Picarbutrazox Effectiveness Added to a Seed Treatment Mixture for Management of Oomycetes that Impact Soybean in Ohio.

None of the current oomycota fungicides are effective towards all species of Phytophthora, Phytopythium, Globisporangium, and Pythium that affect soybean seed and seedlings in Ohio. Picarbutrazox is a new oomyceticide with a novel mode of action towards oomycete pathogens. Our objectives were to evaluate picarbutrazox to determine (i) baseline sensitivity (EC50) to 189 isolates of 29 species, (ii) the efficacy with a base seed treatment with three cultivars with different levels of resistance in 14 field environments; and (iii) if the rhizosphere microbiome was affected by the addition of the seed treatment on a moderately susceptible cultivar. The mycelial growth of all isolates was inhibited beginning at 0.001 µg, and the EC50 ranged from 0.0013 to 0.0483 µg of active ingredient (a.i.)/ml. The effect of seed treatment was significantly different for plant population and yield in eight of 14 and six of 12 environments, respectively. The addition of picarbutrazox at 1 and 2.5 g of a.i./100 kg seed to the base seed treatment compared to the base alone was associated with higher plant populations and yield in three and one environments, respectively. There was limited impact of the seed treatment mefenoxam 7.5 g of a.i. plus picarbutrazox 1 g of a.i./100 kg seed on the oomycetes detected in the rhizosphere of soybean seedlings collected at the V1 growth stage. Picarbutrazox has efficacy towards a wider range of oomycetes that cause disease on soybean, and this will be another oomyceticide tool to combat early season damping-off in areas where environmental conditions highly favor disease development.

Survey of Heterodera glycines population abundance and virulence phenotypes during 2021-2022 in Heilongjiang Province.

Soybean cyst nematode (SCN), Heterodera glycines, poses a significant threat to global soybean production. Heilongjiang, the largest soybean-producing province in China, contributes over 40% to the country's total yield. This province has much longer history of SCN infestation. To assess the current situation in Heilongjiang, we conducted a survey to determine the SCN population density and virulence phenotypes during 2021-2022 and compared the data with a previous study in 2015. A total of 377 soil samples from 48 counties representing eleven major soybean-planting regions were collected. The prevalence of SCN increased from 55.4% in 2015 to 59% in the current survey. The population densities ranged from 80 to 26,700 eggs and juveniles per 100 cm3 of soil. Virulence phenotypes were evaluated for 60 representative SCN populations using the HG type test, revealing nine different HG types. The most common virulence phenotypes were HG types 7 and 0, accounting for 56.7% and 20% of all SCN populations, respectively. The prevalence of populations with a reproductive index (FI) greater than 10% on PI548316 increased from 64.5% in 2015 to 71.7%. However, the FI on the commonly used resistance sources PI 548402 (Peking) and PI 437654 remained low at 3.3%. These findings highlight the increasing prevalence and changing virulence phenotypes of SCN in Heilongjiang. They also emphasize the importance of rotating soybean varieties with different resistance sources and urgently identifying new sources of resistance to combat SCN.

First report of Fusarium verticillioides causing leaf rot on Artemisia argyi in China.

Artemisia argyi is a perennial herb native to East Asia. It is an important traditional Chinese medicinal plant known for its strong flavor and medicinal effects. It is rich in active ingredients and has a wide range of biological activities, including anti-inflammatory, antioxidant, and immune regulation properties. From May to July in 2023, a serious leaf rot outbreak occurred on A. argyi in several farms (approximately 200 acres) in Tanghe county (32°46'44" N, 112°43'13" E), Henan Province, China. The incidence rate reached 65% (n=200). Pale yellow spots (1-2 cm in diameter) first appeared on the leaves, then expanded to form irregular yellowish-brown lesions, eventually causing the entire leaves to wither. Diseased leaves (30) were collected and cut into 5 x 5 mm2 pieces in the areas between infected and healthy tissues. The excised plant tissues were sterilized in 75% ethanol and 1% sodium hypochlorite solution for 30 seconds and one minute, respectively. The tissues were then rinsed with sterile water and placed on potato dextrose agar (PDA) followed by incubating at 25 °C for 3 days. The isolated strains belonged to the genera Fusarium and Alternaria. After pathogenicity verification, 25 purified Fusarium strains were obtained. Three representative strains (AC-Q, AC-X, AC-Y) from different regions were used for further studies. Each strain formed abundant aerial mycelium that was initially white and later developed into purple pigments. Aerial conidiophores were sparsely branched, terminating with verticillate phialides. Macroconidia were slender, straight, and measured 21.8 to 47.5 × 3.1 to 4.4 µm, with two to four septa. Microconidia were clavate and measured 8.31 to 11.6 × 2.1 to 3.5 µm. Morphological characteristics were consistent with the species description of Fusarium verticillioides (Sacc.) Nirenberg 1976 (Leslie and Summerell, 2006). The rDNA internal transcribed spacer (ITS), ß-tubulin gene (tub2), translation elongation factor 1-alpha gene (tef1), calmodulin (cmdA), RNA polymerase II largest subunit (rpb1) and RNA polymerase II second largest subunit (rpb2) were amplified for molecular identification (O'Donnell et al., 2022). The sequences were deposited in GenBank with accession Nos. OR960548, OR960552, OR960555 (ITS), OR972413, OR972414, OR972415 (tub2), OR797685, OR797686, OR797687 (tef1), OR972410, OR972411, OR972412 (cmdA), PP035106, PP035107, PP035108 (rpb1), and PP035109, PP035110, PP035111 (rpb2). BLASTn analysis of AC-Q sequences exhibited 99 to 100% similarity with F. verticillioides sequences (strains CBS 576.78) MT010888 of cmdA, MT0109566 of rpb1, and MT010972 of rpb2. A phylogenetic tree was constructed with concatenated sequences (tub2, tef1, cmdA, rpb1, rpb2), alongside the sequences of the type strains using the neighbor-joining method. The three strains formed a clade with the type strain CBS 576.78 of F. verticillioides, and were separated from other Fusarium spp. These morphological and molecular identifications indicated that the pathogen was F. verticillioides. Pathogenicity was tested on 10 healthy 2-month-old potted seedlings by spraying them with a conidial suspension (106 conidia ml-1), and 5 seedlings were sprayed with sterilized water as a control. The plants were placed in a climate incubator at 28°C and a relative humidity of approximately 90%. Ten days after seedling inoculation, typical lesions were observed on the treated plants, except in the control group. The reisolated strains were identified as F. verticillioides by morphological and molecular characterization, fulfilling Koch's postulates. F. verticillioides is known to cause Fusarium ear rot on maize, as well as diseases on other plants in China such as Brassica rapa (Akram et al., 2020) and Schizonepeta tenuifolia (Li et al., 2024). This is the first report of F. verticillioides causing leaf rot on A. argyi worldwide. Identification of the pathogen is crucial for implementing management approaches to reduce yield losses.

Effects of hybrid, foliar treatments, and infection conditions on bacterial leaf streak of sweet corn.

