Differences Between Barley, Oats and Wheat in the Occurrence of Deoxynivalenol and Other Trichothecenes in Norwegian Grain

The amount of the Fusarium toxins deoxynivalenol (DON). 3-acety-DON. ivalenol and fusarenon × have been determined in about 3000 samples of barley, oats and wheat grown in Norway. The samples were collected in the period 1988–1994. and grouped according to grain species, year of production, district and sample category. The DON content was found to be significantly higher in oats than both barley and wheat in grain produced by ordinary grain producers in Norway. Of samples collected from grain silos. 68.7% of the barley. 97.1% of the oats and 66.3% of the wheat samples were found to contain 30 mg/kg of DON or more. The proportion containing 1000 μg kg or more was 2.1.13.4and0.0% in burley, oats and wheat, respectively. However, these variations in contamination level were not reflected in the results from two field trials, where the grain species were grown side-by-side in the same fields. The differences in contamination level between the grain species seem to be due partly to edaphic and agrotechnical factors and partly to variation in the susceptibility to different Fusarium species in interaction with climatic factors. Nivalenol(≥ 50 μg/kg) was detected in 8.3% of the barley samples. 8.2% of the oats and 0.4% of the wheat samples. Samples collected at the grain silos were then not included.     

SOME OBSERVATIONS ON THE CEREAL-ROOT EELWORM POPULATION OF FIELD PLOTS OF CEREALS WITH DIFFERENT SOWING TIMES AND FERTILIZER TREATMENTS

In the autumn of 1953 an experiment was begun to follow changes in the cereal-root eelworm population of small plots on a field in Shropshire. The plots were cropped with either oats, wheat, barley or rye, sown in the autumn and spring, and some plots had fertilizer. Each plot received the same treatment for 3 years; in the fourth year an indicator crop of spring oats was grown on all the plots.
Under rye and autumn-sown wheat the eelworm population fell to a level which permitted a good oat crop in 1957. Autumn-sown wheat, barley and rye generally produced lower eelworm populations than their spring-sown counterparts, but autumn-sown oats proved to be the most efficient host. The order of host efficiency was oats (best), barley, wheat, rye. The eelworm populations were generally higher on plots receiving fertilizer treatment. In this experiment all oat plots, and spring-sown barley plus fertilizer, produced populations which severely damaged the 1957 oat crop.     

Response of oat cultivars to <Emphasis Type="Italic">Fusarium</Emphasis> infection with a view to their suitability for food use

Oats as a source of antioxidants and complex polysaccharides are currently an important component in human nutrition. Producing healthy, safe and high-quality grain for this purpose depends upon growing oat cultivars with improved resistance to diseases caused by Fusarium spp. producing mycotoxins. Thirteen cultivars of naked (Ábel, Detvan, Izák and Avenuda) and covered (Zvolen, Auron, Atego, Flämingsstern, Kanton, Viktor, Zla?ák, Euro and Ardo) oats were inoculated with conidial suspensions of F. culmorum isolate in the field at flowering in 2006 and 2007. After harvest, reduction in thousand-kernel weight (R-TKW), reduction in panicle-kernel weight (R-PKW), and deoxynivalenol (DON) content in grain and hulls were determined. The ELISA immunochemical method was employed for the quantitative analyses of DON. Values of yield components (R-TKW; R-PKW) were 35.4% and 31.1% lower in dehulled covered oats than in naked oat cultivars. The DON accumulation was highest in hulls as compared with DON content in kernels of naked and covered oat cultivars. Accumulation of DON in dehulled covered cultivars was 34.4% lower than the average contamination in naked cultivars. When the cultivars were compared, there were positive correlations between R-TKW and R-PKW and also between DON content and R-PKW. With a view to growing oat cultivars for production of cereal foods, it was shown that dehulling of covered oat grain resulted in substantially reduced DON content.     

