Morphological variation and experimental host range of Alternaria cinerariae

Abstract

a b s t r a c tAlternaria cinerariae, an important and well-known plant pathogen of cineraria, has been delimited by its narrowly to broadly ellipsoid or ovoid conidia with blunt-tapered false beaks, but without descriptions of its morphological variability and host range. Leaf spot diseases have recently been found on asteraceous plants Pericallis cruenta, Farfugium japonicum, and Gynura bicolor in Japan, with A. cinerariae-like isolates subsequently obtained from the lesions. In this study, we identified these isolates as A. cinerariae using an integrated species criterion based on morphology, phylogeny, and pathogenicity, and examined their morphological variability. Although isolates exhibited morphological differences with respect to sporulation pattern, conidial swelling, and chlamydospore formation, phylogenetic analysis using gpd, rpb2, and tef1 sequences clustered them together in a single clade with a previously recognized A. cinerariae strain. Inoculation tests on 17 species, including five Senecioneae species, were performed to determine the experimental host range of A. cinerariae. The results suggest that A. cinerariae has considerable morphological variation and preferential pathogenicity to Senecioneae plants, and also indicate that G. bicolor should be added as a natural host of A. cinerariae.

Japanese species of Alternaria and their species boundaries based on host range

“…Notes: Morphological variations are present between strains, including the appearance of excessively swollen bodies and chlamydospore (microsclerotia) formation (Nishikawa & Nakashima 2015). There is no ex-type culture and few reference isolates, and the epitype originated near the original type locality; therefore, an ex-epitype isolate was designated and deposited for future studies.…”

“…However, their morphological variation and fundamental pleomorphism complicated species recognition, and thus host plants played a key role in identification. Due to their ubiquitous nature, this approach led to a false inflation of species numbers, resulting in the genus containing more than 400 species (Nishikawa & Nakashima 2015, Lawrence et al 2016. The introduction of a molecular phylogenetic approach has again helped to clarify their taxonomy, reducing many allied genera into one large genus, Alternaria (Woudenberg et al 2013).…”

Morphology and Molecular Characterization of Alternaria argyranthemi on Chrysanthemum coronarium in China

“…Also, the pathogenicity tests revealed that the fungus is the causal agent causing leaf spot and blight disease on the host. Nishikawa and Nakashima [ 19 ] had been tested the pathogenicity of A. cinerariae on C. coronarium ( Glebionis coronaria ) and found it to be non-pathogenic on this plant.…”

First Report of Alternaria alternata Causing Alternaria Brown Spot on Aralia elata in China

“…The colony characteristics were consistent with those known for Alternaria alternata (Simmons 2007). The ITS, gpd, Alt-a1, and tef1 gene regions were amplified using primer pairs ITS1/ITS4, gpd1/gpd 2, Alt-for/Alt-rev, and EF1-728F/ EF1-986R, respectively (Nishikawa and Nakashima 2015;Woudenberg et al 2014). The sequences were deposited in GenBank: MN636331 (ITS), MT012958 (gpd), MT140362 (Alt-a1), and MT133312 (tef1).…”