Identification of Alternaria tenuissima causing brown leaf spot on Paris polyphylla var. chinensis in China

Severe brown leaf spot disease was observed on Paris polyphylla var. chinensis in Sichuan Province, China, in 2017 and 2018. The initial symptoms were many light‐brown small spots with necrotic centres, round or irregular in shape, becoming dark brown, gradually enlarging and eventually coalescing, causing extensive leaf senescence. A fungus was isolated from diseased leaves showing typical symptoms of brown leaf spot. The isolates were cultured on potato sucrose agar, and their morphological characteristics of the causal pathogen were observed under a light microscope. Pathogenicity tests revealed that this fungus was the causal pathogen of the disease. Molecular analyses of the sequences of the ribosomal DNA internal transcribed spacer (ITS) region, translation elongation factor 1‐alpha (TEF) and the RNA polymerase II second largest subunit (RBP2) gene were conducted to confirm the identity of the pathogen. The multi‐gene phylogeny indicated that the causal agent was Alternaria tenuissima. To our knowledge, this is the first report of A. tenuissima causing brown leaf sports on P. polyphylla var. chinensis in China.     

Occurrence of Grey Leaf Spot of Sedum erythrostictum Caused by Cercospora cf. pseudokalanchoes in China

Sedum erythrostictum is a perennial herb in the Crassulaceae family, which is a traditional Chinese medicine used for the treatment of hepatitis, dysentery, herpes zoster and swellings. In 2014, a grey leaf spot disease causing significant damage to plants of S. erythrostictum occurred in the Medicinal Herb Garden of Jilin Agricultural University, Jilin Province, China. The fungus mainly infected the leaves. The necrotic lesions on the leaves were circular or elliptical, amphigenous, greyish brown to brown, slightly concave and surrounded by a dark brown distinct margin. The causal agent from symptomatic tissues was identified as Cercospora cf. pseudokalanchoes based on the symptoms, morphological characteristics, molecular identifications and pathogenicity tests. To our knowledge, this is the first formal report of grey leaf spot of S. erythrostictum caused by C. cf. pseudokalanchoes in China.     

Morphology,phylogeny and pathogenicity of Alternaria species,involved in leaf spot disease of sunflower in northern Iran

Leaf spot disease of sunflower is one of the most important foliar diseases on this crop worldwide. Several fungal groups are known to cause leaf spot disease on sunflower. Species of the genus Alternaria are the most common and serious leaf spot causing fungi on this crop. Leaf spot disease is the most destructive foliar diseases on sunflower in northern Iran; however, the identity of the causal agent remains unknown. The present study was aimed to characterise the identity of the causal agent of the disease by means of morphological and molecular data as well as to evaluate the pathogenicity of the responsible species. For this purpose, a total number of 97 fungal isolates were recovered from sunflower leaves with leaf spot disease symptoms from the sunflower fields in northwestern zone of Iran. All of the isolates were identified as Alternaria alternata based on cultural and morphological characteristics. A subset of isolates was subjected to phylogenetic analysis using sequence data from ITS-rDNA region, gpd and rpb2 genes. Sequence data from ITS-rDNA and gpd did not discriminate A. alternata from the other small-spored Alternaria species. A phylogeny inferred using sequence data from rpb2 gene clustered our isolates in several sub-clades within a single monophyletic clade. Sequence data for the type strain of the other small-spored Alternaria species has to be included in phylogenetic analysis, in order to make sure, whether the observed variations in rpb2 gene sequences are an indication for the population variation in sunflower isolates of A. alternata or define species boundaries among the small-spored Alternaria species. The results of pathogenicity assay on sunflower plants (cultivar Euroflor) under greenhouse condition revealed that A. alternata is pathogenic on sunflower.     

