Colletotrichum acutatum and C. gloeosporioides Cause Anthracnose on Olives

Morphological and cultural features and restriction fragment length polymorphism analysis of ITS regions, including 5.8S rDNA, from 26 isolates of Colletotrichum species revealed that isolates from olive fruits, previously identified as C. gloeosporioides, belong to two taxa: C. acutatum and C. gloeosporioides. Comparison of both ITS sequence data with reference isolates confirmed the presence of both species in olives affected by anthracnose disease.     

Molecular identification of Colletotrichum gloeosporioides causing yam anthracnose in Nigeria

Four forms of Colletotrichum representing three distinct virulence phenotypes were found associated with foliar anthracnose of yam in Nigeria: the highly virulent (= severity of disease) slow-growing grey (SGG); the moderately virulent fast-growing salmon (FGS); the weakly virulent fast-growing grey (FGG); and the moderately virulent fast-growing olive (FGO) morphotype. Isolates of the four forms were identified as C. gloeosporioides , based on morphology. The reaction of monoconidial cultures on casein hydrolysis medium (CHM), PCR-RFLP and sequence analysis of the internal transcribed spacer region of the ribosomal DNA (ITS1-5·8S-ITS2) were used to establish the identity of the yam anthracnose pathogen(s). All yam isolates were distinguished from C. acutatum by the absence of protease activity on CHM. On ITS PCR and enzymatic digestion of PCR products, all FGS, FGO and SGG isolates produced RFLP patterns identical to those of C. gloeosporioides reference isolates, while FGG isolates revealed unique ITS RFLP banding patterns. Sequence analysis of the ITS1 region and of the entire ITS region revealed that SGG, FGS and FGO isolates were highly similar (98–99% nucleotide identity) and showed 97–100% identity to C. gloeosporioides . Less than 93% similarity of these fungal isolates to reference C. acutatum and C. lindemuthianum isolates was observed. The molecular study confirmed that foliar anthracnose of yam is caused by C. gloeosporioides . While a high similarity was found among most C. gloeosporioides fungi from yam, isolates of the FGG form did not cluster with any previously described Colletotrichum species, and probably represent a distinct species.     

Colletotrichum acutatum and Colletotrichum nymphaeae causing blossom blight and fruit anthracnose on olives in southern Brazil

European Journal of Plant Pathology - Olive (O. europaea L.) is an expanding crop in the south of Brazil. Blossom blight and typical anthracnose symptoms on fruit were observed in olive trees in an...     

Epidemiology,histopathology and aetiology of olive anthracnose caused by Colletotrichum acutatum and C. gloeosporioides in Portugal

Anthracnose is an important disease affecting mature olive fruits, causing significant yield losses, and poor fruit and oil quality. In Portugal, high anthracnose incidence was recorded during 2003–2007 with 41% of 908 orchards surveyed displaying disease symptoms. In another 14% of the orchards, the pathogen was recorded in symptomless plants. Disease severity was on average 36%, frequently reaching 100%. In Portugal, anthracnose is endemic to neglected orchards of susceptible cultivars, but under favourable conditions it can also severely affect less susceptible cultivars. Pathogens were genetically heterogeneous, with Colletotrichum acutatum genetic group A2 as the most frequent (80%), followed by group A4 (12%) and group A5 along with C. gloeosporioides (3–4%), while groups A3 and A6 of C. acutatum were sporadic. Important geographic variations were observed in the frequencies of these populations, accompanied by year‐to‐year populational shifts. Epidemiology and histopathology studies showed the presence of the pathogens on vegetative organs year‐round, particularly on olive leaves and branches, and on weeds. These represent inoculum reservoirs where secondary conidiation occurs, and conidia are then dispersed by spring rains reaching flowers and young fruits or by autumn rains reaching pre‐mature fruits. Unripe fruits were colonized without showing symptoms up to penetration of the cuticle, but further colonization and symptom production was completed only as fruits matured. These findings challenge current control practices, particularly the timing of fungicide treatment, and contribute to improved disease management.     

