Characterization, In Vitro Culture, and Molecular Analysis of Thecaphora solani, the Causal Agent of Potato Smut

Abstract

The fungus Thecaphora solani (syn.: Angiosorus solani), the causal agent of potato smut, was cultivated in vitro for the first time. Teliospores obtained from galls of infected potato plants were used to inoculate commonly used solid and liquid media. The teliospores produced two kinds of vegetative tissue depending on the nutrient status of the media. A very slow radial-growing, hyaline, and septate mycelium, as usually seen in most of the in vitro-cultivated filamentous fungi, was obtained in wateragar medium after 30 to 40 days. On the other hand, a white, sponge-like mycelial mass was obtained in HCM + 1% activated charcoal, and on common potato dextrose agar or malt-yeast-peptone solid or liquid media, after 40 to 50 days under lab conditions. The identity among teliospores and the sponge-like mycelial mass was corroborated by DNA fingerprinting and partial sequencing of the large subunit (LSU) rDNA region. The sexual cycle of the pathogen was completed under lab conditions based on the development of teliospores on the sponge-like mycelial mass. The first attempt to reproduce the disease under controlled conditions was successful, inducing a gall in a cv. Desirée potato explant cultivated in vitro inoculated with radial-growing mycelia. Phylogenetic analysis of LSU rDNA data of the genus Thecaphora and other smut fungi confirmed the initial classification of the pathogen as T. solani.

Melanoxa, a new genus in the Urocystidales (Ustilaginomycotina)

“…Flamingomyces For molecular phylogenetic analyses, we additionally used the following sequences from GenBank: Antherospora vaillantii EF653997/EF653979, A. vindobonensis EF653991/ EF653973, A. scillae EF653985/EF653967 , Cintractia axicola AF009847, Doassansiopsis deformans AF009849, D. limnocharidis AF009850 (Begerow et al 1997), Entyloma microsporum DQ185435 (Bauer et al 2007), Farysia chardoniana AF009859 (Begerow et al 1997), Flamingomyces ruppiae DQ185436 (Bauer et al 2007), Floromyces anemarrhenae EU221284 , Gjaerumia ossifragi AY525373 (Bauer et al 2005), Macalpinomyces eriachnes AY740090 (Stoll et al 2005), Melanopsichium pennsylvanicum AF009863 (Begerow et al 1997), Melanotaenium cingens DQ875364 , M. endogenum AJ235294 (Boekhout et al 1995), M. euphorbiae AF009865 (Begerow et al 1997), Melanustilospora ari EF517924 , Mundkurella kalopanacis DQ875351/AF009869 (Begerow et al 1997, Mycosyrinx cissi DQ875368 , Phragmotaenium indicum AF229354 (Bauer et al 2001a), Schizonella cocconii AJ236158 (Piepenbring et al 1999), Sporisorium sorghi AF009872 (Begerow et al 1997), Thecaphora saponariae AF133579 (Begerow and Bauer 2000), T. seminis-convolvuli AF009874 (Begerow et al 1997), T. solani AY344055 (Andrade et al 2004), Urocystis alopecuri EF517945, U. beckmanniae EF517943 , Urocystis colchici AF009878/DQ875355/DQ838576/ EF517933 (Begerow et al 1997Matheny et al 2006;Bauer et al 2008), U. ficariae EF517938, U. floccosa EF517937, U. galanthi EF517922, U. ornithogali EF517935 , U. ranunculi AF009879 (Begerow et al 1997), U. syncocca EF517929 , Ustacystis waldsteiniae DQ875356/AF009880 (Begerow et al 1997, Ustilago maydis AF453938 (Piepenbring et al 2002), Vankya heufleri EF517925/ EF653981/EF667965 , V. ornithogali EF635910/EF210712 (Bauer et al 2007.…”

Competing sexual and asexual generic names in Pucciniomycotina and Ustilaginomycotina (Basidiomycota) and recommendations for use

“… Begerow et al (1997) demonstrated that Thecaphora represents a well-resolved genus in Ustilaginales including the types of T. seminis-convolvuli and T. thlaspeos ; these three generic names are therefore synonyms. Similarly, Andrade et al (2004) and Vánky et al . (2008) demonstrated that Thecaphora includes T. seminis-convolvuli and T. solani (syn.…”

Pest categorisation of Thecaphora solani

“…Pest distribution outside the EU T. solani is indigenous to the Andean region of South America (EPPO, online) ( Figure 1 and Table 2). At the end of the 1980s, the disease was widely distributed in South America (Bolivia, Chile, Colombia, Ecuador, Peru and Venezuela) and in the southern part of North America (Mexico) (Mordue, 1988;Torres, 2001;Andrade et al, 2004). It has also been reported from Panama (McGuire and Crandall, 1967).…”

“…Formation of galls is observed 45-60 days after planting (Torres, 2001). Andrade et al (2004) reported that isolates of the pest were grown in vitro on potato dextrose agar and malt yeast peptone agar at 18-20°C. However, T. solani teliospores have a very low germination capability.…”