Colletotrichum Acutatum Research Articles

Target Mechanism of Iturinic Lipopeptide on Differential Expression Patterns of Defense-Related Genes against Colletotrichum acutatum in Pepper.

Bacillus subtilis KB21 is an isolate with broad spectrum antifungal activity against plant pathogenic fungi. Our aim was to produce and purify antifungal lipopeptides via fermentation using B. subtilis KB21 and verify their antifungal mechanism against pepper anthracnose. When the KB21 strain was cultured in tryptic soy broth medium, the antifungal activity against pepper anthracnose correlated with biosurfactant production. However, there was no antifungal activity when cultured in Luria-Bertani medium. KB21 filtrates showed the highest degree of inhibition of mycelia (91.1%) and spore germination (98.9%) of Colletotrichum acutatum via increases in the biosurfactant levels. Using liquid chromatography-mass spectrometry (LC-MS) and LC-tandem MS (LC-MS/MS) analyses, the component with antifungal activity in the fermentation medium of the KB21 strain was determined to be the cyclic lipopeptide (CLP) antibiotic, iturin A. When the iturin fractions were applied to pepper fruits inoculated with conidia of C. acutatum, the lesion diameter and hyphal growth on the fruit were significantly suppressed. In addition, iturin CLP elevated the gene expression of PAL, LOX, and GLU in the treatments both with and without following fungal pathogens. Overall, the results of this study show that iturin CLPs from B. subtilis KB21 may be potential biological control agents for plant fungal diseases.

Postharvest Rot of Pomegranate Fruit in Southern Italy: Characterization of the Main Pathogens.

Pomegranate (Punica granatum L.) is an emerging crop in Italy and particularly in southern regions, such as Apulia, Basilicata, and Sicily, due to favorable climatic conditions. The crop is affected by several pathogenic fungi, primarily in the field, but also during postharvest phases. The most important postharvest fungal diseases in pomegranate are gray and blue molds, black heart and black spot, anthracnose, dry rot, and various soft rots. The limited number of fungicides allowed for treatment in the field and the lack of postharvest fungicides make it difficult to control latent, quiescent, and incipient fungal infections. Symptomatic pomegranates from southern Italy were sampled and isolated fungi were morphologically and molecularly characterized. The data obtained revealed that various species of Penicillium sensu lato (including Talaromyces genus), Alternaria spp., Coniella granati, and Botrytis cinerea were the principal etiological agents of postharvest pomegranate fruit diseases; other relevant pathogens, although less represented, were ascribable to Aspergillus sect. nigri, Colletotrichum acutatum sensu stricto, and Cytospora punicae. About two thirds of the isolated pathogens were responsible for latent infections. The results obtained may be useful in planning phytosanitary control strategies from the field to storage, so as to reduce yield losses.

First Report of Colletotrichum nymphaeae Causing Anthracnose on Almond in Hungary.