Management and cross-infectivity potential of Colletotrichum acutatum causing anthracnose on bell pepper in Florida

Early anthracnose caused by Colletotrichum acutatum has become an increasingly serious disease on green, unripe bell pepper fruit in Florida. This contrasts with earlier reports of anthracnose occurring on bell pepper primarily as a ripe-rot disease of mature, colored pepper fruit caused by Colletotrichum gloeosporioides. Management of anthracnose on green bell pepper fruit using fungicides and a commercial inducer of systemic acquired resistance, acibenzolar-S-methyl (ASM), was evaluated during three seasons. In two of the three trials, all the fungicides tested including azoxystrobin, fludioxonil + cyprodinil, mancozeb, famoxadone + cymoxanil, copper hydroxide, and ASM significantly increased the number of marketable fruit compared with control plants. These trials identified fungicides that could contribute to a successful pest management program on pepper for controlling anthracnose caused by C. acutatum. The cross-infectivity potential of C. acutatum was investigated on tomato and strawberry by in vitro and field inoculation. Anthracnose lesions formed readily on wound-inoculated detached fruits of all hosts in in vitro assays. Under field conditions, after inoculation, anthracnose lesions occurred on pepper fruit but no lesions of anthracnose were found on either ripe or unripe tomato or strawberry fruit in adjacent plots.     

Honeybees can spread Colletotrichum acutatum and C. gloeosporioides among citrus plants

Postbloom fruit drop (PFD) is an important citrus disease that causes up to 100% yield losses during years in which conditions are favourable for the occurrence of epidemics. The conidia of Colletotrichum acutatum and C. gloeosporioides, causal agents of PFD, are predominantly dispersed by rain splash. At the beginning of epidemics, the distribution of diseased plants is random and the disease progress rate is very high, which is unusual for pathogens spread by rain splash. As the pathogen produces abundant conidia on diseased petals, pollinating insects may contribute to disease dispersal. This study investigated honeybees (Apis mellifera) as dispersal agents of C. acutatum and C. gloeosporioides among citrus plants. Two experiments were carried out in a screenhouse in which citrus plants were protected (or not) in insect‐proof cages. The source of inoculum was placed on one side of the screenhouse, and a honeybee hive was placed on the opposite side. All uncaged plants showed symptoms of the disease, and none of the caged plants exhibited PFD symptoms. The monomolecular model showed a good fit to disease progress in both experiments. Conidium‐like structures of Colletotrichum spp. were identified attached to the bodies of the honeybees by scanning electron microscopy. These results have revealed that honeybees disperse Colletotrichum among citrus plants.     

UV-C照射对草莓炭疽病3种致病菌生活力和致病力的影响

炭疽病是草莓种植中普遍发生、危害严重的病害之一,而UV-C对真菌的生长繁殖有极大的影响。为了探究UV-C辐照对引起草莓炭疽病的3种主要病原菌生长和致病力影响的差异,以果生炭疽菌Colletotrichum fructicola、胶孢炭疽菌C.gloeosporioides和暹罗炭疽菌C.siamense为供试菌,分析UV-C辐照对其分生孢子存活、菌丝生长和产孢能力及对草莓叶片致病力的影响。结果显示,在105～420 J/m~2辐照剂量(辐照30～120 s)范围内,3种炭疽菌孢子的相对存活率对UV-C辐照剂量的响应存在显著差异,C.gloeosporioides的耐受性最强,C.fructicola最为敏感,辐照剂量420 J/m~2(辐照120 s)下,3种炭疽菌孢子的相对存活率在4%或以下,接近分生孢子的致死剂量。840～1 260 J/m~2辐照剂量(辐照4～6 min)下,C.fructicola与C.gloeosporioides菌丝生长对UV-C辐照的耐受性相当;1 680～2 520 J/m~2辐照剂量(辐照8～12 min)下,3种炭疽菌对不同时间的UV-C辐照的耐受性...     

First report of Colletotrichum queenslandicum causing leaf anthracnose on Dracaena cambodiana in China

In June 2021, a leaf spot was found on Dracaena cambodiana on Yongxing island of Sansha City, Hainan Province, China. The disease mainly occurred at the tips or edges of older leaves. About 50% of leaves were showed necrotic symptoms. Similar fungal isolates were obtained from all sterilized sections incubated on PDA. The fungus was identified as Colletotrichum queenslandicum by morphological characteristics and multi-locus phylogenetic analyses with ITS region of rDNA, GADPH, CHS-1, ACT, GS and TUB-2 gene sequences. This is the first report of Colletotrichum queenslandicum causing leaf anthracnose on Dracaena cambodiana.