Bacterial leaf streak (BLS) of corn caused by Xanthomonas vasicola pv. vasculorum was first reported in the United States in 2017. The biology and management of BLS are poorly understood. The objective of this work was to determine the effects of hybrid, foliar treatments, and infection conditions (timing, temperature, inoculation site) on BLS of sweet corn. Field studies were conducted to determine if hybrid or foliar disease management treatments influenced BLS development and yield. Corn leaves were inoculated in plots with X. vasicola pv. vasculorum, and noninoculated plots were used for comparison. The leaf incidence and severity of BLS differed significantly among sweet corn hybrids, suggesting different levels of susceptibility to BLS. Grain yield was significantly reduced (14.7%) by BLS for one hybrid. The corn growth stage at time of infection influenced BLS, with incidence and severity significantly greater following inoculation at stage V6 than V9. Foliar application of Kocide®, LifeGard®, and Kocide®+LifeGard® significantly reduced leaf severity compared to nontreated controls in field studies. Kocide® significantly reduced leaf incidence, but no treatments significantly increased yield vs. controls. In comparisons of inoculation methods in a growth chamber, lesion length on leaves was significantly greater on stalk-inoculated than leaf-inoculated plants. Lesions developed on leaf-inoculated plants only at inoculation sites whereas lesions developed on stalk-inoculated plants on multiple leaves. In controlled environments, lesion length on leaves was significantly greater at 21°C than 27°C and 32°C. This study expands our understanding of factors that influence development and management of BLS of sweet corn.

Discovery of Fusarium pseudograminearum Causing Crown Rot of Winter Wheat in Xinjiang Uygur Autonomous Region, China.

Fusarium pseudograminearum is an important plant pathogen that invades many crops (Zhang et al. 2018). Since it was first discovered in Australia in 1951, F. pseudograminearum has been reported in many countries and regions and caused huge economic losses (Burgess et al. 2001). In 2012, crown rot of wheat caused by F. pseudograminearum was discovered for the first time in Henan Province, China (Li et al. 2012). Wheat (Triticum aestivum L.) is one of the most important food crops in Xinjiang Uygur Autonomous Region (XUAR), with 1.07 million hectares cultivated in 2020. In June 2023, a survey of crown rot disease was carried out in winter wheat cv. Xindong 20 in Hotan area, XUAR, China (80.148907°E, 37.051474°N). About 5% of wheat plants showed symptoms of crown rot such as browning of the stem base and white head. The disease was observed in 85% of wheat fields. In order to identify the pathogens, 36 pieces of diseased stem basal tissue, 0.5 cm in length, were collected and sterilized with 75% alcohol for 30s and 5% NaOCl solution for 2 min, then rinsed three times with sterile water and placed on potato dextrose agar (PDA) medium at 25°C. A total of 27 isolates with consistent morphological characteristics were obtained using single-spore technique (Leslie and Summerell. 2006), and the isolation rate was 75%. The isolates grew rapidly on PDA, produced large numbers of fluffy white hyphae, and pink pigment accumulated in the medium. The isolates were grown on 2% mung bean flour medium and identified by morphological and molecular methods. Macroconidia were abundant, relatively slender, curved to almost straight, commonly two to seven septate, and averaged 22 to 72 × 1.8 to 4.9 µm. Microconidia were not observed. The morphological characters are consistent with Fusarium (Aoki and O'Donnell. 1999). Two isolates (LP-1 and LP-3) were selected for molecular identification. Primers EF1/EF2 (5'-ATGGGTAAGGARGACAAGAC-3'/5'-GGARGTACCAGTSATCATG-3') were used to amplify a portion of the EF-1α gene (O'Donnell et al. 1998). The two 696 bp PCR products were sequenced and submitted to GenBank. The EF-1α gene sequences (GenBank Accession No: PP062794 and PP062795) shared 99.9% identity (695/696) with published F.pseudograminearum sequences (e.g., OP105187, OP105184, OP105179, OP105173). The identification was further confirmed by F. pseudograminearum species-specific PCR primers Fp1-1/Fp1-2 (Aoki and O'Donnell. 1999). The expected PCR products of 518 bp were produced only in F. pseudograminearum. Pathogenicity tests of LP-1 and LP-3 isolates were performed on 7-day-old seedlings of winter wheat cv. Xindong 20 using the drip inoculation method with a 10-µl of a 106 macroconidia ml-1 suspension near the stem base (Xu et al. 2017). The experiment was repeated five times in a 20 to 25°C greenhouse. Control seedlings were treated with sterile water. After 4 weeks, wheat seedling death and crown browning occurred in the inoculated plants with over 90% incidence. No symptoms were observed in the control plants. The pathogen was reisolated from the inoculated plants by the method described above and identified by morphological and PCR amplification using F. pseudograminearum species-specific primers Fp1-1/Fp1-2. No F. pseudograminearum was isolated from the control plants, fulfilling Koch's postulates. To our knowledge, this is the first report of F. pseudograminearum causing crown rot of winter wheat in XUAR of China. Since F. pseudograminearum can cause great damage to wheat, one of the most important food crops in China, necessary measures should be taken to prevent the spread of F. pseudograminearum to other regions.

First Report of Wilt Caused by Fusarium nanum (FIESC 25) on Mungbean (Vigna radiata) in Pakistan.

Mungbean, Vigna radia (L.) R. Wilczek, is ranked 2nd next to chickpea (Cicer arietinum) in total cultivation and production in Pakistan. In August of 2022 and 2023, mungbean plants (cv. PRI Mung-2018) were found wilting in a field at the Ayub Agricultural Research Institute, Faisalabad, Pakistan. Wilted leaves turned yellow, died, but remained attached to the stem. Vascular tissue at the base of the stem showed light to dark brown discoloration. Roots were stunted with purplish brown to black discoloration. Symptomatic mungbean plants were collected from fields at five different locations (20 samples/location). Disease incidence was similar among the five fields, ranging from 5 to 10% at each location depending upon type of germplasm and date of sowing. For fungal isolation and morphological identification, symptomatic stem and root tissues were cut into ~5 mm2 pieces with a sterilized blade. Tissues were surface-sterilized for one min in a 0.5% sodium hypochlorite solution, rinsed twice in sterilized water, air dried on sterilized filter paper, and aseptically placed on potato dextrose agar (PDA) containing 0.5 g/L-1 streptomycin sulphate. Plates were incubated for 3-4 days at 25 ± 2°C with a 12-h photoperiod. Single-spore cultures were used for morphological and molecular analyses. Isolates on PDA grew rapidly and produced abundant white aerial mycelium that turned off-white to beige with age. Macroconidia were hyaline, falcate, typically 3-to-6 septate with a pointed apical cell and a foot-shaped basal cell, measuring 24.5-49.5 x 2.7-4.7 µm (n = 40). Globose to obovate chlamydospores measuring 5.8 ± 0.5 µm (n = 40) were produced singly or in chains and were intercalary or terminal and possessed roughened walls. The morphological data indicated the isolates were members of the genus Fusarium (Leslie and Summerell 2006). To obtain a species-level identification, a portion of translation elongation factor 1-α (TEF1), the largest subunit of RNA polymerase (RPB1), and the second largest subunit of RNA polymerase (RPB2) region were PCR amplified and sequenced using EF1/EF2 (O'Donnell et al. 1998), Fa/G2R (Hofstetter et al. 2007), and 5f2/7cr (Liu et al. 1999) primers, respectively. DNA sequences of these genes were deposited in GenBank under accession numbers MW059021, MW059017 and MW059019, respectively. The partial TEF1, RPB1 and RPB2 sequences were queried against the Fusarium MLST database (https://fusarium.mycobank.org/page/Fusarium_identification), using the polyphasic identification tool. The BLASTn search revealed 99.9% identity of the isolate to F. nanum (Xia et al. 2019), formerly FIESC 25 of the F. incarnatum-equiseti species complex (MRC 2610, NRRL 54143; O'Donnell et al. 2018). To confirm pathogenicity, roots of 3-5 leaf stage mungbean seedlings were soaked in a 106 spores ml-1 conidial suspension of the fungus for 15 min and then planted in 10 cm pots containing sterilized soil. Mock-inoculated plants with sterile water served as a negative control. Twenty pots that were used for each inoculated and control treatment were maintained at 25 ± 2°C, 14:8 h photoperiod, and 80% relative humidity in a growth chamber. After 15 days, leaf yellowing, internal browning from the base of stems and root discoloration was observed in all the inoculated plants. The uninoculated negative control plants remained asymptomatic. Fusarium nanum was re-isolated from artificially inoculated plants and identified by colony growth, conidial characteristics on PDA and molecular analyses (TEF1). To our knowledge, this is the first report of wilt caused by F.nanum on mungbean in Pakistan. In Pakistan, mungbean cultivation in irrigated areas has increased in recent years. It has been introduced frequently in citrus orchards, crop rotation of maize and sesame, intercropping with sugarcane and as green manure. However, citrus, maize, sesame and sugarcane are also hosts of Fusarium spp. Therefore, this information warrants sustainable crop protection and may have an impact on further interaction of F. nanum with other wilt pathogens.

