Brown Symptoms Research Articles

Phenylpropanoid metabolism in relation to peel browning development of cold-stored ‘Nanguo’ pears

Cold-stored ‘Nanguo’ pears are susceptible to peel browning during subsequent shelf life. In this study, ‘Nanguo’ pears were cold-stored for different periods to elucidate the metabolism of phenylpropanoid accompanying browning. Changes in phenolics and flavonoids and the crucial enzyme activity and related gene expression involved in the phenylpropanoid pathway were monitored. It was found that the fruit that underwent long-term storage showed peel browning symptoms prior to softening, and the symptom got worse with increasing shelf life. Meanwhile, the accumulation of reactive oxygen species (ROS) and the decrease of ROS scavenging ability were noted. The content of phenolics and flavonoids and the activity and expression of shikimate dehydrogenase (SKDH), phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL) involved in the phenylpropanoid pathway decreased with prolonged storage. Correlation analysis revealed that browning was positively correlated with ROS accumulation, and the content of phenolics and flavonoids directly affected ROS scavenging ability. In addition, the decrease in phenolics and flavonoids might be owing to the reduced activity of SKDH, PAL, and 4CL and the down-regulated expression of PuPAL and Pu4CL. Collectively, this study indicated that the metabolism of phenylpropanoid is associated with the browning response induced by low-temperature stress.

1-Methylcyclopropene and lemongrass essential oil nanocoatings effect on the preservation of cold stored ‘Rocha’ pear

The effects of coating ‘Rocha’ pear with alginate-based nanoemulsions enriched with lemongrass essential oil (LG) was evaluated and compared to the usual 1-MCP treatment. Fruit were treated with 1-MCP (312 nL L−1) or coated with nanoemulsions: sodium alginate 2 % (w/w) + lemongrass essential oil 1.25 % (w/w) (LG 1.25 %) or lemongrass essential oil 2.5 % (w/w) (LG 2.5 %). Then, fruit were stored at 0 °C and 90–95 % relative humidity (RH), for eight months. Fruit samples were collected at harvest and after two, four, six and eight months of cold storage, and then transferred to shelf-life at 22 °C. Upon removal and after 7 d shelf-life, fruit symptoms of superficial scald and internal browning, ethylene production, color CIE (L*, hue), firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, electrolytic leakage (EL), antioxidant activity and fatty acids of pear peel, microbial growth and sensory analyses were evaluated. Coatings and 1-MCP reduced fruit color evolution and preserved better firmness than control. Coatings and 1-MCP did not affect SSC and TA. Treatments did not influence the sensory quality. Microbial growth was within the safety limits in all treatments. Treatments with 1-MCP and LG-nanoemulsions were similarly efficient to reduce superficial scald, nevertheless the LG-nanoemulsions showed higher internal disorders after 8 months of storage and LG 2.5 % had higher decay at the same period, similar to control. 1-MCP treated fruit had the lowest softening rate after shelf-life up to 4 months and LG 2.5 % showed higher weight loss. Also, ethylene production was higher in control and LG 1.25 % up to 6 months plus shelf-life, while after 8 months there was no difference among treatments. This study suggests that 1-MCP is the most efficient for preserving quality of ‘Rocha’ pear for 8 months, while up to 6 months the best effect is obtained with LG 1.25 % nanocoatings.

Gas exchange model using heterogeneous diffusivity to study internal browning in ‘Conference’ pear

Internal gas gradients in pear fruit during controlled atmosphere storage depend on the effective gas diffusivity of the tissue. The diffusivity varies over the fruit organ due to the heterogeneous tissue microstructure across the fruit. This study implemented effective diffusivity maps reflecting the heterogeneous structure to predict internal gas gradients and relate the result to the occurrence of internal browning. Diffusivity maps of different pears were calculated from X-ray CT based porosity maps. Internal oxygen (O2), carbon dioxide (CO2) and respiratory quotient (RQ) levels were computed using a reaction-diffusion model incorporating the heterogeneous effective diffusivity map. Critical O2 and RQ levels for the shift from respiration to fermentation were defined based on the respiratory-fermentative energy balance of the cells. The model was indirectly validated by comparing RQ level contours with non-destructive 3D images of the internal browning of the pears after storage at 1.0 kPa and 0.5 kPa O2, combined with 0.7 kPa CO2 at 1 °C. The distribution of the internal gas concentrations and RQ was affected by the heterogeneity of the diffusivity. The results also confirmed the incidence of internal browning when the O2 and RQ were under or above critical O2 and RQ limits, respectively. The fermentation process was indicated to be dominant when the tissue’s RQ limit (RQ*) went above 2.12 (or at 0.044 kPa O2). The tissue volumes where O2 and RQ levels were critical corresponded reasonably well to browning-affected tissues of pears with different shapes. The pear with more shallow gas gradients showed less symptoms of browning.

