Chlorotic Lesion Response of Maize toCercospora zeae-maydisand Its Effect on Gray Leaf Spot Disease

Abstract

Chlorotic lesions (CL) developed on certain F 2:3 and F 3:4 families derived from a cross between a previously described CL-resistant maize inbred (NC250A) and a susceptible (S) lesion maize inbred (B73) in response to infection by Cercospora zeae-maydis. CL trait expression was consistent (displayed phenotype across locations at midepidemic assessment) on 12 of the 60 F 2:3 families studied. Heterogeneous (CL/S) lesion phenotypes were displayed by 36 families at midepidemic. Consistent, characteristic S lesions were exhibited by 12 F 2:3 families. Selected F 2:3 families representing each lesion type class produced F 3:4 Progenies that predominantly displayed lesion phenotypes consistent with the parental class. Families exhibiting the CL trait at midepidemic assessment had significantly lower apparent infection rates, percent leaf area affected (PLAA), and area under disease progress curves based on PLAA and lesion area. Heterogeneous families tended to have intermediate mean gray leaf spot severity, whereas disease severity and progress were highest on homozygous S lesion-type families. Because the CL trait was associated with decreased gray leaf spot severity and progress, selection for this trait in a population derived from NC250A x B73 would decrease the impact of epidemics caused by C. zeae-maydis. Segregation analyses of midepidemic CL responses of F 2:3 and F 3:4 families during 1992 and 1993 suggested the presence of a major factor in inheritance of the CL response. Segregation ratios observed at a later assessment date during 1992 did not support monogenic inheritance.