Caio Mattos Pereira

Araceae includes numerous flowering plant species that are cultivated as ornamentals in gardens, pots or by the cut‐flower industry. Relatively little has been published on the fungal pathogens attacking these ornamentals, particularly in Brazil. Here we report the results of a study on Colletotrichum spp. found in association with anthracnose and leaf spot symptoms on Aglaonema commutatum , Anthurium andraeanum , Dieffenbachia amoena , Philodendron imbe and Philodendron tripartitum . Nine isolates of Colletotrichum were obtained from diseased tissues. A polyphasic approach was used to identify these isolates as four novel species: Colletotrichum anthuriicola sp. nov., C. araceiphilum sp. nov., C. imbeicola sp. nov. and C. philodendrifolium sp. nov. Cross‐inoculation assays were conducted using the plant host species listed above, as well as Epipremnum aureum , and showed that all isolates were pathogenic to at least three of the inoculated aroid species. These findings expand the current knowledge of the genus Colletotrichum and its association with members of the Araceae and highlight the need to consider individual ornamental aroids as potential inoculum reservoirs for infection of other cultivated members, given the low host specificity of aroid‐associated Colletotrichum species.

Citrus scab diseases are caused by three species of Elsinoë . These are important diseases affecting citrus production and impacting international trade of fresh fruits, because of quarantine restrictions. Repeated rejections of shipments of Citrus × latifolia (Tahiti lime – TL) fruit imported from Brazil were determined by European quarantine authorities, due to the detection of Elsinoë citricola . These caused great concern to the stakeholders involved and significant economic losses. Paradoxically, E. citricola is an obscure fungal species, known only from a single Citrus × limonia (rangpur lime – RL) tree in Minas Gerais state, Brazil. Neither TL scab nor the association of E. citricola with TL have ever been reported in scientific literature. Here, we undertook an exploratory investigation to verify the occurrence and distribution of E. citricola on RL and TL. Numerous samples were collected from four Brazilian states, but only 11 Elsinoë isolates were obtained from RL (10) and TL (1). Genomic DNA was extracted and analyzed by conventional PCR followed by phylogenetic analysis of the RNA polymerase II gene sequences. Phylogenetic analyses placed all 11 isolates within the E. citricola clade. Our results indicate that E. citricola is the dominant species causing scab on RL in Brazil. This is the first report of the occurrence of E. citricola causing TL scab in the field worldwide. It is fully supported by isolation of the fungus from fruit lesions, deposit of the pure culture in a public culture collection and molecular confirmation of its identity. This single finding resolved the TL scab paradox. The implications are discussed. The need for demonstration of the viability of E. citricola colonies, in imported TL, through isolation or other experimental tool is highlighted as needed to better support quarantine decision-making regarding TL scab. All positive records of E. citricola were from samples obtained from domestic unsprayed orchards. In case the fungus is being inactivated by the treatments in use in TL plantations and in packing-houses in Brazil, additional measures by TL producers, such as an increase in fungicide treatments by the farmers and intensification of post-harvest treatments may prove unnecessary.

Cotton (Gossypium hirsutum, Malvaceae) is the most important fiber crop in the world. There are published records of many fungal pathogens attacking Gossypium spp., causing numerous diseases, including powdery mildews. Recently, in 2022, non-cultivated spontaneous G. hirsutum plants bearing powdery mildews symptoms were found at roadsides in two municipalities of the state of Minas Gerais (Brazil): Varginha and Ubá. Such localities are situated ca. 260 km apart, suggesting a broader distribution of this fungus-host association in Brazil. Samples were taken to the laboratory, and an Ovulariopsis-like, asexual stage of Phyllactinia, was identified forming amphigenous colonies, that were more evident, white and cottony, abaxially. Morphological and molecular data– of the ITS and LSU regions– have shown that colonies from those two samples were of the same fungus species, belonging to a previously unknown species of Erysiphaceae (Ascomycota). The fungus fits into the Phyllactinia clade and is described herein as the new species Phyllactinia gossypina sp. nov. This new species belongs to the ‘basal Phyllactinia group’, a lineage that includes species known only from the Americas. This report expands the list of pathogenic fungi on cotton. It is early to anticipate whether this new powdery mildew represents a threat to cultivated cotton, which is a major crop in Brazil. Nevertheless, further studies about its infectivity to commercial cotton varieties are recommended, since all known Erysiphaceae are specialized obligate plant parasites and several species cause major losses to important crops.

