First report of leaf spot disease caused by Cladosporium pseudocladosporioides on Lonicera caerulea L. in Heilongjiang Province, China.

Blue honeysuckle (Lonicera caerulea L.) has contributed to maintaining the forest's ecological balance and remarkable frost-resistant abilities, helping it withstand extremely cold conditions (-46 °C) and a wide pH range (5 to 8) (Sharma and Lee 2021). Between September 2022 and September 2023, leaf spots were observed on approximately 30% of blue honeysuckle plants of the 'Lanjingling' cultivar grown in a 1.13 ha field in Da Hinggan Ling Prefecture (50.32° N, 124.13° E) in Heilongjiang Province, China. The leaves of the affected plants displayed black-colored spots. To identify the causal agents, 10 healthy and symptomatic leaves were randomly collected from ten healthy and infected individual plants, respectively. Small (3 to 4 mm) segments of the symptomatic tissues were immersed in 5% sodium hypochlorite (NaOCl) for 3 min, rinsed three times with sterile distilled water, dried in a paper towel, and plated on 9-cm Petri dishes containing potato dextrose agar (PDA). Ten fungal colonies developed on the PDA plates with an isolation frequency of 100% from 10 symptomatic leaves, and all colonies displayed a morphology consistent with Cladosporium spp. (Bensch et al. 2018). Cladosporium-like fungi were not isolated from healthy leaves. Dark olive-colored mycelia were observed, with straight unbranched conidiophores bearing terminal light brown-colored limoniform conidia (1.80 to 4.50 × 2.10 to 12.60 µm) and surrounded by a thin line of white mycelium (Delisle-Houde et al. 2024). To confirm this identification, PCR amplification of two representative strains LD-299 and LD-300 genomic DNA was performed with ITS1/ITS4 (White et al. 1990) and ACT512F/ACT783R (Carbone and Kohn 1999) primers. Basic local alignment search tool (BLAST) analyses of the National Center for Biotechnology Information database showed that sequences of the ITS (PP600316, PP600317) and ACT (PP624334, PP624335) all revealed 100% (493/493 nt, 493/493 nt; 181/181 nt, 181/181 nt) shared identity with Cladosporium pseudocladosporioides strain ex-type MF473195 and HM148674 (Bensch et al. 2010), respectively. Using a neighbor-joining phylogenetic analysis based on the ITS and ACT sequences, isolates LD-299 and LD-300 clustered in the same clade of C. pseudocladosporioides. Therefore, based on its morphological characteristics and molecular phylogeny, the two isolates were identified as C. pseudocladosporioides (Cosseboom and Hu 2023). A pathogenicity test was performed using nine healthy two-year-old blue honeysuckle Lanjingling plants. Three plants were inoculated with either the LD-299 or the LD-300 conidial suspension (1 × 106 spores/ml) or with clean water as an experimental control (Aydogdu et al. 2023). All plants were cultured in a greenhouse (28℃, 75% relative humidity, 12 h light and dark cycle), and each experiment was replicated three times. Typical leaf spot symptoms were first observed on the inoculated leaves after 10 days. Morphological and molecular characterization of re-isolated pathogens from the artificially infected leaves indicated that the two isolates were identical, thereby confirming Koch's postulates. Cladosporium pseudocladosporioides previously caused leaf spot disease on artichoke (Cynara scolymus) in Türkiye (Aydogdu et al. 2023). To the best of our knowledge, this is the first report of C. pseudocladosporioides causing leaf spots on blue honeysuckle in China. Blue honeysuckle production losses due to the leaf spots are critical for growers. Therefore, further focus should be given to investigate the host range and geographic distribution of C. pseudocladosporioides.

First report of leaf spot disease caused by Neopestalotiopsis rosae on Lonicera caerulea L. in Heilongjiang Province, China.

