Plant disease最新文献

Red rust disease, caused by the algal pathogen Cephaleuros spp., poses an increasingly significant threat to oolong tea (Camellia sinensis) cultivation. Currently, however, effective management is hindered by a lack of species-specific diagnostic methods and limited analysis of host-response physiological changes. In this study, the region-wide survey was conducted, species-specific molecular diagnostics, multi-scale microscopy, and host biochemical analysis (pigments and antioxidants) were utilized to investigate Cephaleuros diversity, invasion biology, and host responses in oolong tea. Across 785 composite leaf samples, the overall Cephaleuros positivity rate was 30.19%, with incidence significantly higher detection rate in Chaozhou, Guangdong (46.59%) than in Fujian (7.58%). Genotyping via psaA-targeted qPCR revealed strikingly distinct regional distributions: C. parasiticus was predominantly detected in Chaozhou (95.3%), whereas C. virescens was the only identified species in Fujian, with no mixed infections identified. Histological analysis of Chaozhou samples revealed subepidermal thalli beneath both leaf surfaces, accompanied by palisade/spongy necrosis, which suggested deeper tissue invasion by C. parasiticus. To characterize host responses, we quantified photosynthetic pigments and antioxidant enzymes in lesion centers and margins across representative cultivars. In green-leaf cultivars, infection was generally associated with decreases in chlorophyll a and b (with significance varying by cultivar), whereas carotenoid responses were modest and cultivar dependent. In contrast, two etiolated mutants exhibited significant increases in chlorophyll a (2.0-3.7-fold) and carotenoids (~1.5-1.6-fold), and anthocyanin increased by ~62% in the etiolated Juduozai mutant. Antioxidant enzyme activity was spatially structured, with peroxidase (POD) and catalase (CAT) strongly induced at lesion margins (POD increase 39-248%), while lesion centers exhibited reduced activity (5-41%). Superoxide dismutase (SOD) showed a modest increase at the lesion margins (increase 18-31%). A composite "reaction index" (POD+SOD at lesion margins) was used to classify cultivars into high and moderate response categories. These findings provide new insights into the ecological dynamics and host responses associated with Cephaleuros infection in oolong tea and highlight the potential for using these indicators in cultivar selection and disease management strategies.

Oat stem rust, caused by Puccinia graminis f. sp. avenae (Pga), is a devastating fungal disease that poses a serious threat to global oat production. In recent years, with the expansion of oat cultivation area and the shortage of resistant cultivars in China, the prevalence of this disease has shown an increasing trend. There is an urgent need to clarify the population structure and virulence characteristics of P. graminis f. sp. avenae for effective disease management and resistance breeding. From 2023 to 2024, this study collected a total of 186 oat stem rust samples Hebei Province, China. Single isolates were obtained through single-uredinium, and physiological race identification and virulence frequency analysis were conducted using 12 single-gene differential lines. Additionally, two predominant P. graminis f. sp. avenae races were selected to evaluate the seedling and adult-stage resistance of 59 oat cultivars (lines). The results showed that 188 single-uredium isolates were obtained from 158 viable samples (with a survival rate of 85.0%), and seven physiological races were identified: TJD, TJN, TKN, TJB, TBD, TGD, and TJL. Among them, TJD was the predominant race (occurrence frequency 37.7% in 2023, 38.8% in 2024), TJN was the sub-predominant race (28.2% in 2023, 31.3% in 2024), and the frequencies of the remaining five races were all below 17.6%. This indicates that the P. graminis f. sp. avenae population structure in China is relatively stable with low virulence diversity. All isolates were virulent to Pg1, Pg2, Pg3, and Pg4, while avirulent to Pg6, Pg13, and Pg16. The virulence frequency to Pg10 ranged from 3.1% to 20.8%. In total, 31 (52.6%) oat cultivars were resistant to all tested races of P. graminis f. sp. avenae in field test in 2023-2024. This study supplements global P. graminis f. sp. avenae surveillance data, clarifies the race composition and virulence dynamics of P. graminis f. sp. avenae in northern China, and provides a scientific basis for the integrated management of oat stem rust and the breeding of resistant cultivars.

Sugarcane ring spot disease significantly impacts crop yield, necessitating the development of resistant cultivars. This study investigated the pathogenicity, morphology, growth characteristics, and molecular identity of the causal fungal pathogen while assessing the resistance of various sugarcane genotypes. Morphological and molecular analyses identified Curvularia guangxiensis as the primary pathogen. Pathogenicity assays demonstrated that the strain FS1 exhibited greater virulence than the strain BH1, inducing more severe leaf lesions. FS1 also displayed a higher growth rate on potato dextrose agar, triggering earlier symptom onset. A multifactorial analysis of genotype, location, and year revealed significant effects on disease incidence, with broad-sense heritability estimated at 0.7, highlighting substantial genetic and environmental contributions. Cluster analysis categorized sugarcane genotypes into five resistance groups, identifying CP81-1258 and Q202 as highly resistant, while CP88-1762, FN07-2020, and GT94-119 were highly susceptible. These findings provide critical insights for breeding resistant sugarcane cultivars and optimizing disease management strategies.

