Partial resistance of barley to leaf rust, Puccinia hordei. III. The inheritance of the host plant effect on latent period in four cultivars

Abstract

The latent period (LP) in the barley-leaf rust relationship is an important component of the partial resistance complex. The inheritance of the host plant effect on LP was studied in five crosses between four cultivars. The LP, effectuated by the susceptible cultivars L94 and L92, were 8.0 and 8.6 days resp., those of the resistant cultivars Minerva (Mi) and Vada (Va) 16.9 and 17.1 days resp. The mean F1 and F2 values of the crosses L92×L94 and Mi x Va were intermediate between the parental ones. The variances of the F2's were slightly larger than those of the parents and the F1's indicating some segregation. In the crosses between a susceptible and a resistant cultivar the F1 value was half way between the mid-parent and susceptible parent value. The F2 mean lay approximately half way between the mid-parent and F1 value, with a distribution positively skewed and slightly bimodal. There was no transgression, in fact not even the parental values were recovered among nearly 500 F2 plants. The F3-lines of the crosses between susceptible and resistant cultivars showed within line variances from as low as the parental values to as high as or higher than those of the F2. In hte F3's the parental values could be recovered although no transgression occurred.