【Objective】The Yuelu melon is a premium melon variety. After being introduced and cultivated in limited quantities in Hainan, Fujian, and Guangdong provinces, it has demonstrated significant economic value. In 2025, a Fusarium fruit rot disease affecting Yuelu melon was discovered in Guangzhou, with an incidence rate ranging from 5% to 8%. The disease altered the aroma, flavor, and quality of the melon, thereby diminishing its nutritional and commercial value. During cultivation, symptoms were observed exclusively within the fruit, with no visible external manifestations, which significantly increased the challenges associated with disease detection and management. The study aimed to identi fy the pathogen and elucidate its suitable growth conditions, including temperature, pH, light, as well as carbon and nitrogen sources. In addition, the toxicity of various fungicides to the pathogen was evaluated to assess their efficacy, thereby providing insights for effective disease control.【Methods】From April to June 2025, a survey was conducted to assess the incidence and severity of fruit rot in Yuelu melon at the Xiangfeng Special Fruit Industrial Park in Zengcheng District, Guangzhou City. Field symptoms were documented photographically. Diseased tissue samples were collected and, following surface disinfection, they were cultured on potato dextrose agar (PDA) at 26℃ for 3 days using the tissue isolation method. Mycelia from the margins of developing colonies were then transferred to PDA plates. Purified strains were obtained through single-spore isolation and stored at 4℃for subsequent use. Pathogenicity was confirmed through two inoculation methods. The first involved mycelia inoculation: The mycelia surfaces of the tested strains were adhered to the puncture site of the melon fruits, with blank agar discs used as controls. The second method employed spore suspension inoculation: 100 µL of spore suspension (5 × 106 spores · mL-1) was injected into the fruit from the tail end. All treated fruits were incubated at 26℃. Once softening or clear symptoms developed, the pathogens were isolated and purified again for verification in accordance with Koch's postulates. The strains were inoculated on potato dextrose agar (PDA) , synthetic nutrient-poor agar (SNA) , and carnation leaf agar (CLA) in the dark at 26℃for 10 days. Mycelia, conidiophores, conidia attachment patterns, conidia and chlamydospores were observed under an optical microscope, and the size of conidiophores and conidia were measured (n=80) . Genomic DNA was extracted from the tested strains, and the calmodulin (CAM) , translation elongation factor 1-alpha (EF1-α) , and the second largest subunit of RNA polymeraseⅡ (RPB2) gene regions were amplified via PCR. The products were sequenced by Shanghai Sangon Biotech Co., Ltd. The resulting sequences were submitted to the NCBI database to obtain accession numbers. Concurrently, BLAST analyses were performed on NCBI to identify and retrieve sequences of closely related species from GenBank. Sequence alignment was conducted using Mega 7.0 software, followed by manual splicing of the aligned datasets. A phylogenetic tree was constructed using the concatenated sequences of CAM, EF1-α, and RPB2 through the neighbor-joining method implemented in MEGA 7.0 to confirm species identification. Furthermore, the tested strains were cultured in an incubator under varying growth conditions, including temperature, pH, light intensity, carbon sources, and nitrogen sources, to determine the optimal culture environment for mycelia growth and spore production. Subsequently, to evaluate the sensitivity of the pathogen to various fungicides, eight commercial fungicides were tested. Mycelia discs were inoculated onto potato dextrose agar (PDA) plates supplemented with each fungicide at designated concentrations and incubated at 26℃. Colony diameters were measured after 5 days of incubation.【Results】The external appearance of diseased fruits showed no visible symptoms in the field. However, their tail ends felt soft to the press, and internal examination revealed brown, watersoaked rot, occasionally accompanied by a thin layer of white mold on the diseased areas. A total of 27 Fusarium spp. isolates with similar morphological characteristics were obtained. Pathogenicity tests revealed that artificial inoculation with strains YLG-4, YLG-13, and YLG-21 produced symptoms consistent with those observed under field conditions. On PDA medium, the colonies were initially white and later turned light yellow with cotton-like and abundant aerial mycelia. Conidiogenous cells were phialidic, 2.72 to 49.69 µm (n=80) on SNA medium and 3.63 to 52.65 µm (n=80) on CLA medium. Macroconidia were falcate, slightly curved, tapering apically with 1 to 5 septa, (17.45-46.78) µm× (2.62-4.93) µm (n=80) on SNA medium, (15.84-44.27) µm× (2.71-4.95) µm (n=80) on CLA medium, borne false heads from monophialides and polyphialides. Chlamydospores were spherical on both media. The CAM, EF1-α, and RPB2 gene fragments of strains YLG-4, YLG-13, and YLG-21 were amplified and sequenced, producing fragments approximately 550 bp, 840 bp, and 600 bp in length, respectively. BLAST analysis against the GenBank database showed that the nucleotide sequences of the CAM, EF1-α and RPB2 regions from these strains shared 99.29% to 100% identity with corresponding sequences of Fusarium pernambucanum strains CBS 791.70, CBS 132194, CBS 132894, and CBS 133024. A phylogenetic tree was constructed based on the concatenated sequences of CAM, EF1-α, and RPB2 using the neighborjoining method, which demonstrated that YLG-4, YLG-13, and YLG-21 form a cluster with F. pernambucanum. Integrating morphological characteristics and molecular evidence, strains YLG-4, YLG-13, and YLG-21 were identified as F. pernambucanum. The optimal temperature range for mycelia growth of strain YLG-13 was 24-30℃, with the most rapid colony expansion observed at 26-28℃and the highest conidia production occurring at 30℃. Mycelia growth was favorable within a pH range of 5-10, with an optimum at pH 7-9. Light promoted mycelia development. Carbon sources such as glucose and soluble starch, as well as organic nitrogen sources including tryptone, beef extract powder, and yeast extract, were found to enhance both mycelia growth and spore production in YLG-13. Among the eight fungicides tested, all exhibited varying degrees of inhibition on mycelia growth. Fludioxonil showed the strongest inhibitory effect, with an EC50 value of 0.014 7 mg · L-1, followed by prochloraz, which had an EC50 value of 0.637 3 mg · L-1.【Conclusion】In this study, the causal agent of fruit rot in Yuelu melon was identified as Fusarium pernambucanum through pathogenicity tests, morphological characterization, and multi-locus phylogenetic analysis based on the CAM, EF1-α, and RPB2 gene regions. The pathogen showed adaptation to relatively high temperatures and neutral to alkaline conditions. Fungicide assays revealed that fludioxonil and prochloraz exhibited the strongest antifungal activity, suggesting their potential as effective agents for disease control. These findings offer a theoretical foundation for diagnosing and managing this disease.