Almond (Prunus dulcis [Mill.] D. A. Webb) is cultivated in commercial orchards in southwestern Hungary while numerous backyard orchards predominate in Buda Hills and central Hungary. In July 2019, anthracnose symptoms and necrotic twigs were observed across almond genotypes in a meadow orchard of Óbuda and in the genebank collection of the Hungarian University of Agriculture and Life Sciences. Fruits of some genotypes were damaged 100%, whereas others to a lesser degree or asymptomatic. Orange slightly sunken lesions on fruits produced gum. Near the diseased fruits the young shoots shriveled, the stalks became necrotized, on twigs necrosis developed. Isolates obtained from orange conidial masses from epicarp, necrotized tissues from twigs, and stalks were grown on PDA for 7 days at 25 ֯C in the dark. Upper surfaces of the colonies were white to pale gray, black solid mycelial structures were formed, the reverse side varied white to salmon. Acervuli were not formed, but conidia were produced from hyphae. Conidia were unicellular, hyaline, smooth-walled, cylindrical, predominant with both end rounded, or one end acute. Morphometric measurements of conidia showed mean length ± SD × width ± SD = 18.0 ± 2.2 × 4.7 ± 0.6 μm (n = 100). The isolates were morphologically identified as Colletotrichum acutatum sensu lato (Damm et al. 2012). Sexual morph was not observed. Three monosporic isolates were used for molecular identification. Partial nucleotide sequences were amplified from three loci, internal transcribed spacer (ITS), β-tubulin (TUB2) and calmodulin (CAL) after White et al. (1990); Glass and Donaldson (1995) and Weir et al. (2012), respectively. The ITS sequences (GenBank accessions MW425388 to MW425390) of the three isolates revealed that they belong to the C. acutatum species complex while BLAST results showed that TUB2 sequences (GenBank accessions MW428285 to MW428287) had 99.3% identity with C. nymphaeae strain CBS515.78, whereas the CAL sequences (GenBank accessions MW428288 to MW428290) had 100% with C. nymphaeae strain FREC138. The phylogenetic tree containing all the valid species of C. acutatum species complex confirmed that the isolates clustered to C. nymphaeae with high bootstrap support. The fungus was identified as Colletotrichum nymphaeae (Pass) Aa based on molecular biological evidence. In vivo pathogenicity tests were conducted on ten healthy fruits, and ten twigs by inserting mycelial agar plugs (5 mm in diameter) onto wounded pericarp and phloemissues, which were then wrapped in wet cotton and Parafilm®. The control treatments received sterile PDA discs. After 15 days, necrotic lesions 12 to 19 mm in diameter developed on fruit, 9 to 18 mm on twig. Control fruits, and twigs were asymptomatic. Koch's postulates were fulfilled with the reisolation of the pathogen from symptomatic tissues. The ITS, ACT and CAL sequences of the reisolated Colletotrichum were determined and found identical to the original isolates. Anthracnose symptoms are known on almond fruits in several almond growing regions all over the word caused by Colletotrichum acutatum, C. godetiae, C. fioriniae, C. simmondsii, and C. gloeosporioides (Adaskaveg et al. 1997; López-Moral et al. 2000; de Silva et al. 2021; Shabi et al. 1983;). To our knowledge, this is the first report of Colletotrichum nymphaeae causing anthracnose of almond globally.

Fungal endophytes in Fraxinus excelsior petioles and their in vitro antagonistic potential against the ash dieback pathogen Hymenoscyphus fraxineus.

Fungal endophytes were isolated from 250 asymptomatic leaf petioles of Fraxinus excelsior collected from trees showing symptoms of ash dieback in five forest sites in southern Poland. Fungal isolations yielded 1646 colonies representing 97 taxa, including 92 Ascomycota and 5 Basidiomycota species. The most common Ascomycota comprised Nemania serpens (38.0 % of colonized petioles), Diaporthe eres (33.6 %), Venturia fraxini (26.4 %), Diaporthe sp. 1 (20.4 %), Alternaria sp. 1 (14.8 %), Colletotrichum acutatum (14.8 %), Nemania diffusa (14.0 %), Colletotrichum gloeosporioides (12.4 %) and Colletotrichum sp. (12.4 %). The occurrence of all these taxa except Alternaria sp. 1 was significantly different between the studied forest sites. Two yeast species, Vishniacozyma foliicola (4.8 %) and Cystobasidium pinicola (2.8 %), dominated among the Basidiomycota endophytes detected. All the fungal endophytes were tested in dual culture antagonistic assays against two strains of Hymenoscyphus fraxineus, resulting in the development of four interaction types. The interactions included the physical contact of co-partners' mycelia (41.8 %), development of an inhibition zone (47.4 %), growth of endophyte mycelia over H. fraxineus colonies (9.3 %) and growth of H. fraxineus mycelia over endophyte colonies (1.5 %). The strongest antibiotic activity against H. fraxineus, measured by the width of the inhibition zone, was observed for Cytospora pruinosa, Fusarium lateritium, Phoma sp. 2, Pleosporales sp. 2 and Thielavia basicola. A variety of morphophysiological deformations of H. fraxineus hyphae were observed under endophyte pressure: spiral twist of the hyphae, formation of cytoplasmic extrusions, development of torulose hyphae and excessive lateral branching of the hyphae. The strongest antagonistic effects, coupled with the potential to overgrow H. fraxineus colonies, was shown by Clonostachys rosea, Nemania diffusa, N. serpens, Peniophora cinerea, Rosellinia corticium and Xylaria polymorpha. Some of these species were able to attack H. fraxineus hyphae in a mycoparasitic manner. The antagonistic activities included the physical penetration of H. fraxineus hyphae, dissolution of hyphal cell walls, disappearance of pigmentation, disintegration of hyphae and degradation of other fungal structures. In contrast, one of the most commonly detected endophytes in ash leaves, Venturia fraxini, did not show in vitro antagonistic potential against H. fraxineus. Finally, we discuss the potential of the detected fungal endophytes to combat H. fraxineus invasion, the cause of ash decline in Europe.