Recently, interest in cultivating blue honeysuckle (Lonicera caerulea L.) for horticulture and medicinal uses has grown (Sharma and Lee 2021). Between September 2022 and September 2023, a leaf spot disease (Fig. S1) was observed on approximately 20% of 'Lanjingling' blue honeysuckles grown in a 0.18 ha field in Qiqihar city (123.43°E, 47.92°N), Heilongjiang Province, China. Infected plants displayed black leaf spots that expanded to cover the entire leaf. Small, 3 to 4 mm segments of infected tissue were surface sterilized with 75% ethanol for 30 s and 5% sodium hypochlorite (NaOCl) for 3 min, rinsed three times with sterile distilled water, dried on paper towels, and plated in 9 cm Petri dishes containing potato dextrose agar (PDA) (Ma et al. 2023). To induce sporulation, nine purified cultures (Fig. S2) with similar culture characteristics were finally obtained from ten infected plants and they displayed a conidia morphology consistent with Neopestalotiopsis spp., no other fungi were isolated, and the isolation frequency was 90%. Conidiomata (Fig. S3) were brown to black and distributed in concentric rings with an average size of 261.98 (60.30-451.80) µm (n = 50). The conidia (Fig. S3) were fusoid and had four septa, straight to slightly curved, with an average size of 23.48 (13.50-30.30) × 5.42 (4.50-9.30) µm(n = 50), while basal and apical cells were hyaline and the three middle cells were brown with darker septa. PCR amplification was performed with ITS1/ITS4 (White et al. 1990), EFl-728F/EF1-986R (Carbone and Kohn 1999), and Btub2Fd/Btub4Rd (Glass and Donaldson 1995) primers from the genomic DNA of the LD-330. Sequences of ITS (PP033584), TEF (PP048757), and TUB (PP048758) revealed 99 to 100% (499/500, 255/255, and 481/486) shared identity with Neopestalotiopsis rosae sequences (NR145243, KM199524, and KM199430) (Rebollar-Alviter et al. 2020). Therefore, based on morphological characteristics and molecular phylogeny, LD-330 was identified as N. rosae. Six two-year-old healthy plants of the 'Lanjingling' cultivar were selected for a pathogenicity test (Yan et al. 2023). The leaves were surface disinfected with 75% alcohol and then wiped with sterilized water three times. Three plants were inoculated with 10 ml of LD-330 conidial suspension (1 × 106 spores/ml) or with sterile water as an experimental control, respectively. All plants were in closed plastic bag, incubated in a greenhouse at 28 ℃ and 75% relative humidity (RH) under a 12-h light/dark cycle, and each experiment was performed three times (Rebollar-Alviter et al. 2020). Typical leaf spot symptoms were observed on inoculated leaves after 14 days (Fig. S4), whereas no symptoms were detected on water-treated leaves. The same pathogen was reisolated from infected leaves, displayed the same morphological and molecular traits, and was again identified as N. rosae, confirming Koch's postulate. Neopestalotiopsis rosae was previously reported on pecan (Gao et al. 2022), causing black leaf spot disease in China. To our knowledge, this is the first report of a blue honeysuckle leaf spot caused by N. rosae in China and specifically in the Heilongjiang province which has the largest blue honeysuckle cultivation area in the country. Future research should be directed toward developing comprehensive management measures.

First report of leaf spot disease caused by Pseudopithomyces chartarum on Lonicera caerulea L. in Heilongjiang Province, China.

