INHERITANCE OF RESISTANCE TO LEAF FRECKLES AND WILT CAUSED BY CLAVIBACTER-MICHIGANENSE SUBSP NEBRASKENSE IN EARLY MATURING MAIZE INBRED LINES

The inheritance of resistance to leaf freckles and wilt was studied in two greenhouse and two field trials of a set of diallel crosses between 10 early maturing maize inbred lines. Inheritance of resistance in six F2 populations derived from resistant X susceptible and intermediate X susceptible crosses was also studied in the greenhouse and field. General combining ability was much more important than specific combining ability for disease resistance. General combining ability effects were generally consistent between trials, whereas specific combining ability effects were not. Additive genetic effects accounted for most of the variation among generation means in populations derived from resistant X susceptible crosses, and less so in populations from intermediate X susceptible crosses. Broad-sense heritabilities were high, and estimates of gene numbers were low in F2 populations derived from resistant X susceptible crosses. Resistance to leaf freckles and wilt in the more resistant inbred lines appears to be controlled by relatively few genes (3-5) acting in a mostly additive manner. Development of resistant germ plasm using a variety of breeding methods, including pedigree, bulk, backcross, and recurrent selection methods, should be successful, particularly if material is evaluated in more than one environment.