No abstract

Fusarium head blight (FHB) is a major disease of barley (Hordeum vulgare L.) that results in reduced grain yield and quality through the accumulation of the mycotoxin deoxynivalenol (DON). Coincident QTL for FHB severity, DON concentration, and heading date (HD) map to a region of chromosome 2(2H) designated Qrgz-2H-8. It is unclear whether disease resistance at this locus is due to a pleiotropic effect of late HD by delaying the host exposure to the pathogen or a tightly linked resistance gene. The objectives of this study were to develop a set of near isogenic lines (NILs) for the Qrgz-2H-8 region and to genetically dissect the QTL region containing the coincident traits. Two NIL populations were developed consisting of F(2)- and F(4)-derived recombinants from a cross between a BC(5) line carrying the donor parent (Chevron) alleles in the Qrgz-2H-8 region and the recurrent parent M69. Analysis of field and marker data from these NILs revealed that the Chevron alleles conditioning FHB resistance, late HD, and low DON concentration were successfully introgressed into the BC(5) parent line and were segregating among NILs. QTL analysis of the F(4)-derived population showed that the HD QTL is adjacent to the FHB QTL. Furthermore, a single NIL was identified that was similar to the resistant BC(5) parent for FHB severity and the early flowering parent M69 for HD. These results indicate that the relationship between FHB and HD at the Qrgz-2H-8 region is likely due to tight linkage rather than pleiotropy.

Sacc.) Shoemaker], Fusarium graminearum Schwab, and Alternaria spp. (Mathre, 1997). KD results in brown Kernel color and grain protein concentration (GPC) are two of and black discoloration of the lemma and palea, which the most important attributes of barley (Hordeum vulgare L.) grain intended for use in malting and brewing. Grain with protein levels reduces the value of the grain for malting. In severe that are too low or high or that have dark kernel color, which may cases, grain may be rejected for malting and must be result from the disease complex of kernel discoloration (KD), is unacmarketed for feed at a reduced price. The severity of ceptable for the malting and brewing industries. The purpose of this KD varies depending on susceptibility of the cultivars study was to use molecular markers to map quantitative trait loci and environmental conditions (Miles et al., 1987; Wil-(QTLs) for KD and GPC in two recombinant inbred line (RIL) coxson et al., 1980). populations. One population was created by means of the high GPCKD resistance is quantitatively inherited (Singh et al., 1997;Oziel et al., 1996). A recent study suggests that a 495