Effects of long-term barley monoculture on plant-affecting soil microbiota

Effects of soil microbiota on shoot and root growth of barley were tested in a greenhouse tube-growing system. Tubes were filled with a mixture of pure sand and various percentages of soils sampled from plots in three long-term field experiments measuring effects of various crop rotations on yield. Using 3% soil in the sand-soil mixture, shoot dry weight of barley test plants was reduced by about 35% and root depth by about 40% in soils from monoculture plots as compared to soils from crop-rotation plots. Typical root symptoms on poorly growing barley plants started as distinct dark-brown zones which then rapidly spread over the whole root system until the root tips ceased to grow. As tested in one experiment, the barley monoculture soil also affected wheat and oats, but to a lesser degree than it did barley. Most of the depressing effects of monoculture soil on barley were eliminated when soil samples were treated with metalaxyl or heated to 65°C for 2 hours. A Pythium sp. frequently isolated from barley roots showing typical symptoms affected barley, wheat and oats in the same way as did barley monoculture soil.     

EFFECTS OF CULTURAL TREATMENTS ON WHEAT AND ON THE INCIDENCE OF EYESPOT, LODGING, TAKE-ALL AND WEEDS. Field Experiments 1945–8

An experiment was made on the fourth, fifth and sixth successive crops of winter wheat to determine the effects of various treatments on the troubles which result from close cereal cropping. Eyespot and lodging were prevalent in the first year (1946); weeds in the second; eyespot, lodging, take-all and weeds in the third.
Spraying with H₂SO₄ reduced the incidence of eyespot, lodging and weeds, and increased yield of grain on plots which received sulphate of ammonia (by 2.7, 2.2 and 10.0 cwt./acre in successive years).
Sulphate of ammonia increased the incidence at harvest of eyespot and lodging, reduced take-all and consistently increased yield of straw. Eyespot and lodging reduced the effect of the fertilizer on yield of grain, take-all increased it.
Increase in seed rate increased the incidence of severe eyespot and of take-all; it increased lodging except when plants were dwarfed by take-all.
Weight of straw and percentage straws with severe eyespot lesions independently affected lodging, together accounting for 51% of the variance in percentage area lodged at harvest and 64 % of that lodged 33 days earlier.
Mean yields of grain on untreated plots sown with 3.3 1/2 bushels seed/acre fell from 26.0 to 22.5 to 11.7 cwt./acre in successive years, whereas yields of 28.4, 29.9 and 29.1 cwt./acre were obtained on sprayed plots sown with 1 1/2.2 bushels seed/acre which received 4 cwt./acre sulphate of ammonia, showing that high yields were maintained when eyespot, lodging, take-all and weeds were controlled.
By 1948 yields of grain on unsprayed plots had fallen to the level of those on similarly manured plots on the continuous wheat experiment on Broadbalk field. Spraying increased grain by amounts similar to those resulting from one year's fallow on Broadbalk; but fallow had its greatest effects on plots with low nitrogen, spraying on those with high nitrogen.     

Progression of mycotoxin and nutrient concentrations in wheat after inoculation with Fusarium culmorum