Bougainvillea is a widely cultivated ornamental in subtropical and tropical regions. In November 2025, Bougainvillea buttiana in Zhanjiang City, Guangdong Province, China (110°18′36″E, 21°9′36″N), exhibited symptoms including flower abortion, phyllody, and proliferation of axillary shoots with shortened internodes (Fig. S1) and the disease incidence ranged from 10% to 15%. These symptoms differed from those associated with phytoplasma infection in bougainvillea in Brazil, India and Cuba (Silva et al., 2014; Gopala and Rao, 2018; Wei W et al., 2020). Total DNA was extracted from fresh leaves of 9 symptomatic and 3 asymptomatic samples. Nested PCR was conducted with primers P1/P7 followed by R16F2n/R16R2 (Gundersen and Lee, 1996), and secYwbF1/secYwbR1 followed by secYwbF2/secYwbR2 (Wang et al. 2025) specific for phytoplasma 16S rRNA and secY gene fragments, respectively. The two gene target fragments of phytoplasma were obtained exclusively from symptomatic samples and asymptomatic samples tested negative. The PCR products were sequenced and all the gene sequences were identical (GenBank accession: 16S rRNA PX848724; secY PX853972). BLASTn search based on 16S rRNA genes in NCBI Genbank database indicated that our sequence had 99.92% identity with 16SrII-A strains Peanut witches'-broom phytoplasma NTU2011 (NZ_AMWZ01000008.1, 1238/1239 bp) and 'Vigna radiata' phytoplasma BAWM-TWN (NZ_JAOSIS010000033.1, 1238/1239 bp). Meanwhile, the secY gene sequence fragment showed 100% identity with that of phytoplasma NTU2011 (NZ_AMWZ01000013.1) and phytoplasma BAWM-TWN (NZ_JAOSIS010000010.1). Analysis conducted using the iPhyClassifier (Zhao et al., 2009) indicated that BWBZJ2025 belongs to the 16SrII-A subgroup, with a similarity coefficient of 1.00 to the subgroup reference strain L33765 (Fig. S2). Therefore, the strain was designated as strain BWBZJ2025. Phylogenetic analysis based on the concatenated 16S rRNA and secY sequences (Fig. S3) revealed that BWBZJ2025 clustered within the same subclade as the 16SrII-A reference strain PnWB, and ‘Ca. Phytoplasma australasiaticum’ related strain NCHU2014 (16SrII-A) and BAWM-TWN (16SrII-V). Taken together, these results consistently identified strain BWBZJ2025 as a member of the 16SrII-A subgroup, related to ‘Ca. Phytoplasma australasiaticum’. To our knowledge, this study is the first report of a phytoplasma associated with bougainvillea in China. Further research is needed to identify potential vectors for epidemiological monitoring.

Soft rot Pectobacteriaceae (SRP) are destructive pathogens of potato crops, posing a global threat to food security. SRP populations exhibit significant genetic heterogeneity, with the prevalence of potato-infecting species shifting over time. In this study, we identified Pectobacterium aroidearum as a novel agent causing severe tuber soft rot in winter-planted potatoes in Guangdong Province, where it co-occurred with P. brasiliense and P. carotovorum. However, the pathogenic potential of P. aroidearum has been largely uncharacterized. Here, comparative virulence assays demonstrated that P. aroidearum is more aggressive than its counterparts. This heightened virulence was linked to enhanced pathogenic traits, including plant cell wall-degrading enzymes (PCWDEs) production, swimming motility, exopolysaccharide (EPS) production, and air-liquid (AL) biofilm formation. Genomic analysis revealed that while core virulence genes are conserved, a type 1 fimbriae-encoding fim cluster is unique to P. aroidearum. Deletion of fimA, fimC, fimD, and fimH impaired bacterial adhesion, EPS production, AL biofilm formation, and full virulence, functionally characterizing this distinctive factor. Genes within the bacterial cellulose synthesis operon were significantly down-regulated across fim mutants. Accordingly, the mutant colonies showed a marked decrease in calcofluor binding compared with the wild-type strain. Genes with significant up-regulation in the mutants were primarily involved in responses to extracellular stimuli. These findings indicate that the fim cluster underpins the threat posed by this emerging pathogen, which warrants increased attention in disease management. The considerable genetic diversity and frequent gene flow among P. aroidearum isolates from various hosts further highlight its epidemiological risk.