First Report of Clonostachys rosea Causing Bulb Rot on Fritillaria taipaiensis in China.

Taibai Beimu (Fritillaria taipaiensis) is a species of Fritillaria commonly used in traditional Chinese medicine for its antitussive, expectorant, and antihypertensive properties. In April of 2021 and 2022, an incidence 10-30% of yellowing or purpling, wilting, and dying symptoms was observed on Taibai Beimu in Wanyuan, Sichuan province. Infected roots and bulbs displayed spots ranging from brown to black, along with necrotic rot. In severe cases, the entire bulbs rotted. Fifteen symptomatic bulbs were cut into 0.5 × 0.5 cm pieces, surface sterilized in 75% ethanol for 30 s and 1% sodium hypochlorite for 3 min under aseptic conditions, rinsed with sterile water 3 times, and air-dried. The segments were placed on potato dextrose agar (PDA) and incubated at 25℃ for 7 days in the dark. Six Clonostachys-like monospore isolates were obtained. Colonies on PDA reached 32 to 43 mm in diameter in 7 days at 25℃ in the dark, felty to tomentose to granulose aerial mycelia with a white or light yellow appearance, and reverse colors matching. On cornmeal-dextrose agar, primary conidiophores had a Verticillium-like structure with 1 to 3 levels. Stipes were 36.1 to 236.3µm long. Phialides formed in whorls of 2 to 5, 15.3 to 45.7µm long, 1.1 to 3.4µm wide at the base, and 1.03 to 2.41µm wide near opening (n=95). Each producing a small hyaline drop of conidia. Conidia were 3.7 to 11.3µm × 2.1 to 4.1µm (n=110). Secondary conidiophores displayed Penicillium-like structures, and stipes were 23.1 to 142.3µm long. Phialides formed in compressed whorls of 4 to 8 per metula, 7.0 to 16.0µm in length, 1.3 to 3.1µm in width at the base, 1.8 to 3.6µm at the widest point, and 0.8 to 1.8µm near opening (n=50). Conidia were 3.0 to 6.4µm ×1.6 to 3.4µm (n=65). The morphology was consistent with the previous description of Clonostachys rosea (Hans-Josef et al. 1999). The ATP citrate lyase (ACL1), ß-tubulin (TUB2), translation elongation factor 1-α (tef1α), and the nuclear ribosomal internal transcribed spacer (ITS) of three strains were amplified and sequenced using primers acl1-230up/acl1-1220low (Gräfenhan et al. 2011), T1/CYLTUB1R (Crous et al. 2004; O'Donnell and Cigelnik 1997), EF1-728F/EF2 (Carbone and Kohn 1999; O'Donnell et al. 1998), and ITS1/ITS4 (White et al. 1990), respectively. Blastn homology search showed a > 97% similarity to the ex-type strains of C. rosea (CBS710.86). All sequences have been deposited in GenBank (PP394342 to PP394350, and PP396901 to PP396903). A phylogenetic tree was constructed using Bayesian analysis based on the alignment of the combined ACL1, TUB2, tef1α, and ITS sequences through IQ-TREE. The tree displayed clustering with known strains of C. rosea. Pathogenicity was confirmed by inoculating five healthy five-year-old Taibai beimu plants with a spore suspension (1.0 × 106 spores mL-1) of the strain WYEB1101, while sterilized water was used as a control. The inoculation process involved pouring the spore suspension over the wounded bulbs and covering with them sterile soil. Subsequently, all plants were cultivated in sterile soil indoors under natural conditions suitable for Taibai beimu. The pathogenicity assays were repeated twice. After 20 days of cultivation, the infected plants displayed symptoms similar to those observed in the field, while all control plants remained asymptomatic. Sequencing confirmed the re-isolation of C. rosea from the inoculated plants, satisfying Koch's hypothesis. Clonostachys rosea has been previously reported to cause root rot of Chinese medicine herb, such as Astragalus membranaceus and Gastrodia elata (Lee et al. 2020; Qi et al. 2022). To our knowledge, this is the first report of C. rosea infecting Taibai Beimu in China, highlighting a potential risk to this crop.

Biological Control of Rapeseed Clubroot (Plasmodiophora brassicae) Using the Endophytic Fungus Didymella macrostoma P2.

Didymella macrostoma P2 was isolated from rapeseed (Brassica napus), and it is an endophyte of rapeseed and an antagonist of three rapeseed pathogens, Botrytis cinerea, Leptosphaeria biglobosa, and Sclerotinia sclerotiorum. However, whether P2 has a suppressive effect on infection of rapeseed by the clubroot pathogen Plasmodiophora brassicae remains unknown. This study was conducted to detect production of antimicrobials by P2 and to determine the efficacy of the antimicrobials and P2 pycnidiospores in suppression of rapeseed clubroot. The results showed that cultural filtrates (CFs) of P2 in potato dextrose broth and the substances in pycnidiospore mucilages exuded from P2 pycnidia were inhibitory to P. brassicae. In the indoor experiment, seeds of the susceptible rapeseed cultivar Zhongshuang No. 9 treated with P2 CF and the P2 pycnidiospore suspension (P2 SS, 1 × 107 spores/ml) reduced clubroot severity by 31 to 70% on the 30-day-old seedlings compared with the control (seeds treated with water). P2 was reisolated from the roots of the seedlings in the treatment of P2 SS; the average isolation frequency in the healthy roots (26%) was much higher than that (5%) in the diseased roots. In the field experiment, seeds of another susceptible rapeseed cultivar, Huayouza 50 (HYZ50), treated with P2 CF, P2 CE (chloroform extract of P2 CF, 30 µg/ml), and P2 SS reduced clubroot severity by 29 to 48% on 60-day-old seedlings and by 28 to 59% on adult plants (220 days old) compared with the control treatment. The three P2 treatments on HYZ50 produced significantly (P < 0.05) higher seed yield than the control treatment on this rapeseed cultivar, and they even generated seed yield similar to that produced by the resistant rapeseed cultivar Shengguang 165R in one of the two seasons. These results suggest that D. macrostoma P2 is an effective biocontrol agent against rapeseed clubroot.

First Report of Xanthomonas euvesicatoria pv. sesami Causing Leaf Spot on Sesame (Sesamum indicum L.) in South Carolina, USA.

