Studies on amoebae and cysts associated with the isolation of Spongospora subterranea f.sp. subterranea in vitro

Abstract

New evidence is presented to support the contention that the amoeba/cyst colonies isolated from surface-sterilized Spongospora subterranea f.sp. subterranea-infected potato tubers and spore balls have a saprophytic phase but are contaminants and not S. subterranea. Amoebae isolated from infected tissues and spore balls formed colonies associated with bacteria on 1% water agar at 188C and encysted after 5±7 days. These cysts were morphologically distinct from the resting spores of S. subterranea and were formed singly or in a layer, unlike the spore ball (cystosorus) of S. subterranea. Amoebae, cysts and mixtures of amoebae and cysts in primary, secondary and tertiary subcultures failed to infect tomato roots. PCR amplification of DNA from amoebae, cysts and spore balls using the S. subterranea-specific primer pair SsF/R generated a 434-bp product from S. subterranea spore balls only and not from amoebae or cysts. When an amoeba/cyst-specific primer pair AmF/R was designed and used for PCR amplification, a single 411-bp product was generated from DNA of amoebae and cysts, but not from DNA of S. subterranea spore balls. These results are discussed in relation to earlier reports claiming the successful isolation of S. subterranea and other plasmodiophorids in vitro.

Multiplex real-time PCR (TaqMan) assay for the simultaneous detection and discrimination of potato powdery and common scab diseases and pathogens

“…Twenty‐four field isolates of S. subterranea were obtained either from different fields or from the same field with samples taken over several years in the United States and Canada. Each isolate was prepared by the removal of single spore balls from powdery scab lesions of naturally infected potato tubers by the method of Qu et al. (2001).…”

“…Twenty-four field isolates of S. subterranea were obtained either from different fields or from the same field with samples taken over several years in the United States and Canada. Each isolate was prepared by the removal of single spore balls from powdery scab lesions of naturally infected potato tubers by the method of Qu et al (2001). Sixteen Streptomyces strains were obtained from the American Type Culture Collection (ATCC; Manassas, VA, USA) or were isolated from scab lesions on potato tubers according to the method of Wanner (2004) and tested for pathogenicity on radishes and ⁄ or potatoes as described previously (Wanner 2004(Wanner , 2007.…”

Review: Powdery Scab of Potato—Increased Knowledge of Pathogen Biology and Disease Epidemiology for Effective Disease Management

“…It took 22 years until the myth of a saprophytic amoebal stage of a plasmodiophorid was finally 'demolished'. Qu et al (2001) demonstrated clearly, using microscopy, bioassay and specific molecular primers, that the amoeba/cyst colonies isolated from surface-sterilized Sss-infected potato tubers and sporosori have a saprophytic phase but are contaminants and not Sss. An interesting alternative in vitro culture method for Sss has recently been introduced by Qu and Christ (2007).…”

Prevalence of fungal and fungus‐like diseases on potato seed tubers imported from Europe to Jordan

“…The scab lesions were macerated independently in 500 μL sterilized distilled water on a microscope slide and observed under the light microscope. Presence of cystosori in at least one of the slices was considered a positive result for the presence of the powdery scab pathogen (Merz, 1997; Qu et al. , 2001; Montero‐Astua et al.…”