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.     

Osmotic adjustment is a prime drought stress adaptive engine in support of plant production

Osmotic adjustment (OA) and cellular compatible solute accumulation are widely recognized to have a role in plant adaptation to dehydration mainly through turgor maintenance and the protection of specific cellular functions by defined solutes. At the same time, there has been an ongoing trickle of skepticism in the literature about the role of OA in supporting crop yield under drought stress. Contrarian reviews argued that OA did not sustain turgor or that it served mainly for plant survival rather than productivity. This critical review examined 26 published studies where OA was compared with yield under drought stress in variable genotypes of 12 crops, namely, barley, wheat, maize, sorghum, chickpea, pea, pigeon pea, soybean, canola, mustard, castor bean and sunflower. Over all crops a positive and significant association between OA and yield under drought stress were found in 24 out of 26 cases. Considering that it is generally difficult to find a singular plant trait responsible for yield advantage of numerous crops under different drought stress conditions, this evidence is no less than remarkable as proof that OA sustains crop yield under drought stress.     

Rice is more efficient in arsenite uptake and translocation than wheat and barley

Rice is efficient at arsenic (As) accumulation, thus posing a potential health risk to humans and animals. Arsenic bioavailability in submerged paddy soil is enhanced due to mobilisation of arsenite, but rice may also have an inherently greater ability to take up and translocate arsenite than other cereal crops. To test this hypothesis, rice, wheat and barley were exposed to 5 µM arsenate or arsenite for 24 h. Arsenic uptake and distribution, and As speciation in the xylem sap and nutrient solution were determined. Regardless of the As form supplied to plants, rice accumulated more As in the shoots than wheat or barley. Arsenite uptake by rice was double of that by wheat or barley, whereas arsenate uptake was similar between rice and wheat and approximately a third smaller in barley. The efficiency of As translocation from roots to shoots was greater when plants were supplied with arsenite than with arsenate, and in both treatments rice showed the highest translocation efficiency. Arsenite was the main species of As (86–97%) in the xylem sap from arsenite-treated plants of all three species. In the arsenate-treated plants, 84%, 45% and 63% of As in the xylem sap of rice, wheat and barley, respectively, was arsenite. Arsenite efflux to the external medium was also observed in all three plant species exposed to arsenate. The results show that rice is more efficient than wheat or barley in arsenite uptake and translocation, probably through the highly efficient pathway for silicon.     

Analogue-resistant mutants of Azotobacter chroococcum derepressed for nitrogenase activity and early ammonia excretion having potential as inoculants for cereal crops

Spontaneous mutants resistant to methionine sulfoximine (Msx), methyl alanine (Mal) and methyl ammonium chloride (Mac) were derived from A. chroococcum strain A103. Msx and Mal-resistant mutants expressed 1.73 to 10.98% of the fully derepressed nitrogenase activity when grown in Burk's medium containing ammonium acetate. Mac-resistant mutants did not express nitrogenase activity in ammonium acetate supplemented medium. The mutants excreted ammonia even after 2 days of growth and some mutants excreted more ammonia as compared to the parent. Selected mutants were inoculated on wheat (Triticum aestivum) and barley (Hordeum vulgare) under field conditions. Majority of the derepressed mutants increased grain yield of wheat and barley varying from 1.2 to 33.3%. However, host-dependent effects on grain yield were observed with different mutants. Two mutants, Mal 27 and Mac 19 showed significant increase in grain yields of both the crops. The results suggest that metabolic analogue-resistant mutants of Azotobacter have potential for use as a biofertilizer for cereal crops.     

II. Cereal disease: the interplay between resistance and pathogenicity: Inheritance of pathogenicity in Gaeumannomyces graminis var. tritici

Variation in host response of isolates of the eyespot pathogen from different sources was examined over a number of years. Pathogen types were found in intensively-cropped couch-infested cereal sites that were almost as virulent on Agropyron repens (couch) as on wheat or barley. The commonly occurring wheat (W) type isolates from couch-free cereal crops were virulent on wheat and barley but avirulent on couch. Couch (C) types were isolated not only from couch but also from wheat, barley and oat crops with couch infestation. In pathogenicity tests on rye, C. types did not differ in virulence from the more commonly occurring W types. Aegilops ventricosa was equally resistant to both types. W type isolates from wheat and barley were examined to assess differential pathogenicity on wheat and barley. Sequential cropping with single cereal crops was used to separate out possible specific types. Isolates from fourth wheat and fourth barley crops were more pathogenic on the original than on the alternative host. When comparisons were made between isolates from third and fifth consecutive wheat and barley crops only those from barley showed a preference for the original host. An experiment comparing isolates from third and seventh consecutive wheat and barley crops showed a decline in virulence from the short to the longer sequences on the alternative but not on the original host.     

