Received: 5 November, 2009. Accepted: 15 April, 2010. Original Research Paper International Journal of Plant Breeding ©2010 Global Science Books QTL Analysis of a Putative Novel Source of Resistance to Fusarium Head Blight in Hard Winter Wheat Subas Malla 1 • Amir M.H. Ibrahim 2* • Yang Yen 1 • William Berzonsky 1 • Karl D. Glover 1 • Jeffrey Stein 1 1 Plant Science Department, South Dakota State University, Brookings, SD 57007, USA 2 Soil and Crop Sciences Department, Texas A&M University, College Station, TX 77843, USA Corresponding author: * aibrahim@ag.tamu.edu ABSTRACT Host plant resistance is a highly effective approach for managing Fusarium head blight (FHB), an important disease of wheat (Triticum aestivum L.) in many regions of the U.S. and worldwide. This study was conducted to identify QTL linked to an indigenous source of FHB resistance in a South Dakota – adapted winter wheat genotype, SD97060. A population was produced by hybridizing SD97060 with ‘Jagalene’ winter wheat and advancing generations using single seed descent. The F 2:4 , F 2:5 and F 2:6 generations were evaluated after artificially inoculating plants in mist-irrigated field nurseries in 2006 and 2007 and in a greenhouse in 2008, respectively. Disease incidence, severity, Fusarium damaged kernels (FDK) and deoxynivalenol (DON) content were evaluated in the 114 recombinant inbred lines (RILs). Four QTL were detected using phenotypic data obtained from field and greenhouse trials. Two QTL, located at chromo- somes 2BL and 4BL, exhibited stable expression across the two environments. The 2BL QTL conferred resistance to FHB; whereas, the 4BL QTL was associated with susceptibility to FHB. Two QTLs, which did not exhibit stable expression across environments were detected at the 3BS and 3BSc using field and greenhouse data. The 2BL QTL of SD97060 could serve as a valuable source to enhance FHB resistance in wheat without limiting yield potential. _____________________________________________________________________________________________________________ Keywords: Fusarium head blight (FHB), quantitative trait loci (QTL), diversity array technology (DArT) marker, simple sequence repeat (SSR) marker INTRODUCTION Fusarium head blight (FHB) has negatively impacted U.S. wheat production over periods of time since the latter part of the 19 th century (Arthur 1891; McMullen et al. 1997). The disease decreases yield, affects grain quality, and re- sults in the production of mycotoxins in the grain. Ap- proaches to managing the disease have included the use of host plant resistance, field cultivation, fungicide applica- tions, and crop rotation. Field cultivation and the use of fun- gicides have only partially succeeded in helping manage the disease (da Luz et al. 2003; Mesterhazy 2003b). Hence, identifying and employing host plant resistance has been the focus of a more effective means of managing the dis- ease. Snijders (1990) suggested that various FHB resistance genes originate from different geographical regions and could be categorized as being derived from: Eastern Europe, Italy, China, Japan and Brazil. ‘Frontana’, a Brazilian cul- tivar, is an important source, providing resistance to penet- ration and disease spread in the spike (Singh et al. 1995). The Chinese line ‘Sumai3’ and its derivatives, which exhib- it resistance to disease spread in the spike have been widely used in breeding programs throughout the world (Bai and Shaner 1994; Rudd et al. 2001; Mesterhazy 2003a). Buerst- mayr et al. (2002) reported that crossing with Sumai3 resul- ted in poor yield and low grain quality. Primarily because of the poor yield and quality associated with Sumai3, there has been an effort to identify indigenous sources of resistance to FHB within adapted U.S. germplasm. The application of molecular markers and identification of quantitative trait loci (QTL) have helped to accelerate gain from selection in U.S. wheat breeding programs (An- derson et al. 2007), and FHB resistance is a complex trait that is influenced by various environmental factors. Com- plicating evaluations for FHB resistance is the fact that dis- ease symptoms become evident at the adult plant stage, and therefore, phenotypic evaluations require an expenditure of field and greenhouse resources. Use of molecular markers can help optimize resources and to lessen the effects that the environment has on phenotypic expression. A number of studies with different sources of resistance have iden- tified QTL linked to all wheat chromosomes, except 7D (Buerstmayr et al. 2009). FHB infection results in the production of mycotoxins that are harmful to both humans and animals. Deoxyniva- lenol (DON), one of the major mycotoxins, causes feed refusal, emesis, and decreased weight gain in non-ruminants (Yoshizawa and Morooka 1973). Due to concerns of DON in human food products, countries have instituted standard guidelines that limited DON in wheat grain. For instance, the U.S. Food and Drug Administration (FDA) issued a guideline limiting mycotoxins to 1.0 ppm in finished wheat food products (FDA 1993). FHB epidemics have resulted in DON content levels of 10 ppm and higher (McMullen et al. 1997). An advanced winter wheat breeding line developed at South Dakota, SD97060, has exhibited moderate resistance to the FHB. The source of resistance for SD97060 is un- known, and its pedigree does not predict that it would ex- press a Sumai3 or Frontana resistance. Furthermore, SD97060 exhibits high grain yield and is otherwise com- petitive with adapted varieties for agronomic and grain quality performance. The objectives of the study were to (i) identify QTL associated with a reduced disease index, FDK and DON content in SD97060 and to (ii) confirm the nov- elty of these QTL compared with known FHB resistance sources. ®