Ergot Infection Research Articles

Use of optical density as a measure ofClaviceps africanaconidial suspension concentration

Sorghum ergot, caused by Claviceps africana, has remained a major disease problem in Australia since it was first recorded in 1996, and is the focus of a range of biological and integrated management research. Artificial inoculation using conidial suspensions is an important tool in this research. Ergot infection is greatly influenced by environmental factors, so it is important to reduce controllable sources of variation such as inoculum concentration. The use of optical density was tested as a method of quantifying conidial suspensions of C. africana, as an alternative to haemocytometer counts. This method was found to be accurate and time efficient, with possible applications in other disease systems.

Ovary colonization by Claviceps africana is related to ergot resistance in male‐sterile sorghum lines

Ergot, caused by Claviceps africana, has emerged as a serious threat to sorghum hybrid seed production worldwide. In the absence of gene‐for‐gene‐based qualitative resistance in commercial cultivars, varieties with high pollen production that can escape ergot infection are preferred. Recent demonstration of differences in ergot susceptibility among male‐sterile lines has indicated the presence of partial resistance. Using chitin‐specific fluorescin‐isothiocyanate‐conjugated wheat germ agglutin and callose‐specific aniline blue, this study investigated the process of sorghum ovary colonization by C. africana. Conidia germinated within 24 h after inoculation (a.i.); the pathogen was established in the ovary by 79 h a.i., and at least half of the ovary was converted into sphacelial tissue by 120 h a.i. Changes in fungal cell wall chitin content and strategic callose deposition in the host tissue were associated with penetration and invasion of the ovary. The rate of ovary colonization differed in three male‐sterile lines that also differed in ergot susceptibility. This work demonstrates a possible histological basis for partial resistance in male‐sterile sorghum lines that could lay the foundation for variety improvement through further breeding and selection.

The Witch Trials of Finnmark, Northern Norway, during the 17th Century: Evidence for Ergotism as a Contributing Factor

During the 17th century, Finnmark suffered the worst witch trials on record in Norway; at least 137 persons were tried, and about two-thirds were executed. A late 17th century manuscript by district govenor H. H. Lilienskiold provides details of 83 trials based on contemporaneous sources. More than half of these provide evidence of a potentially important role of ergotism in triggering persecutions. In 42 trials, it is explicitly stated that witchcraft was “learned” by consuming it, usually in the form of bread or other flour products (17 cases), in milk or beer (23 cases), or a combination (two cases). In the cases involving milk, several witches testifed that some kind of black, grain-like objects were found in the drink. Medical symptoms compatible with ergotism were recorded in numerous trials, including gangrene, convulsions, and hallucinations; the latter often explicitly stated to occur after consumption of foodstuffs or drink. The majority of the convicted witches were females of Norwegian ethnic origin, living in coastal communities where imported flour formed part of the diet. The few, largely self-supporting Sami affected by the witchcraft trials were mainly men, convicted, for example, carrying out traditional shamanic rituals. All flour available in Finnmark during the late 17th century was imported. Rye (Secale cereale), which is especially prone to ergot infection, formed a major part of the imported grain.

Transmission of Claviceps africana Spores from Diseased to Non-Infected Sorghum by Corn Earworm Moths, Helicoverpa zea

ABSTRACT The potential of corn earworm moths Helicoverpa zea, an important pest of sorghum in Texas, as a passive vector of sorghum ergot, Claviceps africana was assessed. Laboratory-reared (females and males) and field-moths trapped in sex pheromone traps were confined in screen cages with potted male-sterile sorghum line AT×623 that had been artificially infected with sorghum ergot and was producing massive amounts of honeydew that contained spores of the fungus. In the cages, moths were observed feeding on the honeydew. When laboratory-reared moths contaminated with C. africana spores were released for 12 or 48 h in cages containing healthy greenhouse- or field-grown male-sterile sorghum plants at anthesis, the levels of ergot severities on the panicles ranged from 0.5–90%, per panicle. The levels of ergot infection on greenhouse- and field-grown AT×623 exposed to ergot contaminated field-trapped males for 48 h ranged from 0–81.7%. Mean external contamination of laboratory-reared and field-trapped moths placed in a soapy wash was 1.4 × 105 and 4.7 ×104 conidia/ml, respectively. This study demonstrated that contaminated adult corn earworm could transmit the sorghum ergot from diseased to healthy panicles when environmental conditions are favorable for infection. Thus, migrating moths and other highly mobile pest species have the potential to transport C. africana over relatively large distances.