Heavy metals accumulation and distribution in durum wheat and barley grown in contaminated soils under Mediterranean field conditions

Abstract

In the framework of a phytoremediation project in the Apulia region (Italy) a field experiment was carried out in multi-metal contaminated soils. The accumulation and distribution of metals in different plant parts of durum wheat and barley were studied. Further, the application of Bacillus licheniformis strain BLMB1 to soil was evaluated as a means to enhance metal accumulation in plants. The translocation and the bioconcentration factors indicated that wheat and barley do not act as metal accumulators in the field conditions tested, thus phytoextraction by these species would not be recommended as a soil remediation alternative. Application of B. licheniformis improved the accumulation of all metals in roots of wheat and barley, and increased Cd, Cr, and Pb contents in the shoots of barley. Low health risk for humans and animals was evaluated to exist if straw and grain from both cereal crops grown in these contaminated sites are consumed.     

Eyespot of wheat and barley in Scotland in 1944

In August 1944, eyespot ( Cercosporella herpotrichoides Fron.) was found in ninety out of 121 autumn-sown wheat crops distributed over twelve Scottish counties. It was abundant enough in forty fields to be likely to harm subsequent crops, and was causing obvious loss in eleven crops. The disease was found in seventeen out of eighteen spring-sown barley crops, more than half the straws being infected in seven of them. About 4 % of the wheat inspected was lodged mostly by eyespot and about 38 % of the barley mostly non-parasitically. Eyespot increased with the frequency of wheat and barley in the two preceding years, but a few infected crops occurred on fields where no wheat or barley had been grown for many years. In Scotland, where the atmosphere is more humid, eyespot tends to increase more rapidly than in similar rotations in England; lesions are found higher up the straw and the disease is much more prevalent on spring-sown barley. The long rotations practised in Scotland prevent more extensive damage by eyespot.     

Selenium accumulation by sequentially grown wheat and rice as influenced by gypsum application in a seleniferous soil

A field experiment was conducted for 2 years on an alkaline calcareous seleniferous soil to study the effect of different levels of gypsum (0.2 – 3.2 t ha⁻¹) applied to wheat only in the first year on Se accumulation by wheat (Triticum aestivum L.) – rice (Oryza sativa L.) cropping sequence. With gypsum application, grain yield of both rice and wheat crops increased by 0.4 – 0.5 t ha⁻¹; the increase in straw yield was 0.4 – 1.1 t ha⁻¹. Significant reduction in Se accumulation by wheat was observed with gypsum application up to 0.8 t ha⁻¹ and its residual effect was evident on the following crops for 2 years. Reduction in Se accumulation varied from 53 to 64% in wheat grain, 46 to 49% in wheat straw, 35 to 63% in rice grain and 36 to 51% in rice straw with an application of gypsum at 0.8 t ha⁻¹. A corresponding increase in S concentration was observed. In the gypsum-treated plots, the ratio of S:Se increased by 6 – 8 times in wheat and 3 – 6 times in rice. Reduction in Se accumulation by crop plants through gypsum application may help in lowering the risk of Se over-exposure of animals and humans that depend on diet materials grown on high selenium soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Estimation of the chlorophyll content and yield of grain crops via their chlorophyll potential

The results of the assessment of the relationship between the chlorophyll content, crop yield and chlorophyll potential of crops of wheat, barley, and oat are presented. The results of a ground-based remotesensing technique and laboratory data were used to accomplish this assessment. The spectral reflectance data of agricultural crops obtained using a ground-based remote-sensing technique in the Krasnoyarsk region were used to calculate the chlorophyll potential. Long-standing experiments have been carried out in different seasons, under various lighting conditions. Spectral measurements were performed using a double-beam spectroradiometer, which was installed on a mobile work platform at a height from 5 to 18 m. A good correlation between the chlorophyll content, grain yield, and chlorophyll potential of different cultivars of wheat, barley, and oat has been shown. It was also shown that the values of chlorophyll potential are different for wheat, barley, and oat cultivars in the growing season.     

The response of spring barley and winter wheat to Avena fatua population density

Populations of Avena fatua were established in crops of spring barley and winter wheat, and relationships derived between yield and other crop parameters, and weed density. Competitive effects of A. fatua, which were similar to those found in other countries, were greatest at low crop densities. Crop head numbers were reduced proportionately less than crop yield, indicating that competition was affecting other yield components. Competition increased the proportion of thin grain of barley but not of wheat. Competition had little effect on the moisture content and the contamination of the harvested grain by A. fatua, suggesting that at threshold populations these factors are unlikely to be of economic significance. It was concluded that at average crop densities, low infestations of A. fatua are likely to result in cereal yield losses in the region of 1 % for each A. fatua plant m^-2.     

