Search

Citrus black spot (CBS) is a disease caused by the fungus Phyllosticta citricarpa that is associated with significant yield losses. The pathogen forms airborne ascospores that are collected in dead fallen leaves as well as waterborne conidia that are common in lesions on mature fruits and occasionally in leaves and dead twigs. In Brazil, cultural management combined with the application of systemic, protective fungicides is a practice adopted to reduce both inoculum sources. Nevertheless, the removal of mature infected fruits, dead twigs, and dead fallen leaves has not been shown to reduce the extent of disease. Moreover, the increasing use of fungicides has led to the selection of resistant strains, as well as human health concerns. To better understand this pathosystem and how the pathogen overcomes control measures currently in use, we evaluated branches at different growth stages in the field, the viability of the pathogen in detached branches, and the possibility of plant colonization through leaves. We observed that living branches are a reservoir for this pathogen and that once the branches senesce, the pathogen can persist up to 45 days, able to contaminate other plant parts. On inoculated leaves, we observed only a one-point latent infection, without signs of colonization. We also developed a faster protocol to produce pycnidia of the pathogen using autoclaved branches as a substrate, which proved useful for testing alternative compounds to control P. citricarpa. These data may be useful in the search for new effective control measures and their targets. [ABSTRACT FROM AUTHOR]

Verbascum blattaria (Scrophulariaceae family) is a hardy perennial species that is used for the edges and flower beds of low-maintenance gardens. Phoma novae-verbascicola causes light brown necrotic spots on the leaves of V. blattaria seedlings. In order to demonstrate the seed transmission of this pathogen, several V. blattaria seeds belonging to three samples collected in 2013, were tested in vitro to detect the presence of P. novae-verbascicola. Two samples were found to be contaminated and colonies of the pathogen were isolated from the tested seeds. Phoma novae-verbascicola was identified from the morphological features observed in vitro and through an ITS (Internal Transcribed Spacer) analysis. The virulence of one isolate was confirmed by means of a pathogenicity test. This work demonstrates that P. novae-verbascicola can be transmitted by affected V. blattaria seeds. [ABSTRACT FROM AUTHOR]

Endophytic and epiphytic fungal assemblages from stems of S. rotundifolia, a shrubby vine, were studied in order to (1) quantify differences and the degree of overlap between fungal communities of both micro-habitats, and (2) examine whether fungal assemblages are spatially correlated at the local scale (tens to hundreds of meters), in order to understand if dispersal limitation may play a role in structuring these communities. Sampling was conducted over 160 m of growth along a forest edge. The communities showed low overlap (Bray-Curtis Similarity = 0.22), with most species that were common in one habitat appearing rarely if at all in the other, and only Aureobasidium pullulans showing high frequency in both. Epiphytic assemblages proved to be spatially correlated along the 160 m length of the transect, and even more so when adjacent pairs of stems were considered as the unit of comparison rather than individual stems. Endophytic assemblages showed no significant spatial correlation along the transect. Unexpectedly, three species of endophytes showed a pattern in which abundance of colonies peaked at different heights on the stems. Colletotrichum boninense showed peak abundance at 3 cm from the stem base. Phomopsis sp. 1 peaked at 33 cm from the stem base. Endophytic isolates of A. pullulans peaked at 63 cm from the stem tip. It was also found that positive correlative relationships were detected between endophyte-endophyte, and epiphyte-epiphyte pairs. Cross-group interactions seemed to center around crossover species that were not entirely constrained within the surface or interior. [ABSTRACT FROM AUTHOR]

Rain-splash dispersal of Phyllosticta citricarpa (syn. Guignardia citricarpa) conidia (pycnidiospores) from infected oranges was studied in still air and combined with wind. High power microscopy demonstrated the presence of conidia in splash droplets from diseased oranges, which exuded conidia for over one hour during repeated wetting. The largest (5 mm) incident drops produced the highest splashes (up to 41.0 cm). A linear-by-quadratic surface model predicted highest splashes to be 41.91 cm at a horizontal distance of 25.97 cm from the target orange. Large splash droplets contained most conidia (4-5.5 mm splashes averaged 308 conidia), but were splashed <30 cm horizontal distance. Most (80-90%) splashes were <1 mm diameter but carried only 0-4 conidia per droplet. In multiple splash experiments, splashes combined to reach higher maxima (up to 61.7 cm; linear-by-quadratic surface model prediction, 62.1 cm) than in the single splash experiments. In combination with wind, higher wind speeds carried an increasing proportion of splashes downwind travelling horizontally at least 8 m at the highest wind speed tested (7 m/s), due to a small proportion of droplets (<1 mm) being aerosolised. These experiments suggest that P. citricarpa conidia can be dispersed from infected oranges by splashes of water in rainfall events. [ABSTRACT FROM AUTHOR]

