Characterization and Pathogenicity of Colletotrichum Species on Philodendron tatei cv. Congo in Gansu Province, China

Diplocarpon mespilicola sp. nov. Associated with Entomosporium Leaf Spot on Hawthorn in China

Entomosporium leaf spot (ELS) is a serious hawthorn disease that mainly causes premature leaf senescence in various hawthorn growing areas worldwide. Diplocarpon mespili is the most commonly reported pathogen causing hawthorn ELS. From 2016 to 2018, hawthorn ELS disease surveys and samplings were carried out in five regions in three provinces of China. The disease incidence was about 20 to 95%. A total of 186 single-spored Diplocarpon isolates were obtained and identified using morphological and molecular phylogenetic analysis. The results showed that all isolates clustered, suggesting a distinct species that is here proposed as D. mespilicola sp. nov. This is the first report of the pathogen causing ELS on hawthorn in China, and it is similar to the species D. mespili. To explore the influence of temperature on the epidemiology of D. mespilicola, we studied the continuous influence of temperature and time on the germination of conidia by using nine time points and eight temperature gradient observations. This study indicated that the optimum temperature for conidial germination was 20.4°C, and the minimum germination time was 4.9 h. Using this information to develop a predictive model may provide a basis for disease management in hawthorn production in the future.

Colletotrichum litangense sp. nov., Isolated as an Endophyte of Hippuris vulgaris, an Aquatic Plant in Sichuan, China

An unknown endophytic fungus was isolated from the aquatic plant Hippuris vulgaris in Litang county, Sichuan province, China. Phylogenetic analyses inferred from combined ITS, Sod2, Apn2, and TUB2 sequences revealed that the endophyte is a new species belonging to the Colletotrichum graminicola species complex. Morphological characteristics showed that Colletotrichum litangense is characterized by its falcate, lunate to sublunate conidia, and ellipsoidal, ovoid, or lobed appressoria. Pathogenicity tests on several fruits showed that C. litangense could induce anthracnose lesions. As a result of the phylogenetic, morphological, and pathogenicity analyses, we proposed the name Colletotrichum litangense for the new species.

Molecular and Biological Characterization of Two New Species Causing Peach Shoot Blight in China

Peach shoot blight (PSB), which kills shoots, newly sprouted leaf buds, and peach fruits, has gradually increased over the last 10 years and resulted in 30 to 50% of total production loss of the peach industry in China. Phomopsis amygdali has been identified as the common causal agent of this disease. In this study, two new species, Phomopsis liquidambaris (strain JW18-2) and Diaporthe eres (strain JH18-2), were also pathogens causing PSB, as determined through molecular phylogenetic analysis based on the sequences of the internal transcribed spacer (ITS) region, translation elongation factor 1-α (EF1-α) and beta-tubulin (TUB), and colony and conidial morphological characteristics. Biological phenotypic analysis showed that the colony growth rate of strain JW18-2 was faster than that of strains JH18-2 and ZN32 (one of the P. amygdali strains that we previously found and identified). All three strains produced α-conidia; however, JW18-2 could not produce β-conidia on alfalfa decoction and Czapek media, and the β-conidia produced by strain JH18-2 were shorter in length and thicker in width than those produced by strain ZN32. Pathogenicity tests showed that JW18-2 presented the strongest pathogenicity for peach fruits and twigs and was followed by strains JH18-2 and ZN32. The results shed light on the etiology of PSB and provide a warning that P. liquidambaris or D. eres might develop into dominant species after a few years while also potentially benefitting the development of effective disease control management strategies.