Genomic and Experimental Analysis of the Biostimulant and Antagonistic Properties of Phytopathogens of Bacillus safensis and Bacillus siamensis.

The B. safensis RGM 2450 and B. siamensis RGM 2529 strains were isolated from the rhizosphere of plants presenting resilience to abiotic and biotic stress conditions. To understand the implications of bacteria in resilience, a genomic and experimental analysis was carried out on their biostimulant and phytopathogenic antagonist properties. Genome analyses of both strains indicated that they have the potential to synthesize bioactive compounds such as the battery of non-ribosomal peptides, polyketides, extracellular enzymes and phytohormones. These results were consistent with the antagonistic activities of both strains against the phytopathogens Botrytis cinerea, Colletotrichum acutatum, Fusarium oxysporum and Phytophtora cinnamomi. They also showed the capacity to solubilize phosphorus, fix nitrogen and produce indole acetic acid. This was observed in tomato seedlings grown from seeds inoculated with the mixture of strains which presented significantly greater length as well as wet and dry weight in comparison with the treatments individually inoculated with each strain and the control. Accordingly, the combination of B. safensis RGM 2450 and B. siamensis RGM 2529 showed synergistic biostimulant activity. These findings contribute new knowledge of the genomic and metabolomic properties taking part in the symbiotic interactions between these strains and the plants and uphold the combined use of both strains as a biostimulant.

Incorporation of Oil From Hymenaea stigonocarpa and Hymenaea courbaril Into Biofilms Made From Arrowroot Starch: Physicochemical, Biodegradability and Antifungal Activity

Incorporating of fixed oils in biodegradable packaging has an important action on the polymer matrix and biological activities on phytopathogens. This study aimed to evaluate the incorporation of fixed oils from the seeds of Hymenaea stigonocarpa and Hymenaea courbaril in the arrowroot starch biofilm matrix, evaluating the physicochemical parameters of biodegradability and antifungal activity on Colletotrichum acutatum, Colletotrichum gloeosporioides, Aspergillus tubingensis, Aspergillus fumigatus, Aspergillus niger and Rhizopus stolonifer. Both fixed oils from Hymenaea seeds showed biological antioxidant activity in reducing DPPH. Biofilms showed increasing variation in thickness ranging from 0.23-0.43 mm and decreasing moisture content and solubility 15.01-5.14% and 51.07-34.10%, respectively, as oil concentrations increased. The oil concentration also reduced the transparency rate, a considerable variation between the color and biodegradability parameters. However, the biofilms presented a mass reduction of more than 90% for this test. Biofilms still demonstrate considerable antifungal activity for the evaluated phytopathogens. The seed oil of Hymenaea stigonocarpa and Hymenaea courbaril played important roles in developing biopolymer matrices and special biological activity on potential phytopathological agents of fruits and grains.

