Evidence is presented that ergot alkaloids are ubiquitous in tall fescue pastures infected with the clavicipitaceous fungal endophyte Sphacelia typhina (or Acremonium coenophialum). Ergopeptide alkaloids, predominantly ergovaline, constituted 10 to 50 percent of the total ergot alkaloid concentration, which was as high as 14 milligrams per kilogram in sheaths and 1.5 milligrams per kilogram in blades. Ergot alkaloid concentrations were substantially increased by application of large amounts (10 millimoles per liter) of potassium nitrate or ammonium chloride to infected plants in the greenhouse. The results indicate that ergot alkaloids are probably responsible for the toxicity to cattle of this common pasture and lawn grass and that ergotism-like toxicoses may be caused by clavicipitaceous fungi other than Claviceps.

Infection of the sorghum mesocotyl by Helminthosporium maydis (a nonpathogen) and Colletotrichum graminicola (a pathogen) resulted in the rapid accumulation of a pigment complex by two sorghum cultivars. The components of the complex were fungitoxic. The principal compounds have been identified as the 3-deoxyanthocyanidins apigeninidin and luteolinidin. Apigeninidin accumulated in both sorghum cultivars in response to infection and was the predominant pigment. Luteolinidin accumulated in only one of the cultivars. Because of the speed of synthesis, occurrence only in response to inoculation, and fungitoxicity of the individual components, we propose that synthesis of the pigment complex constitutes a defense response and that the compounds apigeninidin and luteolinidin should be considered as phytoalexins.With the exception of the momilactones from rice (1, 2) and the avenalumins from oat (3, 4), phytoalexins have not been identified in members of the Gramineae. In grain sorghum and other sorghum species the cyanogenic glycoside dhurrin is a potential microbial toxicant but is best considered an insect feeding deterrent and phytotoxin rather than a stress metabolite (5-7). Dhurrin, present in relatively high concentration in uninfected tissue, does not increase following microbial infection (8, 9) and the dhurrin content of tissue decreases with maturation (10).The situation in sorghum is further complicated by the fact that seedling leaves exhibit few if any symptoms when inoculated with various fungi. Probably the most pronounced example of this phenomenon is foliar anthracnose caused by Colletotrichum graminicola. In this disease both resistant and susceptible cultivars are resistant in the seedling stage and plants must be about 5 weeks old before they will exhibit symptoms in response to inoculation (11). Such observations have led to the assumption that seedling resistance is the result of the presence of dhurrin (11). However, Fry and coworkers (8,9,12,13) have demonstrated that fungal pathogens of cyanogenic plants produce formamide hydrolyase, which detoxifies hydrogen cyanide, the toxic breakdown product of dhurrin, by converting it to formamide. Therefore, that dhurrin has a role in seedling resistance, either to pathogens or to nonpathogens, is not yet clear.The purpose of this investigation was to evaluate whether resistance in sorghum is associated with the accumulation of previously undetected toxic host metabolites. We describe the rapid accumulation of phytoalexins in the sorghum mesocotyl as a response to attempted infection by a speciespathogenic and a species-nonpathogenic fungus. MATERIALS AND METHODSPathogens, Plant Material, and Inoculation. The fungi Helminthosporium maydis Nisik. and Miy., race 0, and Colletotrichum graminicola (Ces.) Wils. were grown and spore suspensions were prepared for inoculum as described (14,15). Inoculum concentrations were 5 x i04 spores per ml for H. maydis and 106 spores per ml for C. graminicola.Tween 20 was used as a wetting agent (100 tkl per 100 ...

