Yield Trends during Take-all Decline in Spring Barley and Wheat Grown Continuously1

The effects of take-all, nitrogen and cropping sequence on grain yield were compared for spring barley and spring wheat grown in extended monoculture. Initial crops showed least take-all and maximum yields. Yields fell to a minimum more rapidly in wheat than in barley while the take-all intensity increased to a maximum; take-all decline occurred and yields improved from the 4th and 5th years respectively. Without nitrogen, yields were at their lowest level; application of nitrogen increased yields considerably with responses in proportion to the rate applied. At optimum rates, yield losses were 33% for wheat and 11% for barley with maximum disease intensity but only 9% and 3% respectively with take-all decline. Potential maximum yields in the absence of take-all were calculated to be greater with barley than with wheat.     

Take-all in autumn-sown wheat, barley, triticale and rye grown with high and low inputs

Winter cultivars of wheat, barley, triticale and rye were grown under two contrasting husbandry systems (low and high inputs) at two locations (Woburn and Rothamsted) known to be infested with the take-all fungus. The sandy loam at Woburn is less fertile than the silty clay loam at Rothamsted. Root infection in these crops was assessed in spring and summer.
Rye was least infected by the take-all fungus, wheat the most infected and barley and triticale had intermediate levels of infection. Barley yields were less affected by take-all than those of wheat or triticale, because barley was at a later growth stage by the time severe infection occurred. Yields of wheat and barley responded most to the high-input husbandry on the less fertile soil at Woburn. On the basis of quantity of grain, triticale would appear to be a good substitute for wheat on the less fertile soil when inputs are low, but not where they are high. At Rothamsted, yields of wheat and triticale were similar in both input systems. There was no strong support, at either site, for the contention that triticale could be a useful substitute for barley where low or high inputs are used. A total of 177 isolates of Gaeumannomyces graminis var. tritici (the causal fungus of take-all) were obtained from infected roots in these experiments and tested for their pathogenicity on wheat and rye seedlings. These tests revealed a range of pathotypes with varying pathogenicities to wheat and rye, but pathogenicities were not correlated with the host plant from which the fungi were isolated.     

The effects of various crops on the survival and carry-over of the wheat take-all fungus Gaeumannomyces graminis var. tritici

The effects of various crops on the saprophytic survival and carry-over of Gaeumannomyces graminis var. tritici were studied in the glasshouse and field.
In the glasshouse, survival of G. g. tritici was greater in unplanted pots than in pots planted with either cereals or non-cereals. In the field, fallow and various non-cereal crops reduced carryover of take-all but the disease was severe after wheat, barley and triticale. Grain yields were higher after fallow and non-cereals than after cereal crops.     

Tolerence of Wheat and Barley at Different Stages of Growth to 2, 4-D Sprays

Abstract

The tolerance of wheat and barley to 2, 4-D sprayed at six stages of growth, ranging from the 3-leaf stage up to the ripe grain stage, was studied. Five concentrations ranging from 500 to 8000 ppm (a.e.) of 2, 4-D were tested.

All the concentrations sprayed at the 3-leaf stage were phytotoxic to wheat and barley, whereas at the 5-leaf, jointing, and booting-to-heading stages, only 4000 and 8000 ppm were phytotoxic and caused lodging in the two crops. Reductions in plant height were significant at all concentrations used in the case of barley, and at 1000 ppm and above in the case of wheat.

The 8000 ppm treatment, applied at the jointing and anthesis stages, caused significant reductions in the grain yield of wheat; in the case of barley, significant reductions in the grain yield were observed at concentrations ranging from 2000 to 8000 ppm, sprayed at the 3-leaf, booting-to-heading, arid anthesis stages. At the 5-leaf stage, the 1000 ppm treatment gave a highly significant increase of 18.7% in the grain yield over the unweeded check. Significant reductions in the 1000-kernel weight and test weight of the two crops were observed only at the higher concentrations used.

The protein percentages of wheat and barley seeds were significantly increased as a result of the application of 2, 4-D at 2000 to 8000 ppm, sprayed at the 3-leaf, jointing, booting-to-heading, and anthesis stages of growth. However, significant reductions in the protein yield of the two crops were observed at these treatments. No significant effects were observed on the straw yield and germination percentages of wheat and barley as a result of 2, 4-D applications at the various stages of growth.     