Sesame (Sesamum indicum L.) is an annual plant known as one of the first domesticated oilseed crops. It is cultivated worldwide, mostly in Asia, Africa, and the Americas (Singh, 2006). In August 2022 and September 2023, dark angular necrotic spots on leaves and stems (100% incidence), blights, and severe defoliation were observed in a 4-acre rainfed sesame field located in the Colleton County of South Carolina, USA (Fig. S1). Bacterial streaming from cut leaf lesions was observed from diseased plants in both years. Two plants were collected for pathogen isolation in 2023. Symptomatic leaves were surface sterilized with 70% ethanol for 1 min and dried in a laminar flow hood. For each isolate, four sterile toothpicks were used to poke lesion margins and stirred in 300 µl of sterile distilled water in a 2-ml sterile microcentrifuge tube and soaked at room temperature (c. 21 °C) for 10 min. Each bacterial suspension (10 µl) was streaked on nutrient agar (NA) in a Petri dish. Convex and mucoid yellow colonies formed after a 48-h incubation at 28°C in the dark. Two isolates (S813 and S814), one from each plant, were obtained by transferring single colonies to new NA plates. Both isolates were preliminarily identified as Xanthomonas [S813: X. campestris (P = 0.53); S814: X. campestris (P = 0.77)] using a Biolog Microbial Identification System (GEN III Microplate; Identification Database v.2.8.0.15G). PCR amplification of the atpD and dnaK genes was performed for both isolates using the conditions described in Félix-Gastélum et al. (2019). The sequences of both amplicons are 100% identical for each gene between the two isolates. PCR and sequencing of the gyrB gene was also done for S813 with the primers from Young et al. (2008). The atpD (S813/S814), dnaK (S813/S814), and gyrB (S813) sequences (GenBank accessions: PP507118 to PP507120) showed the best match with 100% identity to the corresponding gene sequences [GenBank accessions: KJ491167 (100% coverage), KJ491257 (99% coverage), EU285201 (100% coverage)] of the X. euvesicatoria pv. sesami (=X. campestris pv. sesami) type strain LMG865 (Constantin et al. 2015, Parkinson et al. 2009). A neighbor joining tree with the concatenated sequences of these three genes (2,210 nt) showed that S813 and LMG 865 had the closet relationship with X. euvesicatoria pv. alfalfae (CFBP3836, Fig. S2). To fulfill Koch's postulates, three healthy sesame plants (cultivar Shirogoma) were spray inoculated separately with each suspension of S813 and S814 in sterile tap water until runoff (approx. 5×108 CFU/ml). Two sesame plants were sprayed with sterile tap water and served as negative control. All plants were maintained in a greenhouse at approximately 28/20°C (day/night) with natural photoperiod. Dark leaf spots and leaf yellowing were observed on inoculated plants 7 to 14 days after inoculation. No disease symptom was observed on the control plants. Bacteria were reisolated from leaf spots of the inoculated plants and confirmed to be X. euvesicatoria pv. sesami based on atpD and dnaK sequences. The disease was first reported in Sudan (Sabet and Dowson, 1960), after which it was reported in USA (Isakeit et al., 2012) and Mexico (Félix-Gastélum et al. 2019). To the best of our knowledge, this is the first report of this disease in South Carolina, USA. Since the interest of sesame to the farmers is increasing in the southeastern USA, it is necessary to perform further research to examine the disease distribution and its economic impact.

First report of Stagonosporopsis cucurbitacearum Causing Gummy Stem Blight on Trichosanthes kirilowii Maxim. in China.

Trichosanthes kirilowii Maxim. (Cucurbitaceae), one of the Chinese herbal medicines, is an economically important crop in Anhui Province, China. In recent years, gummy stem blight disease, a major disease of cucurbits, was widespread in many T. kirilowii plantations. The initial symptoms on the naturally infected stems appeared as dark brown water-soaked lesions, and as the disease progressed, vines of T. kirilowii gradually withered. On leaves, brown water-soaked lesions were visible initially, and then lesions enlarged and coalesced, resulting in extensive necrosis of leaves. On fruit, lesions covered with the white mycelium were nearly circular and tan to brown initially. Subsequently, the diseased fruit turned black and rotten commonly known as fruit rot or black rot. A Stagonosporopsis-like organism was consistently isolated from symptomatic stems, leaves and fruits. Fungal isolates were initially white and later turned dark grey or black with woolly to floccose aerial mycelium on PDA medium. Twenty-four isolates from different plantations were selected for further morphological studies. Pycnidia and conidia were formed after inoculating on cucumber fruit for 3 days. Pycnidia were globose to sub-globose, brown, ostiolate and 106.7 to 213.6 µm (average 160.1 µm, n = 50) in diameter. Conidia were hyaline, ellipsoidal, aseptate or one-septate, slightly constricted at the septa, 6.1 to 13.6 × 3.5 to 4.8 µm (average 9.9 × 4.1 µm, n = 50), and contained two or more oil drops. Three different loci of the genomic DNA, including the nuclear ribosome DNA internal transcribed spacer (ITS), RNA polymerase II second-largest subunit (RPB2), and ß-tubulin (TUB2) genes., were amplified using primers ITS1/ITS4 (White et al. 1990), RBP2DF/RBP2DR (Lawrence et al. 2013), and T1/ß-Sandy-R (O' Donnell and Cigelnik 1997; Stukenbrock et al. 2012), respectively and sequenced. A phylogenetic tree was built based on analysis of ITS, RPB2, and TUB2 sequences that deposited in GenBank (MW485497-MW485502 for ITS, MW531661-MW531666 for RPB2, and MW531667-MW531672 for TUB2), using the maximum likelihood method. The phylogenetic tree showed that the isolates fell into a single clade with S. cucurbitacearum. On the basis of morphological and molecular characteristics, the isolates obtained from T. kirilowii were identified as Stagonosporopsis cucurbitacearum. Pathogenicity tests were carried out on stems and leaves of 4-week-old T. kirilowii seedlings and on immature fruit collected from adult T. kirilowii plants. The epidermis, previously injured with a syringe needle, was inoculated with 5-mm-diameter mycelial plugs, and the inoculated areas were then wrapped in water-soaked cotton. Controls were similarly inoculated with agar plugs. The diameters of lesions were measured in two perpendicular directions. Re-isolations from the stem and leaf lesions were performed on the PDA medium. Stagonosporopsis cucurbitacearum, was re-identified based on its colony and conidial characteristics and, therefore, completed Koch's postulates. Gummy stem blight caused by S. cucurbitacearum has been reported in a wide range of hosts, including cucumber, luffa, pumpkin, gourd, muskmelon, cantaloupe, and watermelon (Jiang et al. 2015; Keinath 2011; Zhao et al. 2019). To our knowledge, this is the first report of gummy Stem blight disease on T. kirilowii caused by S. cucurbitacearum in China. The research provides a basis for the development and implementation of effective management strategies. Pathogenicity tests were carried out on stems and leaves of 4-week-old T. kirilowii seedlings and on immature fruits collected from adult T. kirilowii plants. The epidermis, previously injured with a syringe needle, was inoculated with 5-mm-diameter mycelial plugs, and the inoculated areas were then wrapped in water-soaked cotton. Controls were treated similarly but inoculated with agar plugs. Diameters of lesions were measured in two mutually perpendicular directions. Reisolations from the lesions were performed on PDA medium, and was re-identified based on its colony and conidial characteristics to complete Koch's postulates. Gummy stem blight caused by S. cucurbitacearum have been reported in a wide range of hosts, including cucumber, luffa, pumpkin, gourd, muskmelon, cantaloupe, and watermelon (Jiang et al. 2015; Keinath 2011; Zhao et al. 2019). To our knowledge, this is the first report of gummy Stem blight disease on T. kirilowii caused by S. cucurbitacearum in China. The research provides a basis for the development and implementation of effective management strategies.

Occurrence of Fusarium Crown Rot Caused by Fusarium culmorum on Winter Wheat in Xinjiang Uygur Autonomous Region, China.