Two members of the Araceae broadly cultivated as ornamentals, namely Epipremnum aureum (common name golden pothos or, in Brazil, jiboia) and Zantedeschia aethiopica (common name arum lily or, in Brazil, copo‐de‐leite), were observed bearing Cercospora leaf spots. The former is a very common garden plant, whereas the latter is an important crop for the flower industry. An examination of the fungus associated with the disease on each plant revealed a very similar morphology which suggested that those might be conspecific. A polyphasic taxonomic study, including phylogenetic analyses based on act, cal and his3 sequences, was conducted. Both isolates from the two aroids were found to belong to the Cercospora apii complex, but were genetically distinct. Cercospora sp. Q was identified as the etiological agent of the leaf spots on E. aureum, whereas the fungus on Z. aethiopica was found to belong to Cercospora sp. G. Inoculations confirmed the pathogenicity of both isolates to their original hosts, and cross‐pathogenicity assessments revealed that both isolates were capable of infecting both E. aureum and Z. aethiopica. The limited morphological and pathological distinction between the fungi on these two hosts reflects the continued difficulty in the taxonomic treatment and species delimitation for Cercospora sp. G, Cercospora sp. Q, as well as other provisional code‐based Cercospora spp., and other components of the broad C. apii s. lat. complex. The name Cercospora richardiicola (as C. richardiaecola) was mistakenly used for the fungus on Z. aethiopica in earlier publications and this has been corrected herein.

New Zealand (NZ) spinach (Tetragonia tetragonoides) is an important leafy vegetable crop in Brazil and other countries. This plant is used as a substitute for common spinach because it is rustic and tolerant to tropical and subtropical environmental conditions. It is often affected by a leaf and stem spot disease, which increases in severity during the warm climatic periods. Cercospora tetragoniae has been reported as the cause of this disease, but this is based on an early description of a Cercospora-like species on this host in Argentina, first named Cercosporina tetragoniae but later recombined into Cercospora. In the present study, isolates of Cercospora-like fungi were obtained from NZ spinach and beetroot plants in Brazil, and a multigene molecular study including the act, cal, gapdh, his3, ITS, and tef1-α regions was carried out to identify the causative pathogen. Additionally, morphological and cross inoculation studies were conducted with isolates obtained from diseased plants. The pathogen was confirmed as Cercospora beticola, a common and harmful pathogen of beetroot (Beta vulgaris). Cross-inoculations of isolates obtained from NZ spinach and beetroot showed that the isolates are infective to both hosts. This increases knowledge of epidemiology and management of this important disease. Several attempts to re-collect samples from the type locality in Argentina failed. NZ spinach is no longer grown at La Plata (Argentina), the type locality of C. tetragoniae. Therefore, the task of re-collecting the pathogen is still pending, for epitype designation and for a full clarification of the taxonomic status of C. tetragoniae. The possibility of the pathogen being seed-transmitted has been assessed, and evidence obtained justifies further assessment of this aspect.

