INHERITANCE OF RESISTANCE TO EXSEROHILUM-TURCICUM IN PI-209135, MAYORBELA VARIETY OF MAIZE

The maize (Zea mays L.) inbred line H102 selected from the cross C123 x PI 209135 (Mayorbela) is highly resistant to Exserohilum turcicum (P ass) Leonard and Suggs, the cause of northern corn leaf blight (NCLB). To determine the inheritance of disease reaction, H102 was crosses to six inbred lines. Three susceptible, one with polygenic resistance, a nd two with either the Ht1 or Ht2 gene for chlorotic lesion resistance to NCLB were used. The parents, F1s, F2s and backcrosses to susceptib le and polygenic restant parents were inoculated with conidia of E. tu rcicum and rated for disease development using a 0 to 5 scale (complet ely resistant to completely susceptible, respectively) in the field an d greenhouse. The F1s of all crosses were resistant, indicating that t he resistance of H102 is at least partially dominant. Field and greenh ouse evaluations of F2 and BC1 populations of H102 x susceptible cross es show the resistance of H102 to E turcicum to be controlled by a sin gle gene. Field evaluation of F2s of H102 x polygenic resistant lines suggest more than one gene for resistance, one or more from each paren t. Progeny of crosses of H102 x NN14A and NN14B, which carry the Ht1 a nd Ht2 genes for chlorotic lesion resistance, respectively, show the r esistance in H102 to be controlled by a locus other than the Ht1 or Ht 2. Evidence is presented which suggest that field resistance of H102 m ay be controlled by a major gene, with minor additive genes contributi ng to resistance, making the variety 'Mayorbela' a desirable source of resistance to E. turcicum.