The type specimens of Auerswaldia, Auerswaldiella, Barriopsis, Botryosphaeria, Leptoguignardia, Melanops, Neodeightonia, Phaeobotryon, Phaeobotryosphaeria, Phyllachorella, Pyrenostigme, Saccharata, Sivanesania, Spencermartinsia and Vestergrenia were examined and fresh specimens of Botryosphaeriales were collected from Thailand. This material is used to provide a systematic treatment of Botryosphaeriales based on morphology and phylogeny. Two new genera, Botryobambusa and Cophinforma are introduced and compared with existing genera. Four species new to science, Auerswaldia dothiorella, A. lignicola, Botryosphaeria fusispora and Phaeobotryosphaeria eucalypti, are also described and justified. We accept 29 genera in Botryosphaeriales, with Macrovalsaria being newly placed. In the phylogenetic tree, the 114 strains of Botyrosphaeriales included in the analysis cluster into two major clades with 80 %, 96 % and 1.00 (MP, ML and BY) support, with Clade A containing the family type of Botryosphaeriaceae, and Clade B containing Phyllosticta, Saccharata and Melanops species. This group may represent Phyllostictaceae. In Clade A the taxa analyzed cluster in eight sub-clades (Clades A1-8). Clade A1 comprises three distinct subclusters corresponding to the genera Diplodia ( Diplodia Clade), Neodeightonia ( Neodeightonia Clade) and Lasiodiplodia ( Lasiodiplodia Clade) . Clade A2 clusters into three groups representing Phaeobotryosphaeria (100 %) , Phaeobotryon (100 %) and Barriopsis (94 %). Clade A3 incorporates 17 strains that cluster into three well-supported genera ( Dothiorella (86 %), Spencermartinsia (100 %) and Auerswaldia (63 %); the position of Macrophomina is not stable. Clade A4 is a single lineage (100 %) representing the new genus Botryobambusa. Clade A5 is a well-supported subclade incorporating Neofussicoccum. Clade A6 represents the type species of Botryosphaeria, three other Botryosphaeria species and two other genera, Neoscytalidium and Cophinforma gen. nov. Clade A7 comprises two Pseudofusicoccum species and Clade A8 has two Aplosporella species. These sub-clades may eventually require separate families but this requires analysis of a much larger dataset. Our data advances the understanding of Botryosphaeriales, there is, however, still much research to be carried out with resolution of families and genera, linkage of sexual and asexual morphs and differentiation of cryptic species. [ABSTRACT FROM AUTHOR]

The identity of the casual agent of freckle disease of banana was investigated. The pathogen is generally referred to in literature under its teleomorphic name, Guignardia musae, or that of its purported anamorph, Phyllosticta musarum. Based on morphological and molecular data from a global set of banana specimens, several species were found associated with freckle disease. Phyllosticta maculata (from Southeast Asia and Oceania) is introduced as a new name for Guignardia musae, and an epitype is designated from Australia. Phyllosticta musarum (from India and Thailand) is shown to represent a distinct species, and the name is fixed by designation of an epitype from India. Guignardia stevensii is confirmed as distinct species from Hawaii, while Guignardia musicola from northern Thailand is shown to contain different taxa and is regarded as nomen confusum. Phyllosticta cavendishii is described as a new, widely distributed species, appearing primarily on Cavendish, but also on non-Cavendish banana cultivars. [ABSTRACT FROM AUTHOR]

