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Disease determinations

At Plantovita disease tests are undertaken in respect of dry bean samples drawn in terms of the rules of the International Seed Testing Association (ISTA). The samples have to be drawn by officials registered with the South African National Seed Organisation (SANSOR) as seed inspectors. Sampling takes place in accordance with requirements determined by SANSOR.

The testing of Phaseolus vulgaris seed (dry beans, green beans, garden beans, runner beans) for the presence of Pseudomonas syringae pv. phaseolicola, Pseudomonas syringae pv. syringae, Xanthomonas campestris pv. phaseoli, Xanthomonas campestris pv. phaseoli var. fuscans, Colletotrichum lindemutheanum and Sclerotinina sclerotiorum (seed-borne diseases) is mandatory for the certification of seed. These requirements are determined in terms of the Dry Bean Certification Scheme administered by SANSOR. Dry beans can also be tested at Plantovita upon request for the presence of Curtobacterim flaccumfacies pv. flaccumfaciens and Bean common mosaic virus (BCMV). Tests for the presence of Sclerotinia and mosaic virus are only done upon request. Private samples of bean seed may only be tested with the permission of the Chief Executive Officer of the Dry Bean Producers’ Organisation.

The importance of detecting these pathogens is indicated by the diseases caused by each one of them, namely –

  • Pseudomonas syringae pv. Phaseolicola – Halo blight
  • Pseudomonas syringae pv. syringae – Bacterial brown spot
  • Xanthomonas campestris pv. phaseoli – Common blight
  • Xanthomonas campestris pv. phaseoli var. fuscans – Fuscan’s common blight
  • Colletotrichum lindemutheanum – Anthracnose
  • Sclerotinina sclerotiorum – Sclerotinia rot
  • Curtobacterium flaccumfaciens pv. flaccumfaciens – Bacterial wilt
  • Bean Common Mosaic Virus – BCMV

When testing for the presence of these pathogens in dry bean samples, ISTA standards are applied in the case of both certification and private samples as far as possible and where applicable.

Bacterial diseases
are tested by means of a conventional method meaning that the pathogens are isolated and then identified by means of a series of biochemical tests.

When testing for the presence of fungal diseases, the dry bean seed is planted in seed germination paper with cellulose wadding and incubated at standard temperatures for a prescribed period and then investigated for the characteristic presence of the fungi concerned.

The presence of Bean Common Mosaic Virus is monitored by means of serological methodology – the ELISA test. A standard procedure or protocol in accordance to the manufacturers of the test kits is followed to ensure the correct application of this simple but accurate test.

Results of official disease tests may only be conveyed to the inspector concerned and only by means of an e-mail message or fax. Results of tests in respect of diagnostic samples are conveyed directly to the client. This can be the person who submitted the samples or the person responsible for the account, in which case this is indicated on the sample receipt form. Results from bean seed tested as private samples are conveyed telephonically after permission was obtained from the CEO of the Dry Bean Producers Organisation.

Germination and purity determinations

The germination test

The object of the germination test is to determine the germination potential of a seed-lot. The results can be used to compare the quality of different lots and also estimate the field planting value. The benefit of laboratory methods is mainly the control of external conditions and therefore the ability to give the most regular, rapid and complete determination of the germination of the majority of samples of a particular species. In the case of an ISTA test the germination of a seed amounts to the emergence and development of a seedling to a stage where the aspects of its essential structures indicate whether it is able or not to develop further into a satisfactory plant under favourable field conditions.

The purity test

The objectives of the purity test are to determine the following:

  • the percentage composition by weight of the sample being tested and by inference the composition of the seed-lot; and
  • the identity of the various species of seeds and inert particles constituting the sample.

When the purity test has been conducted, pure seed refers to the species stated by the client, or found to predominate in the test, and must include all botanical varieties and cultivars of that species. Germination and purity determination is undertaken at Plantovita by qualified Seed Analysts trained by and registered as such with the Department of Agriculture. Plantovita employs four registered Seed Analysts. All germination and purity investigations are subject to strict ISTA rules. The results of the germination and purity tests from representative samples of seed lots to be certified are sent to SANSOR.

Diagnostic Services

Diagnostic samples are defined as samples which are submitted, but not classified as official and/or certification samples. The samples normally amount to a few plants/pods/seeds having symptoms of virus, fungal and/or bacterial diseases and/or visible physiological deviations. Results in respect of private samples are reported direct to the clients. This can be the person who submitted the sample or the person responsible for the account, in which case this is indicated on the sample receipt form.
Plantovita undertakes the following in the service of the dry bean industry:

  • All samples of all clients are be handled with confidentiality, maintaining the integrity of the samples and keeping the samples secure.
  • Results generated in respect of any sample are conveyed to the client on a confidential basis and records are stored securely for 5 years.
  • Records pertaining to the receipt, processing and testing of samples and the results generated are maintained and subsequently stored securely and confidentially.
  • All samples are tested in accordance with ISTA standards and prescriptions.

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