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Inheritance of race-nonspecific resistance to Exserohilum turcicum in maize synthetic population OhS10 Pratt, R.C.; Lipps, P.E.; Ssango, F.; Hakiza, J.J. & Adipala, E. Abstract Progeny tests of resistant lines derived from maize (Zea mays L.) synthetic population OhS10 were conducted at one location during two years (1993-94) in Ohio (Guerne) and at two locations during one year (1993) in Uganda (Kabanyolo and Namulonge) to examine the inheritance of resistance to Exserohilum turcicum(Pass.), causal agent of northern leaf blight (NLB). Individual plants in single ear derived selfed progenies (S1 and S1:2) were inoculated in a controlled fashion (Guerne, Namulonge) or naturally infected (Kabanyolo). Host responses to infection were characterized by determining area under the disease progress curve (AUDPC), calculated from percent leaf area affected (PLAA) and lesion number counts, and lesion size. The majority of S1 and S1:2 progenies had few lesions, low rates of disease development, and high levels of resistance, indicating that multiple factors govern expression of resistance. Of the progenies tested, S20-4, S30-5, S30-6 and S30-7 exhibited consistently high levels of resistance to NLB. Keywords Breeding, maize, genetics, host resistance

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Pratt, R.C.; Lipps, P.E.; Ssango, F.; Hakiza, J.J. & Adipala, E. Résumé Des tests de descendance des lignees resistantes obtenues a partir d'une population synthetique de mais OhS10 ont ete executes a un endroit pendant deux annees (1993-1994) Ohio (Guerne) et a deux endroits pendant une annee (1993) en Ouganda (Kabanyolo et Namulonge) pour examiner la transmission de la resistance a Exserohilum turcicum (Pass.), qui cause le rouille des feuilles (qui sevit au nord) (NLB). Les plantes individuelles des progenies obtenues par descendance autofecondee issue d'un epis unique (S1 et S1:2) etaient inoculees de facon controee (Guerne, Namulonge) ou infectees naturellement (Kabanyolo). Les reponses des infections etaient caracterisees par la determination de la surface en dessous de la courbe de progres de la maladie (AUDPC), qui etaient calculee a partir du pourcentage de surface de la feuille affectee (PLAA) et le nombre des lesions et la taille de lesions. La majoritedes descendants S1 et S1:2 avaient peu de lesions, un developpement ralentie de la maladie et un niveau de resistance eleve, ce qui indique que plusieurs paramtres influencent l'expression de la resistance. S20-4, S30-5, S30-6 et S30-7 montrent un niveau de resistance eleve contre NLB. Mots Clés amelioration, le mais, la genetique, resistance

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