For example, the greater the concentration of RNA, the greater the probability that it can serve as a template in copy-choice switching. Similarly, the higher the rate of replication, the higher the probability of a replicase undergoing copy- choice switching. Host plants also exert pressure on the rate of recombination. For example, some plants tend to promote the development of defective interfering particles, whereas others plants apparently do not. Mixed infections are common and can be expected at many field sites.
Mixed infections are very common in perennial crops.
Fruit trees, such as apple, pear, and cherry, are routinely infected with multiple viruses. All in all, the scientific literature is replete with reports of mixed infections, but this information has not been collected into a single database. All of these techniques are reliable when used properly with suitable controls.