Verbena × hybrida, also known as common garden verbena, has an important ornamental value for their wide range of flower colors and for attracting hummingbirds and butterflies. During the winter of 2021-2022 (December through February), more than 50% pot-grown verbena plants showed symptoms of powdery mildew in a field trial at a Syngenta Crop Protection research facility in Vero Beach, FL. Symptoms were characterized by the development of white, superficial mycelium on the adaxial side of leaves which, eventually, progressed to covering the whole surface of leaves, causing leaf discoloration, shoot distortion, and eventual plant death. Morphological characterization was carried out by observing powdery mildew colonies under the microscope. This powdery mildew forms dense patches of white mycelia, mainly on the adaxial leaf surfaces. The mycelium was a mat of hyphae with septa. Conidiophores were erect. The foot cells were straight, followed by one to three short cells bearing short chains of up to four conidia. The conidia were hyaline and ellipsoidal to doliiform in shape. Conidial germination is of the Eudoidium type. The conidia ranged from 25 to 32 μm long by 12 to 16 μm wide. The length to width ratio ranged between 1.6 and 2.3, but most were between 2.0 and 2.2. This is further verification of its identity as Golovinomyces ambrosiae and not Golovinomyces latisporus, because the length to width ratio of the latter species is consistently less than 2.0 (Qiu et al. 2020). Chasmothecia were not observed. Additionally, the ITS, GAPDH, and IGS regions were sequenced using the primer pairs ITS4/ITS5 (White et al. 1990), PMGAPDH1/PMGAPDH3R (Bradshaw et al. 2022a), and IGS-12a/NS1R (Carbone and Kohn 1999), respectively. The ITS region (GenBank number=PP924119) cannot distinguish between G. latisporus and G. ambrosiae and as such aligned 100% with both species on GenBank. However, the GAPDH and IGS regions can be used to distinguish G. ambrosiae from G. latisporus (Bradshaw et al. 2022b). The GAPDH (GenBank number=PP931995) and IGS (GenBank number=PP931996) regions aligned 100% with multiple G. ambrosiae sequences from GenBank including ON360708 and MK452567, respectively. The specimen was deposited in the Larry F. Grand Mycological Herbarium (NCSLG 24479). To confirm pathogenicity, \'Tuscany® Pink Picotee\' and \'Quartz XP Violet with Eye\' plugs were transplanted to 10-cm diameter pots containing ProMix potting mix and maintained in a greenhouse (± 26 °C). Inoculation was carried out 21 days after transplanting by touching infected leaves onto healthy leaves of 15 disease-free plants of each variety. Fifteen non-inoculated plants of each variety were used as controls. Typical powdery mildew symptoms and signs were first observed ten days after inoculation and the pathogen was more aggressive on \'Tuscany® Pink Picotee\'. Symptoms were not observed on non-inoculated plants. The fungus was morphologically identical to the one originally recovered from infected plants in the field. There have been many reports of Golovinomyces spp. affecting Verbena spp. worldwide; however, this is the first report of G. ambrosiae causing powdery mildew on Verbena × hybrida in the U.S. (Braun and Cook, 2012, Choi et al., 2021; Bradshaw et al. 2024). Powdery mildews reduce plant quality and decreases the aesthetics value of infected plants, causing great losses to the ornamental industry. Correct identification of the causal agent is crucial to recommend appropriate control methods, as they may differ according to the pathogen species.

