A quantitative trait loci on maize chromosome 5 is associated with root-knot nematode resistance

Authors: Davis, Richard; Harris-Shultz, Karen; Knoll, Joseph - Joe; Krakowsky, Matthew; Scully, Brian

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2024
Publication Date: 3/1/2024
Citation: Davis, R.F., Harris-Shultz, K.R., Knoll, J.E., Krakowsky, M.D., Scully, B.T. 2024. A quantitative trait loci on maize chromosome 5 is associated with root-knot nematode resistance. Phytopathology. 114(7):1657-1663. https://doi.org/10.1094/PHYTO-08-23-0286-R.
DOI: https://doi.org/10.1094/PHYTO-08-23-0286-R

Interpretive Summary: The southern root-knot nematode (RKN) can feed on corn roots in the U.S. Southern Coastal Plain region, which can cause yield losses of 30% or greater. When the population density of RKN increases in the soil, subsequently planted susceptible crops may be damaged. Hybrid corn with RKN resistance could prevent an increase in RKN levels, but no genetic regions that confer resistance have been identified. In this study, a plant population was made by crossing a susceptible and a resistant corn line, which was then evaluated for RKN reproduction and root weight. Molecular markers were used to determine the genetic makeup of this population. Using these molecular markers in conjunction with the RKN reproduction and root weight data, a single region of plant DNA (a quantitative trait locus, or QTL) was identified on chromosome 5 that explained 15% of the variation for the number of RKN eggs produced and 11% of the variation for the number of eggs per gram of root. Plants that molecular markers indicated inherited DNA in the QTL only from the RKN-resistant parent plant had fewer eggs and fewer eggs per g of root than the plants that inherited DNA in the QTL only from the susceptible parent plant. Therefore, this study documents that the first QTL for RKN resistance in corn has been identified.

Technical Abstract: The southern root-knot nematode (RKN) (Meloidogyne incognita) can feed on the roots of maize (Zea mays L) in the U.S. Southern Coastal Plain region and in heavily infested fields may cause yield losses of 30% or greater. Increases in RKN density in the soil may reduce the yield for subsequently planted susceptible crops. The use of maize hybrids with resistance to RKN could prevent an increase in RKN density, yet no genetic regions have been identified that confer host resistance. In this study a B73 (susceptible) x Ky21(resistant) S5 recombinant inbred line (RIL) population was phenotyped for egg number and root weight. This population has been previously genotyped using single nucleotide polymorphisms (SNPs). By utilizing the SNP data with the phenotype data, a single quantitative trait locus (QTL) was identified on chromosome 5 that explained 15% of the phenotypic variation (PV) for the number of eggs and 11% of the PV for the number of eggs per g of root. Plants that were homozygous for the Ky21 allele for the most associated marker Pza03172.3 had fewer eggs and fewer eggs per g of root than the plants that were homozygous or heterozygous for the B73 allele. Thus, the first QTL for RKN resistance in Maize has been identified.