QA vs QC

Molecular markers can be used in Plant Breeding for both Quality Assurance and Quality Control. Quality Assurance (QA) is important for proactively preventing errors and creating a high-quality product (e.g. new plant variety) while Quality Control (QC) is targeted towards identifying defects or errors in the product. Table 1 below summarizes the key concept differences between Quality Assurance and Quality Control activities.

Table 1: Quality Assurance and Quality Control have similar goals but are focused on different steps in the plant breeding process.



  • Focus on preventing defects (errors)
  • Focus on the process used in making a product
  • Proactive process
  • Goal is to test processes so defects are eliminated


  • Aims to identify defects in the finished product
  • Reactive process
  • Goal is to identify defects after a product is developed and before it is released


QA in Plant Breeding

Now that we have defined the general characteristics of Quality Assurance and Quality Control, let's look at these in more detail in the context of utilizing molecular markers in a plant breeding program.  Quality Assurance in plant breeding includes a number of approaches:

  • Define methodology for all aspects of breeding program
  • Develop checklists
  • Develop standards
  • Periodic project audits
    • Internal
    • External (for example, ISO9001, the International Organization for Standardization set of standards)

Examples of having clearly defined methods might include making sure all staff are using the same protocols for DNA extractions, consistency in the number of plants grown in experimental field plots, protocols for drying and storing seed, consistent seed package labeling, etc. Checklists are helpful in making sure that methods are being followed, and can include weekly or daily tasks such as checking that equipment is running properly, seed storage rooms are at the proper humidity and temperature, plants in the greenhouse have been watered, etc. – practical details to confirm that agreed upon methods are being followed.

Standards need to be agreed upon at various stages of the plant breeding process. These can be items such as having a set number of control plots in the field, a certain number of replications, an agreed upon acceptable quality for DNA (as compared to a control). One way to think about setting up Quality Assurance is to consider what, in case of a future problem, would have helped you find the error or explain to an expert what steps you followed? It is better to have these in place before a problem (such as a seed mix-up, mislabeled seed packets, etc.)

Standard Operating Procedures (SOPs) should be put in place for all steps of the breeding program, including checklists and protocols that all staff follow. Periodic audits can help identify gaps in standardizing procedures, for example where various staff may be using different protocols (e.g. various DNA extraction protocols). These audits can be done by someone internal to the group, or better, by a third party, such as a Scientific Advisory Board.

QC in Plant Breeding

The goal of Quality Control in a breeding program is to identify errors that may have slipped through Quality Assurance protocols. QC involves:

  • Routinely test breeding materials throughout the process using all available tools
    • Molecular marker techniques
    • Conventional phenotypic and morphological traits
  • Overall goal of improving the quality of the final product (new varieties)

For example, before a company markets a new variety, they will put it through a series of tests that may include both replicated field tests (does the variety consistently yield what it is expected to? Do plots look homogenous?) and testing with molecular markers, examples of which are in the next section.