Grapes, belonging to the genus Vitis, are one of the world\'s most economically valuable fruit crops, which are widely used as the source of wine, raisins, and juice. The genus Vitis contains about 60 species mainly distributed in Asia, Europe, and North America to northern South America (Wan et al. 2013). In May 2022, severe powdery mildew symptoms were found on wild Vitis bryoniifolia plants at Guizhou Normal University, Guiyang, China. The incidence observed was approximately 85% among 50 V. bryoniifolia plants. Infected leaves appear white powdery patches, eventually leading to chlorosis to necrosis. Mycelia occurred on adaxial and abaxial leaf surfaces, petioles and young shoots. Upon microscopic observation hyphae were hyaline and 3.5-6 μm wide. Hyphal appressoria were solitary and lobed to multilobed. Conidiophores were erect, straight to somewhat flexuous and 80-130 µm long (n = 30). Foot cells were subcylindrical to curved-sinuous at the base, followed by 2-4 cells. Conidia formed singly (occasionally 2-6 in a chain) and were ellipsoid to ovoid in shape with dimensions of 22.5-38 × 12-19.5 µm (n = 50). No fibrosin bodies were observed on conidia. Based on these morphological characteristics, the powdery mildew fungus strongly resembled Erysiphe necator (Braun and Takamasu 2000; Zheng et al. 1987) that has been shown to cause powdery mildew on Vitis (Gadoury et al. 2012; Gaforio et al. 2011; Qiu et al. 2015). To confirm the identification, the ribosomal DNA internal transcribed spacer (ITS) and the ribosomal large subunit (LSU) region were amplified and sequenced using the ITS1/ITS4 primer pair (White et al. 1990) and the NL1/NL4 primer pair (Ziemiecki et al. 1990), respectively. The spliced 1250-bp ITS-LSU sequence (GenBank accession no. PP188565) shared 99.84-100% identity with ITS-LSU sequences of E. necator (LC028995, LC028996, ON073862, LC777882, and OM033353). Based on the phylogenetic analysis of the combined ITS-LSU dataset of Erysiphe species (Takamasu et al. 2015), PP188565 was grouped in a clade with E. necator strains MUMH530, MUMHs141, and VPRI19719. To perform pathogenicity analysis, leaves of three healthy, potted 1-year-old V. bryoniifolia plants were inoculated by gently pressing with diseased leaves. Three non-inoculated healthy plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Powdery mildew symptoms, similar to field conditions were observed on inoculated plants 13 days after inoculation, whereas control plants remained symptomless. Fungus reisolated from inoculated V. bryoniifolia plants was morphologically identical to that on originally diseased plants, and the spliced ITS-LSU sequence of reisolated fungus shared 100% identity with PP188565, fulfilling Koch\'s postulates. Based on the morphological and molecular characterizations, the powdery mildew fungus was identified as E. necator. To our knowledge, this is the first report of powdery mildew caused by E. necator on V. bryoniifolia in China. This work further expands the host range of Erysiphe necator on Vitis species.

