Widespread Occurrence of Ergot in Upper Midwestern U.S. Barley, 2005.

Ergot, caused by Claviceps purpurea (Fr.) Tul., occurs every year on cereals and grasses in North Dakota, but the occurrence on barley (Hordeum vugare L) is generally sporadic with a very low incidence of sclerotia. Disease surveys conducted during the 2005 growing season revealed an unusually widespread occurrence. This is of concern since barley production in North Dakota was estimated at 1.25 million metric tons, 27% of the total 2005 U.S. production. Barley samples (n = 304, ~0.50 kg) collected in all crop-reporting districts of North Dakota, northwestern Minnesota, and northeastern Montana, as part of an annual regional survey of barley crop quality (4), were examined for sclerotia. All barley samples were cleaned for dockage, and ergot (% [w/w]) was estimated on subsamples of ~100 g from a sample divider. Of all barley samples collected, 62% contained ergots. The regional average for ergot infested kernels was 0.06%, and samples ranged from <0.01 to 1.19%. Approximately 15% of all samples were in excess of 0.10% ergots and would have been downgraded to ergoty barley under the Official United States Standards for Grain. Occurrence of ergot was most common in northwestern Minnesota and the three eastern and north-central districts of North Dakota. Ergot was less frequent in the south-central and three western districts of North Dakota and was not detected in samples from northeastern Montana. Floret infection occurs during and up to 15 days after anthesis (2), and in the three eastern and north-central districts of North Dakota that occurred around the last week in June and first week in July. Between 22 June and 4 July, the North Dakota Agricultural Weather Network Stations in that region recorded average daily temperatures of 99% of the 30-year norm, but multiple precipitation events amounted to 227% of the 30-year norm. Rain splash and associated high relative humidity favor conidiation and spread of the fungus (1) and may have contributed to the high disease incidence. Average sclerotia weight for a sample ranged from <10 to 70 mg. However, large sclerotia (37 to 180 mg) often were removed by the no. 6 riddle of the dockage tester and were not counted in the ergot estimates as per U.S. Grading Standards. Samples containing 1.19, 0.81, 0.22, 0.14, 0.05, and 0.02% ergots were analyzed for ergopeptine alkaloids (3). These were found to contain 27.9, 25.4, 2.4, 1.1, 1.7, and 5.7 µg/g ergopeptine alkaloids, respectively. The average ratio of ergosine/ergotamine/ergocornine/ergocryptine/ergocristine was approximately 1:2:2:3:9. There also was widespread occurrence of the Fusarium mycotoxin deoxynivalenol (DON) on North Dakota barley in 2005. While there was no apparent relationship between the level of the DON and the amount of ergot in the samples (r = 0.042), more than 90% of samples with ergot had detectable levels (0.1 to 69 µg/g) of DON. While only DON is routinely measured in the crop survey (4), other tricothecenes and zearalenone have also been detected. This should be of concern to livestock producers and grain processors since the potential interactions of multiple mycotoxins are not well known. References: (1) G. M. Marshall. Ann. Appl. Biol. 48:19, 1960. (2) S. B. Puranik and D. E. Mathre. Phytopathology 61:1075, 1971. (3) G. E. Rottinghaus et al. J. Vet. Diag. Invest. 5:242 1993. (4) P. B. Schwarz et al. J. Am. Soc. Brew. Chem. 64:1, 2006.

Identification of QTLs associated with Fusarium head blight resistance in Zhedar 2 barley.

Fusarium head blight (FHB) in barley and wheat, caused by Fusarium graminearum, is a continual problem worldwide. Primarily, FHB reduces yield and quality, and results in the production of the toxin deoxynivalenol (DON), which can affect food safety. Identification of QTLs for FHB severity, DON level and related traits heading-date (HD) and plant-height (HT) with consistent effects across a set of environments, would provide the basis for marker-assisted selection (MAS) and potentially increase the efficiency of selection for resistance. A segregating population of 75 double-haploid lines, developed from the three-way cross Zhedar 2/ND9712//Foster, was used for genome mapping and FHB severity evaluation. A linkage map of 214 RFLP, SSR and AFLP markers was constructed. Phenotypic data were collected in replicated field trials from five environments in two growing seasons. The data were analyzed using MQTL software to detect quantitative trait locus (QTL) x environment (E) interactions. Because of the presence of QTL x E, the MQM procedure in MAPQTL was applied to identify QTLs in single environments. We identified nine QTLs for FHB severity and five for low DON. Many of the disease-related QTLs identified were coincident with FHB QTLs identified in previous studies. Only two of the QTLs identified in this study were consistent across all five environments, and both were Zhedar 2 specific. Five of the FHB QTLs were associated with HD, and two were associated with HT. Regions that appear to be promising candidates for MAS and further genetic analysis include the two FHB QTLs on chromosome 2H and one on 6H, which were also associated with low DON and later heading-date in multiple environments. This study provides a starting point for manipulating Zhedar 2-derived resistance by MAS in barley to develop cultivars that will show effective resistance under disease pressure.

Fusarium Species Pathogenic to Barley and Their Associated Mycotoxins.

Epidemics of Fusarium head blight (FHB) occurred on barley in Minnesota, North Dakota, and South Dakota from 1993 to 1998. The Red River Valley region was most severely impacted by the disease based on assessments of FHB severity in grain samples harvested from commercial fields. Fusarium graminearum was the primary pathogen causing these FHB epidemics. It comprised from 62 to 64% of all Fusarium species isolated from infected kernels from 1994 to 1996. Fusarium poae (range of isolation 13 to 20%),F. sporotrichioides (10 to 17%), and F. avenaceum (6 to 10%) also were isolated from barley kernels and were likely involved in causing some FHB infection, but to a very limited extent. All four Fusarium species were pathogenic on barley in inoculation tests conducted in both the greenhouse and the field. Mycotoxin screens were performed on barley spikes inoculated with the respective species in the greenhouse. Spikes infected with F. graminearum contained deoxynivalenol and 15-acetyldeoxyni-valenol; those infected with F. sporotrichioides contained T-2 toxin, HT-2 toxin, and T-2 tetraol; and those infected with F. poae contained nivalenol. Some isolates of F. poae also produced 15-acetoxyscirpenol and scirpentriol. Although F. graminearum and DON are recognized as the primary FHB pathogen and mycotoxin, respectively, in barley, the possible presence of other Fusarium species and mycotoxins should not be overlooked.

The effect of grain storage conditions on the viability of Fusarium and deoxynivalenol production in infested malting barley.

A continuing outbreak of Fusarium head blight occurred on barley in the upper Midwest from 1993 to 1995. This resulted in barley with levels of the mycotoxin deoxynivalenol (DON) reaching levels of concern for maltsters and brewers. This study evaluated the effect of 7 months of storage under different conditions (ambient outdoor temperature from October to April), -20 degrees C, 4 degrees C, 24 degrees C with quiescent air, and 24 degrees C with forced air) on the viability of Fusarium and Alternaria infesting stored grain. Additionally, the ability of Fusarium to produce DON after storage and during malting was evaluated. Initial levels of infestation of barley by Fusarium and Alternaria were 85 and 75%, respectively. All storage condition reduced the viability of both molds slightly and significantly for Fusarium. Forced air ventilation at 24 degrees C was the type of storage most effective in reducing the viability of Fusarium, dropping the percentage of infected kernels to 66%. DON levels did not change after 7 months with respect to storage conditions. However, DON levels were lower in malt produced from barley stored at 24 degrees C with or without aeration. On-farm storage of infected barley at elevated temperatures may provide a means to reduce the level of DON in finished malts.