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Phyllosticta sp. on Ginkgo biloba: A. Conidiogeneus cell, B. Conidia, C and D. Symptomatic leaves of host (Bars = 10 µm).
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Species of Phyllosticta are important group of pathogenic and endophytic fungi that are reported from various
crop plants, ornamental and non-fruiting plants. These fungi cause several diseases such as leaf and fruit spots and fruit
rot. In order to identify Phyllosticta species in Guilan province, several collections were examined around the regio...
Citations
Pestalotiopsis leaf fall disease (PLFD) has been on the increase in recent years, resulting in diminished latex yield in many rubber producing countries. Thus far, some reports have pointed to the presence of fungal pathogen(s) other than Pestalotiopsis sp. in the diseased leaves. To decipher the diversity of fungal pathogens, a total of 110 early-stage and another 110 late-stage symptomatic leaves were sampled from 12 Hevea clones in seven different areas in Malaysia during wintering and wet seasons at different times of the year. A total of 487 fungal isolates were obtained; 241 were from the early-stage and 246 from the late-stage symptomatic leaves. These isolates were clustered into 11 morphotypes based on colony appearance and microscopic observation of the spore. The diversity analysis revealed significant differences in morphotype richness and evenness when comparing different rubber clones, seasonal effects, and locations by which the fungal isolates were sampled. Five isolates representative of the five predominant morphotypes associated with PLFD were analysed using the Internal Transcribed Spacer (ITS) markers and BLAST analysis. Their closest relative species were identified as Colletotrichum conoides, Neopestalotiopsis surinamensis, Lasiodiplodia theobromae, Phyllosticta fallopiae and Letendraea cordylinicola. This study enhanced our understanding of PLFD, particularly the diversity and distribution of fungal communities associated with the disease across different rubber clones, seasons, and locations in Malaysia. The identification of these fungal isolates associated with PLFD symptoms paves the way for further research into their pathogenicity and the development of targeted management strategies to mitigate the disease.
During 2017–2018, leaf spots were observed on Japanese privet plants in commercial greenhouses and ornamental nurseries in Tehran, Fars and Bushehr provinces, Iran. Due to the high severity of the symptoms, this study was conducted to identify the causal agents. Based on morphological characteristics and molecular analyses of six loci (ITS, act, tef1, gapdh, LSU, and rpb2), the strains isolated were identified as Phyllosticta capitalensis. Pathogenicity was verified with Koch’s postulates. To the best of our knowledge, this is the first report of P. capitalensis causing leaf spot on Japanese privet in Iran.
Figure 1 Figure 2 Figure 3 Magnolia grandiflora is a medicinal and horticultural plant species in the family Magnoliaceae which is native to North America (Li et al., 2013). Syringa reticulate is a tree in the family Oleaceae which is native to Japan (Green et al., 1995). During autumn 2017, leaf spots were observed on Magnolia grandiflora and Syringa reticulate in an ornamental garden in Hamedan province, Iran. Initial symptoms on M. grandiflora and S. reticulata leaves appeared as irregular, black and necrotic spots, often developing from the tip and sometimes from the edges of the leaves. These lesions slowly grew in size, and appeared long and blackish (Fig. 1). Symptomatic leaves were collected and transferred to the laboratory for further study. In order to identify the causal agent, small pieces were cut from the margin of diseased and healthy tissues of affected leaves. After surface disinfection, the pieces were transferred onto potato dextrose agar (PDA) medium at 27°C in the darkness for seven days. The isolates were transferred to saltwater nutrient agar (SNA) and malt extract agar (MEA) media. For each isolate, the size, colour and shape of 30 pycnidia and conidia, were recorded after 14 days. On PDA, colonies were initially white, gradually becoming greenish to dark green then black, on SNA, colonies were greenish to dark green and on MEA, colonies were grey to black (Fig. 2). Pycnidia with conidia were produced after 14 days. Pycnidia were globose, and brown to black. Conidia were hyaline, one-celled, ovoid to ellipsoid, with a short and thin apical appendage, measuring 9-11 × 5-6 µm (Fig. 3). On the basis of morphological characters, the isolates were identified as Phyllosticta capitalensis. As the cultural and morphological characters of the isolates were very similar, one isolate from each host was selected for molecular analysis. Genomic DNA was extracted as described by Moller et al. (1992). The ITS region was amplified using primers ITS1 and ITS4. A BLAST search using the sequence from the M. grandiflora isolate (GenBank Accession No. MG954332) showed 99.35 % identity with 100% cover to P. capitalensis (KM513574). The Syringa reticulata isolate (MF784271) had 99% identity with 99% cover to P. capitalensis (KP900294). Pathogenicity tests were conducted on healthy leaves of M. grandiflora and S. reticulate in three replicates. Healthy leaves were sprayed with a conidial suspension (1 × 10 6 spores/ml), while control leaves were sprayed with sterile distilled water. Pathogenicity tests were done twice using the same conditions. Black and necrotic spots appeared after 14 days of incubation at 25°C and P. capitalensis was successfully re-isolated from artificially infected leaves, while no symptoms appeared on the control leaves (Fig. 1). Phyllosticta species include endophytes, saprobes and plant pathogens causing several disease symptoms including leaf and fruit spots (Guarnaccia et al., 2017). Phyllosticta capitalensis was previously reported as an endophyte on several species in the family Magnoliaceae (Promputtha et al., 2005). To our knowledge, this is the first report of Phyllosticta capitalensis as the causal agent of leaf spot on Magnolia grandiflora and Syringa reticulata. References 1. Darsaraei H, Khodaparast SA, Zare R, 2016. Study on the genus Phyllosticta (Ascomycota: Phyllostictaceae) from Guilan province (N. Iran). Rostaniha 17, 51-69. 2. Green PS, Chang MC, 1995. Some taxonomic changes in Syringa L. (Oleaceae), including a revision of series Pubescentes. Novon 5, 329-333. http://dx.doi.org/10.2307/3391958 3. Guarnaccia V, Groenewald JZ, Li H, Glienke C , Carstens E, Hattingh V, Fourie PH, Crous PW, 2017. First report of Phyllosticta citricarpa and description of two new species, P. paracapitalensis and P. paracitricarpa, from citrus in Europe. Studies in Mycology 87, 161-185. http://dx.. Complete chloroplast genome sequence of Magnolia grandiflora and comparative analysis with related species. Science China Life Sciences 56, 189-98. http://dx.
