Dimorphism in Neopseudocercosporella capsellae, an Emerging Pathogen Causing White Leaf Spot Disease of Brassicas

Abstract

White leaf spot pathogen: Neopseudocercosporella capsellae causes significant damage to many economically important Brassicaceae crops, including oilseed rape through foliar, stem, and pod lesions under cool and wet conditions. A lack of information on critical aspects of the pathogen’s life cycle limits the development of effective control measures. The presence of single-celled spores along with multi-celled conidia on cotyledons inoculated with multi-celled conidia suggested that the multi-celled conidia were able to form single-celled spores on the host surface. This study was designed to demonstrate N. capsellae morphological plasticity, which allows the shift between a yeast-like single-celled phase and the multi-celled hyphal phase. Separate experiments were designed to illustrate the pathogen’s morphological transformation to single-celled yeast phase from multi-celled hyphae or multi-celled macroconidia in-vitro and in-planta. Results confirmed the ability of N. capsellae to switch between two morphologies (septate hyphae and single-celled yeast phase) on a range of artificial culture media (in-vitro) or in-planta on the host surface before infection occurs. The hyphae-to-yeast transformation occurred through the production of two morphologically distinguishable blastospore (blastoconidia) types (meso-blastospores and micro-blastospores), and arthrospores (arthroconidia).

Synergistic/antagonistic interactions between Neopseudocercosporella, Alternaria, Leptosphaeria, and Hyaloperonospora determine aggregate foliar disease severity in rapeseed

“…Recently, N . capsellae was shown to have significant morphological plasticity that enables it to transform from multicelled conidia to the single‐celled yeast‐like phase depending upon the external stimuli (Gunasinghe et al, 2021), and this probably plays an important role in host invasion in relation to defining virulence of the pathogen, as shown in other studies by Lin et al (2014) for Ophiostoma ulmi , the causal organism of Dutch elm disease, and by Mehrabi et al (2006) for the fungal wheat pathogen Mycosphaerella graminicola . Likewise, Singh et al (2002) reported that preinoculation of B .…”

“…Recently, N. capsellae was shown to have significant morphological plasticity that enables it to transform from multicelled conidia to the single-celled yeast-like phase depending upon the external stimuli (Gunasinghe et al, 2021), and this probably plays an important role in host invasion in relation to defining virulence of the pathogen, as…”