Fig. 9. Regression against time of the mean yield of the top five entries of CIMMYT-derived germplasm expressed as percent of local check for the Elite Spring Wheat Yield Trial (ESWYT 1989–1991) and Semi-Arid Wheat Yield Trial (SAWYT 1992–1997). Between 30 and 50 genotypes were sown in 230 trials conducted between 1989 and 1997. Average yields are less than 2.5 Mg/ha in low-yielding environments and 2.5 to 4.5 Mg/ha in medium-yielding environments. Adapted from Trethowan et al. (2002).