Development and fine mapping of markers closely linked to the SCMV resistance loci Scmv1 and Scmv2 in European maize (Zea mays L.)

摘要

Sugarcane mosaic virus (SCMV) is an important disease in European maize cultivars (Zea mays L.). Because of its non-persistent transmission by aphid vectors, it is not possible to control SCMV directly. Therefore, cultivation of resistant maize varieties is an efficient way to control SCMV infections. The overall objectives of this study were the genetic analysis of SCMV resistance in cross F7 x FAP1360A and the identification of closely linked markers to the SCMV resistance genes Scmv1 on chromosome 6 and Scmv2 on chromosome 3 for map-based cloning and marker-assisted selection (MAS). The technical objectives were to (1) identify in particular the location of Scmv1 and Scmv2 on chromosomes 3 and 6 in cross F7 x FAP1360A, (2) estimate the gene action of the alleles present at these loci, (3) enrich the SCMV resistance regions surrounding Scmv1 and Scmv2 with amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers by applying a modified targeted bulked segregant analysis, tBSA, (4) convert AFLP markers into codominant, simple PCR-based markers as a tool for MAS and map-based cloning of Scmv1 and Scmv2 and, (5) assess resistance gene analogues (RGAs) as potential candidate genes for Scmv1 and Scmv2.Quantitative trait loci (QTL) mapping SSR markers revealed the presence of two QTL on chromosome 6 (Scmv1a and Scmv1b) and one QTL on chromosome 3 (Scmv2). tBSA identified 24 AFLP and 25 SSR markers adjacent to either Scmv1 or Scmv2. AFLP marker E35M62-1, closely linked to Scmv1 on chromosome 6, was successfully converted into an indel marker. For chromosome 3, AFLP marker E33M61-2 was converted into a CAPS marker. Both converted AFLP markers mapped to the same chromosome region as their original AFLP markers. Development of CAPS of the RGAs and mapping in relation to SCMV resistance genes Scmv1 and Scmv2 identified pic19 and pic13 as potential candidates for these resistance genes. In this study, useful markers were developed for applications in MAS. Because inheritance of SCMV resistance is strongly affected by the environment, MAS enables the selection of resistant individuals independently of field experiments. Furthermore, MAS can assist breeders to identify resistant individuals before flowering and to pyramid resistance genes in elite inbred lines. Another benefit of these closely linked markers is their application for map-based cloning. Final evidence, whether there are one or more genes clustered on chromosomes 3 and 6, conferring resistance against SCMV, can only be solved after cloning these genes.