Due to the low chemical control effectiveness of citrus black spot, caused by the fungus Guignardia citricarpa at postharvest, and to the search for alternative control methods, this study aimed to evaluate the in vitro effect of volatile organic compounds (VOCs), produced by yeast Saccharomyces cerevisiae, on G. citricarpa. It was observed that the yeast strains evaluated acted as antagonists by VOC production, whose maximum inhibitory capacity was as high as 87.2%. The presence of fermentable carbon sources in the medium was essential for the bioactive VOC production by the yeast. The analysis of VOCs produced in PDA medium by SPME–GC–MS indicated the presence of high quantities of alcohols as well as esters. An artificial VOC mixture prepared on the basis of the composition of the VOCs mimicked the inhibitory effects of the natural VOCs released by S. cerevisiae. Thus, the VOCs produced by the yeast or the artificial mixtures can be a promising control method for citrus black spot or others postharvest diseases. [ABSTRACT FROM AUTHOR]

In this paper, four fungi collected in Nansei Islands are reported. One is Strasseria garciniae, which must be transferred to the genus Phyllosticta. This fungus was collected in Okinawa Main Island and Iriomote Island. The other three fungi are newly added to the Japanese fungal flora. Phyllosticta ghaesembillae on Codiaeum variegatum and Cercospora asplenii on Asplenium antiquum were collected in Yoron Island. The last one, Coniella australiensis on Eucalyptus robusta was collected in Okinawa Main Island. Their morphology and symptoms on the host plant are described, with some mycological notes. [ABSTRACT FROM AUTHOR]

Abstract  The X-ray crystal structure of phyllostin (8-hydroxy-3-methyl-2-oxo-2,3,4a,5,8,8a-hexahydro-benzo[1,4]dioxine-6-carboxylic acid methyl ester) is reported. Phyllostin was recently and for the first time isolated, together with phytotoxin phyllostoxin and the phyllostictines A–D, from the culture filtrates of Phyllosticta cirsii, a fungal pathogen isolated from diseased Cirsium arvense leaves and evaluated as biocontrol agent of this noxious perennial weed. Phyllostin crystallizes in the monoclinic space group P21 with unit cell parameters: a = 8.371(2), b = 7.026(1), c = 9.918(1) Å, β = 92.013(8)°, Z = 2. The final refinement converged to R1 = 0.0530 for 1026 observed reflections having I > 2σ(I). In the molecule two trans joined six-membered rings are present. The cyclohexene ring adopts a half-chair conformation. The 2-oxo-1,4-dioxan ring adopts a distorted half-chair conformation. The relative stereochemistry of the four chiral centers turns out to be 3R,4aS,8R,8aS. In the crystal packing molecules form infinite chains through O–H···O intermolecular hydrogen bonds. Chains run along the crystallographic a axis forming layers of molecules stacking in the [0 1 0] direction. Graphical Abstract  The X-ray crystal structure of phyllostin (8-hydroxy-3-methyl-2-oxo-2,3,4a,5,8,8a-hexahydro-benzo[1,4]dioxine-6-carboxylic acid methyl ester) (I) is reported. In the molecule two trans joined six-membered rings are present. The relative stereochemistry of the four chiral centers turns out to be 3R,4aS,8R,8aS. [ABSTRACT FROM AUTHOR]

Although the genus concept of Phyllosticta s. str. (teleomorph: Guignardia) as defined by van der Aa is widely accepted, the species concept is still controversial because it is often based on the morphology on host plants. In this study, the culture characteristics within Phyllosticta s.str. were examined, and the phylogenetic relationships among Japanese species of Phyllosticta s.str. and its teleomorph Guignardia were analyzed using 18S rDNA sequences. Phyllosticta s. str. formed a monophyletic clade. ITS-28S rDNA sequences extracted from fungal cultures derived from various host plants were divided into two subgroups. The first group included cultures from a wide range of host plants and were mainly derived as endophytes from a symptom-less plant. In the second group, cultures from each host plant genus formed distinct clades; these were often isolated as leaf pathogens from diverse plants. Isolates belonging to the first lineage generally grew faster on oatmeal agar. To classify species of Phyllosticta it is necessary to consider an integrated approach such as molecular phylogeny, host plant, colony growth, symptoms, and morphological characteristics of the conidiomata. [ABSTRACT FROM AUTHOR]

