Plant disease最新文献

Halo blight of hop, caused by Diaporthe humulicola, was first described in 2018 and is a major concern for growers in the eastern United States and Canada. This pathogen can cause quality and yield losses by desiccating hop cones, leading to shatter. However, traditional disease diagnosis is time-consuming, with morphological features taking up to 30 days to develop in culture. To address this issue, a quantitative PCR (qPCR) assay based on the translation elongation factor 1-alpha (TEF) gene was developed. We assessed capabilities and limitations of this assay for detection of D. humulicola in plant tissue and investigated aspects of the disease through (i) testing of hop rhizomes for the presence of fungal pathogens, (ii) determining the time required to detect D. humulicola in detached hop leaves, and (iii) comparing plating methods with the qPCR assay to monitor D. humulicola in a hop yard. The limit of detection for the assay was 100 fg/μl of DNA. The assay showed no cross-reactivity with other hop pathogens, endophytes, or other Diaporthe species tested. Detection of D. humulicola occurred 1 day after inoculation. The assay detected D. humulicola in both asymptomatic and symptomatic rhizome tissue, but further investigation is required to determine the cause of the observed symptoms. The assay successfully detected the pathogen in individual hop cones and inflorescences throughout the season, with higher positive identification rates than culture-based assays. This assay will provide time-limited diagnosticians with a tool for the detection of D. humulicola.

Allo-inoculum has an important role in fungal disease epidemiology. Understanding the factors that impact the long-distance dispersal of a pathogen is crucial to improve its management. In this study, we studied Pseudocercospora fijiensis allo-inoculum dynamics in Martinique over a period of 18 months. We used trap plants to measure (10 times) the spore abundance across six locations. Lesion densities observed on trap plants were used as a proxy of the allo-inoculum resulting from long-dispersal ascospores. We analyzed how the lesion densities of P. fijiensis measured with trap plants were statistically correlated with (i) weather factors and (ii) the stage of evolution of disease (SED) measured in closest banana plots. The SED measured in neighboring plots did not significantly influence the lesion densities observed on the trap plants. For each variable, we determined the period of time prior to the trap plant exposure that exhibited the strongest correlation with the lesion densities measured on these plants. Rainfall was the variable with the most influence and positively correlated with lesion densities when measured 7 to 4 days before trap plant exposure. Inversely, there was a negative correlation with UV radiation measured 2 to 1 days prior to trap plant exposure. This information complements the knowledge on the biology of the fungus and holds potential for enhancing disease management, especially the importance of rainfall for the allo-inoculum dynamics. These results also showed that if commercial farms have good management of black leaf streak disease, it does not contribute to long-distance contamination.

Tobacco black shank, induced by Phytophthora nicotianae, ranks among the most destructive diseases threatening global tobacco production. Biological control constitutes a crucial method for the environmentally friendly management of this disease, with the discovery of biocontrol agents serving as the initial step in this endeavor. The present research seeks to uncover new biocontrol agents and plant growth promoters effective against P. nicotianae. A strain of endophytic actinomycete isolated from tobacco, designated W71, was identified as Streptomyces rochei. This strain exhibited strong indole-3-acetic acid production capacity and inhibitory activity against P. nicotianae. In greenhouse trials, S. rochei W71 demonstrated significant plant growth promotion effects, markedly improving agronomic traits, root activity, root morphology indices, and antioxidant enzyme activities of tobacco plants. Field trials conducted at the rosette and prosperously growing stages revealed significant enhancements in several key crop parameters following the application of W71 treatment. These improvements encompassed increased maximum leaf length, maximum leaf width, stem girth, and plant height. Additionally, at harvest, W71 was found to facilitate a remarkable 98.91% boost in yield. In vitro inhibition tests demonstrated potent antagonism: live cells of S. rochei W71 suppressed P. nicotianae growth by 96.84%, outperforming the 70.89% inhibition rate of its cell-free culture filtrate. Greenhouse pot trials yielded an 87.53% disease control efficacy against tobacco black shank, and field trials resulted in a 72.68% control efficacy, indicating satisfactory performance. The study results demonstrate that S. rochei W71 possesses both plant growth-promoting properties and biocontrol capabilities against tobacco black shank, making it a promising candidate for use as a plant growth promoter and biological control agent.

