Inheritance of Tolerance to Septoria Leaf Blotch of Wheat

Abstract

The effect of Septoria leaf blotch on yield components and plant height was investigated in parents, segregating populations and selected lines of crosses between tolerant and nontolerant (''Miriam'' .times. ''Bet Dagan 233'') and tolerant and moderately resistant (''Miriam'' .times. ''Yafit'') cultivars. The unselected F3 and F4 bulks were susceptible and suffered moderate losses in yield components. Selection in segregating F3 and F4 populations produced susceptible semidwarf lines that were as tolerant and high yielding as ''Miriam'' under severe Septoria epidemics. Selection for low kernel weight produced dwarf lines with low kernel weight and kernel number that phenotypically resembled the vulnerable dwarf ''Bet Dagan 233''. Tolerance derived from ''Miriam'' seemed incompatible with dwarf plant stature. The rapid achievement of tolerance by selection implied a trait controlled by a small number of additive loci. The resistance of ''Yafit'' apparently was controlled by the joint action of several loci. Plants of ''Miriam'' and the selected lines from crosses with ''Miriam'' maintained high 1000 kernel weight and yield under dry conditions. Tolerance may represent a compensatory response mechanism to physiological stresses that affect the grain-filling process. Breeding for tolerance appears possible if the selection goals are high kernel weight and semidwarf or taller plant stature. Selection for high kernel number per head should be done among promising tolerant lines.