Susceptibility of winter and summer crops to root and crown infection by Bipolaris sorokiniana

The susceptibility of 24 winter and 17 summer crops to infection by Bipolaris sorokiniana was tested in a glasshouse experiment by growing them in soil amended with wheat-barley grain colonized by B. sorokiniana (0.2 g per 100 g soil). At anthesis, infection of both lesioned and randomly selected segments of roots and of crowns was determined by plating them on modified Czapek-Dox Agar. Incidence of infection in winter crops was higher than in summer crops. Guar, mung bean, soybean and sunflower were the least infected of the summer crops while chickpeas and safflower were the least infected of the winter crops. Amongst the taxonomic groups tested, the highest incidence of infection occurred in the gramineous species and the lowest in the leguminous species.
Five summer crops growing in the field were sampled and infection by B. sorokiniana confirmed. Cultivars of wheat, barley, triticale and oats were also screened in a field experiment. Amongst these winter cereals, oats was the least susceptible in both field and glasshouse experiments. Differences between cultivars in susceptibility to common root rot, measured by the degree of lesion development in the subcrown internode, were identified in wheat, triticale and oats but not in barley.     

Importance of the proportion of grassy weeds within legume crops in the perpetuation of Gaeumannomyces graminis var. tritici

Various grass species susceptible to infection by Gaeumannomyces graminis var. tritici were mixed-sown into a legume crop in order to assess their influence on density of inoculum and take-all disease in a subsequent crop of wheat.
In a pot experiment take-all inoculum increased ( P < 0.001) in all treatments containing a proportion (from 20 to 100%, in increments of 20%) of grass in subterranean clover. In a plot trial, most severe take-all occurred in the 20% legume/80% grass stands and least in the 100% legume and 80% legume/20% grass stands. Total grain weight was highest ( P <0.1) after the 100% legume stands. There was no difference in severity of take-all after pure stands of medic, subterranean clover and lupin, but there was more severe take-all after the grass-infested medic stands than after those of subterranean clover ( P < 0.1) or lupin ( P < 0.05). No significant differences ( P > 0.1) in yield occurred in wheat following any of the legumes or mixed stands.     

Effects of different cultivated or weed grasses, grown as pure stands or in combination with wheat, on take-all and its suppression in subsequent wheat crops

Grass species were grown in plots, as pure stands or mixed with wheat, after a sequence of wheat crops in which take-all ( Gaeumannomyces graminis var. tritici ) had developed. Annual brome grasses maintained take-all inoculum in the soil as well as wheat (grown as a continuous sequence), and much better than cultivated species with a perennial habit. Take-all developed more in wheat grown after Anisantha sterilis (barren brome) or Bromus secalinus (rye brome), with or without wheat, than in continuous grass-free wheat in the same year, where take-all decline was apparently occurring. It was equally or more severe, however, in wheat grown after Lolium perenne (rye-grass) or Festuca arundinacea (tall fescue), despite these species having left the least inoculum in the soil. It was most severe in plots where these two grasses had been grown as mixtures with wheat. It is postulated that the presence of these grasses inhibited the development of take-all-suppressive microbiota that had developed in the grass-free wheat crops. The effects of the grasses appeared to be temporary, as amounts of take-all in a second subsequent winter wheat test crop were similar after all treatments. These results have important implications for take-all risk in wheat and, perhaps, other cereal crops grown after grass weed-infested cereals or after set-aside or similar 1-year covers containing weeds or sown grasses, especially in combination with cereal volunteers. They also indicate that grasses might be used experimentally in wheat crop sequences for investigating the mechanisms of suppression of, and conduciveness to, take-all.     

A comparison of controlled environment and field trials for detection of resistance in cereal cultivars to root rot caused by Rhizoctonia solani

A screening test was developed to study the effect of different quantities of inoculum of Rhizoctonia solani on root rot and growth of cultivars of wheat, barley, oats, rye and triticale in a controlled environment and the field in two seasons. The ranking of relative susceptibility to disease of cultivars within a cereal differed between the controlled environment and field experiments, and between seasons in the field. The ranking of relative susceptibility between cereals also differed between experiments. In the controlled-environment experiment, wheat had the highest disease rating, followed by oats, barley, triticale and rye, but in the field barley had the highest rating followed by wheat and then oats. The overall differences between the cereals were small.     

