INHERITANCE OF RESISTANCE TO NET BLOTCH IN BARLEY. I. FACTORS AFFECTING THE PENETRANCE AND EXPRESSIVITY OF GENE(S) CONDITIONING HOST RESISTANCE
Variability in the host-reaction of barley to infection by Drechslera teres was examined in the parents and progeny of selected crosses under different environmental conditions of testing.The Ethiopian variety C.I. 5791 exhibits a consistently high level of resistance under a range of environmental conditions, which is in contrast to the Manchurian variety C.I. 2330. The sensitivity of the genes for resistance possessed by these varieties to environmental modifications is considered to depend upon their respective genetic backgrounds. Furthermore, variability of host reaction in the progeny of these resistant varieties was shown to be influenced by the genetic background of the susceptible parent used.The implications of these findings in the conduct and interpretation of genetic studies and in backcross breeding programs is discussed.