Analysis of Combining Ability for Ergot Resistance in Grain Sorghum

ABSTRACTErgot caused by Claviceps africana Frederickson, Mantle & de Milliano has become an important constraint to F1 hybrid seed production in North and South America. Identification and utilization of sources of host‐plant resistance would contribute to the effective control of this disease. A Design II mating scheme was used to test the combining ability of four reported sources of ergot resistance in sorghum [Sorghum bicolor (L) Moench]—IS8525, IS14131, IS14257, and IS14357. Male‐sterile hybrids of these accessions and a susceptible check, TxARG1, were produced using five cytoplasmic‐genetic male‐sterile seed parents—A3Tx430, A3Tx436, A3Tx7000, A3KS70, and A3Tx2737. Parent lines and hybrids were planted in three replications at three locations and were evaluated for ergot resistance following artificial inoculation at flowering. Differences in ergot severity and ergot breakdown point (EBP) were used to quantify differences in resistance. The combined analysis of variance showed that the expression of ergot resistance was not stable with significant entry × location interaction. The analyses from two locations showed significant differences among hybrids, while the third location showed no differences. Regression analyses were performed to determine the relationship between weather variables at flowering and observed ergot severity. These analyses indicated a strong relationship between maximum daily temperature and ergot severity. Ergot infection was higher in cooler environments regardless of genetic background. IS8525 appeared to have the highest expression of ergot resistance in male‐sterile genetic backgrounds on the basis of EBP and ergot severity ratings; however, the expression of resistance was only effective within a limited temperature range.

AC Remington winter rye

AC Remington, a cultivar of winter rye (Secale cereale L.), was developed at the Semiarid Prairie Agricultural Research Centre, Research Branch, Agriculture and Agri-Food Canada, Swift Current, Saskatchewan. AC Remington is a semidwarf with 20 to 25% shorter straw and improved lodging resistance compared with tall cultivars. AC Remington has good winter survival and is well adapted to the Canadian Prairies. AC Remington has improved grain yield, test weight, kernel weight and Hagberg Falling Number compared with those of the semidwarf cultivar AC Rifle. Plant height, heading, maturity and ergot infection of AC Remington are similar to those of AC Rifle. Key words: Cultivar description, semidwarf, rye (winter), Hagberg Falling Number, Secale cereale L.

On the relation between weather variables and sorghum ergot infection

Sorghum ergot (Claviceps africana) has had a significant impact on seed production and breeders’ nurseries in Australia since it was first found in 1996. In this paper, 3 distinct key development stages of sorghum that are related to ergot infection were identified: flag leaf stage, pollen starch accumulation stage, and flowering period. Relationships between weather variables during these 3 stages and ergot severity as well as pollen viability were analysed using observed data from 2 field trials, a serial planting trial and a genotype trial, conducted at Gatton, Queensland. The duration of the flag leaf stage and of the flowering period was estimated from thermal time. An infection factor was introduced and calculated based on hourly temperature during the flowering period. This infection factor and the mean relative humidity at 0900 hours during the flowering period were the main factors influencing ergot infection. Mean daily minimum temperature during flag leaf stage also had a significant effect on ergot severity, although no significant relation was found between this mean daily minimum temperature and pollen viability. A linear regression model using the above 3 factors accounted for 94% of the environmentally caused variation in ergot severity observed in the genotype trial.