During a survey of plant-inhabiting fungi in a botanical garden in Japan, some noteworthy fungi were collected from leaf spots of some herbal and arboreal plants. Among them, five new species are described, namely: Phyllosticta. ardisiicola on Ardisia crenata, Phy. aspidistricola on Aspidistra elatior, Phy. kerriae on Kerria japonica, Phy. fallopiae on Fallopia japonica, and Pseudocercospora davidiicola on Davidia involucrata. Passalora pyrrosiae, a new combination for Pseudocercospora pyrrosiae on Pyrrosia lingua, is proposed based on its morphological characteristics designating the neotype specimen. [ABSTRACT FROM AUTHOR]

As the first report of monographic studies of the genus Phyllosticta in Japan, four new species, Phyllosticta disanthi on Disanthus cercidifolius, P. hoveniicola on Hovenia dulcis, P. ligustricola on Ligustrum obtusifolium, and Phyllosticta alliacea on Allium fistulosum, are described and illustrated. A new teleomorphic state of P. alliorum, Guignardia alliacea, is confirmed. [ABSTRACT FROM AUTHOR]

Light microscopy of the prepenetration process of Phyllosticta musarum, the banana freckle disease causal agent, on banana leaf was conducted. Germination of conidia started within 2?3h after inoculation (AI) in a film of water at 25C. More than 50 and 90% of conidia germinated at 12 and 72h AI at 25C, respectively. The germination of a conidium usually produced one germ tube, and occasionally two germ tubes, which were borne at the side of the conidium. However, only one germ tube developed into a mature appressorium. Appressoria were dark brown in colour and had different shapes. Most of them were round or slightly lobed. Appressorium formation initiated at 6h AI, and the appressorial formation rate reached more than 50 and 80% at 24 and 48h AI, respectively. A reddish-brown necrosis of host cells appeared under the appressoria as they were forming and was seen at 120h AI. Most appressoria were formed in the grooves between adjacent epidermis cells. The pathogen seems to penetrate directly through the epidermal cuticle layer of the host by forming appressoria and infection pegs. [ABSTRACT FROM AUTHOR]

Pycnidiospores of Phyllosticta citricarpa from pure cultures, symptomatic citrus black spot Valencia orange fruit and peelings were evaluated for their potential to infect and colonise citrus black spot-free Eureka lemon leaf litter in a controlled environment and in the field in different production regions of South Africa. Leaf litter, consisting of freshly detached green and old brown leaves that were exposed to viable pycnidiospores under controlled conditions or in the field underneath citrus trees, were not infected and colonised by P. citricarpa. Ascospores, conforming to Guignardia citricarpa, the pathogen, or G. mangiferae, a cosmopolitan endophyte, were collected with a Kotz Inoculum Monitor from leaves placed in the field only at Tzaneen and Burgersfort. Distinguishing between these two species on ascospore morphology alone is not possible. A diagnostic polymerase chain reaction conducted on representative leaf material from all the treatments revealed the presence of only G. mangiferae on 12.5% of the treatments. This study demonstrated the failure of P. citricarpa pycnidiospores to infect citrus leaf litter under controlled and field conditions. Symptomatic citrus black spot fruit or peel lying on the ground underneath citrus trees, therefore, cannot lead to infection and colonisation of freshly detached leaves or natural leaf litter or represent a source of inoculum in citrus orchards for these leaves. [ABSTRACT FROM AUTHOR]

Isolation of endophytic species of Guignardia (anamorph: Phyllosticta) from healthy leaves of 94 plants (91 species and 3 varieties) in 69 genera, 42 families, was carried out in a test site (Kyoto Herbal Garden) to investigate the host range of Guignardia endophyllicola (anamorph: Phyllosticta capitalensis). Species of Guignardia and Phyllosticta were isolated from the leaves of 67 plants (66 species and 1 variety) belonging to 54 genera, 38 families. Among them, 53 isolates from different plants belonging to 43 genera in 36 families were similar in morphology, and sequence analysis of internal transcribed spacer (ITS) regions of ribosome DNA revealed these isolates to be conspecific with G. endophyllicola. In addition, this fungus was isolated from leaves of various plants collected in different places in Japan and Thailand. Thus, this endophytic fungus has been revealed to live within various vascular plants, angiosperms, gymnosperms, and pteridophytes. [ABSTRACT FROM AUTHOR]

The article presents the first report of freckle disease of banana caused by plant pathogen Phyllosticta capitalensis in Guangxi, Southwest China.