Sorghum ergot, caused by Claviceps africana Frederickson, Mantle & de Milliano, is a disease that affects non-fertilized ovaries in sorghum male-sterile plants and infects hybrids if there is pollen sterility at flowering time. Sphacelia containing macroconidia could play a role in the survival of the pathogen. This study developed risk assessment models and evaluated environmental conditions affecting viability of macroconidia and transition from sphacelial to sclerotial tissues. Effect of weather on ergot severity was evaluated under natural conditions (in monthly planting dates) in nine sorghum genotypes at College Station, Weslaco, Rio Bravo, and Celaya. Panicles were inoculated daily beginning at flower initiation with a suspension of 1.6 x 106 C. africana conidia ml-1. Weather triad values were used to identify weather parameters correlated with the disease. Ergot severity was statistically greater in A-lines than hybrids because of the possible interference of pollen on some dates. Celaya had the greatest amount of ergot in hybrids. A-line ATx2752 had the lowest average ergot severity throughout years, locations and planting dates, as did the hybrid NC+8R18. Maximum and minimum temperature had a negative correlation with ergot at Rio Bravo, College Station and Weslaco, while at Celaya it was positive. The highest correlation was 7 to 9 days before initiation of flowering, suggesting that cooler temperatures during this period could cause male sterility. A-lines showed the same relationships between ergot and maximum and minimum temperatures after initiation of flowering. Minimum relative humidity had a positive correlation with ergot after initiation of flowering in both sorghum plant types. Sphacelia stored under cool temperatures (-3oC to 7oC) maintained conidial viability, and newly-formed sphacelia located on the sphacelia surface had the highest conidial viability. However, they show a greater viability reduction through time compared with conidia from older sphacelia, showing that conidial maturity can play a role in the survival of the conidia. Sphacelia on plants grown at 10oC, 20oC and 30oC with low relative humidity did not had any sclerotial development up to 4 weeks after formation of sphacelia. However, higher temperatures promoted an increase in the sphacelia dry weight during that time.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 62 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical reference.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Neotyphodium species, endophytic fungi associated with cool-season grasses, enhance host fitness and stress tolerance, but also produce biologically active alkaloids including ergot alkaloids associated with fescue toxicosis in grazing animals. One approach to reduce fescue toxicosis is to manipulate genes in the ergot alkaloid pathway. The gene, dmaW, encoding the first pathway-specific step in ergot alkaloid biosynthesis, was cloned previously from Claviceps spp. and its function was demonstrated by expression in yeast. Putative homologs have been cloned from Neotyphodium coenophialum (from tall fescue) and Neotyphodium sp. Lp1 (from perennial ryegrass). In order to confirm the function of dmaW in ergot alkaloid production, dmaW in Neotyphodium sp. isolate Lp1 was knocked out by gene replacement. The dmaW knockout mutant produced no detectable ergovaline or simpler ergot alkaloids. Complementation with Claviceps fusiformis dmaW restored ergovaline production. These results confirmed that the cloned endophyte gene was dmaW, and represented the first genetic experiments to show the requirement of dmaW for ergot alkaloid biosynthesis. Neotyphodium coenophialum, endophyte of the grass tall fescue (Lolium arundinaceum) has two homologs of dmaW. Considering the possible field applications in future, the Cre/lox site-specific recombination system was chosen because of the potential to sequentially knock out both homologs and obtain marker-free dmaW mutants of N. coenophialum. One homolog, dmaW-2, was disrupted by marker exchange, and the marker was eliminated by Cre, thus demonstrating the application of Cre/lox system in N. coenophialum to eliminate a marker gene. The dmaW-2 knockout did not eliminate ergovaline production, indicating that the dmaW-1 was probably also active in N. coenophialum. A putative ergot alkaloid biosynthesis gene cluster was identified in Claviceps purpurea and C. fusiformis. C. purpurea and C. fusiformis produce different subsets of ergot alkaloids. Identification of nine common genes between them suggests the possible role of these genes in the early part of the ergot alkaloid biosynthetic pathway.

