Yr2 was originally allocated to a gene present in Heines VII and Soissonais-Desprez and identified with European pathotypes. Singh and Johnson (1988) showed that whereas Kalyansona responded identically to these wheats when tested with British pathotypes, it was susceptible and the European wheats resistant, when tested with certain pathotypes from other geographic areas, for example pt. 6 E16 from Lebanon. Kalyansona shared at least one gene, presumably Yr2, with Heines VII and Soissonais-Desprez. In addition to Yr2, Heines VII and Soissonais possess a gene (or genes) which was isolated in lines TP981 and TP1295, respectively (Johnson, 1992). An Australian culture avirulent on Heines VII and virulent on Kalyansona produced a low infection type on TP981 and a high response on TP1295, indicating that these genes are not identical (CR Wellings, unpublished 1993). The gene in TP981 was expected to be common in European wheats (Johnson, 1992) and maybe allelic with a gene in Strubes Dickkopf (Johnson and Minchin, 1992). This example illustrates a potential problem when differentials established using the pathogen flora of one geographical area are adopted for testing pathogenic variation in another area. The chromosomal location of the second unnamed gene in Heines VII is unknown.
Reported variability in low infection type may reflect genetic background (Singh et al., 1990) as well as environmental influences (Johnson, 1988).