three plant extracts (cumin (Cuminum cyminum L.), peel fruit of pomegranate (Punica granatum), and fruit of black pepper (Piper nigrum L.)), against Pectobacterium carotovorum subsp. carotovorum (Pcc), a bacterium that causes potato tuber soft rot disease. This disease can result in significant losses to potato production and affects the quality of potatoes during storage, transit and shipment. To conduct the study, five isolates of the pathogenic bacterium were obtained from naturally infected potato tubers. According to the in vitro screening, the most virulence isolate Pcc2 was molecularly identified using 16S rRNA gene partial sequencing. Three plant extracts (cumin, pomegranate, and black pepper), were tested for their antibacterial activity against the bacterium using in vitro experiments. The results showed that all the three plants extract exhibited inhibition of the bacterial growth. Among the three-plant extract, pomegranate was found to have the best inhibitory effect on the bacterium (0.92 cm inhibition zone). Based on the findings of the in vitro experiments, the use of all extract at a concentration of 50 mg was recommended for controlling the soft rot disease in potato tubers during storage conditions. The data demonstrated that pomegranate extract was on the first ranking with bacterial growth reduction percentage estimated (1.4 mm), followed by cumin extract with growth reduction estimated (0.92). The data revealed that all of the tested plant extracts were able to reduce the severity of the disease. Of all the extracts, pomegranate extract showed the highest reduction in disease severity (91.3%). It is evident that the treatments with pomegranate, black pepper, and cumin consistently led to an increase in total phenol content over the course of 21 days. Treatments with methanolic extract of pomegranate, black pepper, and cumin lead to varying degrees of increased peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) activities over the course of the experiment. The data shows that the effectiveness of these treatments generally increases with time. In conclusion, the study showed that all plants extract tested herein has the potential to control potato tuber soft rot disease, which is a major problem affecting potato production.

Peanut (Arachis hypogaea L.) crown rot and root rot are common diseases caused by Aspergillus niger Van Tieghem. Early and accurate detection of A. niger is key to disease management. In this study, the design of two to five sets of loop-mediated isothermal amplification (LAMP) primers was based on the EglA, GOD, Tub, NRPS, Tan, CbhA, and CbhB genes of A. niger. Of these, primer set GOD-91 was selected for optimization of the three-factor LAMP system: the Bst DNA polymerase concentration, the concentration ratio of the inner and outer primers, and the concentration of Mg²⁺. In addition, the optimized LAMP reaction system for A. niger detection was validated for specificity, sensitivity, and on-site feasibility. The specificity test showed that A. niger could be specifically detected with the proposed method without cross-amplification of other pathogenic fungi DNA. Moreover, based on the sensitivity test, the lowest detection limit of this reaction system was 5.1 × 10⁻⁷ ng/µL pAN01 plasmid DNA, after which a standard curve was generated for the quantitative detection of A. niger. The LAMP method was further applied for field sample assessment before and after A. niger infection, successfully detecting A. niger presence in the samples collected in the field. This study yielded a sensitive, specific, and reproducible LAMP system that can be used to assess on-site samples within 45 min. It is an effective approach for the rapid and quantitative detection of A. niger.

Almost 85% of tomato plants in the world are grown in controlled greenhouse. This confined microclimate forms a favorable environment for the fast development of pathogens. This study evaluates the use of Mortierella alpina M01 strain as a plant growth-promoting fungus and biocontrol agent for tomato plants in greenhouses. Its bio-eliciting effect on growth, photosynthetic traits, and fruit yield, together with its protective ability against verticillium wilt and bacterial speck diseases was assessed. The treatment of tomato seeds with M. alpina M01 spore suspension significantly enhanced tomato growth variables such as stem length, leaf and leaflets numbers, and root and fruit biomass. It improved photosynthesis efficiency, stomatal conductance, and transpiration rate. Concerning plant immunity, M. alpina M01 lowered leaf alteration index by 31% and browning index by 86%, mitigating the damage inflicted by Verticillium dahliae in tomato. Likewise, M. alpina M01 was effective in reducing disease score and average of number of lesions caused by Pseudomonas syringae pv. tomato by 48 and 76%, respectively. M. alpina M01 modulated lipid peroxidation triggered by V. dahliae or Ps. pv. tomato infestations, by potentiating H₂O₂ accumulation and the activity of the antioxidant enzymes GPOD or PPO. Finally, phenolic and flavonoid contents increased after inoculation with the bacterial pathogen in M. alpina M01-pre-treated plants, implying primed defenses. These results highlight the potential of M. alpina M01 as a PGPF to improve tomato growth, and as a biocontrol agent against V. dahliae and Ps. pv. tomato in controlled confined environments such as greenhouses.