Effects of summer fallow management on take-all of winter wheat caused by <Emphasis Type="Italic">Gaeumannomyces graminis</Emphasis> var. <Emphasis Type="Italic">tritici</Emphasis>

Crop rotation is the oldest, and perhaps the best cultural practice for reducing the risk of take-all. The effects of crops sown before wheat in a rotation are known in detail, but we know little about the opportunities for reducing take-all risk by planting certain crops in the summer period between wheat harvest and the planting of a subsequent winter wheat crop. We investigated the effects on take-all of five summer fallow crops, two soil tillage treatments and a fungicide seed treatment, in a five site-year experiment. We tested the effects of oats, oilseed rape, mustard, ryegrass and volunteer wheat crops. Bare-soil plots were also included. Take-all epidemics varied with year and site. Summer fallow crops had a greater effect on tilled plots. The incidence and severity of take-all were significantly higher in the wheat volunteer plots, whereas maintaining bare soil provided the lowest level of disease. Oilseed rape had no significant effect on take-all incidence in our experiment. The best candidates for reducing take-all risk appeared to be oats, mustard and ryegrass. These summer fallow crops decreased disease levels only when associated with conventional tillage. Summer fallow crops did not alter take-all decline in the same way as a break crop after a wheat monoculture.     

Enhanced field control of wheat take-all using cold tolerant isolates of Gaeumannomyces graminis var. graminis and Phialophora sp. (lobed hyphopodia)

Cold tolerant isolates of Gaeumannomyces graminis var. graminis ( Ggg ) and Phialophora sp. (lobed hyphopodia), which produced at least comparable growth rates at 5°C to those of pathogenic G. graminis var. tritici ( Ggt ), were shown to control take-all disease in wheat effectively in 2 years of field experiments in New South Wales, Australia. The addition of oat inoculum of these fungi at the rate of 60 kg/ha to the seeding furrow significantly ( P  ≤ 0.05) reduced disease and increased grain yields by 33–45% compared to the Ggt alone treatment. The use of 30 kg/ha of oat inoculum also significantly ( P  ≤ 0.05) reduced disease and increased grain yields by 21–44%. These high levels of take-all control were obtained consistently from four field experiments on three different soil types with different pHs. A treatment inoculated with Ggg alone showed no disease symptoms and produced grain yields similar to that of untreated wheat. This fungus is, therefore, non-pathogenic to wheat. At high rates of inoculation of Ggg and Phialophora sp. (lobed hyphopodia), 65–80% of tillering wheat plants (GS 32) had root systems colonized by these fungi. In contrast, two Pseudomonas spp. and an isolate each of Ggg and Phialophora sp. (lobed hyphopodia), which did not grow at 5°C, were ineffective in controlling take-all. Take-all assessments during heading (GS 61-83) were highly correlated ( R ²=0.6047, P ≤0.0005) with the relative yield increase or decrease of inoculated treatments compared to the Ggt alone treatment. The use of a Ggg isolate (90/3B) and a Phialophora sp. (lobed hyphopodia) isolate (KY) for take-all control has been patented. These fungi are being developed for commercial use.     

The relative resistance of wheat, rye and triticale to take-all caused by Gaeumannomyces graminis

In seven field experiments conducted over 6 years with a wide range of disease severities, triticale was intermediate in resistance to Gaeumannomyces graminis between wheat (susceptible) and rye (resistant). Use of triticale is suggested as an immediately available means of introducing take-all resistance into cereal cultivation.
Octoploid triticale was slightly more susceptible than hexaploid triticale. There was little evidence of consistent variation in resistance among wheat or rye cultivars but a few hexaploid triticale cultivars varied in resistance. The resistance of triticale was not reliably expressed in the glasshouse tests used, so selection for resistance to take-all in a breeding programme would need to be conducted in the field. Individual pairs of rye chromosomes added to wheat did not significantly reduce its susceptibility. The feasibility of transferring the resistance of rye to wheat is considered.     

Role of Fungicides in Maximizing Grain Yield of Barley1

Application of fungicides to cereals normally increases grain yield, this usually being accounted for by control of well-defined diseases. Sometimes, however, yield increases are obtained when apparently trivial amounts of defined diseases are present or when their control seems insufficient to explain the observed benefit. Explanation for these ← unexpected → increases have been sought in: a) control of ← weak → pathogens or organisms not considered pathogenic but which may accelerate leaf senescence, and b) direct effects of fungicides on the plant's physiology. Whatever the precise explanation in individual instances, we may ask whether there is some general relationship linking fungicidal action, plant growth and yield. In barley, recent studies of controlled epidemics of powdery mildew have shown: a) that there is a strong correlation between severity and duration of mildew and reduction in green leaf area (GLA) integrated over time; b) that the grain yield of plants is highly correlated (r values often approaching unity) with values of GLA integrated for the period from seedling emergence to anthesis. The data also show that retranslocation of stored carbohydrate, produced before anthesis, plays an important role in grain filling, and indicate that mildew post anthesis may have little effect on yield. The main implication of these studies is that, in barley, fungicide treatments which increase GLA prior to anthesis are likely to enhance yield. Evidently this may be achieved by different means (control of pathogens, including ← weak → pathogens, or by directly extending the functional life of leaves); the end result, in terms of grain yield, will, however, be the same.     