The long‐term epidemic of Claviceps purpurea on Spartina anglica in Poole Harbour: pattern of infection, effects on seed production and the role of Fusarium heterosporum

An epidemic of the ergot fungus (Claviceps purpurea (Fr.) Tul), a non‐systemic floral pathogen, appeared in populations of Spartina anglica C. E. Hubb in Poole Harbour in the 1980s. Over 70% of inflorescences were infected between 1985 and 1995. Between 1983 and 1995, there was no consistent pattern in the rank order of sites with respect to the proportion of inflorescences infected, and variation in the amount of infection was not related to inflorescence density. Among years, there was significant variation in the total biomass of ergot per inflorescence, but no significant difference in the number of ergots per inflorescence. Log–log regressions of total weight of ergot per inflorescence against the number of ergots per inflorescence showed that in all years resources for each additional ergot were limited.There was no statistically significant difference between the number of seed set on infected and uninfected inflorescences in 1985 or 1995. Further analysis showed that, compared with uninfected inflorescences, there was higher seed output from inflorescences with fewer than 10% of spikelets infected, which balanced reduced seed output from heavily infected inflorescences. At high levels of ergot infection, a lower proportion of uninfected spikelets set seed, compared with spikelets on uninfected inflorescences. This suggests that conditions which favour ergot growth are detrimental to seed production. Compared with uninfected inflorescences, mean and total seed weights were significantly lower in inflorescences with >10% of spikelets infected.The fungus Fusarium heterosporum Nees ex Fr. was found in association with the ergots on Spartina. There was a significant positive correlation between the average severity of Fusarium infection and the number of ergots on an inflorescence. There was a non‐significant negative correlation between severity of Fusarium and mean ergot weight, when ergot number per inflorescence was held constant. These data suggest that any negative effect of Fusarium on Claviceps is small.The high, and temporally and spatially uniform levels of ergot infection probably result from genetic uniformity of Spartina and the lack of zonation in the salt marshes of Poole Harbour. This situation is likely to persist for the foreseeable future.

Ergot resistance in sorghum in relation to flowering, inoculation technique and disease development

Ergot is an important disease of sorghum (Sorghum bicolor) in parts of Africa and Asia. Studies were conducted to determine the relationship between flowering biology and ergot infection, and to develop an artificial field‐screening technique to identify ergot resistance in sorghum. Spikelets resisted infection after anthesis, but each day's delay in anthesis after inoculation supported 8‐3% more ergot. The screening technique consisted of three components: trimming of panicles to remove pollinated spikelets before inoculation, a single inoculation of trimmed panicles, and panicle bagging for 7‐10 days. Inoculated panicles were evaluated by a qualitative visual rating method (on a 1‐5 scale) and a quantitative spikelet counting method. Selected accessions from the world collection of sorghum germplasm were screened at Karama Research Station, Rwanda, for two seasons and 12 ergot‐resistant lines were identified. These were also resistant at ICRISAT Centre, India.

Susceptibility to ergot in Zimbabwe of sorghums that remained uninfected in their native climates in Ethiopia and Rwanda

Forty‐four local Ethiopian and Rwandan sorghums (Sorghum bicolor) were observed to remain free of ergot, or had only low incidence, in their natural equatorial latitudes and were potentially of interest, in the design of male‐sterile lines for F1 hybrid breeding, if they possessed a physiologically based resistance mechanism. These sorghums were therefore also investigated under natural and artificial disease pressures in Zimbabwe where unadapted development and inappropriate long daylength prevented flowering in 18 accessions. Of the remaining 16 Ethiopian and 10 Rwandan accessions which flowered, only one from each country remained free of ergot. The susceptibility expressed was ascribed to observed asynchrony of stigma exsertion with anthesis. In the Rwandan accession that persistently remained free of ergot in Zimbabwe, histology of ovules showed pollination before floret gaping, so that a general principle of disease escape due to efficient pollination is proposed for the Ethiopian and Rwandan sorghums in their native climates. The findings emphasize that cleistogamy is a desirable character for avoiding ergot infection in self‐fertile sorghums and suggest that the Ethiopian and Rwandan sorghums may not generally be useful for breeding ergot‐resistant male‐sterile female lines. However, a few accessions deserve more detailed study as a potential genetic resource, before a firm conclusion that all apparent resistance is disease escape owing to efficient pollination.