The objective of this study was to follow the mycotoxin formation and changes in nutrient composition of wheat (cv. Ritmo) artificially inoculated with Fusarium culmorum. From anthesis until harvest, samples were taken once a week from the inoculated and control plots. The investigations were focused on monitoring the progression of the contamination of the wheat kernels with deoxynivalenol (DON) and zearalenone (ZON). Both the uncontaminated control kernels and the contaminated kernels were examined also for the presence of zearalenone-4-beta-D-glucopyranoside and several trichothecenes at harvest. Furthermore, the impact of the Fusarium inoculation on some nutrients as starch, crude protein, amino acid composition, crude ash, non starch polysaccharides (NSP) as well as viscosity and thousand seed weight (TSW) was examined. Also proteolytic and amylolytic activity as well as the NSP-degrading enzyme activities of inoculated and control samples were analysed at the time of harvest. DON was detected in higher concentrations and in earlier stages, while ZON was found later and in smaller amounts. On average 7.79?mg/kg DM of DON and 100?μg/kg DM of ZON were found in the inoculated kernels at the time of harvest. Neither in the contaminated nor in the control samples glucose conjugates of ZON (Zearalenone-4-beta-D-glucopyranoside) were detected. Moreover, the infection with Fusarium culmorum had pronounced effects on some quality parameters. The crude protein content of the inoculated kernels showed significantly higher values over the whole period compared to the control kernels. The protein content of the inoculated kernels amounted 13.9% DM at harvest, while only a concentration of 12.5% DM was detected in the control samples. Similarly, in almost all stages of development the crude ash content of inoculated samples was higher than in control samples. These distinct differences in kernel composition resulted possibly from the changes of the thousand seed weight. In the present work the grain harvested from the control plots showed a significantly higher TSW (24.2?g) as compared to their inoculated counterparts (15.5?g). Despite lower extract viscosity of inoculated samples at time of harvest, the content of soluble NSP of inoculated plots was higher than in control samples at the same time. Moreover, inoculation resulted in markedly increased activities of protease, amylase and several NSP-degrading enzyme activities. This would suggest that the cell wall penetrating properties of the fungus itself and/or that the fungus induced alterations of the metabolic activity of the embryo or other constituents of the wheat kernel could be responsible.     

The occurrence of culmorin and hydroxy-culmorins in cereals

Forty-five samples from 1988–1995 of naturally contaminated grain, barley, wheat and oats, three samples of mixed feed, and 16 samples of grain artificially inoculated with Fusarium culmorum during the flowering stage were analysed for deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-acetyl-DON), culmorin and hydroxy-culmorins. These compounds are secondary metabolites produced by the fungal species F. culmorum and F. graminearum. Acetonitrile-water extract of the samples was purified on a Mycosep^TM#225 column, derivetized using pentafluoropropionic anhydride (PFPA) and analysed by gas chromatography-mass spectrometry (GC-MS). The amount of each of culmorin, 5-, 12-, 14 and 15-hydroxy-culmorin and one unknown hydroxy-culmorin were determined relative to the amount of DON plus 3-acetyl DON for each sample. The ratio between the total amount of culmorin compounds and the DON compounds ranged from 0.14 to 1.07 in the samples. This study shows that there is a strong correlation between the amount of DON present in the grain and the amount of culmorin and hydroxy-culmorins present. The ratio of each of the culmorin compounds relative to the amount of DON compounds were in the same range in the grain artificially inoculated by F. culmorum as found in an earlier study for F. culmorum strains cultivated on rice, while the hydroxy-culmorin profile in the naturally contaminated grain was more similar to what was found for the F. graminearum cultures in the same study [1]. These results indicate that F. graminearum may be a relatively important source for DON in grain also in relatively cold areas. This revised version was published online in June 2006 with corrections to the Cover Date.     

Progression of mycotoxin and nutrient concentrations in wheat after inoculation with Fusarium culmorum