First Report of Fusarium meridionale Causing Stalk Rot of Ryegrass in China.

Members of the Fusarium graminearum species complex (FGSC) are the main causing agents of head blight, seedling blight, or stalk rot in wheat and other cereals worldwide. Surveys on species composition and mycotoxin production of FGSC populations have mainly focused on food crops such as wheat, maize, and barley, but little is known about the identity of FGSC pathogens present in pasture grass. In April 2021, a survey of grass diseases in the Hongya County (29.90661 N; 103.37313 E) in Sichuan Province was conducted to understand the etiology of stalk rot in perennial ryegrass (Lolium perenne). It was observed in several pastures that about 10% of yield loss in perennial ryegrass was caused by stalk rot. Affected plant stalks were brown to dark brown in colour and appeared soggy. As infections continued or under conditions of high humidity, some plant stalks also became flattened. Perennial ryegrass samples with symptoms of stalk rot or browning of the stem were collected. Symptomatic tissues were cut into short segments (approximately 5 mm), surface-sterilized in 3% sodium hypochlorite solution for 2 min, rinsed three times with sterile distilled water, air dried, plated onto potato dextrose agar (PDA), and then incubated in the dark at 28 °C. After 3 to 5 days, Fusarium-like fungal colonies with reddish-orange mycelium were collected and transferred to new PDA plates for further purification, and the purified cultures were obtained by single spore isolation. Four uniform isolates were obtained and their colonies on PDA resembled typical FGSC colonies (Leslie and Summerell 2006; O'Donnell et al. 2004). Colonies had an average radial growth rate of 8.5 to 11.0 mm/day at 28 °C in the dark on PDA. Conidial characteristics were studied on Spezieller Nährstoffarmer agar (SNA) as described by Wang et al. (2014). Macroconidia were falcate to almost straight, usually with parallel dorsal and ventral lines, 3- to 5-septate, 20.65 to 55.22 μm in length (average 39.16 μm), and 2.38 to 6.93 μm in width (average 4.42 μm) (n = 200). No microconidia were observed. The pathogenicity of the isolated Fusarium strains was then tested on healthy perennial ryegrass (variety Changjiang 1). Ryegrass plants grown for 2 months were inoculated by punching a hole in the stem using a sterile toothpick, followed by an injection of 20 μL macroconidia suspension at a concentration of 105 spores/mL. Ryegrass stems treated with water served as the control. Twenty plants were included in each treatment. After inoculation, the plants were grown in a growth chamber at 25 °C and 90% humidity for 24 h. Stalk tissues at the wound site turned brown after 3 days and the brown area then extended to regions above and below. No symptoms were observed in the water-treated controls. As well, the same pathogen was reisolated from the infected grass stems, but not from the controls. Thus, the isolated Fusarium spp. are a cause of stalk rot in perennial ryegrass based on the fulfillment of Koch's postulates. To identify the Fusarium spp. to species level, portions of the translation elongation factor 1-α (TEF) gene sequences from all four strains were amplified and sequenced as described by Wang et al. (2015). The obtained sequences were identical, and a sequence of isolate SC1 was submitted to GenBank (accession no. MZ964308). BLASTn searches were conducted on the TEF sequence (607 bp) in two databases, revealing it had 100% similarity to the sequence of Fusarium meridionale strain DS27 (accession no. MN629330) in NCBI and strain NRRL28723 from FUSARIUM-ID (http://isolate.fusariumdb.org/). A concatenated four-gene phylogeny (supplementary figure) resolved SC1 and the type specimens of F. meridionale (NRRL28723, 29010, and 28436) in a monophyletic clade with 100% bootstrap support, confirming that the strain SC1 belongs to F. meridionale. Finally, trichothecene productions of F. meridionale strains were evaluated using rice cultures kept at 28 °C in the dark for two weeks, as described by Desjardins and Proctor (2011). LC-MS/MS analysis indicated that the fungus could produce NIV and 4ANIV in rice cultures with average concentrations of 1400.44 and 3144.10 μg/kg, respectively. To the best of our knowledge, this is the first report of F. meridionale causing disease in perennial ryegrass in China. Further research will be necessary to determine its distribution, aggressiveness, and trichothecene production.

First Report of a New Disease Caused by Fusarium tricinctum on Apple Tree in China.

First Report of a New Disease Caused by Fusarium tricinctum on Apple Tree in China.

First Report of Fusarium avenaceum, Fusarium oxysporum, Fusarium redolens, and Fusarium solani Causing Root Rot in Pea in France.

