Genome-wide association study of resistance to Mal de Río Cuarto disease in maize

ROSSI, EZEQUIEL A.; RUIZ, MARCOS; BONAMICO, NATALIA CECILIA;; BALZARINI, MÓNICA GRACIELA

AGRONOMY JOURNAL

AMER SOC AGRONOMY

Año: 2020 vol. 112 p. 4624 - 4633

0002-1962

Argentine maize has been extensively screened for incidence (INC) and severity(SEV) of Mal de Río Cuarto disease (MRC), caused by Mal de Río Cuarto virus(MRCV), family Reoviridae, genus Fijivirus, narrowing the breeding genetic basis.Both traits are highly heritable phenotypic measurements, and quantify the strongdisease impact on grain yield. The adaptation of exotic germplasm to variation ofthose traits has not been explored. The aim of this work was to identify, in a non-localand diverse panel of maize inbred lines, novel genomic regions associated with resistanceto MRC. First, we phenotyped 206 maize inbred lines from the InternationalMaize and Wheat Improvement Center (CIMMYT), in several environments of theMRC-endemic area under natural virus infection, to obtain the best linear unbiasedpredictor (BLUP) of line effects regarding INC and SEV. A multi-environment andmulti-trait mixed linear model was fitted to derive the multivariate BLUPs. Geneticvariance and mean-basis heritability were high in both traits and a significant geneticcorrelation among them was found. Second, we performed a genome-wide associationstudy (GWAS) by linking the BLUPs with 78,376 SNP markers available for186 lines. The GWAS identified new alleles for resistance to MRC in six genomicregions from the exotic germoplasm. Four of them reduce symultaneously the appearanceand severity of disease symptoms. Improved susceptible parental lines throughmarker-assisted recurrent selection would allow us to increase the resistance of maizehybrids to MRC disease.