Olive leaf spot, also called peacock eye disease, is caused by the hemibiotrophic plant pathogen Venturia oleaginea. Disease symptoms develop on the upper side of leaves; infected leaves eventually abscise; and in severe epidemics, the trees are completely defoliated. Despite the vast knowledge gained about the pathogen and the disease since it was first described in 1845, observations made in recent years in commercial olive groves in Israel remain unexplained. The long-term objective of this study was to establish guidelines for disease management strategies in commercial olive groves in Israel. To achieve this, we first needed to comprehend the development and progression of the disease in the region. We determined that in each growing season, infections could occur in both autumn and spring. Furthermore, there were two episodes of disease development: the first between the end of autumn and the beginning of winter, and the second between the spring and early summer. The data were used to propose a model for peacock eye development that implies that V. oleaginea maintains monocyclic and polyetic characteristics in the Mediterranean climatic conditions prevailing in Israel: the disease is monocyclic because it completes only one disease cycle within a certain growing season; it is polyetic because infections occurring in one growing season remain asymptomatic until the succeeding season.

Fusarium head blight (FHB) is a devastating fungal disease in wheat, causing significant yield losses and deterioration of grain quality under severe conditions. In this study, a genome-wide association study was conducted with 448 accessions using genotyping data generated by the 660K SNP array. Nine relatively stable FHB resistance loci were identified on chromosomes 1B, 1D, 2D, 5B, 7A, and 7B. Each QTL accounted for 4.1 to 10.4% of the phenotypic variation. Among them, QFhb.nwafu-7BS and QFhb.nwafu-7BL are novel loci. Polymorphisms of the flanking AQP marker AX-94527414 were developed for QFhb.nwafu-7BL, which could be useful for marker-assisted selection of FHB resistance. Correlation analysis indicated that variation in FHB response was independent of plant height, spike length, and uppermost internode length across the three environments. These results offer new resistance resources for FHB resistance breeding and insights for marker-assisted selection and gene cloning.

Powdery mildew, caused by Podosphaera xanthii, poses a significant threat to watermelon (Citrullus lanatus) cultivation. Development of resistant cultivars is one of the best strategies to manage powdery mildew. To elucidate the genetic basis of resistance, bulked segregant analysis (BSA) was conducted on an F₂ population derived from a cross between resistant (USVL608-PMR) and susceptible (USVL677-PMS) genotypes. A 570-kb region on chromosome 2 was identified using QTLseq, containing 99 single-nucleotide polymorphisms (SNP) and eight putative genes. A tightly linked kompetitive allele specific PCR (KASP) marker was developed and validated across three F₂ populations (USVL608-PMR × USVL677-PMS, USVL608-PMR × 'Sugar Baby,' USVL608-PMR × 'Dixie Lee'), showing a 3:1 segregation ratio and very strong linkage to resistance. Marker-disease resistance linkage was further validated in the F₃ generation of all three populations. RNAseq analysis revealed the upregulation of lipoxygenase (LOX), jasmonic acid (JA), and reactive oxygen species (ROS) pathways after inoculation, suggesting their role in powdery mildew resistance in watermelon. The development of tightly linked KASP markers in three different backgrounds for powdery mildew resistance and a molecular understanding of disease resistance will be useful for breeding and selecting new disease-resistant watermelon cultivars.

Pin nematodes (Paratylenchus spp.) are common plant-parasitic nematodes in North Dakota that can negatively impact field pea (Pisum sativum) production. These nematodes rely on a functional stylet to feed, which develops through molting from a nonfeeding fourth-stage juvenile (J-4) into an adult. Understanding the role of host resistance and root exudates in triggering this molting process is crucial for effective nematode management. In this study, we evaluated 31 field pea cultivars for resistance to P. nanus type B in greenhouse experiments using naturally infested soil and investigated the influence of root exudates on J-4 molting under laboratory conditions. Reproductive factor was calculated as the final nematode population density divided by the initial density. Among the tested cultivars, six were classified as susceptible (Columbia, Carousel, Mystique, Flute, Banner, and Arcadia), 20 were moderately susceptible (DS Admiral, Ginny, Melrose, Korando, Capella, Bacurra, LG Amigo, CDC Striker, Granger, Spider, LG Sunrise, LG Koda, Fergie, SW Midas, Monarch, Nette, Hampton, Greenwood, K2, and Chrome), and five were moderately resistant (Matrix, Agassiz, Salamanca, Viper, and Aragorn). Additionally, root exudates from the susceptible cultivar Columbia induced molting up to 39% in J-4 nematodes, compared with only 6% in exudates from the moderately resistant cultivar Viper. This is the first report examining the effects of field pea root exudates on the molting of J-4 pin nematodes. Further studies on root exudate chemistry could provide deeper insights into host-nematode interactions. Overall, most cultivars supported nematode reproduction, underscoring the need for effective management strategies to mitigate nematode infestations.