First Report of Fusarium avenaceum, Fusarium oxysporum, Fusarium redolens, and Fusarium solani Causing Root Rot in Pea in France.

First Report of Brown Spot on White Button Mushroom (Agaricus bisporus) Caused by Cedecea neteri in Iran.

In autumn 2018, cap discoloration and browning symptoms (up to 20% incidence) were observed on commercially grown white button mushrooms (Agaricus bisporus) in two distinct farms located in Shiraz and Marvdasht Counties in Southern Iran. Symptomatic caps (13 and six caps from Shiraz and Marvdasht Counties, respectively) were characterized by visible brown discoloration with no blotch symptoms, bacterial sticky mass and cap wilting. Isolation of bacterial strains from infected cap tissues was performed on yeast-extract peptone glucose agar (YPGA) according to Hamidizade et al. (2020). The resulted bacterial colonies were oyster-white in color, non-fluorescent, domed convex circular with smooth margins 1-2 mm in diameter. A total of six bacterial strains (Shiraz: Ir1002, Ir1003, Ir1004, Ir1005, Ir1007 and Marvdasht: Ir1027) were isolated from distinct mushroom samples. Standard biochemical and phenotypic analyses (Schaad et al. 2001) showed that the bacterial strains were Gram and oxidase negative, catalase positive and facultatively anaerobic, while no capsule or endospore was observed. All strains were positive in urease production, arginine dihydrolase, hydrolysis of tween 80, and utilization of sucrose and D-sorbitol, while they were negative in amylase, cellulose, lecithinase, pectinase, and protease production as well as casein hydrolysis. Based on these phenotypic characteristics, the strains were supposed to be members of Enterobacteriaceae. They also did not induce hypersensitive reaction (HR) on tobacco (Nicotiana tabacum cv. Turkish) leaves nor did they produce tolaasin when streaked side-by-side with "Pseudomonas reactans" strains on King B medium (Osdaghi et al. 2019). Pathogenicity of the strains was evaluated (repeated twice) on fresh caps of white button mushroom using cut-cap method (Hamidizade et al. 2020). Reference strains of Pseudomonas tolaasii (CFBP 8707) and Mycetocola spp. (CFBP 8708) were used as positive controls, while sterile distilled water was used as a negative control. Brown discoloration appeared 24-36 hours post inoculation on cap surfaces while control caps remained asymptomatic. Koch's postulates were accomplished by re-isolation and identification of bacterial strains from the symptomatic caps using colony morphology and Gram staining. For molecular identification, all initial as well as re-isolated strains were subjected to amplification and sequencing of 16S rDNA and gyrB (Yamamoto and Harayama 1995; Hamidizade et al. 2020). Obtained nucleotide sequences were deposited into NCBI GenBank (16S: MZ298620 to MZ298625; gyrB: MZ313184 to MZ313189). BLAST search using the 16S rDNA and gyrB sequences showed that the strains isolated in this study had 97-99% sequence similarity to the reference strains of Cedecea neteri. Phylogenetic analyses also confirmed close relationship of bacterial strains from this study to C. neteri strains. Pure cultures of representative strains Ir1004 (CFBP 8900) and Ir1027 (CFBP 8896) are deposited in CIRM-CFBP culture collection. This is the first report of C. neteri causing brown spot disease on button mushroom in Iran, while the bacterium has previously been reported to cause soft rot on Pholiota nameko (Yan et al. 2018), and yellow sticky disease on Flammulina velutipes (Yan et al. 2019) in China. Further comprehensive investigations will shed a light on the economic impact of the brown spot disease on mushroom industry in Iran.

Comparison of substrate reactivity of polyphenol oxidase and browning symptom of fresh cut ‘Nam Dok Mai Si Thong’ and ‘Nam Dok Mai No. 4’ mango in vitro and in vivo

ISHS V Asia Symposium on Quality Management in Postharvest Systems Comparison of substrate reactivity of polyphenol oxidase and browning symptom of fresh cut ‘Nam Dok Mai Si Thong’ and ‘Nam Dok Mai No. 4’ mango in vitro and in vivo

Effect of Pre-cooling and Chitosan Treatment on Pineapple (Ananas comosus (L.) Merr.) Quality During Cold Storage

Precooling showed promises treatment for chilling injury symptom in the fruit. The research aimed to determine the effect of pre-cooling dan coating treatment using chitosan to the internal browning symptoms of pineapples during cold storage at 10°C. The pineapples of cultivar “Smooth Cayenne” were treated with 6 treatments, namely P0C0 (no pre-cooling and no chitosan), P0C1 (no pre-cooling and chitosan), P1C0 (1-day pre-cooling and no chitosan), P1C1 (1-day pre-cooling and chitosan), P2C0 (3-day pre-cooling and no chitosan), P2C1 (3-day pre-cooling and chitosan). Fruits qualities were evaluated by their weight loss, firmness, chilling injury, and chemical compounds including titratable acidity, phenol compounds, and reducing sugar. The analyses were performed on day 7, 14, 21, 28, and 28+3 days of storage. Each treatment was replicated three times and the data was analyzed using factorial complete randomized design (CRD). The result showed that pre-cooling and chitosan was able to inhibit chilling injury and prolong the shelf life of “Smooth Cayenne” pineapple.