First Report of Leaf Spot Disease in Angelica dahurica Caused by Phoma bellidis in China

Angelica dahurica is a perennial herb belonging to the Umbelliferae family that has been used as a valuable traditional Chinese medicine. In August 2013, leaf spot disease in A. dahurica was first observed at the Medicinal Herb Garden in Shenyang Agricultural University, Shenyang, Liaoning, China. Morphological assessment, evaluation of culture characteristics, internal transcribed spacer and beta‐tubulin sequence analysis and pathogenicity identified the causal agent as Phoma bellidis. To our knowledge, this is the first report of leaf spot disease in A. dahurica that was caused by P. bellidis.     

Occurrence of Passalora Leaf Spot Caused by Passalora ampelopsidis on Virginia Creeper in Korea

A previously unknown leaf spot disease was observed on Virginia creeper (Parthenocissus quinquefolia) vines in Seoul, Korea. Affected plants exhibited leaf spots and discoloration, resulting in leaf blight and premature defoliation. The causal agent of the disease was identified as Passalora ampelopsidis by comparing morphological characteristics and analyzing the internal transcribed spacer region of the rDNA. Pathogenicity tests were conducted twice with the same results, fulfilling Koch's postulates. Passalora leaf spot on Virginia creeper vines was first recorded in the United States in 1878. Recent reports of Passalora leaf spots on Virginia creeper vines in 2005 in Germany, in 2012 in China and now in Korea indicate the prevalence of the disease.     

First report of Phoma betae on Aloe vera in India

Leaf spot disease of A. vera was observed in nurseries of Gwalior city afterthe post-rainy season. As the disease progressed, the tip of the leaf shrank, then dried and eventually broke. The causal agent was identified as Phoma betae A.B. Frank. This is the first report of leaf spot disease on Aloe vera caused by P. betae in India.     

First Report of Bacterial Leaf Spot of Parsley Caused by Pseudomonas syringae pv. apii in Turkey

Since March, 2011, typical leaf spot symptoms were observed on parsley in several fields inspected in Hatay and Adana provinces of Turkey. Incidence of the disease was 5–15% in the regions. Symptoms were characterized as angular to irregular, initially water soaked later brown to dark black spots. Spots often limited by veins which were visible from both adaxial and abaxial sides of leaves but were not present on stems. Fluorescent bacterial colonies were consistently isolated from typical leaf spots. Biochemical tests, fatty acid methyl ester (FAME) analysis, molecular, pathogenicity tests and sequence of 16S ribosomal DNA of bacterial isolates were performed to identify possible causal disease agent. The causal disease agent was identified as Pseudomonas syringae pv. apii based on symptoms, biochemical, molecular, pathogenicity tests and sequencing. To our knowledge, this is the first report of bacterial leaf spot on parsley caused by Pseudomonas syringae pv. apii in Turkey.     

Identification and Characterization of Paraphoma chrysanthemicola Causing Leaf Spot Disease on Atractylodes japonica in China

Atractylodes japonica is a perennial herb in Compositae family, which is used for stomach disorders as a traditional Chinese medicine (Guo et al. 2006 ). In 2013, a leaf spot disease was first observed on plants of A. japonica in a production field of Fushun County, Liaoning Province, China. The disease had a speckled appearance initially. Lesions with grey–white centre and brown margin gradually developed and enlarged. Eventually, infections usually caused yellowing of the leaves and premature defoliation. The causal agent of infection on plants was identified as Paraphoma chrysanthemicola based on morphological and cultural characteristics, pathogenicity tests and phylogenetic analysis. To our knowledge, this is the first report of a leaf spot disease on A. japonica caused by P. chrysanthemicola in China.     

