Quality Control in Commercial Micropropagation

Introduction: Commercial micropropagation industry is globally operating for two major applications. One is in ornamental plants and another in crop species of agricultural importance.

Imperatives of both applications are different. For ornamental plants, major emphasis is on rapid propagation of latest cultivers of commercial importance. In crop species, significant impovement in net profits per unit area as compared to the expenses on tissue culture plants is the major consideration. In fact, although tissue culture of ornamentals got commercialised first, research in tissue culture has been a center of attraction mainly for ability of this technology to overcome limitations of breeding programmes for improvement in crop productivity. However, what is common for both is the importance of quality control tests and systems.

Present global trade in ornamentals is hardly based on anything more than visual inspection of cultures or ex-agar plants. Situation is not any way different in crop plants. There are no specific quality tests on which the trade is based.

• A good quality culture base will provide a very sound foundation to improve process efficiency and profitability.
• Further, it will lend stable foundation for the trade. It is very easy to arrive at conflicting interpretations on quality of plants supplied in case of a dispute. In such a situation, no industry can prosper. In our opinion, this is a major global impediment in growth of this industry.

> The relationship of producer and buyer should be based on mutually accepted quality attributes, a system of process quality control based on agreed quality tests and a third party inspection based quality assurance system.

> In case of crop plants, such tests are vitally needed to base regulatory mechanisms.

> Many developing countries have become aware and their Governments are very active in promoting application of plant tissue culture to crop plants. However, doing this in absence of meaningful regulatory mechanisms is like inviting impediments in implimentation.

This article is an attempt to put together all the known principles and practices which have direct bearing on production and determination of quality of micropropagated plants and to present a coherent concept which will fill up above gap.

Here we consider only the most popular application i.e. multiplication of released and elite variety of a vegetatively cultivated crop of economic importance.

Strategic imperatives for the quality tests:

• They should be rapid.
• They should aim at identification of variety / cultivars ignoring point mutations / bud mutations which continue to occur in normal population also as a natural phenomenon. In fact, natural frequency of bud mutations is a desirable factor as it is one of the most useful survival tool for a variety.
• Definition of variety should be clear i.e. it is an assemblage of closely similar genotypes, not a group of "uniform" genotypes as is often misunderstood. Thus, the method should be able to make a distinction between two varieties and do not produce confusion where within variety variability is involved.

Potential tests for quality control: Following are the kinds of tests, which would reveal the quality and will be consistent with the imperatives of quality tests:

1. Endophytic bacterial count: Based on microbiological as well as DNA Fingerprinting based methods..
2. Total virus content – assay or determination: Based on DNA Fingerprinting based methods.
3. Genotypic stability / varietal identification by DNA Fingerprinting methods: DNA Fingerprinting based methods
4. Metaphase chromosome count and karytotype: In polyploids, issue could be of making it sure that chromosomal aberrations have not taken place. This can be ascertained by taking metaphase chromosome counts and karyotyping of representative samples.
5. Anatomy of explant, regenerating explant and multiplication cultures: Microtomy base methods to establish whether regeneration is through enhanced axillary proliferation, through adventive bud formation or through callus formation.

What do we have to offer?

1. Services on standardization of tests specific for plants of the client's interest
2. Jobwork testing on routine samples in large numbers
3. Culture indexing programme and Assurance system and culture management system based on above quality tests
4. Culture indexing sevice based on routine analysis on jobwork basis

Expenditure on quality control is always very small compared to the losses you would incurr in their absence

Detailed discussion on theoretical basis for above is available in our detailed unpublished paper which can be available on request.

E-mail: info@tissuecon.com