First Report of Botrytis Blight Caused byBotrytis cinereaonHelleborus nigerin Italy.

HomePlant DiseaseVol. 106, No. 1First Report of Botrytis Blight Caused by Botrytis cinerea on Helleborus niger in Italy. PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Botrytis Blight Caused by Botrytis cinerea on Helleborus niger in Italy.A. Garibaldi, D. Bertetti, G. Tabone, I. Luongo, and M. L. GullinoA. GaribaldiCentre of Competence AGROINNOVA, University of Torino, 10095 Grugliasco, ItalySearch for more papers by this author, D. BertettiCentre of Competence AGROINNOVA, University of Torino, 10095 Grugliasco, ItalySearch for more papers by this author, G. TaboneCentre of Competence AGROINNOVA, University of Torino, 10095 Grugliasco, ItalySearch for more papers by this author, I. LuongoDISAFA, University of Torino, 10095 Grugliasco, ItalySearch for more papers by this author, and M. L. Gullino†Corresponding author: M. L. Gullino; E-mail Address: [email protected]https://orcid.org/0000-0002-7706-1915Centre of Competence AGROINNOVA, University of Torino, 10095 Grugliasco, ItalySearch for more papers by this authorAffiliationsAuthors and Affiliations A. Garibaldi1 D. Bertetti1 G. Tabone1 I. Luongo2 M. L. Gullino1 † 1Centre of Competence AGROINNOVA, University of Torino, 10095 Grugliasco, Italy 2DISAFA, University of Torino, 10095 Grugliasco, Italy Published Online:9 Jan 2022https://doi.org/10.1094/PDIS-06-21-1290-PDNAboutSectionsPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Helleborus niger (Christmas Carol) is a perennial herbaceous plant belonging to the Ranunculaceae family, appreciated for the abundant production of winter flowers. In Italy, it is marketed as potted plant. In January 2021, symptoms of an unknown blight were observed on all the 2-year-old potted plants of H. niger grown in a private garden located in Santa Margherita Ligure (Genova Province, northern Italy). Symptoms appeared on stems and petioles that turned brown, rotted, and collapsed starting from the base. The tepals also were affected and desiccated. A soft, gray mycelium appeared on affected tissues and plants totally lost their aesthetic value. Several affected stems and tepals were immersed in a solution of sodium hypochlorite (NaOCl, 1%) for 30 s. Successively, they were washed in sterilized water. Small pieces were excised from the margin of affected tissues and cultured on potato dextrose agar (PDA, Merck KGaA, Darmstadt, Germany) medium. Plates were incubated at temperatures ranging from 20 to 25°C. Gray fungal colonies developed consistently and produced dark, spheroidal to elongated sclerotia that measured 1.0 to 1.5 × 0.5 to 1.3 (mean: 1.1 × 0.9) mm. After 10 days, colonies produced branched conidiophores that supported unicellular, ovoid conidia measuring 7.9 to 12.1 × 5.2 to 9.2 (mean: 10.3 × 7.8) µm. These characteristics permitted us to identify the fungus isolated from H. niger as Botrytis cinerea Pers.: Fr. (Ellis 1971). The DNA of the isolate 21-1-O1 was extracted with the E.Z.N.A. Plant DNA Kit (Omega Bio-Tek, Norcross, GA, U.S.A.) from a pure culture grown on PDA. Successively, the product obtained from a PCR reaction with primers ITS1/ITS4 (White et al. 1990) was purified and sequenced. A 516-bp sequence (GenBank accession no. MZ417544) was achieved. BLASTn analysis (Altschul et al. 1997) of this sequence had 100% nucleotide identity with the ex-type CBS 156.71 of B. cinerea (GenBank accession no. MH860044). The pathogenicity of the isolate 21-1-O1 was confirmed by inoculating three plants of H. niger with a conidial and mycelial suspension obtained from 20-day-old cultures grown on PDA at 20 to 24°C. Each plant was sprayed with 20 ml of suspension at the concentration of 5 × 104 CFU (conidia and mycelial fragments)/ml. Three control plants were sprayed with sterile water. All plants were closed in a moistened chamber for 8 days and maintained outdoors, under the shade, at temperatures ranging from 17 to 26°C. First symptoms of browning appeared on tepals of inoculated plants about 6 days after inoculation. Later, symptoms developed on stems and petioles, affected tissues rotted and were covered by a gray soft mycelium. The pathogenicity test was repeated once. B. cinerea was reisolated from the affected tissues. Controls remained healthy. B. cinerea has been reported on H. niger in the United States (Anonymous 1960). To authors’ knowledge, this is the first report of B. cinerea on H. niger in Italy as well as in Europe. The economic importance of this disease is nowadays limited in Italy due to the reduced production of H. niger. However, the cultivation of this species might increase, following the selection of genotypes more suitable as potted plants and for cut flower production under the Mediterranean climate.The author(s) declare no conflict of interest.