Hop – Humulus lupulus (Cannabaceae) – is an important and ancient, herbaceous, temperate, perennial crop. It is a vine which, although having other uses, is cultivated predominantly for the brewing industry (Laws 2013). Cultivation of hops in Brazil is relatively new and has increased in the last twenty years. There is only one published record of a fungal disease affecting hop in Brazil – powdery mildew (Fagherazzi et al 2021). In January 2021, leaf spots appeared on all eight hops plants ithe collection maintained in the Infectarium, a disease demonstration garden on the campus of the Universidade Federal de Viçosa (UFV), Viçosa, Minas Gerais, Brazil (https://www.infectario.ufv.br/). Symptoms were small, sub-circular to irregular spots, up to 5 mm, with a whitish to grayish center, surrounded by a dark brown necrotic margin, followed by a narrow yellowish outer margin. Older lesions became larger, grayish-brown, coalesced leading to extensive necrosis and stem dieback. A sample was collected, dried in a plant press, and deposited in the Herbarium of UFV (Acc. No VIC 47534). A dematiaceous fungus was found sporulating in the center of the lesions, when examined with a dissecting microscope. Fungal structures were scraped with a scalpel, mounted in lactoglycerol and observed with a light microscope (Olympus BX51). A pure culture was obtained after conidia were transferred onto PDA plates with a sterile fine-pointed needle. A representative isolate was deposited in the culture collection of the UFV (COAD 3368). The fungus had the following morphology: conidiophores cylindrical, geniculate, proliferating sympodially, 53 to 380 µm × 3 to 6.5 µm, 3 to 15-septate, smooth, with thickened and dark conidial scars, brown; conidia acicular to filiform, 47 to 210 µm × 2.5 to 5 µm, 3 to 17-septate, thin‑walled, smooth, with thickened and dark hila, hyaline. This combination is typical of Cercospora apii sensu lato, as described by Crous and Braun (2003). Genomic DNA was extracted from a 7-day-old culture of COAD 3368 and three loci were PCR amplified, namely: actin (ACT), with 512-F and 783-R primers; calmodulin (CAL), using the primers 228F and 2Rd; and histone H3 gene (HIS3), with the primers CYLH3F and CYLH3R. PCR products were sequenced by Macrogen (Seoul, South Korea) and the resulting sequences were deposited in GenBank (OM677624, OM677625 and OM677626, respectively). A multilocus Bayesian phylogenetic grouped COAD 3368 with Cercospora ‘sp. Q’ (Groenewald et al. 2013). This is a yet unresolved species complex within C. apii. Six 6‑month‑old healthy hop plants (cv. Cascade) were sprayed with a COAD 3368 conidial suspension (105 conidia/ mL) whereas another group of six plants was sprayed with sterile distilled water, serving as controls. Plants were placed in a dew chamber for 5 days and then transferred to a greenhouse bench, where they were observed daily. Thirty days after inoculation, symptoms similar to those observed in the field had developed on all inoculated plants, whereas control plants remained healthy. The fungus growing on inoculated hops produced typical Cercospora conidiophores and conidia. Upon reisolation, pure cultures with the same morphology of COAD 3368 were obtained. There are no previous records of Cercospora ‘sp. Q’ on hops worldwide. Fungi in Cercospora ‘sp. Q’ are known to have a broad host-range. A previous record of Cercospora ‘sp. Q’ leaf spots was published from its observation on Dioscorea cayennensis in the Infectarium (Torres et al. 2016). Damage to the hop plants was severe and it is possible that Cercospora leaf spot will become an emerging threat to commercial hop plantations in Brazil.

During surveys conducted in South America and Africa to identify natural fungal enemies of coffee leaf rust (CLR), Hemileia vastatrix, over 1500 strains were isolated, either as endophytes from healthy tissues of Coffea species or as mycoparasites growing on rust pustules. Based on morphological data, eight isolates—three isolated from wild or semiwild coffee and five from Hemileia species on coffee, all from Africa—were provisionally assigned to the genus Clonostachys. A polyphasic study of their morphological, cultural and molecular characteristics—including the Tef1 (translation elongation factor 1 alpha), RPB1 (largest subunit of RNA polymerase II), TUB (β-tubulin) and ACL1 (ATP citrate lyase) regions—confirmed these isolates as belonging to three species of the genus Clonostachys: namely C. byssicola, C. rhizophaga and C. rosea f. rosea. Preliminary assays were also conducted to test the potential of the Clonostachys isolates to reduce CLR severity on coffee under greenhouse conditions. Foliar and soil applications indicated that seven of the isolates had a significant effect (p < 0.05) in reducing CLR severity. In parallel, in vitro tests that involved conidia suspensions of each of the isolates together with urediniospores of H. vastatrix resulted in high levels of inhibition of urediniospore germination. All eight isolates showed their ability to establish as endophytes in C. arabica during this study, and some proved to be mycoparasites of H. vastatrix. In addition to reporting the first records of Clonostachys associated with healthy coffee tissues and with Hemileia rusts of coffee, this work provides the first evidence that Clonostachys isolates have potential as biological control agents against CLR.