Drought priming during the vegetative stage can enhance post-anthesis drought tolerance by improving photosynthetic capacity in winter wheat

Drought stress during the reproductive period of cereal crops leads to significant yield reductions, therefore, exploring effective methods to improve tolerance to post-anthesis drought is necessary. Pot experiment was carried out to investigate the effects of pre-drought priming on physiological characteristics and grain yield with drought stress at post-anthesis. Moderate water deficits (60–65% of the field capacity) were imposed to prime wheat plants during either the tillering or jointing stages, while severe drought stress (40–45% of the field capacity) was applied during the grain filling stage. The priming treatments significantly improved grain yield resulting in higher biomass. Compared to the control, the grain yield and biomass of the non-priming, tillering priming, and jointing priming treatments were reduced by 15.7, 9.1, and 9.3% and by 11.1, 6.1, and 10.5%, respectively. The primed plants exhibited higher adaptability to subsequent severe drought stress during grain filling, showing higher photosynthetic capacities and light use efficiencies with higher leaf water potentials, soluble protein contents, and Rubisco contents and enhanced enzymatic antioxidant systems. The tillering stage is more responsive to drought priming based on the observed grain yield. These results indicate that moderate drought during the vegetative period is conducive to the development of water-saving agriculture to cope drought stress during grain-filling in wheat.     

Application of Pseudomonas fluorescens isolates to wheat as potential biological control agents against take-all

Two isolates of Pseudomonas fluorescens (2–79 and 13–79) from the USA were evaluated in the UK as biological control agents against Gaeumannomyces graminis var. tritici , the cause of take-all in wheat. Biological control agents were applied as seed coatings in carboxymethyl cellulose (CMC) to seven wheat trials sown in 1987 and 1988 on fen peat and clay soils, and as peat-based and microgranule formulations in one of these trials. In a trial of spring wheat on fen peat, all treatments with biological control agents reduced the percentage take-all infection of crown roots and seminal roots, but the effects of only one isolate were statistically significant ( P <0·05). Effects of biological control agents on infection rates in five other trials were not significant. In the trial in which application methods were compared, peat-based inoculum initially appeared most effective but none of the treatments reduced take-all significantly throughout the season. Application of biological control agents was associated with yield increases in several trials; these were not consistently associated with effects on take-all. These results suggest that the isolates of P. fluorescens have potential to reduce take-all and increase yields of wheat in the UK, but the beneficial effects are inconsistent. There is a need to develop isolates which reliably control severe take-all in a variety of soil types.     

Dynamics of primary and secondary infection in take-all epidemics

ABSTRACT Using a combination of experimentation and mathematical modeling, the effects of initial (particulate) inoculum density on the dynamics of disease resulting from primary and secondary infection of wheat by the take-all fungus, Gaeumannomyces graminis var. tritici, were tested. A relatively high inoculum density generated a disease progress curve that rose monotonically toward an asymptote. Reducing the initial inoculum density resulted in a curve that initially was monotonic, rising to a plateau, but which increased sigmoidally to an asymptotic level of disease thereafter. Changes in the infectivity of particulate inoculum over time were examined in a separate experiment. Using a model that incorporated terms for primary and secondary infection, inoculum decay, and host growth, we showed that both disease progress curves were consistent with consecutive phases dominated, respectively, by primary and secondary infection. We examined the spread of disease from a low particulate inoculum density on seminal and adventitious root systems separately. Although seminal roots were affected by consecutive phases of primary and secondary infection, adventitious roots were affected only by secondary infection. We showed that the characteristic features of disease progress in controlled experiments were consistent with field data from crops of winter wheat. We concluded that there is an initial phase of primary infection by G. graminis var. tritici on winter wheat as seminal roots grow through the soil and encounter inoculum, but the rate of primary infection slows progressively as inoculum decays. After the initial phase, there is an acceleration in the rate of secondary infection on both seminal and adventitious roots that is stimulated by the increase in the availability of infected tissue as a source of inoculum and the availability of susceptible tissue for infection.     

