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Key Message: QTL identified for seedling and adult plant crown rot resistance in four partially resistant hexaploid wheat sources. PCR-based markers identified for use in marker-assisted selection. Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in many wheat-growing regions globally. Complete resistance to infection by F. pseudograminearum has not been observed in a wheat host, but germplasm with partial resistance to this pathogen has been identified. The partially resistant wheat hexaploid germplasm sources 2-49, Sunco, IRN497 and CPI133817 were investigated in both seedling and adult plant field trials to identify markers associated with the resistance which could be used in marker-assisted selection programs. Thirteen different quantitative trait loci (QTL) conditioning crown rot resistance were identified in the four different sources. Some QTL were only observed in seedling trials whereas others appeared to be adult plant specific. For example while the QTL on chromosomes 1AS, 1BS, and 4BS contributed by 2-49 and on 2BS contributed by Sunco were detected in both seedling and field trials, the QTL on 1DL present in 2-49 and the QTL on 3BL in IRN497 were only detected in seedling trials. Genetic correlations between field trials of the same population were strong, as were correlations between seedling trials of the same population. Low to moderate correlations were observed between seedling and field trials. Flanking markers, most of which are less than 10 cM apart, have now been identified for each of the regions associated with crown rot resistance.

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schwein.) Petch), is one of the major diseases of barley (Hordeum vulgare L.) in eastern China, the Upper Midwest of the USA, and the eastern Prairie Provinces of Canada. To identify quantitative trait loci (QTL) controlling FHB resistance, a recombinant inbred line population (F6:7) was developed from the cross Zhenongda 7/PI 643302. The population was phenotyped for resistance to FHB in two experiments in China and four experiments in North Dakota. Accumulation of the mycotoxin deoxynivalenol was determined in one experiment in China and two in North Dakota. Simplified composite interval mapping was performed on the whole genome level using the software MQTL. The QTL FHB-2 from PI 643302 for FHB resistance was found on the distal portion of chromosome 2HL in all six FHB screening environments. This QTL accounted for 14% of phenotypic variation over six environments and was not associated with heading date or plant height. The FHB resistance QTL FHB-2 detected near the end of chromosome 2HL is in a different location from those found previously and is therefore probably unique. Because the QTL was not contributed by the Chinese cultivar Zhenongda 7, it is likely a native QTL present in North American barley. The QTL FHB-2 represents the first reported QTL for native FHB resistance in North American germ plasm and has been given the provisional name Qrgz-2H-14. This QTL should be considered for pyramiding with other FHB QTL previously mapped.