[Objective]Fusarium wilt is prevalent in Chinese water chestnut producing regions of Guangdong Province,severely impacting crop yields.Identifying the pathogen and analyzing its biological characteristics is of significant importance for the effective management of the disease.[Method]Diseased samples were collected from Lechang,Shaoguan,between 2022 and 2024.Strains were isolated using the tissue isolation method.Their taxonomic status was determined based on pathogenicity,morphological characteristics and molecular biological features.The effects of temperature,pH,light,carbon and nitrogen source on the pathogens were measured by mycelium growth method.[Result]34 Fusarium spp.isolates with similar morphological characteristics were obtained.The colony was white on PDA medium.Conidiogenous cells were phialidic,8.46～55.65 μm in length.Microconidia were abundant,oval or spindle-shaped,4.22～12.65 μm × 2.24～3.82 μm,and borne false heads from phialides.Macroconidia were falcate,slightly curved,tapering apically with 3 to 5 septa,and 18.24～36.40 μm × 2.92～4.50 μm.Chlamydospores were spherical,7.85～12.32 μm in diameter.Pot experiments confirmed their pathogenicity to Chinese water chestnut.The phylogenetic trees constructed using combined sequences of the EF-1α,RPB2 and TUB revealed the pathogens clustered with Fusarium commune strains and distinctly differentiated from F.oxysporum.Specific primers amplification further confirmed the pathogens belonged to F.commune.The suitable temperature for mycelium growth of F.commune was 26～30℃,and the suitable pH was 7～8.Carbon source maltose,organic nitrogen source beef extract powder,yeast extract and tryptone were beneficial to mycelium growth,colony diameters reached approximately 60 mm after 120 h incubation at 28℃ in dark.[Conclusion]The study identified F.commune as the causative agent of Chinese water chestnut wilt in Guangdong,providing critical insights for disease control strategies.

The fall armyworm (FAW), Spodoptera frugiperda, is a serious pest that threatens a range of important crops worldwide. It originated in America and rapidly dispersed throughout Africa and Asia in 2018. There are two subtypes, corn-strain (C-strain) and rice-strain (R-strain), that have different host plant preferences, and the individuals damaging maize in China were identified as C-strain. In the present study, we found FAW individuals damaging rice plants in the field of Guangdong Province, China. FAW larvae and male adults were collected, and the majority of FAWs were characterized as CO I R-strain Tpi C-strain, which is similar to the FAWs damaging maize in China. The FAW adults preferred laying eggs on maize plants more than on rice plants. Compared to those that were fed maize leaves, the FAW larvae were unable to survive when fed 4-week-old rice plants, whereas they could complete their life cycle on 2-week-old rice plants, for which the total survival rate was 8%. The pre-adult- and pupal-stage durations were prolonged, and the fecundity of adult females decreased. Thus, the FAWs found in paddy fields showed better fitness on maize than on rice in the laboratory. Owing to their low survival rate on rice plants, they were unlikely to damage paddy fields in large areas, but populations of FAWs in paddy fields should be monitored.

Transplant treatment with chlorantraniliprole (CAP) is a proactive approach to protect transplanted plants from pests during early establishment and has been comprehensively applied in tobacco fields in Guangdong Province, China. However, it is not known whether the high dose of CAP in transplant treatments has lethal or sublethal effects on the generalist predator Rhynocoris fuscipes Fabricius (Hemiptera: Reduviidae). To address this concern, the mortalities of R. fuscipes were assessed when 2nd instar larvae of R. fuscipes were in direct contact with or consuming CAP and when their eggs were exposed to CAP. Furthermore, 2nd instar nymphs R. fuscipes were long-term exposed to CAP until they reached adulthood, and their life table parameters were determined. After exposure to CAP, the activity of detoxification enzymes (P450, CaeE and GST) and the functional respond of R. fuscipes to their preys Agrotis ipsilon larvae were determined. In this study, CAP at all concentrations did not significantly increase the mortality of 2nd instar of R. fuscipes nymphs in comparison with the control. The detoxification enzyme (P450, CarE and GST) activities and the number of A. ipsilon larvae consumed by R. fuscipes in the transplant treatment were not affected by CAP after 3-d or long-term exposure. These results indicated that CAP was harmless to R. fuscipes according to IOBC protocols. However, during the treatment of 2nd instar nymphs with a label rate of 15 g AI/ha and a 5× label rate of 75 g AI/ha, CAP significantly prolonged the pre-adult and pre-oviposition periods, and treated adults had lower oviposition. Attention should be given to the time interval between transplant treatment and the release of this biocontrol agent into the field to minimize the impact of CAP on the predator R. fuscipes.