Characterization of the WRKY gene family in Akebia trifoliata and their response to Colletotrichum acutatum

BackgroundAkebia trifoliata, belonging to the Lardizabalaceae family, is a well-known Chinese traditional medicinal plant, susceptible to many diseases, such as anthracnose and powdery mildew. WRKY is one of the largest plant-specific transcription factor families and plays important roles in plant growth, development and stress response, especially in disease resistance. However, little was known about the numbers, characters, evolutionary relationship and expression of WRKY genes in A. trifoliata in response to plant disease due to lacking of A. trifoliata genome.ResultsA total of 42 putative AktWRKY genes were identified based on the full-length transcriptome-sequencing data of A. trifoliata. Then 42 AktWRKY genes were divided into three major groups (Group I-III) based on the WRKY domains. Motif analysis showed members within same group shared a similar motif composition, implying a functional conservation. Tissue-specific expression analysis showed that AktWRKY genes could be detected in all tissues, while few AktWRKY genes were tissue specific. We further evaluated the expression of AktWRKY genes in three varieties in response to Colletotrichum acutatum by qRT-PCR. The expression patterns of AktWRKY genes were similar between C01 and susceptible variety I02, but distinctly different in resistant variety H05. In addition, it showed that more than 64 percentages of AktWRKY genes were differentially expressed during fungal infection in I02 and H05. Furthermore, Gene ontology (GO) analysis showed that AktWRKY genes were categorized into 26 functional groups under cellular components, molecular functions and biological processes, and a predicted protein interaction network was also constructed.ConclusionsResults of bioinformation analysis and expression patterns implied that AktWRKYs might play multiple function in response to biotic stresses. Our study could facilitate to further investigate the function and regulatory mechanism of the WRKY in A. trifoliata during pathogen response.

RNA-Seq and Gene Regulatory Network Analyses Uncover Candidate Genes in the Early Defense to Two Hemibiotrophic Colletorichum spp. in Strawberry.

Two hemibiotrophic pathogens, Colletotrichum acutatum (Ca) and C. gloeosporioides (Cg), cause anthracnose fruit rot and anthracnose crown rot in strawberry (Fragaria × ananassa Duchesne), respectively. Both Ca and Cg can initially infect through a brief biotrophic phase, which is associated with the production of intracellular primary hyphae that can infect host cells without causing cell death and establishing hemibiotrophic infection (HBI) or quiescent (latent infections) in leaf tissues. The Ca and Cg HBI in nurseries and subsequent distribution of asymptomatic infected transplants to fruit production fields is the major source of anthracnose epidemics in North Carolina. In the absence of complete resistance, strawberry varieties with good fruit quality showing rate-reducing resistance have frequently been used as a source of resistance to Ca and Cg. However, the molecular mechanisms underlying the rate-reducing resistance or susceptibility to Ca and Cg are still unknown. We performed comparative transcriptome analyses to examine how rate-reducing resistant genotype NCS 10-147 and susceptible genotype ‘Chandler’ respond to Ca and Cg and identify molecular events between 0 and 48 h after the pathogen-inoculated and mock-inoculated leaf tissues. Although plant response to both Ca and Cg at the same timepoint was not similar, more genes in the resistant interaction were upregulated at 24 hpi with Ca compared with those at 48 hpi. In contrast, a few genes were upregulated in the resistant interaction at 48 hpi with Cg. Resistance response to both Ca and Cg was associated with upregulation of MLP-like protein 44, LRR receptor-like serine/threonine-protein kinase, and auxin signaling pathway, whereas susceptibility was linked to modulation of the phenylpropanoid pathway. Gene regulatory network inference analysis revealed candidate transcription factors (TFs) such as GATA5 and MYB-10, and their downstream targets were upregulated in resistant interactions. Our results provide valuable insights into transcriptional changes during resistant and susceptible interactions, which can further facilitate assessing candidate genes necessary for resistance to two hemibiotrophic Colletotrichum spp. in strawberry.

Biocontrol Ability and Production of Volatile Organic Compounds as a Potential Mechanism of Action of Olive Endophytes against Colletotrichum acutatum.