Influence of Temperature and Wetness Duration on Infection of Pearl Millet byClaviceps fusiformis

The influence of temperature and wetness duration on infection of susceptible, moderately resistant, and resistant genotypes of pearl millet by Claviceps fusiformis was studied. In greenhouse and field experiments, panicles of pearl millet inoculated with C. fusiformis were subjected to various regimes of temperature (14–35 C) and wetness (95% relative humidity) duration (0–64 h) for a 15-day period. These environmental conditions influenced the level of ergot severity, but the relative ergot reactions of the genotypes were not changed. In susceptible genotypes, temperatures in the range of 14–35 C, with 8 h/day at less than 20 C and 4.6 h/day at greater than 30 C, were more favorable to ergot infection (70–72% severity; 32–49% sclerotial formation) than a temperature range of 21–35 C, with 6.4 h/day at greater than 30 C (53% severity; 23% sclerotial formation). Results indicated that the minimum temperature is more critical for ergot infection than the maximum temperature. In both greenhouse and field experiments, panicle wetness duration of 16–24 h favored ergot infection. In controlled environment experiments, temperature and the interaction of temperature and wetness duration were significant for latent period (P = 0.001). Wetness duration and the interaction of temperature and wetness duration were significant for ergot severity (P = 0.05). Maximum ergot severity (60.5%) and minimum latent period (117 h) were obtained at a 30 C day/25 C night temperature regimes with 24–96 h of panicle wetness.

The path of infection of sorghum by Claviceps sorghi

Claviceps sorghi conidia germinated on exserted stigmas of male sterile sorghum within 1–2 days of inoculation in conditions of high humidity and mean diurnal temperature fluctuations generally in the range 15–30 °C. Hyphae grew through pollen transmission tracts in the style, entering the ovary wall within 3 days. Stigmas did not show any gross response to infection, and susceptibility persisted for several days after floral gaping, though infection was most readily achieved by inoculating gaping florets. Direct infection via the ovary wall can occur but is probably not a significant means of pathogenesis under natural conditions. Six days after inoculation, hyphae of the pathogen were erupting from the lower aspect of the outer ovary wall and also invading the ovule through the chalazal region. Honeydew, containing large numbers of conidia, exuded from infected florets 8–10 days after inoculation. Infected florets eventually produced typical sclerotia of C. sorghi. Detailed definition of the initial path of ergot infection facilitates discussion of possible mechanisms for ergot disease resistance in sorghum with respect to the pathogen indigenous to India.

Relationship between meteorological factors and the occurrence of ergot disease (Claviceps microcephala)of Pearl Millet

Abstract Using four meteorological factors, i.e., atmospheric temperature, relative humidity, sunshine and rainfall, an attempt was made to determine, by a curvilinear regression method, the optimum values for ergot disease (Claviceps microcephala (Wallr.) Tul.) of pearl millet. The optimum values for initiation and spread of the disease were found to be 12 mm mean rainfall, 6 h/day mean sunshine, 75% mean relative humidity and 20°C mean atmospheric temperature from protogyny to early flowering of pearl millet. To quantify the relative importance of these meteorological factors, the coefficient of determination was calculated and this showed that atmospheric temperature contributed 45%, relative humidity 35%, sunshine 10% and rainfall 5% towards the total variation of the ergot infection index.

Control of ergot in pearl millet through pollen management*

SUMMARYFour pearl millet F, hybrids, ICH‐118, ICH‐220, BJ‐104, and ICH‐206, which are highly susceptible to ergot, were grown one/season in isolation plots and in a demonstration plot during the four rainy seasons of 1978‐81, respectively, alone and mixed with an early flowering variety SC‐2(M)5‐4, which is less susceptible to ergot (less than 10% severity) to test the hypothesis that increased pollen availability at the early stages of flowering in hybrids protects the hybrids from ergot infection. In 1978, the hybrid was grown with the pollen donor in a seed mixture (4 parts hybrid and 1 part pollen donor) and in other years one row of the pollen donor was planted between two, four, or eight rows of the hybrid. Ergot inoculations were made 3–4 times at protogyny flowering stage of the hybrids. Significant reductions in ergot infection and considerable increase in grain yields occurred in the hybrids when grown with the pollen donor line. The possible application of this control measure in farmers' fields is discussed.

