Northern (syn. Turcicum) leaf blight (NLB) is a serious and widespread disease of maize (Zea mays L.) throughout the most productive maize growing regions of eastern Africa. The only economical way to control the pathogen (Setosphaeria turcica, anamorph Exserohilum turcicum) and thus the disease, is by genetic resistance. Based on a full diallel with seven inbred lines [five resistant from eastern and southern Africa, KARI and CIMMYT germplasm, respectively, and two susceptible from Europe and the USA] a generation means analysis was conducted. The considered material encompassed 164 entries from the diallel, including the seven parental lines, their F1, F2, BC1 and BC2 generations, plus checks. The trial was planted in the short rainy season 1994 in Kenya and Zimbabwe, and was artificially infected. Incubation period as well as disease severity on four successive dates were recorded on a single-plant basis. From the individual disease ratings, the area under the disease progress curve (AUDPC) was calculated. The study revealed that (i) the heritability of all resistance parameters was high or very high, (ii) reciprocal effects of resistance to NLB were not significant, (iii) general combining ability effects were of more importance than specific combining ability effects at early growth stages with increasing importance of specific combining ability effects towards maturity, and (iv) additive gene action was predominant concerning incubation period while both additive and dominance effects were determining the AUDPC. Some crosses showed substantial heterosis for resistance.

English

9801|AGRIS 9702

Jose Juan Caballero

CIMMYT Publications Collection