Blue honeysuckle (Lonicera caerulea L.) cultivation has gradually expanded in China but continues to be limited by challenges such as leaf spot disease. Between September 2022 and September 2023, a leaf spot disease was observed on approximately 30% of 'Lanjingling' blue honeysuckles grown in a 2.66 ha field (a total of about 11,000 plants) in Jiamusi city (130.47°E, 46.16°N), Heilongjiang Province, China. Affected plants displayed brown necrotic lesions on their leaves that gradually expanded in area until the leaves fell off the plant entirely. Small, 3 to 4 mm segments of infected tissue from 50 randomly selected leaves were surface sterilized with 75% ethanol for 30 s and 5% sodium hypochlorite (NaOCl) for 3 min, rinsed three times with sterile distilled water, dried on paper towels, and plated in 9 cm Petri dishes containing potato dextrose agar (PDA) (Yan et al. 2022). Five pathogens (LD-232, LD-233, LD-234, LD-235, and LD-236) were isolated on PDA and displayed a conidia morphology consistent with Pseudopithomyces spp. (Perelló et al. 2017). The fungal colonies on PDA were villiform, white, and whorled and had sparse aerial mycelium on the surface with black conidiomata. The conidia were obpyriform and dark brown, had 0 to 3 transverse and 0 to 1 longitudinal septa, and measured 9.00 to 15.30 µm × 5.70 to 9.30 µm in size (n = 50). Genomic DNA was extracted from a representative isolate, LD-232, for molecular verification and PCR amplification was performed with ITS1/ITS4 (White et al. 1990), LROR/LR7 (Carbone and Kohn 1999), and RPB2-5F2/RPB2-7CR (Liu et al. 1999) primers. Sequences of LD-232 ITS (OR835654), LSU (OR835652), and RPB2 (OR859769) revealed 99.8% (530/531 nt), 98.8% (639/647 nt), and 99.8% (1015/1017 nt) shared identity with Pseudopithomyces chartarum sequences (OP269600, OP237014, and MK434892), respectively (Wu et al. 2023). Bayesian inference (BI) was used to construct the phylogenies using Mr. Bayes v. 3.2.7 to confirm the identity of the isolates (Ariyawansa et al. 2015). Phylogenetic trees cannot be constructed based on the genes' concatenated sequences because selective strains do not have complete rDNA-ITS, LSU, and RPB2 sequences. Therefore, based on the morphological characteristics and molecular phylogeny, LD-232 was identified as P. chartarum (Perelló et al. 2017; Wu et al. 2023). A pathogenicity test was performed with six healthy, two-year-old 'Lanjingling' blue honeysuckle plants. Three plants were inoculated by spraying the LD-232 conidial suspension (1 × 106 spores/ml) or clean water as an experimental control condition (Wu et al. 2023; Yan et al. 2023). All plants were cultured in a greenhouse at 28℃ under a 12-h light/dark cycle, and each experiment was replicated three times. Typical leaf spot symptoms were observed on inoculated leaves after 10 days. The same pathogens were reisolated from infected leaves, displayed the same morphological and molecular traits, and were again identified as P. chartarum, confirming Koch's postulate. P. chartarum previously caused leaf spot disease on Tetrapanax papyrifer in China (Wu et al. 2023). To our knowledge, this is the first report of blue honeysuckle leaf spot caused by P. chartarum in China. Identification of P. chartarum as a disease agent on blue honeysuckle will help guide future management of leaf diseases for this economically important small fruit tree.

Enhancing Postharvest Quality and Antioxidant Capacity of Blue Honeysuckle cv. 'Lanjingling' with Chitosan and Aloe vera Gel Edible Coatings during Storage.

This study investigated the impact of chitosan (CH, 1%) and aloe vera gel (AL, 30%) edible coatings on the preservation of blue honeysuckle quality during a 28-day storage at -1 °C. Coating with CH, AL, and CH+AL led to notable enhancements in several key attributes. These included increased firmness, total soluble solids, acidity, pH, and antioxidant capacity (measured through DPPH, ABTS, and FRAP assays), as well as the preservation of primary (ascorbic acid) and secondary metabolites (TPC, TAC, and TFC). The TAC and TFC levels were approximately increased by 280% and 17%, respectively, in coated blue honeysuckle after 28 d compared to uncoated blue honeysuckle. These coatings also resulted in reduced weight loss, respiration rate, color, abscisic acid, ethylene production, and malondialdehyde content. Notably, the CH+AL treatment excelled in preserving secondary metabolites and elevating FRAP-reducing power, demonstrating a remarkable 1.43-fold increase compared to the control after 28 days. Overall, CH+AL exhibited superior effects compared to CH or AL treatment alone, offering a promising strategy for extending the shelf life and preserving the quality of blue honeysuckle during storage.

First Report of Postharvest Fruit Rot Caused by Botrytis cinerea on Blue Honeysuckle (Lonicera caerulea L.) Fruit in China.

