Characterizing heterosis in a set of recombinant intercrosses (RIXs) developed from a multiparental maize population

The exploitation of heterosis is one of the leading activities in maize breeding. Here, we\r\ndeveloped an innovative recombinant intercross (RIX) population by crossing pairs of\r\nmulti-parental maize recombinant inbred lines (RILs) to evaluate the heterotic response in a\r\nheterozygous multi-parental population. Field phenotyping was performed on 400 RIX\r\ngenotypes considering 11 agronomic traits and the resistance to Fusarium Ear Rot (FER) in two\r\nconsecutive years.\r\nThanks to the high level of allelic diversity available in parental genomes, a broad range of\r\nphenotypic diversity was observed. The broad-sense heritability (H2) was high for all traits\r\n(H2=0.48 to 0.89) illustrating a strong genetic basis. The heterotic response was computed\r\nbased on RIL values as mid and best parent heterosis showing different magnitudes for different\r\ntraits suggesting effects from partial dominance to over-dominance. GWAS detected 55\r\nsignificant loci associated with agronomic traits across all chromosomes, with allelic effect ranging\r\nfrom 0.28 to 10.90 indicating the contribution of various sized QTLs. Several pleiotropic QTLs on\r\nchromosomes 8 and 3 were detected, indicating that these loci may contain valuable genes for\r\nmultiple traits. RIX collection showed a moderate heritability of FER resistance and 7 putative QTL\r\nwere associated to this trait on chromosomes 8 and 5. The allelic effect estimates indicated the\r\npresence of minor effect QTL with relatively small additive effects on disease resistance.\r\nOur findings confirm the usefulness of the RIX population to decipher heterotic loci in maize and\r\nsupport utilizing this resource in future to accelerate crop improvement.