Cucumis sativus and Ipomoea purpurea: New hosts for Alternaria hydrangeae in China

Alternaria leaf spot is a common disease on various plants worldwide. In this study, an Alternaria species, A. hydrangeae causing leaf spot on Cucumis sativus (cucumber) and Ipomoea purpurea in China was identified based on morphology and multi-locus analysis of the partial ITS, GAPDH, Alt a 1, TEF1, and RPB2 gene regions. The pathogenicity of the present isolates and a representative isolate of A. hydrangeae were assessed on living leaves of C. sativus, I. purpurea and Hydrangea paniculata. Similar symptoms were observed on every plant inoculated with the isolates. The same fungus was re-isolated from inoculated leaves fulfilling Koch's postulates. Morphology of the original and re-isolated isolates showed characteristics similar to A. hydrangeae with some variations. Multi-locus analysis indicated that the present isolate fell into A. hydrangeae clade. This study is the first report of A. hydrangeae as an agent of Alternaria leaf spot in C. sativus and I. purpurea in China, which extends the host range of the fungus.     

New Host Record of Myrothecium roridum Causing Leaf Spot on Abutilon megapotamicum from China

During September 2010, Abutilon megapotamicum plants with dark‐brown concentric spots on leaves were observed in a commercial glasshouse located in Beijing, China. This study was carried out to identify the causal agent of this disease based on Koch's postulates and morphological characteristics. Pathogenicity tests in the glasshouse showed that Myrothecium roridum Tode ex Fr. caused the leaf spot on A. megapotamicum plants, which were the same as those observed in naturally infected plants in the field. Moreover, to confirm the pathogen to species, the rDNA internal transcribed spacer (ITS) of isolate was PCR‐amplified using ITS1 and ITS4 primer pairs and sequenced. DNA analysis revealed a 100% species identity index for M. roridum. To the best of our knowledge, this is the first report of M. roridum on A. megapotamicum in China.     

<i>Aspergillus tubingensis</i> Causes Leaf Spot of Cotton (<i>Gossypium hirsutum</i> L.) in Pakistan

Cotton (Gossypium hirsutum L.) is a key fiber crop of great commercial importance. Numerous phytopathogens decimate crop production by causing various diseases. During July-August 2018, leaf spot symptoms were recurrently observed on cotton leaves in Rahim Yar Khan, Pakistan and adjacent areas. Infected leaf samples were collected and plated on potato dextrose agar (PDA) media. Causal agent of cotton leaf spot was isolated, characterized and identified as Aspergillus tubingensis based on morphological and microscopic observations. Conclusive identification of pathogen was done on the comparative molecular analysis of CaM and β-tubulin gene sequences. BLAST analysis of both sequenced genes showed 99% similarity with A. tubingensis. Koch’s postulates were followed to confirm the pathogenicity of the isolated fungus. Healthy plants were inoculated with fungus and similar disease symptoms were observed. Fungus was re-isolated and identified to be identical to the inoculated fungus. To our knowledge, this is the first report describing the involvement of A. tubingensis in causing leaf spot disease of cotton in Pakistan and around the world.     

Prevalence of Xanthomonas euvesicatoria on Pepper in Brazil

Bacterial spot, caused by Xanthomonas spp., is one of the major diseases of pepper in Brazil, causing considerable losses to crop productivity. The efficient management of the disease is hampered by the high variability of the causal agents. In Brazil, there is no knowledge of which species of Xanthomonas occurs on pepper. In this study, 59 strains of Xanthomonas spp. isolated from different pepper‐producing regions of Brazil were characterized by biochemical and molecular techniques. Results showed the prevalence of X. euvesicatoria as the causal agent of bacterial spot on pepper in Brazil.     

First Report of Myrothecium roridum Causing Leaf Spot on Anthurium andraeanum in China

A new severe disease on Anthurium andraeanum Lind. was observed in the summer of 2011 in Beijing, China. The fungus was isolated from symptomatic leaves, and its pathogenicity was confirmed. Based on the morphological characteristics and molecular analysis, the pathogen was identified as Myrothecium roridum Tode ex Fr. This is the first report of M. roridum causing leaf spot on A. andraeanum in China.     