Blue honeysuckle (Lonicera caerulea L.) fruit is growing in popularity as a natural, functional 'super fruit', but its storage is challenged by pathogen infection. In June 2022, approximately 30% of 100 kg of blue honeysuckle fruits (cv. Lanjingling) obtained in Harbin, China (128.70°E, 44.87°N) showed postharvest fruit rot symptoms after 15 d of storage at 4°C, leading to whole fruit rotting with gray fungal growth (Fig.1 A). Small (1-2 mm) segments of infected tissue were obtained from 20 randomly selected fruits which were surface sterilized with 75% ethanol for 30 s and 5% sodium hypochlorite (NaOCl) for 3 min, rinsed three times with sterile distilled water, dried in paper towel, and plated in 9 cm Petri dishes containing potato dextrose agar (PDA). Five purified cultures were obtained and their front colonies were dark brown (Fig.1 C) on the PDA plates after 5 d at 25°C (Alam et al. 2019; Riquelme-Toledo et al. 2020). The conidia (n = 50) were single-celled, hyaline, either ellipsoid or ovoid, and measured 7.5-15.0 µm (11.7 µm average) × 6.0-11.4 µm (8.3 µm average). The conidiophores (Fig.1 E) were branched at the apex bearing bunches of conidia resembling grape clusters (Ellis 1971). For molecular confirmation, genomic DNA was extracted from a representative isolate LDGS-3 using the Ezup Column Fungi Genomic DNA Purification kit (Sangon Biotech, Shanghai, China). The internal transcribed spacer region (ITS, GenBank ON952502), heat shock protein (HSP60, GenBank OP039103), the second-largest subunit of RNA polymerase II (RPB2, GenBank OP186114) and glyceraldehyde 3-phosphate dehydrogenase (G3PDH, GenBank OQ658508) genes were partially amplified with the respective primers ITS1/ITS4, HSP60f/HSP60r, RPB2f/RPB2r, and G3PDH-F/G3PDH-R (Staats et al. 2005; White et al. 1990). BLAST analysis revealed that the sequences of the four genes showed 100% homology with the MH782039, MH796663, MN448501 and MH796662 sequences for isolates of Botrytis cinerea. Based on morphology and molecular characteristics, the isolate LDGS-3 was identified as B. cinerea. For pathogenicity, twenty healthy blue honeysuckle fruits (cv. Lanjingling) were superficially sterilized with 75% ethanol and washed with distilled water. Ten inoculated blue honeysuckle fruits, which were injected with 10 µL conidial suspension of isolate LDGS-3 (106 spores/mL) displayed fruit rot symptoms (Fig.1 B) inside 9 cm Petri dishes after 10 d at 4°C, while no symptoms were detected on ten fruits inoculated with sterile distilled water (Alam et al. 2019). The same isolate that was reisolated from infected fruits with the same morphological and molecular traits was also identified as B. cinerea, confirming Koch's postulates. B. cinerea was previously reported in Henan Province, China in hawthorn (Zhang et al. 2018). To our knowledge, this is the first report of postharvest fruit rot caused by B. cinerea on blue honeysuckle fruit in China, which will aid future management of this emerging postharvest disease.

Critical review on anthocyanins in blue honeysuckle (Lonicera caerulea L.) and their function.

Blue honeysuckle (Lonicera caerulea L.) is an emerging commercial fruit in the world, has been known for its multiple anthocyanins in the berries, cyanidin-3-glucoside (C3G) is a major anthocyanin in berries and it makes up 76-92% of the total anthocyanins content, with high antioxidant capacity, and widely used in food products. In this review, recent studies related to anthocyanins in blue honeysuckle were sorted out, including the current status of research on anthocyanins in blue honeysuckle berries, especially C3G, qualitative and quantitative analysis of anthocyanins in berries, extraction and purification methods of anthocyanins from blue honeysuckle, in addition, biological effects of blue honeysuckle, and recommended utilization. Blue honeysuckle contains polyphenols, flavonoids, anthocyanins, minerals, and multiple bioactive compounds, it has been extensively reported to have significant antioxidant, cardioprotective, anti-inflammatory, neuroprotective, anticancer, and anti-diabetic functions, and has been used in a variety of food products as raw materials.

First report of leaf spot disease caused by Alternaria tenuissima on Lonicera caerulea L. in Heilongjiang Province, China.