Olive anthracnose, mainly caused by Colletotrichum acutatum, is considered a key biotic constraint of the olive crop worldwide. This work aimed to evaluate the ability of the endophytes Aureobasidium pullulans and Sarocladium summerbellii isolated from olive trees to reduce C. acutatum growth and anthracnose symptoms, and to assess A. pullulans-mediated changes in olive fruit volatile organic compounds (VOCs) and their consequences on anthracnose development. Among the endophytes tested, only A. pullulans significantly reduced the incidence (up to 10-fold) and severity (up to 35-fold) of anthracnose in detached fruits, as well as the growth (up to 1.3-fold), sporulation (up to 5.9-fold) and germination (up to 3.5-fold) of C. acutatum in dual culture assays. Gas chromatography–mass spectrometry analysis of olives inoculated with A. pullulans + C. acutatum and controls (olives inoculated with C. acutatum, A. pullulans or Tween) led to the identification of 37 VOCs, with alcohols being the most diversified and abundant class. The volatile profile of A. pullulans + C. acutatum revealed qualitative and quantitative differences from the controls and varied over the time course of microbial interactions. The most significant differences among treatments were observed at a maximal reduction in anthracnose development. At this stage, a set of VOCs, particularly Z-3-hexen-1-ol, benzyl alcohol and nonanal, were highly positively correlated with the A. pullulans + C. acutatum treatment, suggesting they play a critical role in anthracnose reduction. 6-Methyl-5-hepten-2-one and 2-nonanone were positively associated with the C. acutatum treatment and thus likely have a role in pathogen infection.

Identification and Characterization of Bacillus tequilensis GYUN-300: An Antagonistic Bacterium Against Red Pepper Anthracnose Caused by Colletotrichum acutatum in Korea.

Anthracnose is a fungal disease caused by Colletotrichum species and has detrimental effects on many crops, including red pepper. This study used Bacillus tequilensis GYUN-300 (GYUN-300), which exhibit antagonistic activity against the fungal pathogen, Colletotrichum acutatum. This pathogen causes anthracnose that manifests primarily as a fruit rot in red pepper. There have been little efforts to identify antagonistic bacteria from mushrooms; this strain of bacteria was identified as B. tequilensis using BIOLOG and 16S rDNA sequencing analysis. The genetic mechanism underpinning the biocontrol traits of GYUN-300 was characterized using the complete genome sequence of GYUN-300, which was closely compared to related strains. GYUN-300 inhibited mycelial growth and spore germination of C. acutatum under in vitro conditions. Important antagonistic traits, such as siderophore production, solubilization of insoluble phosphate, and production of lytic enzymes (cellulase, protease, and amylase), were observed in GYUN-300, These trains promoted growth in terms of seed germination and vigorous seedling growth compared to the non-treated control. When red pepper fruits were treated with GYUN-300, the preventive and curative effects were 66.6 and 38.3% effective, respectively, in wounded red pepper fruits; there was no difference between the preventive and curative effects in non-wounded red pepper fruits. Furthermore, GYUN-300 was resistant to several commercial fungicides, indicating that GYUN-300 bacterial cells may also be used synergistically with chemical fungicides to increase biocontrol efficiency. Based on in vitro results, GYUN-300 played a role to control anthracnose disease effectively in field conditions when compared to other treatments and non-treated controls. The results from this study provide a better understanding of the GYUN-300 strain as an effective biocontrol agent against red pepper anthracnose; this form of biocontrol provides an environment-friendly alternative to chemical fungicides.

Mitogen-Activated Protein Kinase CsPMK1 Is Essential for Pepper Fruit Anthracnose by Colletotrichum scovillei.

The phytopathogenic fungus Colletotrichum scovillei, belonging to the Colletotrichum acutatum species complex, causes severe anthracnose disease on several fruits, including chili pepper (Capsicum annuum). However, the molecular mechanisms underlying the development and pathogenicity of Colletotrichum scovillei are unclear. The conserved Fus3/Kss1-related MAPK regulates fungal development and pathogenicity. Here, the role of CsPMK1, orthologous to Fus3/Kss1, was characterized by phenotypic comparison of a target deletion mutant (ΔCspmk1). The mycelial growth and conidiation of ΔCspmk1 were normal compared to that of the wild type. ΔCspmk1 produced morphologically abnormal conidia, which were delayed in conidial germination. Germinated conidia of ΔCspmk1 failed to develop appressoria on inductive surfaces of hydrophobic coverslips and host plants. ΔCspmk1 was completely defective in infectious growth, which may result from failure to suppress host immunity. Furthermore, ΔCspmk1 was impaired in nuclear division and lipid mobilization during appressorium formation, in response to a hydrophobic surface. CsPMK1 was found to interact with CsHOX7, a homeobox transcription factor essential for appressorium formation, via a yeast two-hybridization analysis. Taken together, these findings suggest that CsPMK1 is required for fungal development, stress adaptation, and pathogenicity of C. scovillei.