Factors affecting incidence and severity of leaf spot disease on lettuce caused by Septoria birgitae

In the 1990s during wet seasons a new disease causing brown leaf spots on lettuce (Lactuca sativa) was found for the first time in many lettuce‐growing areas of Austria and Germany. The causal agent, a new pathogenic species called Septoria birgitae, may be responsible for total crop loss. To study how temperature, inoculum density and leaf wetness period influence disease incidence and severity of leaf spot on lettuce caused by S. birgitae, we carried out in vivo experiments in growth chambers and in the field. Additionally, we evaluated the relevance of infected plant debris acting as a primary inoculum source in soil for subsequent crops. S. birgitae produces spores over a wide temperature range between 5°C and 30°C, and can infect plants at temperatures between 10°C and 30°C, with an optimum between 20°C and 30°C. Spores of S. birgitae at a density of at least 10³ conidia mL^–1 are essential for disease outbreak on lettuce. Because leaf wetness is crucial for releasing conidia from pycnidia, we studied the impact of leaf wetness duration on disease development under various temperature conditions. For relevant leaf spot disease development on lettuce in vivo, a leaf wetness duration of at least 24 h and temperatures higher than 10°C were necessary. Leaf spot disease development in the field required several leaf wetness periods longer than 20 h at approximately 15°C at the beginning of crop cultivation. Incorporating S. birgitae infected plant debris in soil as a primary inoculum was not relevant for leaf spot disease outbreak in the next year. However, in cases of continuous cropping of lettuce on the same field and in the same season, Septoria‐infected lettuce debris may become more relevant.     

Inhibitory effect of Trichoderma isolates on growth of Alternaria alternata,the causal agent of leaf spot disease on sunflower,under laboratory conditions

Several species of the genus Alternaria are involved in leaf spot disease of sunflower, with Alternaria alternata being the dominant species responsible for this disease in Iran and many other sunflower-producing areas, worldwide. The disease causes a progressive destruction of the photosynthetic apparatus, resulting in annual yield loss. The routine disease management strategies are not effective for disease control; hence, alternative measures for disease management are of great interest. In the present study, the efficacy of Trichoderma harzianum T22 and Trichoderma sp. on biological control of the causal agent was evaluated under laboratory conditions. The effect of Trichoderma isolates on dry weight (DW) and radial growth (RG) rate of A. alternata was evaluated using dual culture, volatile and non-volatile cellular metabolites. The results obtained in this study revealed that in both Trichoderma isolates, non-volatile cellular metabolites had the highest inhibitory effect on DW and RG rate of the causal agent. Owing to explicit inhibitory effect of non-volatile cellular metabolites on A. alternata, the inhibitory effects of different concentrations of non-volatile cellular metabolites were evaluated on DW and RG rate of the A. alternata. The obtained results showed that non-autoclaved 75 and 50% concentrations and undiluted (100%) autoclaved non-volatile cellular metabolites from Trichoderma sp. had the highest inhibitory effect on DW and RG rate of the causal agent. The overall results of this study reveal that Trichoderma spp. have excellent efficacy on biological control of A. alternata under laboratory condition; such that, further studies on the potential of Trichoderma spp. in biological control of Alternaria leaf spot disease of sunflower under green house and field conditions are necessary.     

Phytotoxins produced byTubakia dryina

Tubakia dryina, the causal agent of red oak (Quercus rubra) leaf spot, produced the phytotoxins isosclerone, 3-hydroxyisosclerone, 6-hydroxyisosclerone and 6-hydroxymellein in liquid culture. All toxins caused large necrosis when placed on leaves of red oak. Necrosis was also caused on white oak and eight different weed species. All toxins were non-specific phytotoxins.     