Infection by the fungal endophyte Acremonium coenophialum affected the accumulation of inorganic and organic N in leaf blades and leaf sheaths of KY 31 tall fescue (Festuca arundinacea Schreb.) grown under greenhouse conditions. Total soluble amino acid concentrations were increased in either the blade or sheath of the leaf from infected plants. A number of amino acids were significantly increased in the sheath, but only asparagine increased in the blade. Infection resulted in higher sheath NH4+ concentrations, whereas N03-concentrations decreased in both leaf parts. The effects on amino acid, N03-, and NH4+ concentrations were dependent upon the level of N fertilization and were usually apparent only at the high rate (10 millimolar) of applica- feeding (2,4,5,11,21). Many effects similar to those in endophyte-infected tall fescue have also been demonstrated in other endophyte-infected species of fescue and in perennial ryegrass (Lolium perenne L.) ( 14, 21).The underlying physiological basis for the various effects on tall fescue which result from this endophyte infection, and the extent to which the grass and fungus are responsible, are largely unknown. Two lines of evidence suggest that at least N metabolism is one aspect that may be affected. The first is from greenhouse studies which show that high rates of N fertilization increased the concentrations of one class of endophyte-synthesized N bases, ergot alkaloids, in endophyteinfected tall fescue (16). Second, other classes of nitrogenous metabolites that are insect feeding deterrents are associated with endophyte infection. Furthermore, the expression of cattle toxicoses has been quantitatively related to rates of N fertilization (3,7,21). Thus, in tall fescue, both fungal and host N metabolism may be contributing factors to various characteristics which are peculiar to the infected plant.Because of the possible involvement of N metabolism in these important aspects of the tall fescue-endophyte association, comparative studies were made of infected and uninfected plants under greenhouse conditions to determine whether N metabolism is affected by the endophyte. Aspects considered in this study included the accumulation of inorganic and organic nitrogenous compounds, the activities of major enzymes of N assimilation, and the metabolism of amino acids. A

Clarifying the role of grasses parasitized by a tribe of clavicipitaceous endophytes (Balansiae) in the etiology of the many cattle (Bos taurus) ergot toxicity syndromes is essential for identifying the correct toxic grass and establishing the proper pasture management practice necessary to eliminate toxicity. The distinction is required as the management practice used to prevent ergot toxicity by Clavicepsdoes not apply because of the systemic habit of the Balansiae. Research is reviewed, which established that endophytic parasites of many genera of warm‐season perennial weed grasses and tall fescue (Festuca arundinaceaSchreb.) are producers of toxic ergot alkaloids. This group of fungi is distinct from the closely related genus Clavicepsin being an intercellular parasite of leaf tissue. These fungi are parastic on nine tribes of grasses that have a wide geographic distribution in the western hemisphere. Nine ergot alkaloids belonging to the clavine group have been isolated from four species of Balansiacultured in laboratory media, and several of these have been isolated from parasitized grasses. Ergot alkaloid production by the remaining nine species of Balansiahas not been examined. The endophyte of tall fescue produced both the clavine and ergotamine peptide groups of alkaloids in culture and in the grass. The production of ergot alkaloids by weed grass endophytes is host‐related; therefore, each parasitized weed grass must be assessed for alkaloid production. All isolates of B. epichloe(Weese) Diehl from smutgrass (Sporobolus poiretiiRoem. and Schult.) and 54% of the isolates of B. henningsiana(Moell.) Diehl from broomsedge (Andropogon virginicusL.) produced the following alkaloids in culture: chanoclavine, ergonovine, ergonovinine, and agroclavine. Isolates of these two fungi from other grass genera did not produce alkaloids. While no extensive survey has been done to date, all infected tall fescue examined contains ergot alkaloids. The main peptide alkaloid produced by the tall fescue endophyte is ergovaline. The effects of this peptide alkaloid on cattle have not been determined. However, the total alkaloids produced in culture by B. epichloereduced the serum prolactin levels in cattle and along with prior published accounts on the physiological effects of the clavine and peptide ergot alkaloids, established that these alkaloids can cause toxicity symptoms in cattle consuming infected plant material. Thus, pasture management practices must include procedures that will prevent the growth of grasses that serve as host for endophytic fungi.

A procedure is described for the quantitative extraction and HPLC analysis of cyclic hydroxamic acids and related compounds including 2-(2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one) 0-Dglucopyranoside (DIMBOA-glc) and the demethoxy analogue DIBOA-glc; their respective aglycons, DIMBOA and DIBOA; and their respective 2(3H)-benzoxazolinone derivatives, MBOA and BOA. The six compounds were separated within 15 min on a C18 reversed-phase column using a linear gradient of acetic acid and methanol. The minimum detection limit for DIMBOA-glc and DIMBOA was 0.20 nmol. DIMBOA-glc concentrations, which ranged from 8 to 2600 pg/g fresh weight, were measured by this procedure in methanolic extracts of corn leaves and seedlings on samples of 0.05-0.10 g; DIBOA-glc was also detected in many of the samples. DIMBOA, DIBOA, MBOA, and BOA were detected in aqueous extracts of corn samples after hydrolysis of the glucosides by endogenous 0-glucosidases.

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