Wheat (Triticum aestivum L.) is the predominant grain crop and plays a pivotal role in grain production in Xinjiang Uygur Autonomous Region (XUAR), China. Its cultivated area constitutes approximately half of the total sown area of grain crops in XUAR, with 1.14 million hectares in 2021. Fusarium crown rot (FCR) of wheat, caused by Fusarium culmorum (W.G. Smith) Sacc., is one of the most devastating soil-borne diseases known to seriously reduce grain yield (Ma et al. 2024; Saad et al. 2023). In 2016, FCR of wheat, caused by F. culmorum, was firstly identified in Henan Province, China (Li et al. 2016). In June 2023, during the investigation of FCR of wheat in Aksu Prefecture, XUAR, FCR on winter wheat (cv. Xindong 20) was found (82.761349°E, 41.612202°N). The grain-filling period for winter wheat in early June coincided with a period of high temperatures and water demand in Aksu Prefecture. Approximately 8% of the Xindong 20 wheat plants exhibited symptoms of white heads and browning at the stem base, with the disease present in 82% of the wheat fields surveyed. To identify the pathogens, 20 samples of diseased stem basal tissue, each 0.5 cm in length, were collected and sterilized with 75% alcohol for 30s and 5% NaOCl solution for 2 min, followed by three rinses with sterile water. These samples were then plated onto potato dextrose agar (PDA) medium at 25°C for 5 days. A total of 17 isolates with consistent morphological characteristics were obtained using single-spore technique, with an isolation rate of 85%. The isolated strains exhibited rapid growth on PDA, producing fluffy, pale-yellow hyphae, and accumulating a pale-yellow to dark red pigment on the bottom of the medium. On carnation leaf agar (CLA), these strains formed orange colonies due to the aggregation of a large number of macroconidia. The macroconidia were short and thick, with three to four septa and rounded apical cell, averaging 31.94 to 40.96 × 5.62 to 6.71 µm (Magnification of ×400). Microconidia were not observed. These morphological characters were consistent with those of F. culmorum (Leslie and Summerell. 2006). Two isolates (D-9 and D-11) were selected for molecular identification. The EF-1α gene fragment was amplified using primers EF1/EF2 (5'-ATGGGTAAGGARGACAAGAC-3'/5'-GGARGTACCAGTSATCATG-3') as previously described by O'Donnell et al. (1998). The two 665 bp PCR products were sequenced and submitted to GenBank (GenBank Accession No: PP763247 and PP763248) with 99. 7% identity to the published F. culmorum sequences (e.g., OP985478, OP985477, MG195126, KX702638). The molecular identification was further confirmed by F. culmorum species-specific PCR primers FcOIF/FcOIR (Nicholson et al. 1998). The expected PCR products of 553 bp were produced only in F. culmorum. Strains D-9 and D-11 were used to conduct the pathogenicity experiment on 7-day-old winter wheat (cv. Xindong 20) using drip in the lower stem inoculation method with a 10-µl of 106 macroconidia ml-1 suspension, and the control 7-day-old winter wheat were treated with sterile water (Xu et al. 2017). The experiments were replicated five times in a greenhouse at temperatures ranging from 20℃ to 25℃. After 4 weeks, all inoculated wheat seedlings showed stem base browning or even death. No symptoms were observed on the control plants. The fungus was reisolated from all inoculated wheat plants by the method described above and identified by morphological and PCR amplification using F. culmorum species-specific primers FcOIF/FcOIR. No F. culmorum was isolated from the control wheat plants, fulfilling Koch's postulates. To the best of our knowledge, this is the first report of F.culmorum causing FCR on winter wheat in XUAR, China. Considering wheat is the predominant grain crop and plays a pivotal role in grain production in China, necessary measures should be taken to prevent the spread of F. culmorum to other regions.

First Report of Panicle Wilting on Rice (Oryza sativa L.) Caused by Fusarium kyushuense in Heilongjiang Province, China.

Heilongjiang is the largest rice-producing province in China, with annual yield of 28.9 million tons cultivated on 3.8 million hectares (Liu et al. 2021). During field surveys from July to August (2021-2022), symptoms of wilting were observed on rice panicles across Baoqing county (46.32°N, 132.20°E), Shuangyashan city, Heilongjiang province, China. Disease incidence ranged from 10 to 35%, and yield losses were estimated to be 5 to 20% over 7 surveyed fields of 18.5 ha in total. Initially, infected panicles exhibited carmine to brownish spots at the flowering and early grain-filling stages, which gradually merged into large and irregular lesions and spread to the entire panicle surface. Eventually, panicles became wilting and decayed at the ripening stage. To identify the etiological agent, thirty-five symptomatic panicles were collected randomly from 35 plants at different positions in 7 fields. The fragments (approximately 3 mm2) were dissected from margins of individual lesions, surface-disinfested with 70% ethanol for 30 s followed by 2% sodium hypochlorite for 2 min, and rinsed three times in sterilized water. The pieces were then dried and placed onto half-strength potato dextrose agar (PDA) supplemented with 50 µg/mL of streptomycin sulfate. After incubation at 28°C for 4 days, nineteen cultures were obtained and purified using the single-spore isolation method. On PDA plates, the colonies produced fluffy and cottony aerial mycelia and were white to yellowish with deep-yellow to red-brown pigments. The microconidia were hyaline, elliptical or clavate, zero to one septum, measuring 6.3 to 19.2 × 2.6 to 5.1 µm in size (n = 50). On carnation leaf agar (CLA), the macroconidia were thick-walled, falcate to almost straight, three to five septa, apical cell hooked to tapering, basal cell foot-shaped, measuring 27.4 to 47.8 × 3.6 to 5.4 µm in size (n = 50). No chlamydospore was observed. The internal transcribed spacer (ITS) region of ribosomal RNA, translation elongation factor (TEF-1α) gene, and ß-tubulin (ß-TUB) gene were amplified and sequenced using primers ITS1/ITS4 (White et al. 1990), EF1/EF2 (O'Donnell 2000), and T1/T22 (O'Donnell and Cigelnik 1997) from three representative isolates (PJ58, PJ69 and PJ83), respectively. The obtained sequences were deposited in GenBank (accession nos. ON527509, OQ772202 and OQ777725 for ITS; ON573222, OQ784926 and OQ784927 for TEF-1α; ON573223, OQ784928 and OQ784929 for ß-TUB, respectively). BLASTn analysis revealed 99.8 to 100% homology with the corresponding sequences of Fusarium kyushuense (MH892849 for ITS, AB674297 for TEF-1α, and GQ915442 for ß-TUB, respectively) in GenBank. Maximum likelihood phylogeny based on the concatenated sequences of ITS, TEF-1α and ß-TUB grouped three representative isolates in the F. kyushuense clade. Combined with the morphological and molecular characteristics, the fungus was identified to be F. kyushuense. Pathogenicity of the three isolates of F. kyushuense was evaluated on a susceptible rice cultivar Nanjing 46 at the booting stage. The upper part of a healthy panicle was inoculated by injecting 2 ml of a conidial suspension (1 × 106 spore/ml) obtained from a 7-day-old PDA culture of each isolate. The negative control was treated with sterile distilled water. The experiment was performed thrice with ten replicated plants for each treatment. All plants were placed in a humid chamber at 25°C with a 12-h photoperiod and 80% relative humidity. Twenty days after inoculation, it was found that the inoculated panicles showed typical reddish to brownish lesions, whereas control plants remained symptomless. Pathogens were reisolated from the artificially inoculated panicles and confirmed by morphological and molecular tests, fulfilling Koch's postulates. In recent years, this species has been associated with stalk rot and ear rot of maize (Cao et al. 2021; Wang et al. 2014) and wilt of tobacco (Wang et al. 2013). Also, it was mentioned as a producer of mycotoxins, especially trichothecenes and HT-2 toxin (Varga et al. 2016). To our knowledge, this is the first report of F. kyushuense causing panicle wilting on rice in China. The appropriate control strategies should be made to reduce the risk of disease due to food security concerns and potential threats to rice production.