Molecular screening of the VIR strawberry varieties collection for the presence of a marker for the anthracnose black rot resistance gene <i>Rca2</i>

Background. Anthracnose black rot caused by the phytopathogenic fungus Colletotrichum acutatum Simmonds became an extremely harmful disease of strawberries in Southern Russia. The disease is widespread throughout the world, and relatively recently it appeared in Russia. Yield losses due to the disease reach up to 80%; besides, the pathogen causes significant plant losses in mother plantations. The most reliable protection against the pathogen is the cultivation of resistant varieties. In strawberries, resistance is controlled by different genes, including Rca2. To identify this gene, molecular markers STS_Rca2_240 and STS-Rca2_417 have been developed. The purpose of this study was to use the markers for screening the VIR collection of strawberry varieties at the VIR Maikop Experiment Station (Maikop ES VIR). Material and methods. The present work studied 135 varieties of Fragaria × ananassa (Duchesne ex Weston) Duchesne ex Rozier, 83 domestic and 52 foreign ones. The domestic varieties included 17 created at the Maikop ES. Plants were evaluated for anthracnose field resistance in the Republic of Adygea from 2018 to 2021. Molecular screening was performed using STS_Rca2_240 and STS-Rca2_417, the molecular markers closely linked to the Rca2 gene. Microsatellite primers EMFv020 were used to control the PCR. The cultivar ‘Sudarushka’, in which the presence of STS_Rca2_240 marker was described in the literature, served as a positive control. Results and discussion. The marker Rca2_240 was detected in 22 cultivars from 135 studied. Among domestic varieties, the frequency of the marker was 18.1%, while among the foreign varieties it was slightly lower and amounted to 13.0%. Among the 17 varieties created at the Maykop SE, the marker was found in three: ‘Majkopskaya rannyaya’, ‘Peryt’, and ‘Shapsugskaya’. The association of the diagnostic fragment with resistance was 73.0%. The marker efficiency was not very high due to the significant number of resistant varieties which do not generate the diagnostic fragments. The resistance in such varieties can be provided by other genes, for example, FaRCa1. The STS-Rca2_417 marker was not effective during screening. Conclusion. Twenty-two varieties with the STS_Rca2_240 marker were identified in the VIR collection, maintained at the Maykop ES VIR, 16 of which were resistant to C. acutatum. These varieties represent a valuable breeding material. The STS-Rca2_240 marker can be used as an important diagnostic trait for the certification of varieties.

Biocontrol Activity of Aspergillus terreus ANU-301 against Two Distinct Plant Diseases, Tomato Fusarium Wilt and Potato Soft Rot.

To screen antagonistic fungi against plant pathogens, dual culture assay (DCA) and culture filtrate assay (CFA) were performed with unknown soil-born fungi. Among the different fungi isolated and screened from the soil, fungal isolate ANU-301 successfully inhibited growth of different plant pathogenic fungi, Colletotrichum acutatum, Alternaria alternata, and Fusarium oxysporum, in DCA and CFA. Morphological characteristics and rDNA internal transcribed spacer sequence analysis identified ANU-301 as Aspergillus terreus. Inoculation of tomato plants with Fusarium oxysporum f. sp. lycopersici (FOL) induced severe wilting symptom; however, co-inoculation with ANU-301 significantly enhanced resistance of tomato plants against FOL. In addition, culture filtrate (CF) of ANU-301 not only showed bacterial growth inhibition activity against Dickeya chrysanthemi (Dc), but also demonstrated protective effect in potato tuber against soft rot disease. Gas chromatography-tandem mass spectrometry analysis of CF of ANU-301 identified 2,4-bis(1-methyl-1-phenylethyl)-phenol (MPP) as the most abundant compound. MPP inhibited growth of Dc, but not of FOL, in a dose-dependent manner, and protected potato tuber from the soft rot disease induced by Dc. In conclusion, Aspergillus terreus ANU-301 could be used and further tested as a potential biological control agent.