Potato (Solanum tuberosum L.) is a globally important staple crop, and China has contributed more than 20% of the world's production. In Guangdong Province, potato has become one of the most important winter crops, increased the farmer income. However, the potato were seriously affected by soft rot disease caused by Pectobacterium spp. in the past decade. In February 2024, typical symptoms of potato soft rot were observed on the plants of cultivar "Daxiyang" in Enping City, Guangdong Province, where the disease incidences ranged 3%-5% in the investigated fields. The stems adjacent to the tubes showed typical inky black symptoms, and the plants appeared yellow. The interior of the tubes appeared water-soaked and had developed to overall decay, with an evident smell. Eleven symptomatic plants were collected and used to isolate the causal agents. Pieces of tube tissue (about 5×5 mm) were removed between the rot-symptomatic and non-symptomatic margins, and surface sterilized using 75% ethanol for 30 s and 2% NaClO for 1 min. The pieces were rinsed in sterile water for three times, and then plated on Luria-Bertani (LB) medium agar for 36 h at 30°C. The produced colonies were selected for hypersensitive test on tobacco, and the colonies with a positive reaction were subcultured three times. Two representative strains, EP51-2 and EP51-3, were processed for gene sequencing, including house-keeping genes, danX, leuS, and recA (Portier et al. 2019). The gene sequences (GenBank accessions no. PP870934 to PP870939) of these two representative strains were matched with Pectobacterium aroidearum strain NCPPB 929 (CP166097.1) with identities ranging from 97.15 to 100% and the coverage of 100%. The sequences of three genes were concatenated and used for phylogenetic analyses, along with representative strains from 19 other Pectobacterium species. Phylogenetic analyses supported that EP51-2 and EP51-3 were grouped into P. aroidearum with the representative strains. Koch's postulates were applied to determine the pathogenicity of P. aroidearum strain EP51-2. According to the external inoculation method on potato stems (Czajkowski et al. 2010), each of six pots of healthy potato plants was inoculated at the basal stem with 100 µl of bacterial suspension (108 CFU/ml), while six pots inoculated with LB served as controls. The plants were then kept at 30°C and maintained at 95% humidity. After 2 days, all six plants inoculated with the bacteria exhibited typical symptoms on the stems, which progressed to the collapse of the whole plant; the controls remained symptom-free during the observation. Single colonies reisolated from the symptomatic stem of the inoculated plants were confirmed using PCR and sequencing with recA primers as described above, and the causal agent was identified as P. aroidearum strains, fulfilling Koch's postulates. P. aroidearum has been reported on Chinese cabbage (Xie et al. 2018) and leaf mustard (Chu et al. 2024) in China, as well as on crops in the family Araceae, such as konjac (Wei et al. 2021), taro (Zhou et al. 2022), and Pinellia ternata (Du et al. 2024). To our knowledge, this is the first report of P. aroidearum causing potato soft rot in China. This pathogen has been prevalent in the taro fields in Guangdong Province and has caused severe losses. This report highlights an expansion of the host range for this pathogen. Attention should be focused on this newly emerging pathogen affecting potatoes, and immediate measures should be implemented to control its spread.

Bacterial soft rot caused by coinfection with Dickeya spp. and Pectobacterium spp. in hosts can cause successive changes in fields, and it is difficult to prevent the spread of and control the infection. Pectobacterium spp. are prevalent in the growing areas of tuberous crops, including taro and potato. Recently, Dickeya fangzhongdai has emerged as a virulent pathogen in taro. To determine the prevalence status of the causal agents and evaluate the potential spreading risks of D. fangzhongdai, screening and taxonomic classification were performed on phytopathogenic bacteria collected from different taro-growing areas in Guangdong Province, China, and biological and genomic characteristics were further compared among typical strains from all defined species. The causative agents were verified to be phytobacterial strains of D. fangzhongdai, Pectobacterium aroidearum and Pectobacterium colocasium. P. aroidearum and P. colocasium were found to form a complex preferring Araceae plants and show intensive genomic differentiation, indicating their ancestor had adapted to taro a long time prior. Compared with Pectobacterium spp., D. fangzhongdai was more virulent to taro corms under conditions of exogenous infection and more adaptable at elevated temperatures. D. fangzhongdai strains isolated from taro possessed genomic components of additional T4SSs, which were accompanied by additional copies of the hcp-vgrG genes of the T6SS, and these contributed to the expansion of their genomes. More gene clusters encoding secondary metabolites were found within the D. fangzhongdai strains than within the Pectobacterium complex; interestingly, distinct gene clusters encoding zeamine and arylpolyene were both most similar to those in D. solani that caused potato soft rot. These comparisons provided genomic evidences for that the newly emerging pathogen was potentially equipped to compete with other pathogens. Diagnostic qPCR verified that D. fangzhongdai was prevalent in most of the taro-growing areas and coexisted with the Pectobacterium complex, while the plants enriching D. fangzhongdai were frequently symptomatic at developing corms and adjacent pseudostems and caused severe symptoms. Thus, the emerging need for intensive monitoring on D. fangzhongdai to prevent it from spreading to other taro-growing areas and to other tuberous crops like potato; the adjustment of control strategies based on different pathopoiesis characteristics is recommended.

为明确广东韶关烟草镰刀菌根腐病菌种类及致病力,在珠玑、始兴、南雄和乌茎采集根腐病样本,用组织分离法分离病原菌,盆栽接种带菌麦粒测定其致病性,观察菌株形态,基于EF-1α和β-Tub基因序列构建发育树鉴定病原菌.结果表明,获得45株镰刀菌,通过形态特征和分子技术鉴定为茄病镰刀菌Fusarium solani、共享镰刀菌F.commune、藤仓镰刀菌F.fujikuroi和尖孢镰刀菌F.oxysporum,分别占比 42.22%,26.67%、20.00%和 11.11%,对烟草均有致病性,强弱排列为F.commune≈F.fujikuroi＞F.oxysporum＞F.solani.本研究可为广东韶关地区烟草镰刀菌根腐病的防治提供依据.

