Diagnostic samples are defined as ad hoc samples not categorised as official and/or certification samples. These samples normally consist of a few tubers/plants/pods/seeds/stalks/stems with or without disease symptoms. A unique benefit which Plantovita offers is that the Technicians become specialists in respect of the diagnosis of potato and dry bean diseases on account of their focussing on these crops. 

Diagnostic samples must be accompanied by a Sample Investigation Form. If an official of Potato Certification Service or a SANSOR inspector submits a diagnostic sample, the official/inspector must complete the documentation. A sample number will be allocated, which will serve as reference in all communications in connection with the sample. Good practice is when a client identifies a submitted sample through his/her own unique number or description of the sample. This allows the laboratory and the client to match results and samples.

Diagnostic samples may also be submitted by private clients (producers and private companies). Private clients are requested to provide sufficient information for the completion of the Sample Investigation Form by the person who submits the sample or the Technician who receives and handles the sample. The laboratory allocates a unique number to the sample. This number serves as reference number in all communication with the client in connection with the sample. 

Only one sample is handled at a time in order to limit the risk of contamination between samples. The sample is investigated properly for typical disease symptoms, for example wilt, necrosis, discolouration, rotting, mould (fungal growth) and any lesions or slime and moisture secretions typical of some pathogens.

As soon as the Technician can by means of this investigation ascertain which disease is involved, the sample is referred to a specific or even to more than one disease laboratory of Plantovita where it is tested in terms of the relevant protocols. 

The techniques used at present entail conventional (biochemical) tests, serological tests (the ELISA test) and molecular tests (PCR).  

Diagnostic samples are handled with the same care as official and other private samples. Attention is paid to a diagnostic sample until an answer can be provided to the client. If Plantovita does not have the necessary testing material or methodology at its disposal for the confirmation of a suspected diagnosis, the sample may, with the permission of the client, be sent to a university or the Department of Agriculture. This is communicated to the client and only done with his/her permission.

The results of the diagnostic investigation are conveyed to the client on the Sample Investigation Form.


  • All samples of any client are handled with confidentiality, maintaining the integrity thereof and keeping the samples secure.
  • Results generated in respect of any sample are sent on a confidential basis to the client and records are stored for 5 years securely.
  • Records pertaining to the receipt, processing and testing of samples, as well as the test results are generated, maintained and subsequently stored securely and confidentially.
  • All samples are tested in accordance with Good Laboratory Practise standards and official protocols

To date the Diagnostic Section has identified the following pathogens and physiological deviations:



  • Bacterial wilt – Ralstonia species complex
  • Black leg/soft rot (non-specific) Soft rot causing Enterobacteria
  • Streptomyces spp. – Common scab.


  • Macrophomina phaseolina: Charcoal rot
  • Sclerotinia sclerotiorum: White mold
  • Verticilium dahlia and V. albo-atrum: Verticilium wilt
  • Phytophthora erythroseptica: Pink rot
  • Pythium ultimum var. utlimum and P. debaryanum: Leak
  • Phytophthora infestans: Late blight
  • Botrytis cineria Pers. :Fr.: Grey mould
  • Phoma foveata and Phoma Exigua var. exigua: Gangrene
  • Alternaria solani: Early blight
  • Rhizoctonia solani: Stem cancer and black scurf
  • Fusarium spp.: Fusarium-dry rot and Fusarium-wilt
  • Alternia alternata.: Brown spot and black pit
  • Spongospora subterranea subsp subterranea: Powdery scab
  • Helminthosporium solani: Silver scurf
  • Colletotrichum coccodes: Black dot / Anthracnose


  • Internal brown spot and heat necrosis
  • Hollow heart
  • Black heart
  • Tuber malformation
  • Tuber Cracking
  • Jelly end
  • Enlarged lenticels
  • Elephant hide
  • Chill injury



  • Pseudomonas syringae pv. syringae van Hall: Bacterial brown spot
  • Xanthomonas campestris pv. phaseoli (Smith) Dye f. sp fuscans: Fuscan’s blight
  • Pseudomonas syringae pv. phaseolicola (Burkholder) Young et al.: Halo blight


  • Alternaria alternata (Fr.:Fr.) Keissl. (= A. tenuis Nees) , Alternaria brassicae (Berk.) Sacc. f. sp. phaseoli C. Brun,
  • Alternaria brassicicola (Schwein.) Wiltshire: Alternaria leaf and pod spot
  • Phaeoisariopsis griseola (Sacc.) Ferraris: Angular leaf spot
  • Colletotrichum lindemuthianum (Sacc. & Magnus) Lams.-Scrib.: Anthracnose
  • Macrophomina phaseolina (Tassi) Goidanich: Ashy stem blight (charcoal rot)
  • Phoma exigua Desmaz. var. diversispora (Bubak) Boerema = P. diversispora Bubak, Phoma exigua Desmaz. var. Exigua = Ascochyta phaseolorum Sacc.: Black node disease (Ascochyta leaf spot)
  • Rhizoctonia solani Kühn, Thanatephorus cucumeris (A. B. Frank) Donk [teleomorph]: Damping-off and stem rot,
  • Pythium spp.: Damping-off, Pythium
  • Phytophthora nicotianae Breda de Haan var. parasitica (Dastur) G. M. Waterhouse: Downy mildew
  • Phytophthora phaseoli Thaxt.: Downy mildew (of lima)
  • Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burkholder) W. C. Snyder & H. N. Hans.: Fusarium root rot
  • Fusarium oxysporum Schlechtend.:Fr. f. sp. phaseoli J. B. Kendrick & W. C. Snyder: Fusarium yellows (Fusarium wilt)
  • Botrytis cinerea Pers.: Fr., Botryotinia fuckeliana (de Bary) Whetzel [teleomorph]: Grey mould
  • Phyllosticta phaseolina Sacc.: Phyllosticta leaf spot
  • Trichothecium roseum (Pers.:Fr.) Link: Pink pod rot
  • Erysiphe polygoni DC., Oidium balsamii Mont. [anamorph]: Powdery mildew
  • Pythium ultimum Trow, Pythium irregulare Buisman, Pythium paroecandrum Drechs., Pythium myriotylumDrechs.,
  • Pythium aphanidermatum (Edson) Fitzp.: Pythium diseases
  • Uromyces appendiculatus (Pers.: Pers.) Unger: Rust
  • Sclerotium rolfsii Sacc., Athelia rolfsii (Curzi) Tu & Kimbrough [teleomorph]: Southern blight
  • Rhizoctonia solani Kühn, Thanatephorus cucumeris (Frank) Donk. [anamorph]: Web blight
  • Sclerotinia sclerotiorum (Lib.) de Bary: White mold (Sclerotinia rot)

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