QTLs to Maize streak virus tolerance in maize.

Abstract

Maize streak disease (MSD) caused by the Maize streak virus (MSV; genus Mastrevirus) transmitted by leafhoppers, is an economically important disease of maize endemic in Sub-Saharan Africa. This disease is controlled using maize tolerant varieties - genotypes upon infection produce mild streak symptoms and no significant negative effect on yield. A mapping population of 250 F2 lines derived from a cross between a drought tolerant inbred maize and MSV tolerant line (No.1368) were artificially inoculated with viruliferous Cicadulina triangular one week post planting. Severity of MSV on the inoculated maize plants were scored on a scale of 1 to 5, 1 for highly resistant and 5 for highly susceptible. Quantitative Trait Loci (QTLs) conferring tolerance to MSV was mapped using 269 SNP markers. A linkage map comprising 11 linkage groups was constructed using Haldane mapping function at LOD 3.0. Composite interval mapping method was used to estimate the dominance and additive effect of the QTL. One QTL of major effect was identified on chromosome 3 at an LOD 3.6 explaining above 60% of phenotypic variance. Frequency distribution of MSD severity was bimodal signifying the presence of a major gene in the MSV tolerant parent. The identification of major QTL, upon validation, opens the avenue for marker-assisted breeding to introgress genes confering MSV tolerance into other elite varieties.