Bidens pilosa L., an annual herbaceous plant with a wide distribution, possesses novel medicinal properties. In January 2021, a powdery mildew disease outbreak was documented on B. pilosa plants located in the roadside areas in Shenzhen, Guangdong Province, China, with 60 to 80% disease incidence. Initial symptoms manifested as small, irregular white powdery patches, primarily on the adaxial surfaces of leaves. Subsequently, the colonies expanded, forming coalescent colonies that spread across the leaves, petioles, and stems, eventually leading to the distortion and senescence of leaves. Hyphae are hyaline, flexuous to straight, septate, with thin walls and a width ranging from 2 to 8 μm. Hyphal appressoria are nipple-shaped. Conidophores are erect or slightly flexuous, ranging from 80 to 150 µm in length and 12 to 18 µm in width (n = 30). Typically, these conidophores bear chains of 2 to 5 immature conidia, displaying a sinuate outline. Foot-cells, located at the base of conidophores, are cylindrical and erect, approximately 33 to 100 µm in length and 6 to 10 µm in width (n = 30). Conidia are hyaline, ellipsoid-ovoid to barrel-shaped, and lack fibrosin bodies. Primary conidia are ellipsoid-ovoid in shape, characterized by a rounded apex and a subtruncate base, 25 to 40 µm × 15 to 22 µm in width. Secondary conidia are barrel-shaped with truncate or subtruncate ends, 27 to 35 µm × 15 to 20 µm in width. Germ tubes exhibit a longitubus pattern and are prominently produced at the perihilar or apical region of the conidia. No chasmothecia were observed in the collected samples. In order to conduct a molecular-level identification, mycelium and conidia were collected from B. pilosa leaves. Genomic DNA was subsequently extracted from these samples. The internal transcribed spacer (ITS), intergenic spacer (IGS) and beta-tubulin (tub2) sequences were performed using primer pairs ITS1/ITS4, IGS-12a/NS1R, and tub2, respectively (Carbone and Kohn 1999; Scholin et al. 1994; White et al.,1990). A 568-bp ITS, a 366-bp IGS, and a 354-bp tub2 sequences (GenBank accession nos. OR647592, OR978282 and OR978283) were obtained. The ITS sequence exhibited over 99.6% similarity to Golovinomyces ambrosiae (MT929773) and G. cichoracearum (MH590731). The IGS sequence displayed 100% similarity to G. ambrosiae (MK383490) and G. ambrosiae (OK349420). The tub2 sequence displayed 100% similarity to G. ambrosiae (MW981257) and G. ambrosiae (MW981256). Phylogenetic analysis of IGS, ITS and tub2 also grouped obtained sequences within the G. ambrosiae complex. Based on the analysis of morphological characteristics and sequence identity, the pathogen was identified as G. ambrosiae. In order to satisfy Koch\'s postulates, an infected leaf was carefully pressed onto leaves of six healthy young B. pilosa plants, each grown in a separate pot. Additionally, a control group consisted of six non-inoculated plants. All plants were placed in a greenhouse: 25°C, 14/10-h light/dark photoperiod, and relative humidity 50%. After 10 days, the inoculated leaves exhibited powdery mildew colonies similar to those observed in the original infected plants. At 16 days, the inoculated leaves exhibited discoloration and premature leaf drop. The pathogenicity test was conducted twice. Microscopic observation and sequencing confirmed that isolated fungus was identical to the original pathogen. G. ambrosiae has previously been documented on B. pilosa in Fuzhou, Fujian Province, China (Mukhtar et al., 2022). However, to the best of our knowledge, this study represents the first report of powdery mildew caused by G. ambrosiae on B. pilosa in Shenzhen, Guangdong Province, China.

Plants form two immune systems, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI), to combat Blumeria graminis f. sp. tritici (Bgt) infection during the evolutionary process. In PTI, receptor-like kinases (RLKs) play important roles during pathogen infections. Based on our previous reports, there were 280 TaRLKs identified in early response to powdery mildew infection, which were divided into 34 subfamilies in this study. Differences in gene structures, cis-acting elements, and expression levels implied the function diversity of TaRLKs. TaRLK2.4, a member of LRK10L-RLKs subfamily, contained 665 amino acids, and located on the cell membrane. The main objective of this study was to investigate the role of the receptor-like kinase gene TaRLK2.4 in conferring powdery mildew resistance in wheat. Real-time quantitative PCR results indicated that TaRLK2.4 expressed during Bgt infection process, and exhibited a transgressive expression characteristic in disease resistance NILs (BJ-1). To elucidate the function of TaRLK2.4 during Bgt infection, the comprehensive analysis of virus induced gene silence and over-expression demonstrated that TaRLK2.4 promoted powdery mildew resistance positively. In summary, these results contribute to a deeper understanding of the complex and diverse biological functions of RLKs, and provide new genetic resources for wheat molecular breeding.

