Monday, November 13, 2006

Identification of Quantitative Trait Loci for Resistance to Eyespot in Maize.

Marcelo Melani and Marcelo Carena. North Dakota State Univ., 480 A Loftsgard Hall, Fargo, ND 58105-5051, United States of America

Eyespot (caused by Aureobasidium zeae (Narita and Hiratsuka) Dingley (syn. Kabatiella zeae Narita and Hiratsuka) is a fungal leaf disease of maize (Zea mays L.) that can cause significant grain yield reductions. Genetic resistance to eyespot exists in maize and it is the most recommended method of disease control. The objectives of this study were to identify quantitative trait loci (QTL) for eyespot resistance and to determine the relationship between eyespot resistance and late maturity. Two segregating populations (F2:3 families) derived from the crosses of B100 (resistant) x ND284 (susceptible) and B37 (resistant) x ND284 maize inbred lines were evaluated across two North Dakota locations in 2004 and 2005. Eyespot ratings were taken at approximately 7-d intervals after the R1 stage on a plot basis by a scale ranging from 0 (resistant) to 9 (susceptible). Single nucleotide polymorphism markers and composite interval mapping were utilized for the QTL analyses. A total of 22 QTL were discovered for eyespot resistance across all maize chromosomes except chromosome 9. The consistency of the QTL over four environments and two populations was high. Early and late ratings detected different QTL for eyespot resistance. The total percentage of the phenotypic variation explained for eyespot resistance differed among traits and populations ranging from 16.1 to 70.1%. Broad-sense heritability estimates ranged from 48 to 82%. Additive and dominance effects were present in most QTL for eyespot resistance. A significant negative correlation was found between eyespot ratings and days to flowering (DTF), but the correlation coefficients were always low.  Few QTL for DTF appear to correspond to QTL for eyespot resistance, but the ones on chromosome 8 had the largest genetic effects and explained the largest amount of the phenotypic variation for both traits.

Handout (.pdf format, 240.0 kb)