Aplicação de diferentes tratamentos de revestimento para melhorar a capacidade de armazenamento e a qualidade do fruto da romã (Punica granatum L., cv. Wonderful) durante o armazenamento prolongado

Abstract This study was carried out on pomegranate fruits cv. “Wonderful” with the aim of maintaining fruit quality and water content, reducing weight loss, chilling injury and browning symptoms during cold storage at 5 °C and 90% RH for 60 d followed by simulated shelf life at 20 °C for 14 d. Coating treatments included gum arabic at 5% and 10%, paraffin at 10% and 20%, chitosan at 1% and 2%, and beeswax at 5% and 10%. All conducted coatings treatments significantly maintained fruit quality as compared to the control (uncoated ones). Chitosan at 2% significantly preserved fruit quality, firmness, visual appearance, husk colour, ascorbic acid and anthocyanin content, furthermore it reduced browning, peroxidase enzyme activity and decay incidence. Paraffin at 10% and beeswax at 10% were effective in maintaining fruit water content, in addition to the significant preservation of husk distention using paraffin at 20%, moreover, application of gum arabic at 5% maintained moderate rates of fruit respiration and total soluble solids content as compared to control.

Reaction of Different Pepper (Capsicum annuum L.) Cultivars to Isolates of Verticillium dahliae Kleb. from Various Hosts

Although Verticillium dahliae is one of the limiting factors in pepper (Capsicum annuum L.) has no effective control measures, the most effective method is planting resistant cultivars. This study was carried out under controlled climatic conditions to determine the response of some economically important pepper cultivars grown in Turkey against some isolates of V. dahliae. Bafra F1, Ergenekon F1 hybrid cultivars and Sena, Sera Demre 8, Doru 16 registered domestic pepper cultivars were used in this study. V. dahliae isolates (Bisak 16, Kahramanmaraş, Karpuz-2, Karpuz-4, Kayseri) obtained from different regions and hosts and diagnosed were used as a source of inoculums. The disease severity on inoculated plants in pots were calculated according to severity of the wilting (0-5 scale) and browning of stem cut (0-3 scale). Significant differences were observed between pepper cultivars in terms of susceptibility to V. dahliae isolates. According to the study results, when the leaf symptoms were evaluated, varieties resistant to wilt disease were Ergenekon F1 and Bafra F1, while Sera Demre-8 was determined as a susceptible variety. According to the browning symptoms of stem cut, while the resistant variety was Ergenekon F1, Sena was determined as the sensitive variety.

Comparative transcriptome reveals molecular mechanism in apple genotypes differing in CO2 tolerance in CA storage

Internal browning is physiological storage disorder in many apples often associated with high CO2 during controlled atmosphere (CA) storage. However the underlying molecular mechanisms leading to internal browning are poorly understood. This study examined changes in the apple transcriptome associated with internal browning related to high CO2 in CA storage by comparing the responses of a CO2 sensitive cultivar ‘Han Fu’ and the CO2 tolerant cultivar ‘Golden Delicious’. The apples were harvested at optimum maturity for long term storage and stored in a CA of 3 % O2 and 6 % CO2 at 4 ℃ for 60 d. The CO2 sensitive ‘Han Fu’ showed severe browning symptoms within 30 d storage in CA, while no internal browning symptoms were detected in ‘Golden Delicious’ even after 60 d storage under the same storage conditions. PPO activity was higher in ‘Han Fu’ apples after 30 d storage. Differences in the expression profile between cultivars were assessed using RNA-sequencing techniques to identify candidate genes associated with internal browning in a cultivar specific manner. The RNA sequencing results showed that higher expression of the related to apetala 2 (RAP 2) and pyruvate decarboxylase (PDC) encoding genes in ‘Golden Delicious’ apples were associated with higher CO2 tolerance in this cultivar. Conversely, the higher expression of key genes from lactate production (lactate dehydrogenase, LDH), lipid catabolic (patatin-like protein, PLP), polyphenol biosynthesis (phenylalanine ammonia-lyase, PAL), polyphenol oxidase (PPO) were associated with the internal browning development in ‘Han Fu’ apple in CA storage condition. A conceptual model elucidating the molecular mechanism of browning development in ‘Han Fu’ and CO2 acclimation in ‘Golden Delicious’ during storage in CA is proposed. The further elucidation of this mechanism will lead to a theory to optimize cultivar breeding in apple.

