Dynamic gene action at QTLs for resistance to Setosphaeria turcica in maize

• Published in: Theoretical and applied genetics 1999-05, Vol.98 (6/7), p.1036-1045
• Main Authors: Welz, H.G, Schechert, A.W, Geiger, H.H
• Format: Article
• Language: English
• Subjects: additive effect; additive gene effects; Analysis; Biological and medical sciences; blight; Chromosome mapping; Chromosomes; Classical genetics, quantitative genetics, hybrids; Corn; crossing; disease resistance; Diseases and pests; Fundamental and applied biological sciences. Psychology; Genetic aspects; genetic effects; Genetics of eukaryotes. Biological and molecular evolution; genotype-environment interaction; inbred lines; lines; linkage groups; loci; No Child Left Behind Act 2001-US; Plant genetics; Plant immunology; Plant resistance; Pteridophyta, spermatophyta; Quantitative trait loci; quantitative traits; Setosphaeria turcica; Software; Vegetals; Zea mays
• ISSN: 0040-5752; 1432-2242
• DOI: 10.1007/s001220051165

Cultivars with quantitative resistance are widely used to control Setosphaeria turcica (Luttrell) Leonard & Suggs, the causal organism of northern corn leaf blight (NCLB). Here the effectiveness of quantitative trait loci (QTLs) for NCLB resistance was investigated over the course of host plant development in inoculated field trials. A population of 194-256 F(2:3) lines derived from a cross between a susceptible Italian (Lo951) and a highly resistant African inbred line (CML202) was tested in three environments in Kenya. The traits assessed were the incubation period (IP), the percentage disease severity (DS 1 to 5, taken biweekly), and the area under the disease progress curve (AUDPC). Considering all resistance traits and environments, a total of 19 putative QTLs were detected by composite interval mapping using a linkage map with 110 RFLP markers. In the combined analysis across environments, nine QTLs were significant (LOD >3.0) for DS 3, recorded around flowering time, explaining 71% of the genotypic variance. Four of these nine QTLs displayed significant (P < 0.05) QTL x environment (QTL x E) interaction. Most QTLs were already significant in the juvenile stage (IP) and became less effective after flowering. Across environments, three QTLs conditioned adult-plant resistance, in the sense that they were only significant after flowering. Six QTL alleles on chromosomes 2, 4, 5, 8, and 9 of CML202 should be useful for marker-assisted backcrossing.