Pollination Effects on Pearl Millet Ergot

Pollination of inflorescences of 3 male-sterile lines of Pennisetum americanum before, or at the same time as, inoculation with Claviceps fusiformis conidia reduced ergot to <3% of infected florets. Pollination 16 h after inoculation reduced ergot to 7-21% compared with 60-86% for inoculated, nonpollinated checks. Pollen germinated in 1 h when incubated in a 10% sucrose sol. whereas conidia did not germinate in <16 h of incubation. Results from inoculation of inflorescences of male-sterile lines at different stages of flowering in the absence of pollen, and observations on the effects of pollination on stigma morphology and longevity, lead to the conclusion that infection occurs mainly through the stigmas. Pollination protects against infection probably because it induces rapid withering of stigmas. The results help explain the increased ergot susceptibility of pearl millet F1 hybrids compared with traditional cvs., and have important implications for resistance screening and for the development of cultural control measures.ADDITIONAL ABSTRACT:Pollination of three male-sterile lines of Pennisetum americanum before or at the same time as inoculation with Claviceps fusiformis greatly reduced ergot infection and pollination 16 h after inoculation also reduced infection. Heaviest infection followed the inoculation of unpollinated inflorescences at the stage when most stigmas were receptive. It is suggested that pollination protects against infection by inducing rapid withering of the stigmas, and that the observed susceptibility of F1 hybrids, compared with traditional varieties, is caused by delayed pollination. It is emphasized that plants being screened for ergot resistance should not become pollinated before inoculation and it is suggested that ergot control in F1 hybrids may be improved by selecting for reduced protogyny or by growing an early-flowering variety with hybrid crops

Role of weed grasses in the etiology of ergot disease in wheat

SUMMARYForty isolates of the ergot fungus Claviceps purpurea collected from nineteen gramineous host species were used to inoculate male‐sterile wheat. The isolates segregated into highly and weakly infective groups. The marked pathogenicity, on wheat, of the fungal strains occurring on certain grass species has been correlated with distinctive patterns of alkaloids within the sclerotia.Analysis of the alkaloid content of 241 samples of naturally occurring ergot sclerotia from twenty gramineous host species has confirmed the existence of host restricted strains characterized also by their particular spectra of alkaloids.Similarity of the alkaloid spectra of ergot sclerotia from blackgrass (Alopecurus myosuroides) and wheat, ease of cross‐infection from blackgrass to wheat and an association between blackgrass infestation and the occurrence of ergot sclerotia in surveyed wheat crops have confirmed the hypothesis that the presence of this early flowering weed grass increases the risk of high levels of ergot infection in wheat.

CROSS-POLLINATION IN MALE STERILE WHEAT IN ONTARIO

Seed set on male sterile lines of soft winter wheat in Ontario seeded in a ratio of 2:1 and 1:1 of female to male rows, respectively, averaged 47.2 and 54.7% over a 2-year period. Increased seed set was obtained by either manipulation of planting date to improve coincidence of flowering of the male and female lines or by using a muitilineal pollinator rather than a single variety pollinator. Seed set on male sterile lines declined sharply with increasing distance from the pollen source. The mean seed set in six male sterile lines with a pollen source on the west side 0.2, 1.5, and 3.0 m away was 28.8, 10.3, and 6.7%, respectively. Severe ergot infection indicated a potential disease problem in Ontario.