The objective of this study was to follow the mycotoxin formation and changes in nutrient composition of wheat (cv. Ritmo) artificially inoculated with Fusarium culmorum. From anthesis until harvest, samples were taken once a week from the inoculated and control plots. The investigations were focused on monitoring the progression of the contamination of the wheat kernels with deoxynivalenol (DON) and zearalenone (ZON). Both the uncontaminated control kernels and the contaminated kernels were examined also for the presence of zearalenone-4-beta-D-glucopyranoside and several trichothecenes at harvest. Furthermore, the impact of the Fusarium inoculation on some nutrients as starch, crude protein, amino acid composition, crude ash, non starch polysaccharides (NSP) as well as viscosity and thousand seed weight (TSW) was examined. Also proteolytic and amylolytic activity as well as the NSP-degrading enzyme activities of inoculated and control samples were analysed at the time of harvest. DON was detected in higher concentrations and in earlier stages, while ZON was found later and in smaller amounts. On average 7.79 mg/kg DM of DON and 100 microg/kg DM of ZON were found in the inoculated kernels at the time of harvest. Neither in the contaminated nor in the control samples glucose conjugates of ZON (Zearalenone-4-beta-D-glucopyranoside) were detected. Moreover, the infection with Fusarium culmorum had pronounced effects on some quality parameters. The crude protein content of the inoculated kernels showed significantly higher values over the whole period compared to the control kernels. The protein content of the inoculated kernels amounted 13.9% DM at harvest, while only a concentration of 12.5% DM was detected in the control samples. Similarly, in almost all stages of development the crude ash content of inoculated samples was higher than in control samples. These distinct differences in kernel composition resulted possibly from the changes of the thousand seed weight. In the present work the grain harvested from the control plots showed a significantly higher TSW (24.2 g) as compared to their inoculated counterparts (15.5 g). Despite lower extract viscosity of inoculated samples at time of harvest, the content of soluble NSP of inoculated plots was higher than in control samples at the same time. Moreover, inoculation resulted in markedly increased activities of protease, amylase and several NSP-degrading enzyme activities. This would suggest that the cell wall penetrating properties of the fungus itself and/or that the fungus induced alterations of the metabolic activity of the embryo or other constituents of the wheat kernel could be responsible.     

Effects of Break Crops on Yield and Grain Protein Concentration of Barley in a Boreal Climate

Rotation with dicotyledonous crops to break cereal monoculture has proven to be beneficial to successive cereals. In two fields where the soil had been subjected to prolonged, continuous cereal production, two 3-year rotation trials were established. In the first year, faba bean, turnip rape and barley were grown, as first crops, in large blocks and their residues tilled into the soil after harvest. In the following year, barley, buckwheat, caraway, faba bean, hemp and white lupin were sown, as second crops, in each block and incorporated either at flowering stage (except barley) or after harvest. In the third year, barley was grown in all plots and its yield and grain protein concentration were determined. Mineral N in the plough layer was determined two months after incorporation of crops and again before sowing barley in the following year. The effect of faba bean and turnip rape on improving barley yields and grain protein concentration was still detectable two years after they were grown. The yield response of barley was not sensitive to the growth stage of second crops when they were incorporated, but was to different second crops, showing clear benefits averaging 6-7% after white lupin, faba bean and hemp but no benefit from caraway or buckwheat. The effect of increased N in the plough layer derived from rotation crops on barley yields was minor. Incorporation of plants at flowering stage slightly increased third-year barley grain protein concentration but posed a great potential for N loss compared with incorporation of crop residues after harvest, showing the value of either delayed incorporation or using catch crops.     

Natural Fusarium Grain Infection Level in Wheat, Barley and Oat after Early Application of Fungicides and Herbicides

In Norway, early application of fungicides against cereal leaf diseases (before Zadoks 60) is common practice amongst farmers. Whether this procedure has any effect on Fusarium infection of the mature grain has been little investigated. To evaluate effects on Fusarium grain infection, cereal grains were sampled during 1996, 1997 and 1998 from 12 field trials where early spraying against fungal diseases in spring wheat, spring barley and oats was carried out. Percentage infected grains and frequency of different Fusarium species was analysed in every grain sample. The effect of fungicides, glyphosate and postemergence herbicides on Fusarium grain infection was studied. Significant increase in Fusarium infection was detected in fungicide‐treated plots compared with untreated plots. Fusarium avenaceum and F. tricinctum were the most frequent species detected. The internal ranking of Fusarium species remained the same after spraying. No significant effects were found on the level of Fusarium infection after glyphosate treatment in autumn or herbicide treatment during the growing season.     