     

Characterization and epidemiology of Colletotrichum acutatum sensu lato (C. chrysanthemi) causing Carthamus tinctorius anthracnose

In 2012, Colletotrichum isolates were collected from field‐grown safflower (Carthamus tinctorius) crops in central Italy from plants exhibiting typical anthracnose symptoms. Colletotrichum isolates were also collected from seed surfaces and from within seeds. The genetic variability of these isolates was assessed by a multilocus sequencing approach and compared with those from Colletotrichum chrysanthemi and Colletotrichum carthami isolates from different geographic areas and other Colletotrichum acutatum sensu lato‐related isolates. Phylogenetic analysis revealed that all of the strains isolated from C. tinctorius belonged to the species described as C. chrysanthemi, whereas all of the strains belonging to C. carthami had been isolated from Calendula officinalis. Phenotypic characterization of isolates was performed by assessing growth rates at different temperatures, morphology of colonies on potato dextrose agar (PDA) and the size of conidia. All C. chrysanthemi isolates from safflower had similar growth rates at different temperatures, comparable colony morphologies when grown on PDA and conidial sizes consistent with previously described C. chrysanthemi isolates. Pathogenicity tests were performed by artificially inoculating both seeds and plants and confirmed the seedborne nature of this pathogen. When inoculated on plants, C. chrysanthemi caused the typical symptoms of anthracnose on leaves. This is the first record of this pathogen on C. tinctorius in Italy, and it presents an updated characterization of Colletotrichum isolates pathogenic to safflowers in Europe.     

PCR-based detection of Colletotrichum acutatum on strawberry

An oligonucleotide primer ( Ca Int 2) was synthesized from the variable internal transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) from Colletotrichum acutatum . PCR with primers Ca Int2 and ITS4 (from a conserved sequence of the rDNA) amplified a 490 bp fragment from several isolates of C. acutatum but not from other members of the genus Colletotrichum . Amplification of this fragment was achieved from 100 fg of fungal DNA. These primers amplified a fragment of the same size from DNA extracted from strawberry tissues infected by C. acutatum . Southern hybridization analysis confirmed the 490 bp fragment from C. acutatum DNA and infected strawberry to be identical. The species-specific primer ( Ca Int2) developed in this work could be used for the accurate identification of C. acutatum and its detection on other host plants.     

芒果胶孢炭疽菌漆酶lac1与致病力的相关性分析

为了明确芒果炭疽病病菌(Colletotrichum gloeosporioides)漆酶与该菌侵染相关致病因子之间的关系,本文以愈创木酚为底物筛选获得的高产漆酶菌株A2为材料,测定了漆酶粗提液对芒果炭疽病病菌致病力的影响,并通过半定量RT-PCR法,分析了在不同侵染时段漆酶基因lac1和其他酶基因的表达。结果表明,漆酶粗提液单独不能致病,但能促进该病原菌在寄主中的扩展;在侵染过程中,lac1表达与黑色素合成酶(thd和scd)基因表达相关性更高,与细胞壁降解酶(ecg和pel)基因表达也有一定相关性,但不及前者高。芒果胶孢炭疽菌分泌的漆酶有助于该菌在侵染芒果过程中的扩展,且对侵染相关致病因子黑色素合成酶和细胞壁降解酶基因的表达有一定影响。初步推测,漆酶lac1除了能通过降解芒果组织中的酚类物质、促进病原菌的扩展之外,也可以通过干扰与致病力相关的黑色素合成和细胞壁降解酶的产生来影响芒果胶孢炭疽菌致病力。     

Isolation and pathogenicity of Colletotrichum spp. causing anthracnose of strawberry in south west Spain

Anthracnose, caused by Colletotrichum spp., is a major disease of cultivated strawberry, Fragaria × ananassa. This study identifies the Colletotrichum spp. which causes strawberry anthracnose in the southwest of Spain. A survey of the region was carried out, and the strains isolated were identified as C. acutatum by using the polymerase chain reaction (PCR) with genus and species-specific primers, demonstrating that this species is currently the causal agent of strawberry anthracnose in the studied region. The pathogenicity of C. acutatum and C. gloeosporioides strains was evaluated on two principal strawberry cultivars (cvs Camarosa and Ventana) under field conditions, the latter being more pathogenic than the former.     

