A Protocol for Marker-assisted Selection of a Fusarium Head Blight Resistance Gene Derived from Sumai 3

Two complementary approaches are being pursued at the University of Arkansas to develop FHB-resistant cultivars for the Mid-south. Following a severe outbreak of FHB in 1991, the breeding program initiated a crossing program between adapted soft wheat genotypes and 22 FHB lines from CIMMYT and Eastern Europe. These populations were advanced as bulks for 5 years. Then lines were developed using pedigree selection and were evaluated in headrows for their adaptability and resistance to other diseases. F7 lines representing 50 populations were advanced and evaluated for FHB resistance in an inoculated screening nursery along with resistant and susceptible checks in the field in 2000. Selected lines with good adaptability and high grain yield are being tested in a replicated inoculated nursery in 2001. Four of the highest yielding lines were entered in the Uniform Winter Wheat Scab nursery. All four lines have a different resistant parent in the pedigree. In addition to field test, the selected lines will be tested in the greenhouse for Type 2 resistance. During the winter of 1999-2000, crosses were made in the greenhouse to pyramid resistance genes using F3 Arkansas breeding lines with resistant parentage. The F3 lines were derived from a number of adapted southern soft wheats crossed to two germplasm lines and Ernie. The F3 lines were crossed to an adapted genotype with an alternate resistance Type. Lines from crosses between adapted genotypes and FHB resistance sources are being selected for both agronomic traits and resistance to release resistant cultivars adapted to the Mid-south as soon as possible. To develop adapted germplasm lines with high levels of FHB resistance as well as more durable types of resistance to leaf rust, stripe rust, and leaf blotch, sources of these resistances (primarily CIMMYT spring wheat cultivars and lines) were crossed in 1995 to two adapted cultivars (Agripro Mason and Pioneer 2684) with short vernalization requirement (to facilitate multiple generations per year) and photoperiod sensitivity (to confer wide adaptation). Filial, backcross (BC), and topcross (TC) populations from these crosses were grown as space-planted bulks for three seasons, and selections were made for heading date, plant type, yield potential, visual grain quality, and resistance to leaf rust, FHB, and leaf blotch. In 1999, 120 heads were selected from 117 of the best F4, BCF3, and TCF3 populations and grown as headrows in 2000. After selection for agronomic traits and stripe rust resistance during 2000, 548 lines were advanced to greenhouse and multi-location testing, including two locations in Louisiana in collaboration with the LSU breeding program. During the summer of 2001, the best lines will be made available to breeders and intercrossed within the Agripro Mason and Pioneer 2684 gene pools to combine resistances. 2000 National Fusarium Head Blight Forum 245 Variety Development and Uniform Nurseries THE NEED FOR UNIFORMITY IN DESIGNATING TYPES OF SCAB RESISTANCE W.R. Bushnell* USDA-ARS, Cereal Disease Laboratory, St. Paul, MN, 55108 *Corresponding author: PH: (612) 625-7781, E-mail: billb@cdl. umn.edu