Warming impacts on the dry matter accumulation,and translocation and nitrogen uptake and utilization of winter wheat on the Qinghai-Xizang Plateau

Aims Global warming is expected to be the strongest in high altitude mountainous areas, which are more ecologically fragile and economically marginalized. The Qinghai-Xizang Plateau is among such areas most vulnerable to global warming, and more than 80% of its population depends on subsistence agriculture. The aim of this study is to understand the impacts of warming on indigenous crop production, which can help to devise better strategies for crop adaptation and food security in this area.Methods A field warming experiment using a facility of free air temperature increase was conducted to simulate the predicted warming level in Caigongtang town, Lhasa City, China. The experiment consisting of two treatments (warmed and non-warmed) was performed using a completely random design with three replicates. An infrared heater (180 cm in length and 20 cm in width) of 1 500 W was suspended 1.5 m above the ground in each warmed plot. In each non-warmed plot, a ‘dummy’ heater of same dimensions was also suspended to mimic the shading effects. The warming treatment was performed from the sown date to the harvest date. We measured dry matter and nitrogen accumulation, partition and translocation of winter wheat (Triticum aestivum) using ‘Shandong 6’ under warming and control treatments.Important findings Results showed that, with 1.1 °C increase in daily mean air temperature during winter wheat growing season, the dry matter accumulation rate at population level from sowing to anthesis stage, grain dry matter partition ratio and contribution of dry matter translocation amount to grain after anthesis were 27.5%, 5.6% and 68.6% higher, respectively, in the warmed plots than those in the non-warmed plots. Meanwhile, warming increased nitrogen accumulation rate at population level of winter wheat. Nitrogen distribution proportions in grain and nitrogen translocation efficiency from vegetative organs to grain after anthesis in the warmed treatment were 6.0% and 5.5% higher than those in the non-warmed treatment, respectively. Compared with non-warmed treatment, warming decreased harvest index by 3.1%, though the difference was not statistically significant. Grain yield, nitrogen uptake efficiency, nitrogen partial factor productivity and nitrogen harvest index were 8.1%, 20.8%, 8.1% and 6.0% higher, respectively, in the warmed plots than those in the non-warmed plots. In conclusion, an increase in daily mean air temperature of about 1.1 °C can enhance plant growth during the pre-anthesis phase by mitigating the low temperature limitation, and accelerate dry matter and nitrogen partition and translocation to the grain after anthesis in winter wheat. These results suggest that warming may benefit winter wheat production through increasing nitrogen use efficiency in high altitude areas.     

Digestibility of whole-crop barley and oat silages in dairy heifers

This study evaluated the digestibility of whole-crop cereal silage (WCCS) made from oats and six-rowed barley harvested at the heading, early milk and early dough stages, and two-rowed barley harvested at the early milk and early dough stages of maturity. The eight WCCSs were fed to 32 Swedish Red heifers in a changeover design over three periods of 28 days each. The heifers were first fed ad libitum for 17 days and then at 0.95 of ad libitum for 11 days of each period. During the last 5 days all faeces and orts were collected to determine the digestibility of the silages. Only the maturity stage effect was significant for the WCCS organic matter (OM) digestibility and the average OM digestibility was higher at the heading stage (698 g/kg) than at early milk (647 g/kg) and early dough (652 g/kg) stages of maturity. For neutral detergent fibre (NDF) digestibility the crop × maturity stage effect was significant. The NDF digestibility decreased from the heading to the early milk stage for both six-rowed barley (746 to 607 g/kg) and oats (698 to 596 g/kg). There was no further significant decrease in NDF digestibility for six-rowed barley at the early dough stage (577 g/kg), but for two-rowed barley it decreased from the early milk (682 g/kg) to the early dough (573 g/kg) stage, and also for oats the NDF digestibility was lowest at the early dough stage (507 g/kg). The decrease in NDF digestibility during maturation was to a large extent compensated by an increase in starch concentration in the crops. The starch digestibility was lower for six-rowed barley at early dough stage (948 g/kg) than at early milk stage (977 g/kg), and was also lower compared with oats (979 g/kg) at early dough stage. The average crude protein (CP) digestibility was higher at the heading (646 g/kg) and the early milk (642 g/kg) stages than at the early dough stage (599 g/kg), and oats had higher average CP digestibility (650 g/kg) than six-rowed (613 g/kg) and two-rowed (624 g/kg) barley. Delaying the harvest of WCCS from the heading to the early milk and dough stage of maturity will decrease the OM digestibility; as a result there is a decreased NDF digestibility.     