Development of protocols for detection of Colletotrichum acutatum and monitoring of strawberry anthracnose using real-time PCR

Real-time PCR (TaqMan®) assays were developed for the specific detection and discrimination of Colletotrichum spp., C. acutatum and C. gloeosporioides causing anthracnose in strawberry using the most divergent area of the internal transcribed spacers (ITS1 and ITS2) and 5·8S ribosomal RNA (rRNA) gene region. The specificity of the new assays was tested using DNA from six species of Colletotrichum and nine fungal species commonly found associated with strawberry material, and additionally by comparing the sequences with those from databases using a blast search. The sequences only showed identity with homologous sequences from the desired target organisms. The new assays were 10–100 times more sensitive than conventional PCR methods previously published for the diagnosis of strawberry anthracnose. When real-time PCR was compared with ELISA methods, PCR improved the sensitivity of the identification by obtaining positive results for samples of strawberry plant material that tested negative with ELISA. The development of C. acutatum was monitored using artificially infected strawberry crowns from two strawberry cultivars (Camarosa and Ventana) and a real-time PCR assay specific for this species between January and June 2006. The amount of C. acutatum detected using real-time PCR varied significantly by month ( P  < 0·001), but not by cultivar ( P  = 0·394). The new assays were shown to be useful tools for rapid detection and identification of these pathogens and to allow rapid and accurate assessment of the casual agents of anthracnose in strawberry.     

Two subpopulations of Colletotrichum acutatum are responsible for anthracnose in strawberry and leatherleaf fern in Costa Rica

Strawberry, Fragaria × ananassa, and leatherleaf fern, Rumohra adiantiformis, are two important crops in Costa Rica. One of the most severe diseases affecting these crops is anthracnose, caused by members of the fungal genus, Colletotrichum (teleomorph; Glomerella). Eighty single-spore isolates from strawberry and leatherleaf fern were identified as Colletotrichum acutatum by species-specific PCR, and were further characterised by Universally Primed PCR (UP-PCR) fingerprinting analysis, and sequence analysis of the ribosomal internal transcribed spacer (ITS) region. Morphological differences, genotypic variation revealed by UP-PCR fingerprinting analysis, and a single sequence polymorphism within the ITS2 region were found between the isolates from strawberry and leatherleaf fern, respectively. The UPGMA cluster analysis of the fingerprints clearly separated the isolates derived from strawberry and leatherleaf fern into two different clusters. Pathogenicity assays on detached strawberry fruits confirmed the apparent difference between the two groups of isolates. It is therefore suggested that the pathogens responsible for strawberry anthracnose fruit rot and leatherleaf fern anthracnose in Costa Rica, belong to two distinct subpopulations of C. acutatum.     

First report of anthracnose on tillandsia caused by Colletotrichum sp. in Japan

Journal of General Plant Pathology - In July 2018, tillandsia (Tillandsia sp.) plants with brown to dark brown lesions on the leaves and pseudobulbs were found in Japan. Based on morphological and...     

Species of the Colletotrichum gloeosporioides and C. boninense complexes associated with olive anthracnose

The taxonomic status of Colletotrichum gloeosporioides sensu lato (s.l.) associated with olive anthracnose is still undetermined and the pathogenic ability of this species complex is controversial. In the present study, isolates obtained from olive and provisionally identified as C. gloeosporioides s.l. on the basis of morphological and cultural features were reclassified using ITS and TUB2 as DNA barcode markers and referred to seven distinct species, recently separated within C. gloeosporioides (C. aenigma, C. gloeosporioides sensu stricto (s.s.), C. kahawae, C. queenslandicum, C. siamense and C. theobromicola) and C. boninense (C. karstii) species complexes. Furthermore, isolates of C. kahawae were ascribed to the subspecies ciggaro by analysing the GS gene. A single isolate, not in either of these two species complexes, was not identified at the species level. In pathogenicity tests on detached olive drupes some of these species, including C. aenigma, C. kahawae subsp. ciggaro, C. queenslandicum, C. siamense and C. karstii, were shown to be weakly pathogenic. Moreover, they were found very sporadically on olive. In contrast, some isolates of C. gloeosporioides s.s. and isolates of C. theobromicola proved to be virulent on both green and ripening olives. This study gives a better insight into both the aetiology and the epidemiology of olive anthracnose and might have implications for biosecurity and quarantine because C. theobromicola has never been reported in major European olive‐producing countries.