Epiphytic colonization of Ustilaginoidea virens on biotic and abiotic surfaces implies the widespread presence of primary inoculum for rice false smut disease

• Published in: Plant pathology Vol. 63; no. 4; pp. 937 - 945
• Main Authors: Fan, J, Guo, X.‐Y, Huang, F, Li, Y, Liu, Y.‐F, Li, L, Xu, Y.‐J, Zhao, J.‐Q, Xiong, H, Yu, J.‐J, Wang, W
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Science 01-08-2014; Blackwell; Wiley Subscription Services, Inc
• Subjects: Arabidopsis; Arabidopsis thaliana; Biological and medical sciences; Brassicaceae; cellophane; chlamydospores; conidia; conidiophores; Digitaria sanguinalis; disease control; disease outbreaks; Echinochloa crus-galli; Echinochloa crusgalli; epiphytes; epiphytism; Fundamental and applied biological sciences. Psychology; fungi; green fluorescent protein; heading; humidity; hyphae; inflorescences; inoculum; leaves; Leptochloa; Leptochloa chinensis; Nicotiana benthamiana; Oryza sativa; Parasitic plants. Weeds; pathogens; Phytopathology. Animal pests. Plant and forest protection; Poaceae; rice; rice false smut; smut diseases; Solanaceae; surface water; Ustilaginoidea virens; Weeds; Monocotyledones; Plant pathology; Plant pathogen; Disease; Epiphyte; Environmental factor; rice false smut; Abiotic factor; Fungi; Arabidopsis thaliana; Cruciferae; Gramineae; Dicotyledones; Angiospermae; Primary; weeds; Fungi Imperfecti; Biotic factor; Weed; epiphytism; Biochemical marker; Arabidopsis; Ustilaginoidea virens; Oryza; Green fluorescent protein; Spermatophyta; Experimental plant; Colonization; Inoculum
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/ppa.12167

Ustilaginoidea virens (Uv), the causative agent of rice false smut disease, infects developing rice spikelets at the booting stage, and transforms individual grains of the panicle into smut balls. Epidemics of the disease occur when the rice booting and heading stages coincide with rainy days. Using a green fluorescent protein (GFP)‐labelled Uv isolate that can form false smut balls on rice panicles, it was found that under high humidity and free water conditions the Uv isolate could colonize leaves of plants belonging to various families including the Poaceae (Oryza sativa, Echinochloa crusgalli, Digitaria sanguinalis and Leptochloa chinensis), the Brassicaceae (Arabidopsis thaliana) and the Solanaceae (Nicotiana benthamiana) without symptoms. Over several days, some conidia could germinate on the leaves of these plants and in water on the surface of Parafilm and cellophane, form hyphae and differentiate conidiophores to generate a large number of secondary conidia, while other conidia were able to directly produce secondary conidia. Conversely, in the absence of water some conidia could either bud to form new conidia or were converted into chlamydospores. These data indicate that Uv is one of a few fungal pathogens reported to have epiphytic characteristics. The rapid generation of a large number of spores on biotic and abiotic surfaces greatly increases the inoculum that can infect rice spikelets, resulting in the occurrence of rice false smut disease epidemics. These findings are important in the development of disease control strategies.