The effects of a paclobutrazol-based growth regulator on the yield, quality and ease of management of oilseed rape

A mixture of paclobutrazol and chlormequat chloride plant growth regulators (JF10405, Parlay C) was tested on field crops of two ‘double zero’ oilseed rape cultivars in two seasons. Application rate and timing of JF10405 were varied. Very large plots enabled the use of commercial farm equipment to treat and harvest the experiments. Untreated plots showed considerable lodging at harvest in all experiments. Treatment with JF10405 had only small effects on the height of mature plants but, generally, reduced lodging substantially even at the lowest rate tested. All JF10405 treatments increased seed yields, several significantly so, particularly a 2.50 litre/ha rate, although the optimum timing varied between experiments. Seed oil contents were little affected, but levels of glucosinolates were significantly decreased in some instances. Treatments giving good control of lodging also took less time to harvest, especially when cutting against the direction of the lodging. The results-are discussed in relation to the means by which these improvements in seed yield and quality were achieved, and crop management facilitated.     

Interaction between barley yellow dwarf virus and rust in wheat, barley and oats, and the effects on grain yield and quality

In three separate experiments, the upper leaf surface of the fifth formed leaf of wheat cv. Highbury, the fourth and fifth leaves of barley cv. Julia and the third and fourth leaves of oat cv. Mostyn were inoculated in a spore settling tower with wheat brown rust (Puccinia recondita f. sp. tritici), barley brown rust (P. hordei) or oat crown rust (P. coronata f. sp. avenae), respectively. Fewer pustules developed on distal portions of leaves of plants infected with barley yellow dwarf virus (BYDV) than on similar portions of leaves from virus-free plants. There were no significant differences in the number of pustules on proximal leaf portions. In barley and oats, the number of pustules on distal leaf portions was negatively correlated with the amount of yellowing of the leaf areas scored. In wheat, symptoms of BYDV were mild and leaves were little affected by yellowing. The latent period of rust on wheat and oats was not affected by BYDV. In barley, BYDV reduced the latent period of rust on leaf 5, but not on leaf 4, and reduced it on proximal, but not distal, leaf portions. In other experiments, BYDV reduced the yield of wheat and oats by 44% and 66%, respectively, while BYDV-infected barley was almost sterile. The appropriate rust reduced the yield of wheat, barley and oats by 33%, 13% and 86%, respectively. When infected with both BYDV and rust, yield of wheat and oats was reduced by 63% and 91%, respectively. Neither BYDV nor rust affected the percentage crude protein content of wheat grain, nor did rust affect that of barley. In oats, BYDV and rust each significantly increased crude protein of grain, but rust infection of BYDV-infected plants tended to reduce it.     

The duration and rate of grain growth, and harvest index, of wheat (Triticum aestivum L.) in response to temperature and CO2