First report of Calonectria ilicicola causing red crown rot of soybean in Indiana.

Soybean (Glycine max [L.] Merr.) samples from commercial fields in Decatur and Spencer counties, Indiana were submitted to the Purdue Plant and Pest Diagnostic Lab in August to October 2022. Plants exhibited whole-leaf to interveinal chlorosis of the foliage, red to dark brown external lesions on the crown spreading from the soil-line upward, and severe root rot. In the fields, patches of diseased plants were observed, with greater than 50% of the plants affected and yield loss up to 50%. Orange to red perithecia were present on the exterior of symptomatic stem tissue and ranged in size from 329 to 433 × 232 to 306 µm (n = 10). Stems were surface sterilized in 10% Clorox (0.825% NaOCl) for 1 min, then rinsed with sterile distilled water and dried. In a laminar flow hood, sections of symptomatic stem tissue were plated on using quarter-strength potato dextrose agar (QPDA) and incubated under fluorescent lights on a 12-hr light/dark cycle at 20°C. After 6 days, fungal colonies with fluffy aerial hyphae, which were white near the colony margins and orange to burnt-red near their center, grew uniformly from the stem tissue plated. Elongate, cylindrical hyaline conidia with zero to three septations measuring 45.5 to 73.8 × 4.4 to 6.7 µm (n = 22) grew in clusters from symptomatic stem tissue within the plate. Perithecia developed after 14 days. Falcate, hyaline ascospores with one to two septa measuring 29.4 to 54.7 × 4.6 to 6.8 (n = 23) µm developed within the perithecia. Calonectria ilicicola Boedijn & Reitsma was confirmed based on morphological characteristics (Padgett et al. 2015). Isolate PPDL 22-01457B was used for DNA extraction using the ZR Fungal/Bacterial DNA Miniprep kit (Zymo Research, Irvine, CA). The internal transcriber region (ITS), actin (ACT) and ß-tubulin (TUB2) genes were amplified (Carbone and Kohn 1999; Glass and Donaldson 1995; O'Donnell and Cigelnik 1997; White et al. 1990). Amplicons were sent for Sanger sequencing (Genewiz, Inc., South Plainfield, NJ), submitted to Genbank, and assigned accession numbers ITS: OQ932995, Actin: OR484986, and ß-tubulin: OR546281. Sequences were analyzed using the NCBI BLASTn tool with results showing 99.5 to 100% identical to C. ilicicola (GenBank accessions LC500063, OQ303403, CP085825, respectively). To perform Koch's Postulates, 90 soybean seeds (CP3620E) were planted in potting media (Berger, Saint-Modeste, Quebec, Canada) in a seed flat with 45 of the plants used as controls and grown under grow lights for 16hr light/8hr dark at 20℃. Individual seedling crowns were inoculated 3 days post-emergence with a 5 to 10 ml spore and hyphal suspension that was scraped from the surface of a 14-day old QPDA culture after adding 300 mL deionized (DI) to each plate grown at 20 to 22°C. The control plants received sterile-DI water. Plants were covered in a plastic bag for 72 h. Plant stems were sprayed with sterile-DI water once a day for seven days. Symptoms were observed after four days, but significant crown rot and lesions developed after two weeks before wilting and dying. Calonectria iliciola was isolated uniformly from symptomatic plants and identified morphologically. Control plants showed no symptoms. Inoculations were repeated 3 times with similar results. As of fall 2023, red crown rot has been confirmed in Adams and Rush counties in Indiana. Red crown rot has been confirmed in several Midwest states (Kleczewski et al. 2019, Neves et al. 2023), but the extent of its distribution and disease management strategies are still limited.

Gray mold disease on bottle gourd caused by Cladosporium tenuissimum in China.

Bottle gourd [Lagenaria siceraria (Mol.) Stand] is a widely cultivated succulent crop species. In December 2022, a serious bottle gourd disease occurred in the protected vegetable planting base of Xingguo County, Ganzhou City, Jiangxi Province, China, with 85% of the 2,100 plants having gray mold disease-like symptoms, including gray spots on the infected fruit. They quickly expanded at suitable temperature and humidity, forming a gray mold layer with inward depressions, which spread to the fruit stem causing watery rot, and the flesh turned black and started to rot. To isolate the pathogen, fruits of the diseased plants were surface-disinfected with 75% ethanol for 30 s, immersed in 0.1% HgCl2 for 1 min, rinsed thrice with sterile water, and cultured on a potato-dextrose agar (PDA) medium at 28°C. Mycelia from the diseased tissue were subcultured on fresh PDA medium to obtain pure cultures. After incubation at 25°C for 7 days, olive-green colonies (~2.5 mm·d-1) developed. Cultures developed numerous elliptical and limoniform conidia measuring 2.69~9.79 µm to 2.10~5.92 µm (average 5.62×3.12 µm) (n=20). The morphological characteristics of the pathogen resembled those of Cladosporium spp. Fungal genomic DNA was extracted, and the internal transcribed spacer (ITS), partial translation elongation factor-1 alpha (TEF-1α), and actin (ACT) regions were amplified with primers ITS1/4, TEF-728F/986R, and ACT-512F/783R, respectively, and sequenced (Bensch et al. 2012; Jo et al. 2018). Basic Local Alignment Search Tool analysis (BLAST) revealed that the ITS (accession no. OQ186729), ACT (OQ240962), and TEF-1α (OQ240963) sequences of isolate hjt4 shared the highest similarity (99-100%) with those of Cladosporium tenuissimum (accessions no. OM232068, OM256530, OM256526) (Duccio et al. 2015). A phylogenetic tree of the isolate hjt4 and its close relatives within Cladosporium was constructed using the MEGA X neighbor-joining method. The pathogen was identified as C. tenuissimum based on morphological and molecular characteristics. A specimen (JXAU-H2022982) was deposited at the Herbarium of the College of Agronomy, Jiangxi Agricultural University. To confirm its pathogenicity, seven-day-old healthy bottle gourd fruits were disinfected with 75% ethanol, 1 mm-deep wounds were made with sterilized scalpels, and the plants were inoculated with PDA plugs (0.8 cm in diameter) containing actively growing mycelia of isolate hjt4. Plants inoculated with sterile PDA plugs served as controls. Each group contained three fruits, and the experiment was performed in triplicate. All fruits were incubated in a biochemical incubator at 28°C. After 3 days, the fruit surface shrank, and the flesh turned to a black colour and rotten, which rapidly spread to the branches. Control fruits did not develop any symptoms. Reisolated colonies showed the same morphological traits as those of the inoculation isolates, whereas no target colonies were isolated from the control fruits. The pathogen was previously reported to cause leaf blight disease in Coriandrum sativum (Zhou et al. 2022) and sooty spots on Cape gooseberry (Miyake et al. 2022), among others. To our knowledge, this is the first report of gray mold disease caused by C. tenuissimum on bottle gourd in China. The findings provide an important foundation for monitoring and controlling the spread of this disease.

Detection of Beet curly top virus in Solanum jamesii, Artemisia tridentata, Helianthus annuus, and Cannabis sativa in Utah.

