Genetic Dissection of Resistance to Common Rust (Puccinia Sorghi) in Tropical Maize (Zea mays L.) by Combined Genetic Mapping and Genomic Prediction

Abstract

Background: Common rust is one of the major foliar diseases of maize, leading to significant grain yield losses and poor grain quality. The most sustainable strategy for controlling common rust is to develop resistant maize varieties, which requires a further understanding of genetic dissection of common rust resistance. Results: In this study, an association panel and two bi-parental doubled haploid (DH) populations were used to perform genome-wide association study (GWAS), linkage mapping, and genomic prediction analyses. All the populations were phenotyped in multi-environment trials for common rust resistance and genotyped with genotyping-by-sequencing (GBS) single-nucleotide polymorphisms (SNPs). GWAS revealed six SNPs significantly associated with common rust resistance at bins 1.05, 1.10, 3.04, 3.05, 4.08, and 10.04, respectively. The SNP effect of each SNP ranged from 0.13 to 0.17. Linkage mapping identified six quantitative trait loci (QTL) in the first DH population (DH1) and two QTL in the second DH population (DH2), distributed on chromosomes 1, 2, 3, 4, 6, 7, and 9, respectively. The phenotypic variation explained (PVE) of each QTL ranged from 3.55% to 12.45%. A new major QTL was detected in DH1 on chromosome 7 in the region between 144,585,945 and 149,528,489 bp, it had the highest LOD score of 7.82 and the largest PVE value of 12.45%. The genomic regions located at bins 1.05, 1.10, and 4.08 were detected by both GWAS and linkage mapping. GRMZM2G114893 (bin 1.05) and GRMZM2G138949 (bin 4.08) were identified as the putative candidate genes conferring common rust resistance. The genomic prediction accuracies observed in the association panel and two bi-parental DH populations were 0.61, 0.51, and 0.10, respectively. Conclusions: These results provided new insight into the genetic architecture of common rust resistance in maize and a better understanding of the application of genomic prediction for common rust resistance in maize breeding.