Transgressive segregation for resistance to <i>Pyrenophora teres</i> in barley

Abstract

Populations of F 1 , F 2 , F 1 × parent 1 (BC1), F 1 × parent 2 (BC2), and F 3 resulting from two crosses between four susceptible varieties of barley used in national and international breeding programmes were tested at the seedling stage for their resistance to an isolate of Pyrenophora teres which is virulent to the parental varieties. Infection type, average lesion size, and number of lesions per unit leaf area were used to assess disease reaction. In the two crosses, F 2 and especially F 3 generations (produced by self pollination of selected resistant F 2 plants) showed more resistance expressed by infection type and average lesion size than either parent. The frequency distributions of F 2 and F 3 generations derived from these crosses were continuous and showed transgressive segregation for resistance. The results indicated that the four cultivars used in this study possessed additive genes for resistance to P. teres. Thus useful resistance could be obtained following crossing of susceptible cultivars and selection in succeeding generations.