BACKGROUND: Powdery mildew (caused by Blumeria graminis f. sp. tritici (Bgt)) and leaf rust (caused by Puccinia triticina (Pt)) are prevalent diseases in wheat (Triticum aestivum L.) production. Thinopyrum ponticum (2n = 10x = 70, EeEeEbEbExExStStStSt) contains genes that confer high levels of resistance to these diseases.
RESULTS: An elite wheat-Th. ponticum disomic substitution line, DS5Ag(5D), was developed in the Bainong Aikang 58 (AK58) background. The line was assessed using genomic in situ hybridization (GISH), oligo-nucleotide probe multiplex (ONPM) fluorescence in situ hybridization (FISH), and molecular markers. Twenty eight chromosome-specific molecular markers were identified for the alien chromosome, and 22 of them were co-dominant. Additionally, SNP markers from the wheat 660 K SNP chip were utilized to confirm chromosome identification and they provide molecular tools for tagging the chromosome in concern. The substitution line demonstrated high levels of resistance to powdery mildew throughout its growth period and to leaf rust at the adult stage. Based on the resistance evaluation of five F5 populations between the substitution lines and wheat genotypes with different levels of sensitivity to the two diseases. Results showed that the resistance genes located on 5Ag confered stable resistance against both diseases across different backgrounds. Resistance spectrum analysis combined with diagnostic marker detection of known resistance genes of Th. ponticum revealed that 5Ag contained two novel genes, Pm5Ag and Lr5Ag, which conferred resistance to powdery mildew and leaf rust, respectively.
CONCLUSIONS: In this study, a novel wheat-Th. ponticum disomic substitution line DS5Ag(5D) was successfully developed. The Th. ponticum chromosome 5Ag contain new resistance genes for powdery mildew and leaf rust. Chromosomic-specific molecular markers were generated and they can be used to track the 5Ag chromosome fragments. Consequently, this study provides new elite germplasm resources and molecular markers to facilitate the breeding of wheat varieties that is resistant to powdery mildew and leaf rust.

BACKGROUND: Powdery mildews (Erysiphaceae, Ascomycota) are common plant disease agents and also cause stress for forest and fruit trees worldwide as well as in Taiwan. The powdery mildew Erysiphe bulbouncinula on Koelreuteria host trees was considered an endemic species in China. While in China the host was K. paniculata and only the teleomorph stage found, the anamorph and the teleomorph were both recorded for the host in Taiwan, K. henryi. We aimed to clarify the relationship of the powdery mildews recorded under E. bulbouncinula with an apparently disjunct distribution.
RESULTS: Specimens of powdery mildew on K. henryi from Taiwan were characterized based on the anamorph morphology and DNA sequences. They revealed a new record of Sawadaea koelreuteriae for this host species and Taiwan and a new species of Erysiphe, E. formosana, sister to E. bulbouncinula from China.
CONCLUSIONS: In Erysiphe on Koelreuteria hosts, speciation of plant parasitic fungi seems to be correlated with disjunct host and geographic distribution possibly shaped by extinction of potential host species which are known only as fossils. Two of the three extant East Asian species of Koelreuteria are now known as hosts of specific Erysiphe species. We may predict a further not yet discovered Erysiphe species on the third East Asian species, K. bipinnata, in South and Southwest China. In the speciation in Sawadaea, the extinction events in Koelreuteria can be excluded from being involved.

Phytoseiid predatory mites are one of the most important groups of biocontrol agents, commonly used in biological control. The ability to produce these predatory mites economically, at high density on cheap factitious food sources, is a major contributor to their success. Astigmatid mites are the most widely used factitious food for this purpose. In this study, we investigated the potential application of the leaf-dwelling astigmatid mite Czenspinskia transversostriata (Oudemans) (Acari: Winterschmidtiidae) as a prey mite in biological control. We tested whether C. transversostriata is a suitable food source for the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), both in the laboratory and on cucumber plants. Based on a reproduction trial, C. transversostriata proved to be an equally good food source compared to both pollen of Typha angustifolia L. (Poales: Typhaceae) and a frequently used prey mite Carpoglyphus lactis L. (Acari: Carpoglyphidae). In a pre-establishment trial on cucumber plants, populations of A. swirskii reached equally high densities when supplemented with C. transversostriata, compared to C. lactis. Lastly, we show that C. transversostriata is capable of feeding and reproducing on powdery mildew growing on cucumber plants, thereby slowing down the development of the pathogenic fungus. Results derived from this study show that C. transversostriata may have multiple potential applications in biological control programs.