Studies of the incidence, severity and distribution of false rust (Synchytrium psophocarpi), leaf spot (Pseudocercospora psophocarpi) and powdery mildew (Oidium sp.) on winged bean (Psophocarpus tetragonolobus) in Papua New Guinea

The incidence, severity and distribution of false rust, (Synchytrium psophocarpi), leaf spot (Pseudocercospora psophocarpi) and powdery mildew (Oidium sp.) on winged beans (Psophocarpus tetragonolobus) were evaluated on pure lines and mixed stands grown in Papua New Guinea between 1976 and 1978. Almost all of the 148 pure lines were susceptible to false rust and leaf spot and the incidence of these diseases increased with plant age. Standard area diagrams were superior to disease keys in evaluating disease severity. Levels of false rust on 10 promising agronomic lines differed according to the locality where the lines were grown. Two Thai lines showed resistance to false rust but P. scandens was immune to false rust and leaf spot. Surveys of 51 sites containing mixed stands of winged beans in the Eastern Highlands, Western Highlands, East New Britain, East Sepik, Madang and Morobe Provinces of Papua New Guinea indicated that leaf spot and false rust were present in both the wet and dry seasons and the apparent absence of disease was probably due to time and size of samples. The diseases appeared to be present in all the traditional winged bean growing areas of Papua New Guinea. It was difficult to obtain evidence of differences in palatability of tissues infected with false rust. The value of surveys and disease assessment in relation to evaluation of crop losses of winged bean caused by these pathogens and selection for resistance is discussed.     

Fungal foliar diseases of Rauwolfia serpentina in wild,its seasonal occurrence,seed transmission and disease management

Rauwolfia serpentina is an important medicinal herb. Studies were conducted to determine causal organisms of foliar diseases in R. serpentina in Bhadra Wildlife Sanctuary during 2006–2009. The foliar disease incidence and its distribution and disease severity in nine state forest regions of the sanctuary were determined. The seedborne nature and transmission of the causal organism was also determined. The management of seedborne inoculum was done by seed dressing with fungicides. The effect of foliage infection on secondary metabolite content was also determined. Results of the present study indicated that Cercospora rauwolfiae is major leaf spot disease causing pathogen. The disease is homogeneously distributed through the study area. The foliar disease severity was high in Kagemanegiri forest during October–November. The minor leaf spot disease caused by Alternaria alternata occurred occasionally. Alternaria alternata is seedborne and seed transmitted and could be managed by seed treatment with Captra or Hyzeb. The secondary metabolites like alkaloids and steroids decreased with increase in foliar infection by C. rauwolfiae, while phenol and flavonoid contents increased. The study suggested that R. serpentina is affected in wild by C. rauwolfiae and A. alternata. The latter pathogen is seedborne and seed transmitted and controlled by seed treatment.     

Zonate Leaf Spot of Prunus mandshurica Caused by Hinomyces pruni in Korea

Zonate leaf spots and severe defoliation were observed on Manchurian apricot (Prunus mandshurica) growing in a humid location in Korea from 2011 through 2013. The main symptoms included greyish green to brownish grey and zonate leaf spots without border lines, which mostly led to premature defoliation. The morphological characteristics of the causal agent were consistent with Hinomyces pruni. Identification was supported by analysing the sequence of the internal transcribed spacer region of ribosomal DNA from an isolate. The pathogenicity of the isolate was confirmed by artificial inoculation. This is the first report of zonate leaf spot caused by H. pruni on Manchurian apricot globally as well as in Korea.     

Notes on some plant-inhabiting fungi collected from the Nansei Islands (1)

In the course of a survey on plant diseases and their pathogenic fungi in the Nansei Islands, some noteworthy fungi were collected. Among them, four fungi newly found in Japan were described with some mycological and pathological notes. These species are Septoria gardeniae Savelli, causing circular leaf spot of Gardenia; Phyllosticta cordylinophila Young apud Stevens, causing brown leaf spot of Cordyline; Phyllosticta drummondii Vanef et van der Aa, causing brown needle blight of Araucaria; and Phyllachora minuta Hennings, causing tar spot of Hibiscus.