Heritability with positive Interaction Variance

    Variety 2 consistently outperforms Variety 1 by more than 50% under poorer environmental conditions (e.g., nutrient-poor soil at EQ = 50). Variety 1 outperforms Variety 2 only in a much better environment (e.g., added fertilizer at EQ = 80). In intermediate environments (EQ = 65 ~ 75), the two varieties perform equally well, with considerable variance. Although increased yield always occurs with increased environmental quality, the differential response of the two varieties is not predictable from experiments in either extreme environment separately. A naive conclusion is that Variety 2 is "better" than Variety 1. However, Variety 1 in a better environment (EQ=70) produces the same yield (70) as Variety 2 in a poorer environment (EQ=60). Choice of which variety to plant will depend on a trade-off between the cost of environmental improvement and the price of increased yield.

Figure ©2002 by Griffiths et al.; all text material ©2016 by Steven M. Carr