GENETIC ARCHITECTURE OF MAIZE CHLOROTIC MOTTLE VIRUS IN TROPICAL MAIZE GERMPLASM
Maize chlorotic mottle virus (MCMV) is a serious threat to maize growing small holder farmers’ food security in Sub-Saharan Africa (SSA). In addition, the ability of MCMV to interact with other members of Potyviridae leads to maize lethal necrosis (MLN) and causes up to 100% yield loss. Three doubled haploid (DH) populations and IMAS association panel lines were evaluated in the screen house for MCMV in the quarantine field for MLN at CIMMYT-MLN screening facility in the Maize Research Station of KALRO (Kenya Agriculture and Livestock Research Organization), Naivasha. The study aimed at gaining insights into the genetic architecture underlying the resistance to MCMV and further validate the identified genomic regions in independent population. Linkage mapping with three doubled haploid (DH) populations was combined with a genome-wide association study (GWAS) of 395 diverse tropical and subtropical maize lines using 293,106 SNPs under controlled conditions. For all populations, phenotypic variation for MCMV were significant, and heritability was moderate to high. Few promising lines with high tolerance to MCMV were identified to be used as potential donors. SNPs significantly associated with MCMV were identified and the candidate genes were found to relate to plant defense. The number of significant SNPs varied for individual and across locations. The total variance explained by significantly associated SNPs ranged from 31% for MCMV early to 26% for MCMV late. Linkage analysis revealed that most QTL are in chromosome 3 and the remaining QTL identified were distributed in other chromosomes. The number of QTL associated with MCMV resistance ranged from one to five QTL in both early stage and late stage of MCMV infection. The proportion of phenotypic variance explained by each QTL ranged from 4.8% to 10.4% in CML 494×CML 550, from 2.2% to 59.1% in CML 504×CML 550 and in CML 511 × CML 550 it ranged from 16.8% to 28.1 %. These results indicate that MCMV resistance in maize is controlled by a major QTL in chromosome 3 and several minor QTLs with smaller effect on other chromosomes. Information obtained from this study can be used for developing functional molecular markers for marker-assisted selection (MAS) and for implementing genomic selection (GS) to improve MCMV resistance in tropical maize.
- SITONIK CHELANG’AT.pdf
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