Influence of take-all epidemics on winter wheat yield formation and yield loss

ABSTRACT The effects of take-all epidemics on winter wheat yield formation were determined, and disease-yield relationships were established to assess the agronomic efficacy and economic benefits of control methods. Epidemics were generated in naturally infested fields by varying cropping season, crop order in the rotation, and experimental fungicide seed treatment. Disease incidence and severity were assessed from tillering to flowering. Yield components were measured at harvest. Models simulating the formation of the yield components in the absence of limiting factors were used to estimate the losses caused by take-all. Losses were predicted by the disease level at a specific time or the area under the disease progress curve, reflecting accumulation during a specific period. Losses of grain number per square meter and 1,000-grain weight were linked to cumulative disease incidence between the beginning of stem elongation and flowering, and disease incidence at midstem elongation, respectively. Yield losses were accounted for by both cumulative disease incidence between sowing and flowering, and disease incidence at midstem elongation. Results confirm the importance of nitrogen fertilization in reducing the impact of take-all on wheat.     

Fungicide and nitrogen applications in relation to the improvement of disease control and yield in winter barley

In crops of winter barley, cvs Igri and Halcyon, crop structure and intensity of foliar diseases were altered by delaying the main top dressing of nitrogen until mid-April. A single application of fungicide then was sufficient to decrease substantially the severity of fungal disease and improve grain yield at harvest.
Disease control and yield responses were greatest when fungicides were applied during a 3-week period after the main nitrogen application in April. No additional yield benefits were obtained by making two fungicide applications at growth stage (GS) 31 and GS 39.     

Continuous Cereal Growing in Denmark; Experimental Results1

In Denmark, results from 3 long-term trials showed that yields from barley monoculture were satisfactory on clay soil provided that sufficient nitrogen was supplied. Root diseases, in particular take-all (Gaeumannomyces graminis (Sacc.) Arx et Olivier), often stabilized at a rather low level after a period of decline. Mono-culture of winter wheat gave poor yields compared with barley monoculture. Break crops of white mustard and oats in barley monoculture had a beneficial effect, especially on sandy soil.     

Changes in agronomic practices and incidence and severity of diseases in winter wheat in England and Wales between 1999 and 2019

In continuation of the annual national surveys of winter wheat, which began in 1970, samples from between 250 and 350 randomly selected wheat crops in England and Wales between 1999 to 2019 were visually assessed for disease symptoms during the milky ripe development stages (GS 73–75). Septoria tritici blotch was the most prevalent and severe foliar disease each year, although annual levels fluctuated considerably and there was no overall significant change over the two decades. Incidence of brown rust, yellow rust, take-all, and barley yellow dwarf virus also showed no significant overall change during the survey period, whereas glume blotch, powdery mildew, eyespot, and sharp eyespot all showed significant decline. Fusarium ear blight has significantly increased in both incidence and severity, causing a serious epidemic in 2012, when 96% of crops were affected. Tan spot has been the third most prevalent foliar disease since 2009 although severity is still very low. Regional disease levels were consistent over the two decades, providing reliable baselines to measure changes in seasonal disease severity. There were significant changes in agronomic practice with a rise to predominance of minimum tillage over the use of ploughing, decreases in overall disease susceptibility of cultivars grown, a major increase in the use of oilseed rape in the rotation and a long-term trend towards earlier sowing. Fungicide use increased considerably, with over 98% crops sprayed and an average of 3.5 applications made per crop each year since 2014. Implications of changes over the last 21 years are discussed.     

Nitrogen effect on competition between winter cereals and littleseed canarygrass

Field experiments were conducted in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between littleseed canaryglass (Phalaris minor Retz.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) or triticale (Triticosecale). The presence of 400P. minor plants per square meter until early March did not have an adverse effect on dry weight of any crop. However, their further presence significantly reduced dry weight of wheat and triticale, but not that of barley. Grain yield of wheat and triticale was reduced 48% and 47%, respectively, by season-long competition ofP. minor, whereas the corresponding reduction for barley was only 8%. Crop yield reduction due toP. minor competition resulted mainly from reduction in ear number and less from reduction in 1000-grain weight. Nitrogen fertilization (150 kg N ha⁻¹), compared with control (0 kg N), slightly increased yield of all crops grown without weed competition. The same treatment also increased dry weight and competitive ability ofP. minor against wheat and triticale, compared with that of control (0 kg N); the split application of nitrogen (50 kg N ha⁻¹ before crop sowing and 100 kg N ha⁻¹ in early March) caused a slightly greater increase inP. minor dry weight than did 150 kg N ha⁻¹ applied once before crop sowing. Dry weight ofP. minor grown with barley was not affected by nitrogen fertilization, but it was severely reduced compared with that ofP. minor grown with wheat or triticale. http://www.phytoparasitica.org posting April 22, 2003.