Winter wheat (Triticum aestivum L. cv. Hereward) was grown inthe field inside polyethylene-covered tunnels at a range oftemperatures at either 380 or 684 µmol mol^–1 CO₂.Serial harvests were taken from anthesis until harvest maturity.Grain yield was reduced by warmer temperatures, but increasedby CO₂ enrichment at all temperatures. During grain-filling,individual grain dry weight was a linear function of time fromanthesis until mass maturity (attainment of maximum grain dryweight) within each plot. The rate of progress to mass maturity(the reciprocal of time to mass maturity) was a positive linearfunction of mean temperature, but was not affected by CO₂ concentration.The rate of increase in grain dry weight per ear was 2.0 mgd^–1 greater per 1 C rise, and was 8.0 mg d^–1 greaterat 684 compared with 380 µmol mol^–1 CO₂ at a giventemperature. The rate of increase in harvest index was 1.0%d^–1 in most plots at 380 µmol mol^–1 CO₂ andin open field plots, compared with 1.18% d^–1 in all plotsat 684 µmol mol^–1 CO₂. Thus, the increased rateof grain growth observed at an elevated CO₂ concentration couldbe attributed partly to a change in the partitioning of assimilatesto the grain. In contrast, the primary effect of warmer temperatureswas to shorten the duration of grain-filling. The rate of graingrowth at a given temperature and the rate of increase in harvestindex were only independent of the number of grains per earabove a critical grain number of 23–24 grains per ear({small tilde}20 000 grains m^–2). Key words: Winter wheat, grain growth, temperature, CO₂, harvest index, critical grain number     

Resistance to Fusarium head Blight and Deoxynivalenol Accumulation in Chinese Barley

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe is a devastating barley disease world-wide, causing significant yield losses and contaminating cereal products with mycotoxins. Barley grain contaminated with deoxynivalenol (DON) is associated with gushing and may be rejected by the malting and brewing industry. Genetically inherited resistance is the most effective option for the control of the disease. A total of 266 barley cultivars and breeding lines originating from China were evaluated for FHB resistance and concentration of DON in grain. Plants were inoculated with isolates of F. graminearum under field conditions by injecting conidia into a single spikelet of each spike. FHB symptoms were evaluated by visual inspection, and DON content was analysed by HPLC. Significant differences in FHB ratings and DON levels were observed among cultivars. Visual symptoms of FHB varied from 4.88 to 71.75% of infected spikelets 21 days after inoculation and from 7.86 to 113.33 area under the disease progress curve units (AUDPC). Twenty-seven lines were more resistant to FHB than the control resistant cultivar Zhedar 2 and with fewer than 12% infected spikelets. Twenty-one of the above lines originated from the area in the mid to low valley of Yangtze River, where FHB epidemics are frequent. DON levels ranged from 0.05 to 24.39 mg/kg among the tested barley lines. Correlation coefficients were significant between FHB symptom ratings and DON levels. However, there was no significant correlation between symptom rating and plant height and no significant correlation between symptom rating and heading date.     

Trichothecene Content of Rye and Wheat Genotypes Inoculated with a Deoxynivalenol- and a Nivalenol-producing Isolate of Fusarium culmorum

Head blight caused by Fusarium culmorum may lead to yield reduction and the contamination of cereal grain with the mycotoxins deoxynivalenol (DON), 3-acetyl deoxynivalenol (3-ADON), nivalenol (NIV), fusarenone-X (FUS), and others. In this study, the covariation between DON and NIV accumulation of 12 rye and eight wheat genotypes that differed in resistance were analysed by inoculating them with a DON-and a NIV-producing isolate, respectively, in three locations. The resistance traits head blight rating and plot yield relative to the uninoculated plots of the same genotype were assessed and the contents of DON, 3-ADON, NIV, and FUS in the grain were analysed by gas chromatography with mass spectrometry. The NIV-producing isolate was significantly (P=0.05) less aggressive and led to a considerably lower mean NIV content in the grain compared with the aggressiveness and mean DON content of the DON-producing isolate (19.5 mg NIV/kg grain versus 48.4 mg DON/kg). Wheat and rye genotypes significantly differed in their DON and NIV accumulation. All genotypes reacted in a similar manner to both chemotypes of F. culmorum for the resistance traits and the respective mycotoxin contents with the exception of one wheat variety, that caused a change in rank order for mycotoxin content. In conclusion, resistance to head blight and tolerance to mycotoxin accumulation seems to be most likely the same for DON- and NIV-producing isolates of F. culmorum .     

