Phytophthora pseudocitrophthora, A New Pathogen of Carnations Causing Root Rot and Basal Stem Necroses in Türkiye

First Report of Phytopythium vexans Causing Stem and Leaf Necrosis on Rubber Tree (Hevea brasiliensis): Biological Characteristics and Fungicide Sensitivity

The findings provide a theoretical foundation for accurate disease diagnosis, epidemiological surveillance, and the development of effective chemical control strategies for rubber plantations.

First report of Globisporangium irregulare causing wilt and root rot on greenhouse-grown common sage in the United States

In February 2024, common sage plants (Salvia officinalis) in a commercial greenhouse in Randolph County, North Carolina were submitted to the NC State University Plant Disease and Insect Clinic. Sage plants in multiple trays were observed to have symptoms of wilting, chlorosis, and root rot. Plants had necrotic roots and necrotic areas on leaves, and eventually entire plants collapsed. Symptomatic root segments were rinsed in sterile deionized water, blotted dry, and placed on CMA-PPP selective medium (Eckert and Tsao 1962). Three isolates, each from a different symptomatic plant, were transferred to acidified potato dextrose agar. The morphological structures from each isolate matched the description of Globisporangium irregulare (formally Pythium irregulare) reported by van der Plaats-Niterink (1981). DNA samples were extracted from mycelium mats of the three isolates using the DNeasy Plant Mini Kit (Qiagen, Germantown, MD). The cytochrome oxidase subunits I and II (COI and COII) (Martin 2000; Robideau et al. 2011) and internal transcribed spacer (ITS) regions 1 and 4 (White et al. 1990) were amplified. The amplicons were sequenced and analyzed by BLASTn in NCBI GenBank. The isolates were confirmed to be Globisporangium irregulare with ≥98% identity match and 100% query coverage to type isolate sequences with the following accession numbers HQ708678, GU071760, and HQ643595 for COI, COII, and ITS, respectively. Isolates from this study were deposited in GenBank under accession numbers PP965484–PP965486, PP965487–PP965489, and PP965682–PP965684. To complete Koch’s postulates, ten 14-day-old sage plants were inoculated with 20 mL of 1 × 10 4 oospores/mL of G. irregulare (isolate NC_65624), following a modified protocol (McGehee and Raudales 2021). Individual plants were grown in 5.7 × 5.7 × 6-cm cells cut from six-cell tray inserts filled with a soilless peat-perlite substrate. Plants were maintained indoors on growth carts at 26°C, 50% relative humidity, and a 14-h photoperiod. Wilting occurred 5 days after inoculation, and 60%–70% of inoculated plants showed reduced growth, wilting, and root rot after 14 days. Ten non-inoculated control plants remained symptomless. G. irregulare was recovered from symptomatic roots from all inoculated plants using the method mentioned previously. The experiment was conducted twice. To my knowledge, this is the first report of G. irregulare infecting common sage. G. irregulare has been reported on other herbs such as cilantro (Infante et al. 2018) and clary sage (Reeves et al. 2021). Recognizing G. irregulare as a pathogen of common sage is important for effective disease management and reducing losses in the greenhouse. Preventing root rot caused by oomycetes in greenhouse production systems requires consistent sanitation protocols, avoidance of over-fertilization and over-irrigation, and responsible use of fungicides to minimize disease risk.

First report of Phytophthora ramorum causing leaf blight on Ceratonia siliqua in the United States

To the authors' knowledge, this is the first report of P. ramorum occurring on C. siliqua globally and the first confirmation of Koch’s postulates for this host-pathogen combination.

Multilocus evidence of Phytophthora palmivora and P. tropicalis as causal agents of cacao black pod disease in southern Mexico

Taxonomy, Biological Characterization, and Fungicide Sensitivity of a New Species, Cladobotryum hypsigum, Causing Cobweb Disease in Gold Mushroom (Pholiota conissans) in China.

Pholiota conissans is an economically important edible mushroom in China; however, its production has been severely impacted by cobweb disease during the fruiting stage, leading to substantial yield losses. In this study, a fungal pathogen was identified as the causal agent of cobweb disease. The strains were isolated from infected fruiting bodies collected in November 2021 and were identified as a new species Cladobotryum hypsigum sp. nov., based on morphological characteristics and a multi-locus phylogenetic analysis of four gene regions (ITS, RPB1, RPB2, and TEF). Pathogenicity tests were conducted by inoculating healthy mushrooms with a spore suspension of representative isolates. The resulting symptoms were consistent with those observed in cultivation settings, and the same pathogen was successfully re-isolated, thus fulfilling Koch's postulates. Biological characterization indicated that the optimal conditions for mycelial growth were a temperature of 25°C and pH 5. Sucrose and yeast extract were the most suitable carbon and nitrogen sources, respectively. In vitro fungicide sensitivity assays, performed using the hyphal growth inhibition method against six common fungicides, demonstrated that Carbendazim was the most effective agent. The IC50 values for Carbendazim were 0.7742 µg/mL for the pathogen and 4.827 µg/mL for the host mushroom, indicating significant selectivity. These findings provide a scientific basis for developing effective strategies to manage cobweb disease in P. conissans cultivation.

First report of Cladosporium uredinicola causing leaf spot on eggplant (Solanum melongena L.) in Iraq

Leaf spot diseases represent a major constraint to eggplant production under favourable environmental conditions. Therefore, potential pathogenicity of the fungus Cladosporium uredinicola on the leaves of eggplant (Solanum melongena L.), cultivar 'Barcelona F1', was confirmed in this study. Symptomatic leaf tissues   were obtained from several greenhouse locations in Basrah governorate, southern Iraq. The first isolation of the fungus was done on potato dextrose agar (PDA) plates, followed by the investigation of morphological and microscopic features. Cladosporium uredinicola fungal growth on the PDA medium was olive-green to dark olivaceous-brown pigmentation and irregular margins, while the microscope conidiophores were light to medium olive colorin colour, smooth to finely roughened, bearing short terminal chains of 2–5 conidia. Pale olivaceous-brown, ellipsoid to oblong in shape, smooth-walled conidia were observed with 0–3 transverse septa. The internal transcribed spacer (ITS) region was targeted for confirming the identification; the ITS sequence was deposited in the National Center for Biotechnology Information (NCBI) GenBank database under accession number PV961371.1. Pathogenicity trials were followed under greenhouse conditions, revealing the pathogenic effect of C. uredinicola on eggplant leaves, showing necrotic lesion symptoms, which initially appeared after five days post-inoculation as small brown, circular to irregular margins, subsequently extended and coalesced into large spots and patches with chlorosis symptoms and ended with leaf abscission. The fungal pathogen was re-isolated from diseased leaves to confirm Koch's postulates. The current study represents the first report of C. uredinicola as a potential pathogen on eggplant leaves in Iraq.