First Report of Root Rot of Tobacco Caused by Fusarium brachygibbosum in China.

Tobacco (Nicotiana tabacum L.) is an important cash crop in China, with an estimated production of 2.2 million tons every year (Berbeć and Matyka, 2020). In June 2020, a root rot disease was observed on tobacco (cv. Zhongyan 100) in four surveyed counties (Mianchi, Lushi, Duguan and Lingbao) in Sanmenxia. Diseased plants exhibited leaf chlorosis and purplish to brown vascular discoloration of stem, taproot and lateral roots. The disease incidence ranged from 15% to 40% in 11 surveyed fields, 36.7 ha in total. Twenty five diseased tissues were surface sterilized in 75% ethanol and placed on potato dextrose agar (PDA) medium. Fifteen single-spore isolates were obtained from 25 diseased tissue samples. All cultures growing on PDA had white colonies with abundant aerial mycelia initially, turning into yellow to orange in the center and produced red pigmentation after seven days of growth. The 7-day-old cultures grown on carnation leaf agar (CLA) produced macroconidia that were curved with 3-5 septa, had wide central cells, slightly pointy apex, and measured 17.0-45.9 μm long×3.0-4.6 μm wide (n=50). The microconidia formed on CLA were slightly curved, ovoid with zero to two septa, measuring 5.4-15.5 μm long×2.0-3.2 μm wide (n=50). Spherical chlamydospores (7.58-13.52 μm; n=50) were terminal or intercalary, single or in chains. Such characteristics were typical of Fuarium brachygibbosum (Tirado-Ramírez et al. 2018). DNA from one representative single-spore isolate (MC1) was extracted, and the translation elongation factor 1-alpha (EF1-α), RNA polymerase I largest subunit (RPB1) and second largest subunit (RPB2) genes were amplified with primers EF1/EF2, F5/G2R and RPB2F/R respectively (O'Donnell et al. 1998, 2010), and sequenced. Sequences were submitted to GenBank under accession numbers MT947796 (EF1-α), MW679536 (RPB1) and MW430664 (RPB2). The consensus sequences showed 99.70%, 99.94% and 100% identity to the sequences of F. brachygibbosum strain NRRL 34033 (accession no. GQ505418.1, HM347172.1 and GQ505482.1, Wang et al 2021). Morphological and molecular results confirmed this species as F. brachygibbosum (Al-Mahmooli, et al., 2013, Rentería -Martínez, et al., 2018). Pathogenicity tests were performed on tobacco seedlings grown on autoclaved tobacco specific substrate (Tobacco specific matrix, Ainong Biotechnology Co. Ltd, China). Healthy six-leaf stage tobacco seedlings (n=30; Zhongyan 100) were inoculated by placing 7-days old wheat seed (15 seeds per plant) infested with MC1 around the root. Thirty seedlings inoculated with sterile wheat seeds served as controls. All the plants were maintained in a growth chamber at 25±0.5℃ and 70% relative humidity. The assay was conducted three times. Typical symptoms of foliage chlorosis and root browning were observed 7-14 days after inoculation. The pathogen was reisolated from the necrotic tissue from all inoculated seedlings and was identified by sequencing partial EF1-α and RPB2 genes. Control plants remained asymptomatic and no pathogen was recovered from the control plants. Fusarium brachygibbosum is known as a pathogen of grains and cash crops in China (Shan, et al., 2017, Xia, et al., 2018). To our knowledge, this is the first report of F. brachygibbosum causing root rot on tobacco. We believe that our results will help to better understand rhizome fungal diseases affecting tobacco production in China. Acknowledgements: Funding was provided by the Science and Technology Project of Henan Provincial Tobacco Company (2020410000270012), Independent Innovation Project of Hennan Academy of Agricultural Sciences (2020ZC18) and Research and Development project of Henan Academy of Agricultural Sciences (2020CY010).