Proquinazid is a new-generation fungicide authorized in the EU for combating powdery mildew infections in high-value crops. Due to the perishable nature of fruits, alternative analytical methods are necessary to protect consumer\'s health from pesticide residues. Currently, immunoassays are a well-established approach for rapidly monitoring chemical contaminants. However, the production of high-quality immunoreagents, such as antibodies and bioconjugates, is essential. This study presents a newly designed hapten that maintains the characteristic moieties of proquinazid unmodified. The linear aliphatic substituents of this molecule were used to introduce the spacer arm. A three-step synthesis strategy was optimized to prepare a hapten that displays the entire 6-iodoquinazolin-4(3H)-one moiety with excellent yields. The N-hydroxysuccimidyl ester of the hapten was activated and purified to prepare a protein conjugate with high hapten density, which was used as an immunogen. Antibodies were raised and competitive enzyme-linked immunosorbent assays were developed. To enhance the assay\'s sensitivity, two additional heterologous haptens were prepared by modifying the halogenated substituent at C-6. The optimized assays demonstrated low limits of detection in buffer, approximately 0.05 μg/L. When applied to the analysis of proquinazid in QuEChERS extracts of strawberry samples, the immunoassays produced precise and accurate results, particularly in the 10-1000 μg/kg range.

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) seriously threatens wheat production worldwide. It is imperative to identify novel resistance genes from wheat and its wild relatives to control this disease by host resistance. Dasypyrum villosum (2n = 2x = 14, VV) is a relative of wheat and harbors novel genes for resistance against multi-fungal diseases. In the present study, we developed a complete set of new wheat-D. villosum disomic introgression lines through genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH) and molecular markers analysis, including four disomic substitution lines (2n=42) containing respectively chromosomes 1V#6, 2V#6, 3V#6, and 6V#6, and four disomic addition lines (2n=44) containing respectively chromosomes 4V#6, 5V#6, 6V#6 and 7V#6. These lines were subsequently evaluated for their responses to a mixture Bgt isolates at both seedling and adult-plant stages. Results showed that introgression lines containing chromosomes 3V#6, 5V#6, and 6V#6 exhibited resistance at both seedling and adult-plant stages, whereas the chromosome 4V#6 disomic addition line NAU4V#6-1 exhibited a high level of adult plant resistance to powdery mildew. Moreover, two translocation lines were further developed from the progenies of NAU4V#6-1 and the Ph1b mutation line NAU0686-ph1b. They were T4DL·4V#6S whole-arm translocation line NAU4V#6-2 and T7DL·7DS-4V#6L small-fragment translocation line NAU4V#6-3. Powdery mildew tests of the two lines confirmed the presence of an adult-plant powdery mildew resistance gene, Pm4VL, located on the terminal segment of chromosome arm 4V#6L (FL 0.6-1.00). In comparison with the recurrent parent NAU0686 plants, the T7DL·7DS-4V#6L translocation line NAU4V#6-3 showed no obvious negative effect on yield-related traits, providing a new germplasm in breeding for resistance.

Wheat powdery mildew is an important fungal disease that seriously jeopardizes wheat production, which poses a serious threat to food safety. SJ106 is a high-quality, disease-resistant spring wheat variety; this disease resistance is derived from Wheat-wheatgrass 33. In this study, the powdery mildew resistance genes in SJ106 were located at the end of chromosome 6DS, a new disease resistance locus tentatively named PmSJ106 locus. This interval was composed of a nucleotide-binding leucine-rich repeat (NLR) gene cluster containing 19 NLR genes. Five NLRs were tandem duplicated genes, and one of them (a coiled coil domain-nucleotide binding site-leucine-rich repeat (CC-NBS-LRR; CNL) type gene, TaRGA5-like) expressed 69-836-fold in SJ106 compared with the susceptible control. The genome DNA and cDNA sequences of TaRGA5-like were amplified from SJ106, which contain several nucleotide polymorphisms in LRR regions compared with susceptible individuals and Chinese Spring. Overexpression of TaRGA5-like significantly increased resistance to powdery mildew in susceptible receptor wheat Jinqiang5. However, Virus induced gene silence (VIGS) of TaRGA5-like resulted in only a small decrease of SJ106 in disease resistance, presumably compensated by other NLR duplicated genes. The results suggested that TaRGA5-like confers partial powdery mildew resistance in SJ106. As a member of the PmSJ106 locus, TaRGA5-like functioned together with other NLR duplicated genes to improve wheat resistance to powdery mildew. Wheat variety SJ106 would become a novel and potentially valuable germplasm for powdery mildew resistance.