Synthesis and Antifungal Activity of Novel Tetrahydrogeranyl Quaternary Ammonium Salts

Due to the excessive use of antifungal agents, drug resistance and ecological problems are increasing. Some antifungal agents are difficult to degrade and have high toxicity and several side effects. In this study, 15 novel tetrahydrogeranyl quaternary ammonium salts (8a–8o) were synthesized from the natural compound citral. The structures of the quaternary ammonium salts were characterized by Fourier transform infrared, proton nuclear magnetic resonance, carbon-13 nuclear magnetic resonance spectroscopy, and mass spectrometry, and the antifungal activities of these compounds at a concentration of 0.25 mg/mL against 10 plant pathogenic fungi were tested. The results showed that compound 8i had the best antifungal activity, and its inhibition rates against Rhizoctonia solani, Phytophthora parasitica var. nicotianae, Sphaeropsis sapinea, Fusarium oxysporum f. sp. niveum, and Poria vaporaria reached 100%. For Fusarium verticillioides, the inhibition rate of compound 8i was 93.28%, which was higher than that of chlorothalonil. In addition, it was found that the inhibition rates of compounds with N,N-di- n-propyl group (8l, 8m) against R solani, F oxysporum f. sp. niveum, S sapinea, P parasitica var. nicotianae, F verticillioides, Colletotrichum acutatum, and Coriolus versicolor were higher than compounds with N,N-diethyl and N,N-dimethyl groups (8a, 8b, 8j, 8k). The inhibition rates of compounds with morpholine groups (8n, 8o) were generally low.

New method for detecting Collectorichum species found in Korea using image analysis

Colletotrichum acutatum spp. infects various economical crops worldwide and causes massive loss on their yields. Among those, Capsicum spp., which known as chili pepper, is on a critical issue by those pathogens. Due to the lack of their genetic markers in Korea, the unidentifiable various species of C. acutatum obstructs the mechanism studies of these pathogens and the selection of disease resistant breed lines. Therefore, we screened RGB images of the colonization progresses of pathogens to identify the species of Ca40042, K1, NN, AS2, and SW1 by time and temperature. Cultivated pathogens such as Ca40042, K1, and SW1 were detectable on quantified shape and color data of images from specific temperature conditions, while other pathogens were difficult to recognize. Although several limitations exist in identification results of current experiment, but also, we can expect this method can suggest the possibility to replace the genetic marker methods which is now unavailable in Korea.

Evaluation of disease alert systems for postbloom fruit drop of citrus in Florida and economic impact of adopting the Citrus Advisory System

Gama, A. B., Peres, N. A., Singerman, A., and Dewdney, M. M. 2021. Evaluation of disease alert systems for postbloom fruit drop of citrus in Florida and economic impact of adopting the Citrus Advisory System. Crop Protec. XX: xx-xx.Postbloom fruit drop of citrus (PFD) is caused by Colletotrichum abscissum in the Colletotrichum acutatum species complex. PFD does not occur annually but some growers tend to apply fungicides during flowering every year, wasting resources and negatively impacting the environment. Due to its sporadicity, the Fungicide Application Decision system (PFD-FAD) and the Citrus Advisory System (CAS) were developed in Florida and Brazil in 2001 and 2017, respectively, to aid in PFD management. Our objectives were to compare the recommendations from CAS and PFD-FAD, a weekly fungicide treatment schedule, and a nontreated control. We also aimed to assess the economic impact of adopting CAS over the other fungicide schedule treatments with low- and high-risk aversion profile scenarios. Weather conditions were not favorable to PFD in seven field trials. We performed one fungicide application based on CAS over four seasons. An average of approximately 2 and 3 fungicide applications per trial was performed based on PFD-FAD and the weekly treatments, respectively. Average cost to manage PFD following CAS, PFD-FAD, and the weekly treatments were, respectively, $17.52, $186.87, and $272.35. The reduction in management costs related to CAS also translates to reduced use of commercial fungicide formulations in small properties by 382 and 573 L compared to PFD-FAD and the weekly treatments, respectively. CAS recommendations greatly reduced production costs and fungicide usage without compromising disease control and citrus yield in years of low weather favorability for PFD in Florida.