Historically, beet curly top virus (BCTV; Geminiviridae, Curtovirus) is known for destroying the sugar beet industry in Utah and has been a persistent problem in the state since then (Ball, 1917). Starting in June of 2022, we began identifying plants in San Juan County, Utah with chlorosis and leaf curling. Of note, Solanum jamesii, the Four Corners potato, Artemisia tridentata, big sagebrush, and Helianthus annuus, common sunflower, were found with general chlorosis, severe leaf curling and in the case of the sage brush, completely lacking in smell whereas nearby sage plants without the yellowing were intensely fragrant. In August 2023, Cannabis sativa plants for hemp production were found with severe leaf curling in Juab County, Utah. Samples were collected and stored at -80°C for future work. DNA was extracted using the IBI Genomic Plant DNA kit (IBI Scientific, Dubuque, IA) and subjected to rolling circle amplification using Phi29 polymerase (NEB, Ipswich, MA). The primer set BCTV2 (Strausbaugh et al. 2008) for BCTV detection was then used on a subset of the RCA-positive samples for either one (A. tridentata, H. annus, and S. jamesii) or two (C. sativa) plants displaying classic BCTV symptoms, to amplify a 518 bp region. This amplicon was then sequenced by the Sanger method to a 4x coverage. The resulting sequences (accession nos. OR698900 to OR698904) share 98.94 to 99.80% nucleotide identity to the Worland strain (accession no. KU892789.1) for all samples. To confirm the detection, a triple antibody sandwich ELISA kit from Nano Diagnostics (San Jose, CA) was used on these, and other plants of similar species and symptoms from across the state. Samples that tested positive include 3/3 symptomatic H. annuus plants, 1/1 symptomatic S. jamesii, 3/3 symptomatic A. tridentata. The A. tridentata samples were collected from Juab, San Juan, and Utah Counties. None of three asymptomatic A. tridentata plants tested were ELISA positive. Of the C. sativa plants tested by ELISA, 9/9 of the plants displaying classic BCTV symptoms in that host were positive and 6/6 of the plants without classic BCTV symptoms were ELISA positive. The findings of these novel hosts indicate the need for increased testing and analysis of economically relevant crops and native flora across the state. These findings represent a concern for conservation in the case of S. jamesii and a potential threat to the growing hemp industry in the state due to the severity of BCTV symptoms on these plants. Additionally, the finding of A. tridentata as a host may represent a significant finding for the epidemiology of BCTV in the Mountain West region as A. tridentata is distributed from Mexico to Canada along the Rocky Mountain range and is found in much of the Western US in arid regions. This is the first report, to our knowledge, of S. jamesii and A. tridentata as hosts for BCTV and the first peer reviewed reports for H. annuus and C. sativa as hosts for BCTV in Utah.

First report of Cassava Bacterial Blight caused by Xanthomonas phaseoli pv. manihotis in the Amazonian forest of Ecuador.

Xanthomonas phaseoli pv. manihotis (Xpm) is a plant pathogenic bacterium known as the causal agent of cassava bacterial blight (CBB). CBB is the most limiting bacterial disease affecting cassava (Manihot esculenta Crantz), characterized by diverse symptoms including angular water-soaked leaf lesions, blight, wilting, stem exudates, stem cankers and dieback. CBB has been reported in most cassava-growing regions around the world, and, under conducive conditions, crop yield losses can reach up to 100% (Zárate-Chaves et al. 2021). While Xpm genetic diversity is remarkably high in South America (Bart et al. 2012) and cassava originates and was domesticated in the Amazon basin (Allem 2002), reports of CBB in the Amazonian region are missing. To fill this gap, in October 2018 we surveyed for CBB symptoms in cassava fields of the Orellana Province, located in the Amazon forest of the Republic of Ecuador. Adult cassava plants exhibiting typical angular, water-soaked leaf lesions were found in polyculture plots, i.e. intercrops of cassava with other species such as plantains and fruit trees (a.k.a. chakras). After surface disinfection with 5% sodium hypochlorite followed by 70% ethanol, white Xpm-like colonies were isolated from diseased leaf tissues of four plants on YPGA medium (yeast extract, 5 g/l; peptone, 5 g/l; glucose, 5 g/l; agar-agar, 15 g/l) supplemented with cephalexin (40 mg/l) and cycloheximide (50 mg/l). Pathogenicity tests were performed on peat-potted, 2-month-old cassava plants of the cultivar 60444. Bacterial suspensions were adjusted to an OD600 of 0.2 (2 × 108 CFU/ml) in sterile 10-mM MgCl2 and syringe infiltrated in fully-expanded leaves. In parallel, 20 µl of each bacterial suspension adjusted to an OD600 of 0.02 (2 × 107 CFU/ml) were inoculated on stems inside a hole previously punched with a sterile needle in the junction of the third-top petiole. Sterile 10-mM MgCl2 was used for mock inoculations in both leaves and stems, and experiments were replicated in three plants. Plants were incubated in a greenhouse at 28 ± 1°C with a 12-h photoperiod. Infiltrated leaves developed watersoaking 3 days post inoculation, while wilted leaves, stem exudates, and dieback were observed 21 days after stem inoculation. Control plants remained symptomless. White Xpm-like colonies were re-isolated from symptomatic leaves (Fig S1). One colony of each of the four Xpm isolates (before and after re-isolation) was assessed using diagnostic PCRs (Bernal-Galeano et al. 2018; Flores et al. 2019), using strain Xam668 as positive control. All four candidates were positive for both diagnostic tools. The sequences of the housekeeping genes atpD, dnaK, efp, glnA, gyrB and rpoD of our isolates were extracted from full genome sequences obtained through Oxford Nanopore Technologies (ONT) (GenBank OR288194 to OR288217) and compared to their homologs in four close Xanthomonas species and a reference Xpm strain (Table S1). The sequences of the tested strains aligned with that of Xpm CIO151 (GCA_004025275.1) (Arrieta-Ortiz et al. 2013) with nucleotide identity above 99.92% (Fig S2). The four strains were named CIX4169, CIX4170, CIX4171 and CIX4172, stored in the IRD Collection of Xanthomonas, where they are available upon request. To our knowledge, this is the first report of CBB in the Amazonian region and in Ecuador, where cassava is a central element for local culture and economy. Further surveys will be necessary to evaluate the distribution and prevalence of CBB in other ecozones of Ecuador where cassava is cultivated.

First Report of Alternaria alternata Causing Leaf Spot on Smooth Bromegrass (Bromus inermis Leyss.) in China.