Intensive fungicide regimes are commonly used on Buxus spp. in the United States to manage boxwood blight (BWB), a plant disease caused by Calonectria pseudonaviculata (CPS). BWB causes losses in both nursery production and landscapes. The disease is often found within boxwood canopies, where achieving adequate spray coverage and penetration is difficult. The efficacy of the systemic triazole fungicide flutriafol (Fungicide Resistance Action Committee group 3) was evaluated over time by detached leaf assays. The efficacy of several concentrations of flutriafol against three CPS isolates and at several spore concentrations was assessed in the lab. Flutriafol was also applied by drench or sprench (portmanteau of spray and drench, a high-volume foliar application with substantial soil wetting) to container- or field-grown boxwood plants. The triazole fungicide propiconazole, which was previously shown to be efficacious against BWB, and no-fungicide water application were included as control treatments. Leaves of boxwood 'Common', 'Winter Gem', 'Green Velvet', or 'Suffruticosa' were collected periodically, challenged with CPS conidia, and rated for percent symptomatic area over 14-day incubations. In general, lower disease incidence and severity developed on leaves collected from fungicide-treated plants than on leaves from water-treated control plants regardless of the application method. Flutriafol provided protection from CPS infection on leaves from drench-treated boxwood for at least 20 weeks. However, there was a delay of 1 to 4 weeks observed between fungicide application and maximum efficacy depending on treatment and trial. This delay was shorter among leaves from plants treated with higher flutriafol doses or via sprench applications.

We recently provided new insights into the etiology of Venturia oleaginea, the causal agent of peacock eye disease in olive. We identified two distinct periods of infection events during each growing season: the first in autumn and the second in the spring. In addition, we reported the occurrence of two episodes of disease development: the first at the end of autumn/beginning of winter and the second in the spring and early summer. The main goal of the current study was to experimentally examine the practical implementation of these new insights. Four experiments were performed in the 2021/2022 and 2022/2023 seasons in commercial groves under natural epidemics. The results demonstrated that application of one or two sprays before or after the first major rain event in the season (the presumed time of infections that generate the second disease episode) significantly reduces disease development. The level of disease suppression achieved by these sprays was not inferior to the level of disease control achieved by nine consecutive sprays in a season. The effect of the application in one season on peacock eye development in the following season was evaluated in the same groves, and it was found that if the disease is not controlled during two consecutive seasons, its severity increases markedly in the succeeding season. However, if the disease is properly managed in the first season, its severity in the succeeding season may be minute or even nonexistent.

Aegilops geniculata Roth is a valuable donor for improving common wheat (Triticum aestivum) because of their close relationship. In this study, W181009 was identified as a BC₁F₁₂ progeny resulting from the cross between 'Chinese Spring' and Ae. geniculata SY159. Cytological examination, fluorescence in situ hybridization, and functional marker analysis confirmed that W181009 carried alien chromosomes 2M^g and 6U^g from Ae. geniculata SY159. Using the specific locus amplified fragment sequencing (SLAF-seq) technique, we successfully developed specific markers for W181009 with an effective rate of 54.23%. Subsequently, the deletion of chromosome 6B in W181009 was confirmed using deletion nullisomic-tetrasomic lines. Notably, W181009 showed immune resistance to powdery mildew at all growth stages. To further study the source of the powdery mildew (Blumeria graminis) resistance gene in W181009, a genetic population was created using W181009 and Shaanyou225 for analysis. Both F₁ and BC₁F₂ plants carried chromosome 6U^g, and they exhibited strong resistance against powdery mildew, indicating that the resistance in W181009 originated from chromosome 6U^g. Furthermore, the presence of only chromosome 6U^g can be easily identified by using two specific SLAF-seq markers. The study results provide the basis for further genetic research and breeding to improve powdery mildew resistance using W181009.