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Evaluate pathogen strains for their general and specific virulence

This is a function when the biplot is used in visual analysis of host genotype by pathogen strain two-way data. For the evaluation of the virulence of the pathogen strains, the following biplot is most informative:

Note this biplot has the following settings (compare with host genotype evaluation):

1. host genotypes are treated as testers and pathogen strains as entries;

2. tester-centered model (centering = 2);

3. entry-focused scaling (SVP =1);

4. the average-tester coordination view.

Interpretations:

• The red lines points to greater general virulence of the strains. Therefore, the general virulence rank is:

S48 > S78 >>> Average > other strains. 

• The virulence of S-qnb85i is highly unstable (i.e., specific): It is highly virulent to host H22 but much less so to H-Betzes. This suggests strong specific virulence or vertical resistance.

• The strains fall into three distinct groups: S48+S78; S-qnb85i, and others.

• Host H22, H8, and H-Betzes are best testers to differentiate the strains.