Blue honeysuckle (Lonicera caerulea L.) is a perennial plant of the Caprifoliaceae family and Lonicera genus, the largest genus in the plant kingdom. Between September 2021 and September 2022, a leaf spot disease was observed on ~20% of blue honeysuckles of the 'Lanjingling' cultivar grown in a 3.33 ha field at the Xiangyang base (126.96°E, 45.77°N) of the Northeast Agricultural University, Harbin (Heilongjiang Province, China). Leaf spots first presented black mildew centers, gradually covering large areas of the leaf until it eventually fell off. Small 3-4 mm segments of infected tissue from 50 randomly selected leaves were surface sterilized with 75% ethanol and 5% sodium hypochlorite, rinsed in sterile distilled water, and transferred to 9 cm Petri dishes containing potato dextrose agar (PDA) after drying. Finally, two isolated pathogens were obtained through single spore culture on PDA; they appeared as gray-black colonies and were named LD-12 and LD-121. The observed LD-12 and LD-121 conidia displayed a morphology consistent with Alternaria spp. They were obpyriform and dark brown, with 0-6 transverse and 0-3 longitudinal septa, measuring 6.00-17.70 µm × 9.30-42.30 µm and 5.70-20.70 µm × 8.40-47.70 µm for LD-12 and LD-121, respectively (n = 50). Genomic DNA was extracted from the two isolates for molecular verification, and PCR amplification was performed with ITS1/ITS4 (White et al. 1990), GPD1/GPD2 (Woudenberg et al. 2015), EFl-728F/EF1-986R (Carbone and Kohn 1999), RPB2-5F2/RPB2-7CR (Liu et al. 1999), and Alt-for/Alt-rev (Hong et al. 2005) primers. Sequences of LD-12 ITS (OQ607743), GPD (OQ623200), TEF (OQ623201), RPB2 (OQ658509), and ALT (OQ623199) revealed 99-100% of identity with Alternaria tenuissima sequences (KC584567, MK451973, LT707524, MK391051, and ON357632). Sequences of LD-121 ITS (OQ629881), GPD (OQ850078), TEF (OQ850075), RPB2 (OQ850076), and ALT (OQ850077) revealed 99-100% identity with A. alternata sequences (MN826219, ON055384, KY094927, MK637444, and OM849255). Nine two-year-old healthy plants from the 'Lanjingling' cultivar were selected for a pathogenicity test. Three plants were inoculated with either the LD-12 or LD-121 conidial suspension (1 × 106 spores/ml) or with clean water as an experimental control condition (Mirzwa-Mróz et al., 2018; Liu et al., 2021). All plants were cultured in a greenhouse at 28℃ under a 12-h light/dark cycle, and each experiment was performed three times. Typical leaf spot symptoms were observed on inoculated leaves after 10 d. The same pathogens reisolated from infected leaves displayed the same morphological and molecular traits. They were again identified as A. tenuissima and A. alternata, confirming Koch's postulate. A. tenuissima and A. alternata were previously reported on Orychophragmus violaceus (Liu et al., 2021) and L. caerulea (Yan et al., 2022) in China. This study is the first report of a blue honeysuckle leaf spot caused by A. tenuissima in China. In the future, effective biological and chemical control should be used to prevent blue honeysuckle leaf spots in China.

C3G quantified method verification and quantified in blue honeysuckle (Lonicera caerulea L.) using HPLC-DAD.

Blue honeysuckle is a source of anthocyanins with great potential as a food colorant, and a healthy and functional food material, and contains much cyanidin 3-glucoside (C3G), which has many benefits for human health. A rapid, reliable, accurate quantification method of anthocyanin content in different varieties of blue honeysuckle is critical to help in breeding and selecting excellent varieties which are used in the food processing industry and healthcare industry. Our objective was to verify the modified quantification method of C3G and quantified C3G content in three blue honeysuckle varieties of 'Berel', 'Lanjingling' and 'Wulan' using the modified HPLC method by Agilent 1200 system and CAPCELL PAK C18 column (150 mmⅹ4.6 mm, I. D., 5 µm, Japan), with detection at 530 nm, the solvent flow rate was 1 mL/min, the temperature of the column chamber is 35 °C. The results indicated that the modified method was validated in terms of linearity (R2 = 0.999), precision (RSD = 0.61%), stability (RSD = 5.23%), and recovery with a good level, and C3G can be quickly quantified in blue honeysuckle. In addition, 'Wulan' contains the highest C3G level compared with 'Lanjingling' and 'Berel'.