Colletotrichum species are important fungal plant pathogens associated with citrus pre- or postharvest disease globally. Seventy-three Colletotrichum isolates were collected from diseased leaves, fruits, and twigs of lime, tangerine, and pomelo in the provinces of Chiang Mai, Nakhon Pathom, and Lampang in Thailand. Colletotrichum siamense, C. gloeosporioides, C. fructicola, C. gigasporum, C. kokhaense sp. nov., C. plurivorum, and C. tropicicola were identified using morphological characters and multigene phylogenetic analysis (combinations of internal transcribed spacer, glyceraldehyde-3-phosphate dehydrogenase, Apn2-Mat1-2 intergenic spacer and partial mating type, glutamine synthetase, β-tubulin, actin, and histone depending on the species complex). C. siamense was the most prevalent species in Thailand, C. gigasporum was reported for the first time as a pathogen of citrus globally, and the new species C. kokhaense in the magnum species complex was described. Pathogenicity tests confirmed that C. siamense, C. gloeosporioides, C. gigasporum, C. kokhaense sp. nov., and C. plurivorum were pathogenic to citrus fruits, seedlings, and in planta shoots, with C. gigasporum being the most aggressive species. The non-wound inoculation technique provided good discrimination between high and low aggressive species compared with wound inoculation, where most species appeared to be very aggressive. Knowledge of Colletotrichum species causing citrus disease and their pathogenic ability will assist the development of effective disease management strategies.

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.

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.

The transition from manual to mechanical planting in Florida has raised concerns about the impact of mechanical harvesting on seed cane integrity, increasing the potential for infection by naturally occurring soilborne pathogens. Surveys conducted during the 2023 and 2024 planting seasons identified Thielaviopsis sp. and Fusarium sp. in 43 and 38% of the 569 sampled seed cane, respectively. Statistical analyses revealed a positive correlation between muck soils and Thielaviopsis; however, Fusarium incidence appeared to be independent of soil type. Among sugarcane varieties, CP07-2320 exhibited negative correlation to Thielaviopsis but was positively correlated to Fusarium. In contrast, CP96-1252 was particularly correlated to Thielaviopsis and negatively correlated to Fusarium. Of particular interest to growers, CPCL05-1201 demonstrated moderate correlation to both pathogens. Spatial analyses using kernel density estimation highlighted pathogen hotspots, aligning with varietal correlation trends to the two pathogens. This study provides insights for local growers, enabling more informed decisions for targeted disease management, particularly in optimizing variety selection and field practices to mitigate disease risks. These contributions support the sustainable transition to mechanical planting in sugarcane production while offering broader implications for managing soilborne diseases in other agricultural systems.

Sugar beet cultivation is significantly impacted by Heterodera schachtii, requiring effective and sustainable management practices to ensure crop productivity and soil quality. The efficacy of nine compost- and manure-based organic amendments was investigated for their potential to manage sugar beet cyst nematode (SBCN) populations and enhance sugar beet yield and quality. A multiphase research approach was employed, which included laboratory egg-hatching assays, greenhouse trials, and microplot experiments conducted under semi-field conditions. In laboratory egg-hatching experiments, poultry and swine manure consistently demonstrated significantly lower hatching rates compared with water and other treatments, suggesting their potent inhibitory effects on nematode reproduction. The suppressive effects of organic amendments were confirmed in greenhouse trials, where poultry manure and Layer Manure were shown to reduce cyst, egg, and juvenile populations at higher application rates. In microplot trials, these amendments maintained their effectiveness, achieving significant reductions in SBCN populations and enhancing sugar beet yield and Brix percentage, which indicated improved sugar content. Furthermore, organic amendments were found to stimulate beneficial soil nematode populations, with poultry manure increasing bacterivore and fungivore nematodes. The results underscored the potential of organic amendments, particularly poultry manure and Layer Manure, as alternatives to chemical nematicides. These amendments were demonstrated to offer a multifaceted approach to nematode management while improving crop productivity and soil quality.

Pear decline, caused by 'Candidatus Phytoplasma pyri', has emerged in Chilean pear orchards in recent years. While several Cacopsylla species are potential vectors of 'Ca. P. pyri', the disease's full epidemiological cycle remains uncertain. Cacopsylla bidens, present in Chilean orchards, has recently been reported as a vector. This study conducted year-long surveys in two commercial pear orchards across different Chilean regions, capturing C. bidens in zones with 'Ca. P. pyri'-infected pear trees. All developmental stages were collected, with peak abundances occurring in March and April. Outside the study zones, C. bidens were found in pine trees but not in adjacent cultivated areas. Two seasonal morphotypes, summer and winter forms, were identified. Molecular analysis detected 'Ca. P. pyri' in a high proportion of insects, with maximum infection rates in March and April. These findings advance our understanding of 'Ca. P. pyri' spatial and temporal dynamics and its potential role in 'Ca. P. pyri' spreading under Chilean field conditions.

Durian (Durio zibethinus) is an economically important tropical fruit endemic to Southeast Asia. Hainan is a new region for durian cultivation. Foliar diseases of durian were common at all durian orchards during field surveys carried out from October 2023 to October 2024 in Hainan, China. In this study, Fusarium species associated with durian foliar disease in Hainan (China) were studied based on multilocus phylogenetic analyses using translation elongation factor 1-α (tef1), partial RNA polymerase second largest subunit (RPB2), and calmodulin (CaM). Six Fusarium species including F. pernambucanum, F. sulawesiense, F. hainanense, F. irregulare, F. mangiferae and F. concentricum were identified. Pathogenicity tests showed that all six species were pathogenic to detached wounded and unwounded durian leaves except F. irregulare, which only induced visible symptoms on wounded durian leaves. The findings from this study expand the pathogenic fungal species on durian as this is the first report of these Fusarium spp. causing durian leaf disease worldwide.