Alternaria alternata Causing Disease on Sugar Beet (Beta vulgaris) Steckling in Arizona, USA

Sugar beet (Beta vulgaris. L) is an economically important crop which is contributing 55% of the total sugar in the USA. In April 2018, irregular dark brown symptoms were observed in sugar beet stecklings in Arizona where different sugar beet cultivars were grown for seed production (Figure 1). The symptoms covered approximately 5% on the sugar beet root surface. Symptomatic beet root tissue were excised from the junction of diseased and healthy tissue. Small pieces (5mm²) were surface sterilized with 10% sodium hypochlorite for 1min, rinsed thrice with sterile distilled water, air dried and transferred to clarified V8 (CV8), and Potato Dextrose Agar (PDA), and incubated at 24°C with a 12h photoperiod for 5 days. White-dark green velvety colony appeared on both media (Figure 2). Isolates were developed by the single spore isolation technique. Conidia were obclavate or oviod, two to four transverse septa, and pale brown, often in chains (4 to 8 conidia) and or solitary (Figure 3). The dimension of conidia varied from 20.21-40.15 x 7.50-14.12 μm [1- 3]. Based on the morphological characters, the fungus was tentatively identified as Alternaria species. Genomic DNA were extracted via Qiagen kit. A total of 40ng genomic DNA was used to generate a library using NEBNext® Fast DNA Fragmentation & Library Prep Set for Ion TorrentTM for sequencing in Ion TorrentTM Personal Genome MachineTM System.

Chitosan-enriched salicylic acid coatings preserves antioxidant properties and alleviates internal browning of pear fruit under cold storage and supermarket conditions

Pear being climacteric in nature undergoes alterations in antioxidant properties during storage due to intense metabolic activities. In an attempt to maintain antioxidants level, pears were treated either with chitosan (CH) coatings alone (CH 1.0 and 2.0 %) or were incorporated with 2.0 mM salicylic acid (SA) and stored for a period of 67 d under cold temperature (0 – 1 °C and 90–95 % RH) and 20 d under supermarket conditions (20–22 °C and 80–85 % RH). Evaluation study for different physico-chemical attributes of pears suggested that the SA loaded CH coatings restricted the climacteric peak and delayed the polyphenol oxidase (PPO) enzyme activity. As compared to control, these composite coatings promoted the preservation of total phenolics content (TPC), ascorbic acid (AsA) and retained higher total antioxidant activities (TAA) in fruit till 67 d of cold storage period and 20 d under supermarket conditions. Furthermore, CH 2.0 % + SA 2.0 mM coatings strictly impeded the development of internal browning (IB) symptoms of pears throughout storage period. Combined coatings of CH plus SA contributed higher efficacy in terms of maintaining the functional properties of fruit as compared to individual coatings of CH or SA dip.

Multimodal Molecular Imaging and Identification of Bacterial Toxins Causing Mushroom Soft Rot and Cavity Disease.

Soft rot disease of edible mushrooms leads to rapid degeneration of fungal tissue and thus severely affects farming productivity worldwide. The bacterial mushroom pathogen Burkholderia gladioli pv. agaricicola has been identified as the cause. Yet, little is known about the molecular basis of the infection, the spatial distribution and the biological role of antifungal agents and toxins involved in this infectious disease. We combine genome mining, metabolic profiling, MALDI‐Imaging and UV Raman spectroscopy, to detect, identify and visualize a complex of chemical mediators and toxins produced by the pathogen during the infection process, including toxoflavin, caryoynencin, and sinapigladioside. Furthermore, targeted gene knockouts and in vitro assays link antifungal agents to prevalent symptoms of soft rot, mushroom browning, and impaired mycelium growth. Comparisons of related pathogenic, mutualistic and environmental Burkholderia spp. indicate that the arsenal of antifungal agents may have paved the way for ancestral bacteria to colonize niches where frequent, antagonistic interactions with fungi occur. Our findings not only demonstrate the power of label‐free, in vivo detection of polyyne virulence factors by Raman imaging, but may also inspire new approaches to disease control.

First Report of Alternaria alternata Causing Leaf Spot on Beta vulgaris in North Dakota, USA