From March to June 2022, Fusarium tobacco root rot broke out in Shaoguan Guangdong Province, China, affecting approximately 15% of tobacco production fields, with an incidence of 24% to 66%. In the early stage, the lower leaves showed chlorosis, and the roots became black. In the later stage, the leaves became browned and withered, the root cortices were broken and shed, and only a small number of roots were left. Eventually, the entire plant died. Six diseased plant samples (cv. yueyan 97) from Shaoguan (113.8°E, 24.8°N) were collected as test materials. The diseased root tissues (4×4 mm) were surface-sterilized using 75% ethanol for 30 s and 2% NaOCl for 10 min, rinsed 3 times with sterile water and incubated for 4 days on potato dextrose agar (PDA) medium at 25 °C. Fungal colonies were subcultured on fresh PDA, grown for the next 5 d and purified by single-spore separation. Eleven isolates with similar morphological characteristics were obtained. Their colonies were white and fluffy, and the bottoms of the culture plates were pale pink after 5 days of incubation. The macroconidia were slender, slightly curved and measured 18.54~45.85 µm×2.35~3.84 µm (n=50), with 3 to 5 septa. The microconidia were oval or spindle shaped, with one to two cells, and measured 5.56~16.76 µm×2.32~3.86 µm (n=50). Chlamydospores were absent. Such characteristics are typical of the genus Fusarium (Booth C, 1971). The SGF36 isolate was chosen for further molecular analysis. The TEF-1α and β-tubulin genes (Pedrozo et al.2015) were amplified. Based on a phylogenetic tree (neighbor-joining method and 1,000 bootstrap values) obtained using multiplex alignments of concatenations of these two genes from 18 Fusarium species, SGF36 was grouped into a clade with Fusarium fujikuroi strain 12-1 (MK443268.1/MK443267.1) and F. fujikuroi isolate BJ-1 (MH263736.1/MH263737.1). To further identity the isolate, five additional gene sequences (rDNA-ITS (OP862807.1), RPB2, histone 3, calmodulin, and mitochondrial small subunit) (Pedrozo et al.2015), were subjected to BLAST searches in GenBank, and the results indicated that they were most similar to F. fujikuroi sequences, with sequence identities greater than 99%. The phylogenetic tree obtained using six genes except mitochondrial small subunit gene showed that SGF36 was grouped together with four F. fujikuroi strains to form a single clade. Pathogenicity was determined by the inoculation of wheat grains with fungi in potted tobacco plants. The SGF36 isolate was inoculated onto sterilized wheat grains, which were then incubated at 25 °C for 7 d. Thirty wheat grains with fungi were added to 200 g of sterilized soil, which was then mixed well and placed into pots. One six-leaf-stage tobacco seedling (cv. yueyan 97) was planted in each pot. A total of 20 tobacco seedlings were treated. Another 20 control seedlings were treated with wheat grains without fungi. All seedlings were placed in a greenhouse at 25 °C with 90% relative humidity. After 5 d, the leaves of all inoculated seedlings showed chlorosis, and the roots became discolored. No symptoms were observed in the controls. The fungus was reisolated from symptomatic roots and confirmed to be F. fujikuroi based on the TEF-1α gene sequence. No F. fujikuroi isolates were recovered from control plants. F. fujikuroi was previously reported to be associated with rice bakanae disease (Ram et al., 2018), soybean root rot (Zhao et al., 2020) and cotton seedling wilt (Zhu et al., 2020). To our knowledge, this is the first report of F. fujikuroi causing root wilt on tobacco in China. The identification of the pathogen may help to establish appropriate measures for controlling this disease.

Petunia hybrida is commonly cultivated for ornamental use in urban parks greening and street embellishment in China. In March 2022, 60% of P. hybrida plants cv. Wave Purple (n≈1800) from an ornamental plant nursery under natural conditions in Tianhe district (N 113°21'21", E 23°9'3.5"), Guangzhou, Guangdong Province, China, were affected with soft rot disease. The distribution of the disease was generally uniform. Infected plants initially exhibit small water-soaked lesions at the base of the stem, which then extended to the leaves. Eventually the diseased plant collapsed and died. Nine diseased plants were collected, and affected tissues cut into small fragments (5 × 5 mm), which were disinfested in 75% ethanol (30 s) and 2% sodium hypochlorite (60 s), followed by three rinses with sterile distilled water. The sterilized sections were macerated in 200 μl sterile water, and streaked on Luria-Bertani (LB) agar medium and incubated at 28°C for 48 h. Single colonies were restreaked three times to obtain purified isolation. Sixteen bacterial strains with similar morphology were isolated, and their colonies were yellowish white, round, and convex with smooth surfaces on LB agar plate. The representative strain BDQ1 was selected for further analyses and the 16S rDNA gene (GenBank Accession ON982467) were amplified using primer pair 27F/1492R, revealed above 99% sequence identity with some Pectobacterium brasiliense isolates (GenBank Accession Nos. CP046380(1421/1422), MN393966(1419/1422), and CP020350(1419/1422)) using BLASTn. A multilocus phylogenetic analysis by neighbor-joining method (1,000 bootstrap values) based on six housekeeping gene sequences of gyrA (GenBank Accession No. ON995454), icdA (ON995455), mdh (ON995456), mtlD (ON995457), proA (ON995458), and rpoS genes (ON995459) (Ma et al. 2007; Waleron et al., 2008). The results of phylogenetic analysis showed BDQ1 strain belong to the P. brasiliense clade. Pathogenicity tests were performed on ten healthy P. hybrida cv. Wave Purple plants by injecting 10 µl of bacterial suspensions of BDQ1 (108 CFU/ml) into the stems; another 10 healthy control plants were injected with 10 µl of sterile water. All plants were grown at 25-30°C and 60% humidity in natural light/dark cycle. After 3 d, all inoculated plants showed soft rot symptoms resembling to those observed in the nursery, while control plants remained healthy. Bacteria were successfully reisolated from the symptomatic tissues and identified to be P. brasiliense by PCR mentioned above. P. brasiliense is considered a very aggressive pathogen, which has been reported in Eurasia and Africa (Oulghazi et al. 2021). To our knowledge, this is the first report of P. brasiliense causing bacterial soft rot on P. hybrida in China. This pathogen may pose threat to P. hybrida production in area with warmand humid climate in China. The current study expands the known host range of P. brasiliense and helped raise attention on controlling pathogen spread.

