The Person Model Diversity in Time

The Person (1966) model (Fig. 4.7) provides a classic example of population genetics, the movement of single genes within a population. It is also an example of genetic heterogeneity and genetic flexibility over time. J.M. McDermott (Personal Communication, 1983) used a computer simulation to show that stability is quickly reached with as few as three pairs of genes.

The Person model can function only with an annual species of host in which the population is replaced entirely each season. Each new population has a predominant vertical resistance that is quite different from that of the previous season. Such rapid changes are clearly impossible with a perennial species of host.

This model is still a system of locking. Most of the locks are the same, but the standard lock changes each season. As with the n/2 model, the vertical resistance controls allo-infection, and there is a reduction in the frequency of matching infection. Person

(1966) pointed out that the effectiveness of his model is enhanced when the host has dominant R-genes in a multiple-allelic series in one locus, and the matching genes in the parasite are recessive and non-allelic.

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