Start Date: Jul 15, 2008
End Date: Jul 14, 2013
We will use marker-assisted backcrossing to pyramid the head rot and stalk rot tolerant QTL into two recently released lines with stalk rot resistance, CONFSCLR2 and RHA 453. It is well documented that most QTL underlying traits of interest are population-specific, so we will use the best lines from our mapping populations as the tolerant donors and monitor QTL recombination with previously-identified markers. First, we will screen for polymorphism of the QTL-linked DNA markers between the donor and the recipient parental lines and identify a group of markers to be used in the project. We will use the alternative backcross and selection strategy designed specifically for this project to ensure success. The initial marker genotyping will be carried out in the BC1F1 generation and the selected lines will then be subjected to an additional cycle of backcrossing before evaluation in multiple-location trials for resistances to head and stalk rot. In 2008, we will 1) screen for polymorphism between the donor lines (two lines possessing the most favorable QTL as revealed by DNA markers and phenotypic evaluation) and recipient lines (CONFSCLR2 and RHA 453), and select a group of markers to be used for this project; 2) to develop segregating BC1F1 populations by making crosses between the donor and recipient lines; and 3) to initiate marker-assisted selection and identify individuals to produce progeny for the first cycle of field evaluation of head rot and stalk rot resistances in the 2009 growing season. This proposal addresses the following research need of the Sclerotinia Initiative Strategic Plan: "PM 1.7.2: Use marker-assisted selection approaches for Sclerotinia resistance in sunflower" and "PM 3.0.3: Develop new DNA markers for QTL identification and marker assisted Selection".