Studies on parasitic cultivation of ergot [Claviceps purpurea (Fr.) Tul.] in India

Experiments were undertaken to standardise the techniques involved in large-scale cultivation of ergot [Claviceps purpurea (Fr.) Tul.]. It was found that the rye crop planted from the last week of September up-to the middle of October to be more suitable for obtaining a good yield of ergot. The spore suspension of the ergot fungus raised on wheat or rye grain medium retained its infective ability even after storing for about 3 days at room temperature (20±2° C.) and for about 5 days when stored under refrigerated conditions (5°C.). Among the four synthetic liquid media tested the medium described by Amiciet al. (1967) proved to be more suitable for raising the ergot inoculum on a large scale and it also retained its infectivity even after diluting twenty times of its volume. Rye plots, if inoculated two times by the needle board puncture method with the inoculum containing about 41,000 spores/mm.3 was found to be sufficient to yield maximum quantity of ergot sclerotia. The yield of the ergot sclerotia obtained from the plots inoculated by the needle board puncture method was found to be almost two times the yield obtained from those plots which were inoculated by spray method. Variation in alkaloid content has been observed in the ergot sclerotia obtained from the same strain and also within the same sclerotium. Experiments carried out on the probability of contamination of the ergot infection to the other cereal crops indicated that there are very little chances of ergot infection spreading to the other cereal crops and also the over-summering of the ergot sclerotia in the field under the natural conditions of the Jammu region.

Report on an Outbreak of Alleged Ergot Poisoning by Rye Bread in Manchester

It is impossible to say with certainty that the outbreak of illness in Manchester was due to ergot, but the evidence available strongly supports the view that ergot was the cause. The train of symptoms and pathological changes, though not necessarily peculiar to ergot poisoning, are strongly suggestive of this origin and this conclusion is reinforced by the fact that all the sufferers consumed rye bread made from rye which contained a significant proportion of ergot. The ergot isolated from this rye, after being kept for many months under conditions which were unfavourable for the preservation of its toxic properties, was found at the expiration of this period to contain some toxin and the amount found was consistent with the ergot having been highly active when fresh and therefore quite capable of causing the outbreak of illness which developed at a period shortly after the harvest when the toxic properties of ergot are greatest.As a result of my inquiry the following facts of interest have emerged:1. A considerable quantity of rye is grown in England and Wales and more than half of it is allowed to ripen. The districts in which most of it is grown are Yorkshire, Lancashire, Cheshire, Monmouth and Essex. Rye in this country is seldom, if ever, free from ergot and the degree of infection varies from year to year in each district according to the season, weather, seed and other conditions.2. Rye bread is eaten to a large extent (in Liverpool and Manchester at any rate) by Jews, and rye for these towns is obtained almost exclusively from Lancashire and Yorkshire.3. The rye grain is usually not treated in any way before milling, that is to say, no attempt is made to remove any ergot which may be present; it is ground into meal in the condition in which it comes from the threshing machine.4. On the assumption that some of the rye consumed in Manchester contained 1 per cent. of ergot, a half-pound loaf of bread of which this rye is a constituent would contain 4 to 5 grains of ergot. Although this is a relatively small dose, it is possible that if consumed over lengthy periods, especially if the ergot were in an actively toxic state, pathological conditions might ensue.5. The samples of rye actually examined by the Public Analyst were not found to be toxic. This may possibly be accounted for on the ground that the method employed for extracting the toxin was not satisfactory, or to the fact that the ergot examined was at least six months old, by which time it would normally have lost most if not all of its toxicity.6. Damp weather favours the growth of ergot and the climatic conditions of the summer of 1927 were just those most suited to the development of ergot. It is probable therefore that the rye crop was heavily infected and the ergot rich in toxins.The clinical characters of the outbreak, so far as they have been recorded, strongly support the view that ergot was responsible; all the necessary factors and conditions for the production of illness were present and it is not surprising that it occurred.In view of the potential danger the obvious preventive measures to which I have already referred should be put into operation. Rye crops should be grown with such precautions as to reduce the risk of ergot infection to a minimum. Millers of rye for human consumption should install the necessary machinery to remove, so far as possible, any small proportion of ergot which the rye may contain.