Sugar beet is an economically important crop which is contributing 55% of the total sugar in the USA. In June 2018, irregular dark brown somewhat circular spots were observed on sugar beet leaves in Hickson, North Dakota. The symptoms covered approximately 5% on the lower leaves. Symptomatic leaf tissue were excised from the junction of diseased and healthy tissue. Small pieces (5 mm²) were surface sterilized with 10% sodium hypochlorite for 1 min, rinsed thrice with sterile distilled water, air dried and transferred to Potato Dextrose Agar (PDA), and incubated at 24°C with a 12-h photoperiod for 5 days. Dark-green velvety colony appeared in two weeks. Three isolates were developed by the single spore isolation technique. Conidia were club-shaped, two to four transverse septa, and pale brown, without any beak, often in chains (4 to 8 conidia) and or solitary. The dimension of conidia varied from 25-40x7-14 μm [1,2]. Based on the morphological characters, the fungus was tentatively identified as Alternaria species. Genomic Deoxyribonucleic Acids (gDNAs) were extracted from the culture generated from a single spore using Qiagen kit. ITS4/ITS5 were used to amplify the fragments of the Internal Transcribed Spacer (ITS) region. The amplified PCR products were cleaned and sent for Sanger sequencing by GenScript (GenScript, Piscataway, NJ). The sequences from GenScript were congruence to the reference sequence ID MT126620.1. The entire sequences were deposited at NCBI (GenBank accession nos. MK441717). Koch postulates were followed by spraying conidia suspension (5×105 conidia/ml) to 8-week age of 20 plants of and kept in humidity chamber at 28-30 °C, 80-85 % RH. Mock-inoculated seeds were also sown as a control. Three weeks of post inoculation, the similar irregular dark brown symptoms observed in twelve plants. No symptoms were found in the mock. The experiment was conducted twice. The fungus was reisolated from the diseased leaf tissue, as described above. Macroscopic and microscopic analysis indicated the similar dark-green colony and morphology, respectively. Molecular detection performed using the same ITS primers and sent for Sanger sequencing by GenScript, this study further confirmed that the isolate was similar to A. alternata [3]. Another close species of Alternaria was recently reported in sugar beet to cause leaf spot in Minnesota [4,5]. To our best knowledge, this is the first report of A. alternata causing leaf spot on sugar beet in North Dakota.

Demographic consequences of mitigating strategies in planktonic invertebrates facing global browning of freshwater ecosystem

Recently, it has been reported that freshwater browning has less effect on planktonic invertebrate abundances than would be expected from current knowledge regarding of the biochemical activity of dissolved organic matter. It may be that the weak responses of whole communities to browning are masked because the individual mitigating strategies of community components have disparate demographic consequences. To examine the above hypothesis, individual-, population- and community-level responses of freshwater invertebrates to varying concentrations of terrestrial dissolved organic matter (tDOM) were investigated. Common cladocerans of the Chydoridae family, Chydorus sphaericus and Acroperus harpae, were used in the experiment which revealed that species employed different strategies to cope with tDOM. C. sphaericus maintained high production of asexual offspring at the cost of individual body growth, so any decreases in the population sizes were not observed. A. harpae, conversely, invested mainly in the production of resting eggs and increased survivability, which resulted in smaller populations. Invertebrate communities showed similar resilience and temporal stability across tDOM concentrations. Therefore, the influence of tDOM was apparently negligible at community level, since the effects of the mitigating strategies of the two species complemented one another. This experiment showed that symptoms of freshwater browning might be difficult to observe at population and community level due to effective mitigating strategies performed at the level of individuals. The effects of browning on freshwater invertebrates might be better considered in the context of alterations in the demographic rates together constituting life-cycle strategies to maintain species survival.

Pathological Properties of Cryptococcus pseudolongus on the Mycelia and Fruit Body of Lentinula edodes

Recently, Cryptococcus pseudolongus has been reported as a new pathogen of shiitake (Lentinula edodes). However, its pathological properties are not much known. To further understand its impact on the mushroom, we investigated the pathogen’s interactions with the mycelium of shiitake, histopathological properties, host range, and sensitivity to diverse antifungal agents. The strain C. pseudolongus DUCC 4014 inhibited the mycelial growth of L. edodes strain (cultivar Sanjo 701ho) and caused browning in the mycelia confronted with the yeast on PDA. Spray inoculation of the yeast caused an abnormal browning symptom on the cap and/or gills of three shiitake cultivars grown on sawdust media in vinyl bags. Scanning electron microscopic images of the abnormally browned parts of shiitake fruit body illustrated that mushroom tissues were loosed and dispersed in the middle and edge of the cap and the arrangement of basidiospores borne on basidia in the gills was disturbed compared to those of normal shiitake fruit body. Spray inoculation also led to developing abnormal browning on the harvested fruit body, indicating C. pseudolongus could be a problem during mushroom storage. But the yeast was not able to induce abnormal browning on mushrooms of Pleurotus ferulae, Pleurotus fostreatus, and Agaricus bisporus. But it induced browning only on button mushroom (A. bisporus) when they were inoculated after wounding. Tests with 16 kinds of fungicides revealed that the cell growth of C. pseudolongus could be inhibited by benzalkonium chloride at MIC 7 μg/ml and benomyl at MIC 3 μg/ml.