The black cutworm, Agrotis ipsilon (Lepidoptera: Noctuidae), is a critical soil pest of tobacco (Nicotiana tabacum) in the early season. Although numerous studies have shown that chemical insecticides through soil-surface or foliar application provide adequate management of black cutworms, relatively little is known about the efficacy of transplant applications. Here, we evaluated the efficacy of insecticide transplant treatment against black cutworm in tobacco in pots and in the field. We also investigated the impact of chlorantraniliprole on tobacco, including dynamic residue concentrations in tobacco and variation in agronomic traits of treated seedlings. Bioassays showed that LC50 of chlorantraniliprole was 0.28 mg AI/L against black cutworm. In a potted plant experiment, chlorantraniliprole treatment at 15, 30, and 75 g AI/ha reduced the number of damaged tobacco seedlings and increased the mortality of black cutworm within 30 d. When tobacco seedlings were treated with chlorantraniliprole 24 h before transplanting in the field, the control efficacy of chlorantraniliprole treatment at 75 g AI/ha was 45.5%-59.6% at 20 d after treatment. The concentration of chlorantraniliprole in tobacco seedlings treated with 15 g AI/ha was found to degrade to 0.033 mg/kg after 28 d (t1/2 = 2.54 d), which affected the height of seedlings but not the number of leaves after 28 d. Chlorantraniliprole treatment of seedlings during transplanting is a practical and effective strategy to manage black cutworm in tobacco.

旨在建立一种快速、可靠的斜纹夜蛾成虫带核型多角体病毒(Spodoptera litura Nucleopolyhedrovirus,SpltNPV)的分子检测方法,以克服目前常规PCR技术很难检测到斜纹夜蛾成虫带病毒的缺陷.以SpltNPV的蜕皮甾体尿苷二磷酸葡萄糖转移酶(ecdysteroid UDP-glucosyltransferase,egt)基因为检测对象,基于该基因序列设计了巢式PCR引物,其中一对外侧引物egt-F/R和一对内侧引物egt1-F/R,并研究斜纹夜蛾成虫带毒的巢式PCR检测可靠性.结果表明:基于egt基因的巢式PCR方法可以特异性扩增SpltNPV的DNA,引物egt-F/R的扩增检测最低限为1 0-7 μg/μL;且基于引物egt-F/R的两轮普通PCR无法检测出成虫带毒,而采用巢式PCR方法可有效扩增出目的egt片段,巢式PCR检测方法的灵敏度比两轮普通PCR检测方法提高2个数量级.因此,本研究成功建立了基于SpltNPV的egt基因的巢式PCR检测技术,该方法为斜纹夜蛾成虫带毒、传毒等流行病学研究提供了可靠的技术支撑.

提高农药沉积率是实现农药减量增效的有效途径,在农药药液中添加喷雾助剂对于提高农药沉积率具有增效作用.本研究采用诱惑红示踪法,在氯虫苯甲酰胺药液中添加不同浓度的草本精油助剂,在水稻破口期进行田间小区实验测定农药沉积率,并且测定各处理药液的表面张力和黏度.研究结果表明:药液中添加助剂后,CK(0倍)、3000倍、1500倍和750倍处理后的平均农药沉积率分别为36.42％、46.30％、52.62％和50.25％;差异显著性分析发现添加助剂后,药液在水稻植株上的沉积率均显著大于对照处理(P<0.05);药液表面张力和黏度测定结果表明,添加助剂的药液表面张力和黏度均显著低于不添加助剂的药液(P<0.05).研究结果说明农药药液中添加助剂改变了其表面张力和黏度值大小,有利于药液在植株上粘附沉着,从而提高了农药沉积率.

