|Holland, Jim - Jim|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/11/2006
Publication Date: 12/20/2006
Citation: Jines, M.P., Balint Kurti, P.J., Robertson-Hoyt, L.A., Molnar, T., Holland, J.B., Goodman, M.M. 2006. Mapping resistance to southern corn rust in a semi-tropical recombinant inbred topcross population.. Theoretical and Applied Genetics. 114:659-667. Interpretive Summary: Southern corn rust is a serious problem in corn grown in tropical and sub-tropical regions and can also cause significant yield losses in temperate areas in some years. A gene for southern corn rust resistance has been identified from NC300, a maize line derived from tropical maize varieties. This gene has a very large and consistent effect over environments.
Technical Abstract: Recombinant inbred (RI) lines derived from a cross between NC300, an all-tropical, temperate-adapted line, and B104, a stiff-stalk line were genotyped at 113 loci spaced throughout the genome, and topcrossed to the sister-line tester FR615xFR697. The 143 topcrosses were evaluated for resistance to southern corn rust (SCR) disease, caused by Puccinia polysora Underw., in four environments . Time to flowering was measured in two environments. Quantitative Trait Loci (QTL) were mapped for both traits. The entry mean heritability estimate for SCR resistance was 0.93. A multiple interval mapping (MIM) model, including four QTL, accounted for 87.8% of the variation for mean disease rating across environments. One QTL, located on the short arm of chromosome 10, explained 82.7% of the phenotypic variation, with the NC300 allele increasing resistance. Composite interval mapping (CIM) demonstrated that similar proportions of variation were explained within each test environment by this QTL. Three partial resistant QTL from the MIM model each accounted for less than 2.0% of the variation. Significant (P<0.001), but relatively minor, topcross-by-environment interaction occurred for SCR rating, and resulted from the interaction of the major QTL with the environment. Maturity and SCR ratings were slightly correlated, but QTL for both traits did not co localize. A high heritabilitiy, the detection of a major QTL, and the bimodal distribution of resistant ratings collectively demonstrated that resistance was simply inherited and the major QTL is likely a dominant resistant gene. The gene is independent of plant maturity and further provides effective resistance to hybrids.