Smooth bromegrass (Bromus inermis Leyss.) is an important forage crop in northern China. In July 2021, leaf spot symptoms were observed on smooth bromegrass in Ewenki Banner, Hulunbuir, Inner Mongolia. In an area of approximately 0.12 hectares, 95% disease incidence was observed. Ten diseased plants were collected for pathogen isolation. Leaf tissues near the lesions were cut into 5 × 5 mm pieces, surface-disinfested in 75% ethanol for 3 min, and rinsed with sterile distilled water. The pieces were placed on water agar in petri plates and incubated at 25℃ for three days. The resulting colonies were flushed with sterile water and a spore suspension was serially diluted and plated on potato dextrose agar (PDA). A single-spore colony was obtained. Ten isolates were obtained and designated HE1 to HE10. The colony morphology was identical for all isolates, grayish white in color on the upper surface and light black on the underside. The mycelia were light gray and velvety. Conidia were light brown to brown in color and oblate, oblong or oval. The conidial dimensions were typically between 15 to 43 µm by 8 to 9 µm in size. The conidia possessed one to six transverse septa, with slight to distinct constrictions at each division, and zero to two longitudinal septa. These morphological characteristics resembled Alternaria alternata (Fr.) Keissl.. DNA was extracted from three isolates, HE3, HE4 and HE5, using the CTAB method. Polymerase chain reaction (PCR) was performed on the extracted DNA with a set of primers ITS1/ITS4, H31a/H31b, gpd1/gpd2, TEF1-728F/TEF1-986R, and RPB2-5F2/fRPB2-7cR. The amplicon sequences from the three isolates were analyzed using the BLAST in GenBank (https://www.ncbi.nlm.nih.gov/). The results showed a high sequence identity, ranging from 99 to 100%, with the A. alternata strain YTMZ-20-2 across all the genetic markers tested. The strong match reinforced the identification of the strains as A. alternata. The sequences were deposited in GenBank (Table S1). The three fungal isolates were identified as A. alternata based on their morphological and genetic data. To conduct Koch's postulates, the representative isolate HE4 was used. Smooth bromegrass seed was soaked in water for four days and sown in potting soil contained in plastic pots (10 cm diameter × 15 cm height, five seeds/pot) in a greenhouse under a 16-h photoperiod at temperatures between 20 to 25°C and 60% relative humidity. When the plants reached a height of approximately 20 cm, the plants in three pots (replicates) were sprayed with a spore suspension (106 conidial/ml) at 10 ml/pot, and three pots were sprayed with sterile water for control. Five days after inoculation, the plants exhibited leaf spot symptoms similar to those previously described, while the control plants remained unaffected. The causative fungus was successfully re-isolated from the diseased plants and confirmed morphologically and molecularly on its identity as described above. This experiment was independently conducted three times. This is the first report of A. alternata causing leaf spot on smooth bromegrass in China. Since there is risk that the disease could seriously reduce the yield of the forage crop smooth bromegrass, further research is needed.

First report of soybean root rot caused by Fusarium falciforme in the Republic of Korea.

Phytopathogenic Fusarium species causing root and stem rot diseases in susceptible soybean (Glycine max (L.) Merrill) are a major threat to soybean production worldwide. Several Fusarium species have been reported to infect soybean plants in the Republic of Korea, including F. solani, F. oxysporum, F. fujikuroi, and F. graminearum (Cho et al., 2004; Choi et al., 2019; Kang et al., 2020). During the nationwide survey of soybean diseases in 2015, soybean plants showing symptoms of leaf chlorosis, wilting, and shoot death were found in soybean fields in Seosan, Chungnam. Fusarium isolates were obtained from the margins of sterilized necrotic symptomatic and asymptomatic regions of the stem tissues of diseased samples by culturing on potato dextrose agar (PDA). To examine the morphological characteristics, isolates were cultured on PDA at 25°C in the darkness for 10 days. Colonies produced white aerial mycelia with apricot pigments in the medium. Macroconidia were hyaline, slightly curved in shape with 3 or 4 septa, and their average length and width were 34.6± 0.56 µm (31.4 to 37.8 µm) and 4.7±0.16 µm (4.1 to 5.8 µm), respectively (n = 20). Microconidia were elongated, oval with 0 or 1 septum, and their average length and width were 11.4±0.87 and 5.2±0.32 µm, respectively (n = 20). The colonies and conidia exhibited morphological similarities to those of F. falciforme (Xu et al., 2022). Using the primers described by O'Donnell et al. (2008), identity of a representative strain '15-110' was further confirmed by sequencing portions of two genes, the translation elongation factor 1-alpha (EF-1α) and the second largest subunit of RNA polymerase II (RPB2). The two sequences (GenBank accession No. OQ992718 and OR060664) of 15-110 were 99% similar to those of two F. falciforme strains, 21BeanYC6-14 (GenBank accession nos. ON375419 and ON331931), and 21BeanYC6-16 (GenBank accession nos. ON697187 and ON331933). To test the pathogenicity, a single-spore isolate was cultured on carnation leaf agar (CLA) at 25℃ for 10 days. Pathogenicity test was performed by root-cutting assays using 14-day-old soybean seedlings of 'Daewon' and 'Taekwang'. Ten-day-old mycelia of 15-110 were collected from the CLA plates by scraping with distilled water, and the spore suspension was filtered and diluted to 1 × 106 conidia/mL. The roots of the soybean seedlings were partially cut and inoculated by soaking in the diluted spore suspension for two hours. The seedlings were then transplanted into 12 cm plastic pots (11 cm in height) and grown in a growth chamber at 25°C, 14h light/10h dark for 2 weeks. The infected plants exhibited wilting, observed brown discoloration on the root, and eventually died within 2 weeks, whereas the control plants inoculated with sterile water remained healthy. F. falciforme 15-110 was reisolated from infected plants, but not from the uninoculated controls. The morphology of the re-isolated fungus on PDA and its target gene sequences were identical to those of the original colony. To the best of our knowledge, this is the first report of root rot in soybean caused by F. falciforme in the Republic of Korea. Fusarium spp. induce a range of diseases in soybean plants, including root rot, damping-off, and wilt. Given the variable aggressiveness and susceptibility to fungicides among different Fusarium species, it is imperative to identify the Fusarium species posing a threat to soybean production. This understanding is crucial for developing a targeted and tailored disease management strategy to control Fusarium diseases.

Evaluation of Compost and Manure Amendments for Suppressing Heterodera glycines Ichinohe, 1952.

Soybean cyst nematode is a major pest of soybean crops, causing significant yield losses and economic impact. Current management strategies primarily rely on resistant varieties, cover crops, and seed treatments. However, there is a growing interest in developing sustainable, ecologically based approaches to integrate SCN risk reduction into soybean production systems. This study aimed to evaluate the efficacy of various compost and manure amendments in suppressing SCN populations and promoting soybean productivity. An in vitro egg hatching assay was conducted to screen the inhibitory effects of different compost and manure extracts on SCN egg hatching. Results indicated that poultry manure, Layer Ash Blend®, and swine manure extracts significantly inhibited SCN hatching compared to other treatments across multiple time points. Greenhouse trials further validated the effectiveness of Layer Manure®, poultry manure, High Carbon Dairy Doo®, and Seed Starter 101® in suppressing SCN cysts, eggs, and juveniles. A field microplot trial confirmed the practical promise of Layer Ash Blend® and poultry manure in SCN management, with significant reductions in SCN populations and increased soybean yields. The study also investigated the impact of these amendments on promoting the population of bacterivorous and frugivorous nematodes, contributing to a biological diverse soil ecosystem. Overall, the results indicate that amending SCN-infested soil with specific compost or manure formulations can effectively suppress nematode populations while improving soybean productivity. These findings contribute to the development of sustainable strategies for SCN management in soybean production systems.

Occurrence and management of the emerging pathogen Epicoccum sorghinum.

Epicoccum sorghinum is a notorious fungal pathogen that causes leaf spot symptoms on a wide range of plants, leading to devastating losses in crop production and quality. Here, all reports regarding the occurrence and management of E. sorghinum are covered for the first time. E. sorghinum has been detected in tropical and subtropical climate areas during the rainy season, mainly from March to August, since 2016. Although E. sorghinum shows broad host spectrum, the disease incidence is especially notorious in cereal crops and ornamental plants, suggesting that these plants are especially susceptible. Control methods based on synthetic fungicides, plant extracts, and microbial biocontrol agents have been reported. However, most agents were applied using only in vitro conditions, restricting the information about their actual applicability in field conditions. Additionally, E. sorghinum can colonize cereal grains and synthesize the carcinogenic mycotoxin tenuazonic acid, posing an enormous hazard for human health. Furthermore, although E. sorghinum is an emerging pathogen that is currently causing yield penalties in important crops, there is lack of information about its pathogenic mechanisms and virulence factors, and there is currently no commercial antifungal agent to manage E. sorghinum. Collectively, it is imperative to conduct in vivo studies to determine the efficacy of antifungal agents and the most effective methods of application in order to develop suitable management strategies against E. sorghinum.