The pyrrolizidine alkaloids (PAs) and ergot alkaloids are known natural toxicants found in livestock forage. These alkaloids contribute to large economic losses in livestock throughout the world. An understanding of the mechanisms of toxicity and development of better diagnostic tools for better management practices was investigated. Variability exists in the toxicity of PAs in ruminants where cattle are more susceptible and sheep are more resistant. The mechanism of PA resistance in sheep has been attributed to hepatic metabolism or rumen microbial degradation of PAs to non-toxic moieties. The hepatic metabolism of the PA senecionine was investigated in cattle and sheep liver microsomes. The level of a toxic pyrrole metabolite 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine pyrrole (DHP) formed in cattle and sheep were similar. However, the level of a non-toxic N-oxide metabolite was greater in sheep than in cattle. Cytochrome P450 and flavin monooxygenases (FMOs) responsible for PA oxidative metabolism were similar in both ruminant species. Therefore, hepatic metabolism of PAs is not solely responsible for resistance observed in sheep versus cattle. Ergot alkaloids present in endophyte-infected plants also cause toxicity in livestock. HPLC is the typical method used to quantify ergot alkaloid content; however, it is costly and time-consuming. An enzyme-linked immunosorbent assay (ELISA) developed with lysergol as the hapten was evaluated to ascertain its feasibility as an analytical tool for the ergot alkaloids found in forage plants. The ELISA detected the presence of lysergic acid but was not a reliable assay for the ergopeptine alkaloids such as ergovaline. The genetic divergence in mice previously selected into ergot alkaloid susceptible and resistant lines was studied after ten generations of relaxed selection. Physiologically no difference was seen between the susceptible and resistant line for average daily weight gain. However, hepatic metabolism of the ergot alkaloid ergotamine showed differences between genders and between animals on diets containing no ergot alkaloids or a high concentration of ergot alkaloids. Four major biotransformation products were identified as hydroxylated ergotamine isomers based on mass spectroscopic analysis. / Graduation date: 2003

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 59 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 52-64). Also available on the World Wide Web.

Ergot, caused by the fungal pathogen Claviceps purpurea (Fr.) Tul., attacks the floral organs of many grassy species resulting in sclerotia production rather than grain. Infection causes reduced yields, downgrading, and poisoning if consumed by humans or animals. Few recent studies have been conducted on ergot in wheat (Triticum spp.), and prevention is the only means of control. The objectives of this study were to determine if western Canadian spring wheat differed in reaction to infection with C. purpurea and if levels of inoculum would affect disease intensity in a field setting. Three variables were measured for the field experiments to determine disease reaction, including percent sclerotia by weight, number of sclerotia per spike, and weight per sclerotium. In the first experiment, nine wheat cultivars were tested using three inoculum levels. No significant differences were detected among inoculum levels. In the second and third experiments, ninety-two cultivars were studied in field and controlled conditions. Honeydew production, sclerotial size, and the percent of florets aborted were added as variables in the growth chamber experiment. Pearson correlations were calculated using cultivar means for the field and controlled environments. Results indicate that there are differences in disease reaction among cultivars and market classes, but these differences varied depending on the evaluation method used. In the field, CWAD wheat had the smallest sclerotia, but had more per spike compared to the CWRS and CWES market classes. There were no significant differences among these market classes for percent sclerotia by weight. In the growth chamber, CWAD wheat generally had the lowest ergot infection levels. When comparing the market classes within T. aestivum (CWRS, CPS, and CWES), there were no significant differences except for honeydew production. The correlation between environments was not significant for any of the variables, suggesting alternate resistance mechanism expression. In the field, reduced infection may be due to an escape mechanism, while artificial inoculation in a controlled environment may detect a physiological resistance mechanism. However, a group of cultivars with Grandin parentage showed promising results in both environments, and might confer resistance that could be integrated into disease resistance breeding programs.

Endophyte-infected tall fescue produces many ergot alkaloids, which have been shown to be vasoconstrictive in various vessel types of bovine. On the other hand, substantial evidence has been reported on the vasodilative effects of formononetin and biochanin A in different vessel types in humans and rats. So, a study was conducted using mesenteric vasculature collected from heifers shortly after slaughter. After 2-h incubation with formononetin (F), biochanin A (B), or an ergovaline-containing tall fescue seed extract (EXT) and their combinations, vessels were mounted in a multi-myograph to determine their ergotamine-induced contractility. Results indicated that F and B at 1 × 10-6 M and their combination did not impact the contractile response to ergotamine in mesenteric vasculature. The pre-myograph incubation of mesenteric vasculature with EXT altered the contractile response manner to ergotamine. However, at higher concentration, F and B may alleviate the reduction of vasoconstriction caused by prior exposure to EXT. To our knowledge, this study was the first to investigate the interaction of ergot alkaloids and isoflavones on in vitro bovine mesenteric vasculature. However, further investigations are necessary to understand the mechanism behind the interaction of ergot alkaloids and isoflavones on vasoactivity.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 73-86). Also available on the World Wide Web.