评估不同植保器械的农药喷施效率为水稻上农药减量控害和统防统治工作提供理论技术支撑.本研究参照NY/T 2677—2015《农药沉积率测定方法》,在广东省南雄市全安镇晚造直播水稻田开展农药喷施试验,分析了分别采用手动喷雾器、电动喷雾器和植保无人飞机喷施的农药沉积率及雾滴参数.结果表明:在同一水稻生育期使用不同植保器械喷施的农药沉积率差异显著,表现为植保无人飞机>电动喷雾器>手动喷雾器.在水稻苗期使用手动喷雾器、电动喷雾器和植保无人飞机的平均农药沉积率分别为18.33％、24.58％和35.84％,在水稻封行期的结果分别为24.72％、35.28％和45.15％,在水稻破口期的结果分别为32.39％、40.29％和52.42％.同一植保器械在水稻不同生育期喷施农药的沉积率也存在显著差异,表现为破口期>封行期>苗期.不同冠层的沉积量结果显示:采用植保无人飞机喷施的药液沉积量由上至下递减,采用手动和电动喷雾器喷施的药液主要沉积在水稻植株的上层和中层.植保无人飞机喷施药液的雾滴显著小于手动和电动喷雾器处理,且均匀度更好,同时植保无人飞机喷雾雾滴分散度优于手动和电动喷雾器处理.相对于传统施药器械,使用植保无人飞机喷施显著提高了农药沉积率和药液雾化效果.

HomePlant DiseaseVol. 106, No. 8Occurrence of Root and Stem Rot Caused by Rhizoctonia solani AG-4 HGI on Torenia fournieri in China PreviousNext DISEASE NOTE OPENOpen Access licenseOccurrence of Root and Stem Rot Caused by Rhizoctonia solani AG-4 HGI on Torenia fournieri in ChinaS. B. Jiang, Q. Y. Yang, B. R. Lin, J. X. Zhang, H. F. Shen, X. M. Pu, D. Y. Sun, Y. B. Bai, and Z. Q. TangS. B. JiangKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, Q. Y. Yang†Corresponding author: Q. Y. Yang; E-mail Address: [email protected]Key Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, B. R. Linhttps://orcid.org/0000-0003-2616-9296Key Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, J. X. ZhangKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, H. F. ShenKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, X. M. PuKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, D. Y. SunKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, Y. B. BaiKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China, and Z. Q. TangKey Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaAffiliationsAuthors and Affiliations S. B. Jiang Q. Y. Yang † B. R. Lin J. X. Zhang H. F. Shen X. M. Pu D. Y. Sun Y. B. Bai Z. Q. Tang Key Laboratory of New Techniques for Plant Protection in Guangdong, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China Published Online:29 Jun 2022https://doi.org/10.1094/PDIS-09-21-2111-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleTorenia fournieri (wishbone flower) is widely cultivated for ornamental and medicinal use in southern China. In July 2021, severe root and stem rot of T. fournieri was observed in approximately 70% of the 3,000 plants grown in an ornamental plant nursery under natural conditions in Guangzhou, Guangdong Province, China. Lesions on the roots and basal stems were water-soaked and dark brown. In late infection, the whole plant wilted and died. Eventually, infected plants lose their ornamental and economic value. Fifteen diseased samples were collected, and diseased tissues (4 × 4 mm) were surface sterilized in 1% NaOCl for 45 s, rinsed with sterile water, dried, and incubated for 3 days on potato dextrose agar (PDA) medium at 25°C in the dark. Pure cultures were obtained by transferring hyphal tips to new plates of PDA and incubated at 25°C for 5 days. A fungus was consistently isolated from symptomatic root and stem samples (100% isolation rate). The colonies on PDA medium were initially white and turned light brown with age, and no sclerotia was present after 15 days. Hyphae were 3.78 to 11.10 μm wide, and had a constriction at the base of hyphal branches, septa near the branch, and right-angled branching. Multinucleate hyphal cells (3 to 12 nuclei per cell) were determined by 4′,6-diamidino-2-phenylindole staining (Yang et al. 2013). These characteristics matched those described for Rhizoctonia solani (Sneh et al. 1991). A representative isolate LZ1 was chosen for molecular identification; the internal transcribed spacer (ITS) region was amplified using the primers ITS1/ITS4, and the resulting sequence (633 bp) was deposited in GenBank (accession no. MZ798228). A BLASTn search of the ITS sequence exhibited 99% identity with that of R. solani AG-4 HGI (MK430998). The phylogenetic analysis (neighbor-joining method and 1,000 bootstrap values) showed LZ1 was clearly assigned to the group of R. solani AG-4 HGI. For pathogenicity testing, 10 healthy T. fournieri plants (approximately 18-cm high) were planted into plastic pots filled with sterilized soil. Inoculum of R. solani was produced by adding a PDA agar plug (5 mm in diameter) from a 6-day-old colony to a flask with 150 ml of potato dextrose broth (PDB) that was shaken at 150 rpm at 25°C for 7 days, and poured evenly into the sterilized soil (50 ml per pot). Sterile PDB was poured on another 10 plants as controls. All the inoculated plants were placed in a greenhouse at 25°C with 70 to 90% humidity. After 14 days, rot symptoms of the roots and basal part of stems similar to those in the nursery were observed on all inoculated plants, while no visible symptoms were observed on the controls. We reisolated the fungal pathogen from the inoculated plants and identified it as R. solani AG-4 HGI by microscopy and the molecular characteristics mentioned above. R. solani AG-4 HGI was previously reported causing Impatiens walleriana stem rot and muskmelon fruit rot in Liaoning, China (Sun et al. 2015). To the best of our knowledge, this is the first report of R. solani AG-4 HGI causing root and stem rot on T. fournieri in China as well as worldwide. This finding expands the host range known for R. solani AG-4 HGI and will assist in developing effective control strategies for this disease to minimize losses.The author(s) declare no conflict of interest.References:Sneh, B., et al. 1991. Identification of Rhizoctonia Species. American Phytopathological Society, St. Paul, MN. Google ScholarSun, H., et al. 2015. Plant Dis. 99:1653. https://doi.org/10.1094/PDIS-01-15-0066-PDN Link, ISI, Google ScholarYang, Y. G., et al. 2013. Plant Dis. 97:840. https://doi.org/10.1094/PDIS-09-12-0896-PDN Abstract, ISI, Google ScholarFunding: Funding was provided by the Science and Technology Project of Guangzhou City (201704030120), Science and Technology Project of Guangdong Province (2016B020202003), and Natural Science Foundation of Guangdong Province (2015A030312002).The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 106, No. 8 August 2022SubscribeISSN:0191-2917e-ISSN:1943-7692 Download Metrics Article History Issue Date: 29 Jul 2022Published: 29 Jun 2022First Look: 24 Jan 2022Accepted: 13 Jan 2022 Page: 2266 Information© 2022 The American Phytopathological SocietyFundingScience and Technology Project of Guangzhou CityGrant/Award Number: 201704030120Science and Technology Project of Guangdong ProvinceGrant/Award Number: 2016B020202003Natural Science Foundation of Guangdong ProvinceGrant/Award Number: 2015A030312002KeywordsRhizoctonia solaniroot and stem rotTorenia fournieriThe author(s) declare no conflict of interest.PDF downloadCited byEnhanced Resistance to Fungal and Bacterial Diseases Due to Overexpression of BSR1, a Rice RLCK, in Sugarcane, Tomato, and Torenia11 February 2023 | International Journal of Molecular Sciences, Vol. 24, No. 4

