Diverse modes of gene action contribute to heterosis for quantitative disease resistance in maize

Authors: Hudson, Asher; WAGNER, MAGGIE - University Of Kansas; Sermons, Shannon; Balint Kurti, Peter

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2025
Publication Date: 3/24/2025
Citation: Hudson, A.I., Wagner, M., Sermons, S.M., Balint Kurti, P.J. 2025. Diverse modes of gene action contribute to heterosis for quantitative disease resistance in maize. Genetics. https://doi.org/10.1093/genetics/iyaf049.
DOI: https://doi.org/10.1093/genetics/iyaf049

Interpretive Summary: Genes conferring quantitative disease resistance have been identified in many studies. However, the modes of action of these genes (in other words, dominant, recessive, overdominant, epistatic action etc.) is often not determined. In this study we use a recombinant inbred and two backcross populations to determine the global architecture of gene action for resistance to two important maize diseases, southern leaf blight and gray leaf spot. We identify resistance genes with many different modes of action: dominant resistance, dominant susceptibility and additive. We also identify one overdominant locus (where the heterozygote gives a more extreme phenotype than either homozygote), though this could also be explained by the close linkage of deleterious recessive alleles on opposite chromosomes, a phenomenon known as pseudo-overdominance. Several epistatic interactions are also reported. Heterosis or hybrid vigor is the improved performance of a hybrid compared to its parents and is due, by definition, to non-additive gene action. We identify some level of heterosis for disease resistance. We propose that the non-additive genetic effects we identify are likely the cause of this heterosis.

Technical Abstract: Disease resistance in plants can be conferred by single genes of large effect or by multiple genes each conferring incomplete resistance. The latter case, termed quantitative resistance, may be difficult for pathogens to overcome through evolution due to the low selection pressures exerted by the actions of any single gene and, for some diseases, is the only identified source of genetic resistance. We evaluated quantitative resistance to two diseases of maize in a bi-parental mapping population as well as backcrosses to both the parents. Quantitative trait locus analysis shows that the genetic architecture of resistance to these diseases is characterized by several modes of gene action including additivity as well as dominance, overdominance, and epistasis. Heterosis or hybrid vigor, the improved performance of a hybrid compared to its parents, can be caused by non-additive gene action and is fundamental to the breeding of several crops including maize. In the backcross populations and a diverse set of maize hybrids we find heterosis for resistance in many cases and that the degree of heterosis appears to be dependent on both hybrid genotype and disease.