Grain yield and incidence of take-all (Ophiobolus graminis Sacc.) in wheat grown in different crop sequences

The yield of wheat and the incidence of take-all were measured in crops grown in six different 4-year sequences, repeated in 3 successive years. The first crop of winter wheat grown after oats or beans yielded 13–23 cwt/acre (1632–2887 kg/ha) more grain than wheat after wheat or barley. Spring wheat after oats yielded 2–5 cwt/acre (250–625 kg/ha) more than spring wheat after wheat. The smaller yields of wheat after wheat or barley were caused mostly by greater prevalence of take-all. Regression analysis indicates that each 1 % increase in straws with take-all decreased yield of winter wheat by 0·6%. Take-all was more prevalent in the second and third successive wheat crops after oats than in the fourth crop.     

Response of Barley Genotypes to Fusarium Head Blight under Natural Infection and Artificial Inoculation Conditions

Forty-eight spring barley genotypes were evaluated for deoxynivalenol (DON) concentration under natural infection across 5 years at Harrington, Prince Edward Island. These genotypes were also evaluated for Fusarium head blight (FHB) severity and DON concentration under field nurseries with artificial inoculation of Fusarium graminearum by the grain spawn method across 2 years at Ottawa, Ontario, and one year at Hangzhou, China. Additionally, these genotypes were also evaluated for FHB severity under greenhouse conditions with artificial inoculation of F. graminearum by conidial suspension spray method across 3 years at Ottawa, Ontario. The objective of the study was to investigate if reactions of barley genotypes to artificial FHB inoculation correlate with reactions to natural FHB infection. DON concentration under natural infection was positively correlated with DON concentration (r = 0.47, P < 0.01) and FHB incidence (r = 0.56, P < 0.01) in the artificially inoculated nursery with grain spawn method. Therefore, the grain spawn method can be used to effectively screen for low DON. FHB severity, generated from greenhouse spray, however, was not correlated with DON concentration (r = 0.12, P > 0.05) under natural infection and it was not correlated with DON concentration (r = −0.23, P > 0.05) and FHB incidence (r = 0.19, P > 0.05) in the artificially inoculated nursery with grain spawn method. FHB severity, DON concentration, and yield were affected by year, genotype, and the genotype × year interaction. The effectiveness of greenhouse spray inoculation for indirect selection for low DON concentration requires further studies. Nine of the 48 genotypes were found to contain low DON under natural infection. Island barley had low DON and also had high yield.     

The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth and yield of winter cereals

In 1986/1987 and 1987/1988 wild rabbits (Oryctolagus cuniculus) were trapped and enclosed in a 0.3 ha site in which two varieties of winter barley (Igri and Panda) and two of winter wheat (Norman and Mission) were grown in a split plot block design experiment. The level of rabbit population was varied to emulate natural variation in numbers throughout the growing season and was regulated to produce a peak density of 77 rabbits ha^-* in the first year, and 33 rabbits ha^-1! in the second year. Grazing was managed by the use of exclosure fences around plots to produce four treatment levels - protected, autumn grazed, spring grazed and totally grazed regimes. Rabbit damage was assessed using stem and leaf damage indices several times through the growth of the crops. Yields were measured in terms of head number, grain weight and total yield. There was no evidence of varietal preference among the four cereal varieties on the basis of damage assessments. In the first year the totally grazed treatment led to an increase in the number of unripe heads present at harvest which would indicate a delayed harvest date in a field crop. Winter wheat showed a trend towards higher yield loss in spring-damaged plots, possibly linked to the time of tillering in this crop. Yield losses overall were highest in those plots grazed in either the autumn or throughout the entire season. The level of peak rabbit population did not appear to influence the degree of loss in either year. The results indicate that there may be a threshold of rabbit damage early in the growth of the crop which contributes most to the yield loss. This emphasises the importance of protecting a winter cereal crop at its establishment phase.