Different LED Light Wavelengths and Photosynthetic Photon Flux Density Effect on Colletotrichum acutatum Growth.

The study aimed to evaluate the effect of different photon flux density (PFD) and light-emitting diodes (LED) wavelengths on strawberry Colletotrichum acutatum growth characteristics. The C. acutatum growth characteristics under the blue 450 nm (B), green 530 nm (G), red 660 nm (R), far-red 735 nm (FR), and white 5700 K (W) LEDs at PFD 50, 100 and 200 μmol m−2 s−1 were evaluated. The effect on C. acutatum mycelial growth evaluated by daily measuring until five days after inoculation (DAI). The presence of conidia and size (width and length) evaluated after 5 DAI. The results showed that the highest inhibition of fungus growth was achieved after 1 DAI under B and G at 50 μmol m−2 s−1 PFD. Additionally, after 1–4 DAI under B at 200 μmol m−2 s−1 PFD. The lowest conidia width was under FR at 50 μmol m−2 s−1 PFD and length under FR at 100 μmol m−2 s−1 PFD. Various LED light wavelengths influenced differences in C. acutatum colonies color. In conclusion, different photosynthetic photon flux densities and wavelengths influence C. acutatum growth characteristics. The changes in C. acutatum morphological and phenotypical characteristics could be related to its ability to spread and infect plant tissues. This study’s findings could potentially help to manage C. acutatum by LEDs in controlled environment conditions.

In vitro screening of antagonistic activity of microorganisms against anthracnose disease

Anthracnose disease can be successfully controlled by chemical pesticides in conventional fruit growing. However, in organic farming, in order to maintain environmental safety and fulfill consumer demand for pesticide-free food, the control of this disease is a major problem. The use of biocontrol agents with the antagonistic mechanism of control of many phytopathogens is an innovative alternative for cost-effective and eco-friendly production. The antagonistic activities of Trichoderma viride and Bacillus subtilis were tested in vitro against Colletotrichum acutatum, one of major plant pathogens responsible for anthracnose. The microbial antagonists inhibited mycelial growth in the dual culture. T. viride exhibited strong antagonism against C. acutatum isolates (80%). The B. subtilis isolate also had a strong effect on inhibiting the development of C. acutatum (37.5%). The results of this study identified T. viride and B. subtilis as promising biological control agents for further testing against anthracnose disease in fruits.

Volatiles Produced by <i>Streptomyces</i> spp. Delay Rot in Apples Caused by <i>Colletotrichum Acutatum</i>

Volatiles Produced by <i>Streptomyces</i> spp. Delay Rot in Apples Caused by <i>Colletotrichum Acutatum</i>

Volatiles produced by Streptomyces spp. delay rot in apples caused by Colletotrichum acutatum.

Volatile organic compounds (VOCs) produced by microorganisms may prevent postharvest rot in fruits. Here, it was examined if VOCs from different species of Streptomyces can control infection in apples caused by the fungal pathogen Colletotrichum acutatum. Incubation of C. acutatum-infected apples in semi-closed boxes with actively growing strains of three Streptomyces (S. coelicolor, S. diastatochromogenes and Streptomyces strain 2R) showed that VOCs reduced rot areas of the apples by 45-66% after 8 days and 39-57% after 10 days, relative to infected apples incubated without Streptomyces. No differences in inhibition among the three strains were seen. In contrast, a mutant strain of Streptomyces that lacks major genes involved in biosynthesis of secondary metabolites, did not reduce development of rot in the apples. Furthermore, Streptomyces VOCs reduced radial hyphal growth of C. acutatum on agar. Several of the VOCs produced by three Streptomyces strains have previously shown fungicidal properties. Although the specific VOCs being active in inhibition of C. acutatum remain to be determined, VOCs may have a great potential as biofumigants to minimize postharvest diseases in fruits.