Bacterial soft rot of banana, caused by Dickeya zeae, is spreading rapidly in important banana growing areas in China and seriously threatens banana production. In this study, we sequenced the high-quality complete genomes of three typical banana strains, MS1 (size: 4,831,702-bp; genome coverages: 538x), MS_2014 (size: 4,740,000-bp; genome coverages: 586x) and MS_2018 (size: 4,787,201-bp; genome coverages: 583x), isolated in 2009, 2014, and 2018, respectively. To determine their genomic and phenotypic diversity with respect to their hosts of origin, they were compared with other D. zeae strains, including another representative banana strain MS2 from China. The sequenced strains were similar in utilization of carbon source and chemical substrates, and general genomic features of GC content, and tRNA and rRNA regions. They were also conserved in most virulence determinants, including gene-encoding secretion systems, plant cell wall degrading enzymes, and exopolysaccharides. We further explored their genomic diversity in the predicted genomic islands (GIs). These GIs were rich in integrases and transposases, where some genomic dissimilarity was observed in the flagellar gene cluster and several secondary metabolite gene clusters. Different constituents of core biosynthetic modules were found within the bacteriocin and aryl polyene (APE) pigment gene clusters, and the strains from banana showed different phenotypes with respect to antibiosis effects and colony pigmentation. Additionally, clustered regularly interspaced short palindromic repeat (CRISPR) and prophage elements, such as type I-F and III-A CRISPR arrays and an intact prophage of MS1-P5, contributed to bacterial diversity. Phylogenetic tree analysis and genome-genome nucleotide comparison confirmed the genomic divergence among the strains isolated from banana. Considering these characteristics, MS2 and MS_2014 probably diverged later than MS1, while MS_2018 was different and more similar to foreign strains isolated from other hosts in several characteristics. Strain MS_2018 caused severe symptoms on banana varieties previously considered moderately resistant or moderately susceptible, including varieties of Cavendish (Musa AAA) and Plantain (Musa ABB). Our study of genomic and phenotypic diversity raises public attention to the risk of spreading new pathogenic variants within banana growing regions and supports development of predictive strategies for disease control.

为揭示复合亚氯酸钠(500 mg/L)杀灭烟草花叶病毒(Tobacco mosaic virus,TMV)的机理,采用荧光定量RT-PCR检测药剂处理后的病毒CP基因和Rep基因表达量,并利用间接酶联免疫吸附法测定了TMV CP的破坏程度;同时接种心叶烟,通过枯斑数统计分析了TMV的侵染活性;利用大片段步移RT-PCR检测TMV相关基因片段的损伤,并使用透射电镜观察药剂处理后病毒粒子被破坏的情况.结果显示:①药剂处理30 min可以完全抑制TMV CP基因的表达,处理60 min可完全抑制TMV Rep基因的表达.此时,TMV CP被完全破坏,病毒也完全丧失了对枯斑寄主心叶烟的侵染能力.②药剂处理30 min时,TMV的183kDa-1、183kDa-2、183kDa-3、183kDa-4、54kDa、CP&MP基因编码区等6个区域中的183kDa-2、183kDa-4和CP&MP区域首先被损伤,但接种叶叶脉和接种叶叶柄上的这3个区域可以正常扩增.处理45 min时,接种叶叶脉、接种叶叶柄和接种叶上部叶片的183kDa-1、183kDa-3和54kDa区域可以正常扩增,而其他3个区域不能正常扩增;对照叶、茎、接种叶下部叶片的6个区域均不能正常扩增.处理60 min时,各部位的基因组片段扩增结果均呈阴性.因此,可以确定药剂处理导致的CP损伤是造成病毒侵染性丧失的主要因素,核酸损伤与病毒失活无关.③透射电镜观察发现,药剂处理1.5 h后病毒粒体完全断裂成碎片状.