Effects of waterlogging and drought on winter wheat and winter barley grown on a clay and a sandy loam soil

Summary The effects of winter waterlogging and a subsequent drought on the growth of winter barley and winter wheat have been examined. We used lysimeters containing soil monoliths with facilities to control the water table and a mobile shelter to control rainfall. Winter wheat was grown on a clay and on a sandy loam, but winter barley only on the clay soil. Lysimeters were either freely-drained during the winter or waterlogged with the water table 10 cm below the soil surface from 2 December until 31 March (that could occur by rainfall with a return period of 2 to 3 years). The lysimeters then were either irrigated so that the soil moisture deficit did not exceed 84 mm, or subjected to drought by limiting rainfall (equivalent to a 1 in 10 dry year in the driest area of England) so that the deficits reached maximum values of 150 mm in the clay and 159 mm in the sandy loam by harvest.Winter waterlogging restricted tillering and restricted the number of ears for all crops; grain yield of the winter barley was decreased by 219 g/m² (30%), and that of winter wheat by 170 g/m² (24%) and 153 g/m² (21% on the clay and sandy loam respectively.The drought treatment reduced the straw weight of winter barley by 75 g/m² (12%) but did not significantly depress the grain yield. For winter wheat on the clay, where the soil was freely-drained during the winter, drought depressed total shoot weight by 344 g/m² (17%) and grain weight by 137 g/m² (17%), but after winter waterlogging, drought did not further depress total or grain weight. In contrast, the winter wheat on the sandy loam was not significantly affected by drought.From these results, which are discussed in relation to other experiments in the United Kingdom, it seems that winter waterlogging is likely to cause more variation in the yield of winter barley and winter wheat than drought.     

Effect of previous crops on the incidence of eyespot on winter wheat

Surveys of winter wheat from 1939 to 1946 show that eyespot (Cercosporella herpotrichoides Fron.) occurs throughout Britain and that its incidence depends largely on previous cropping and on weather. Examination of 551 crops on land whose cropping for the previous 4 years was known showed that the incidence rose steadily with increasing numbers of preceding wheat and barley crops: where neither crop had been taken for 4 years the proportion of crops with more than 70% infected straws was 2%, rising to 45% where three or four such crops had been taken and the average straws infected rose from 6 to 55%.
The percentage infection to be expected in various groups of crops was calculated from previous cropping; it was compared with the actual infection and so used to assess the importance of other factors in determining the incidence of eyespot. High spring rainfall, early sowing and a dense plant increased incidence and low spring rainfall, late sowing and a thin plant reduced it.
Eyespot was not usually severe on newly ploughed grassland until the third or fourth crop of wheat, but under very wet conditions it was sometimes severe in the second crop.
Oats is much less susceptible than wheat or barley, but some crops were found with a third of their straws infected.
A brief survey of winter wheat in Holland suggested possible causes for the rise and fall of eyespot in recent years and for its present lower incidence there as compared with East Anglia.     

THE EFFECT OF DATE OF SOWING ON THE INCIDENCE OF POWDERY MILDEW ON SPRING-SOWN CEREALS

Delaying the date of sowing of spring-sown barley in 1953 and wheat in 1954 from February to April increased the incidence of powdery mildew, Erysiphe graminis DC., from May onwards. Before then, conditions did not favour the rapid spread of mildew.
From mid-June, infected barley produced necrotic lesions. These developed sooner on the early- than on the late-sown crops, and on the lower than upper leaves. Perithecia were first seen on 29 June. They were abundant on the wheat by 20 July.
Mildew reduced the yield of barley sown on 30 March and 28 April 1955 by 8 cwt./acre. The percentage loss was greater in the late- than in the early-sown crops. The number of ears per metre of row, the weight of 100 ears and the 1000-grain weights were reduced. Altering the seed rate from 1 ½ to 2½ bushels/acre did not affect the incidence, or the effect, of mildew on grain yield.     

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.     

Commercial Crop Yields Reveal Strengths and Weaknesses for Organic Agriculture in the United States

Land area devoted to organic agriculture has increased steadily over the last 20 years in the United States, and elsewhere around the world. A primary criticism of organic agriculture is lower yield compared to non-organic systems. Previous analyses documenting the yield deficiency in organic production have relied mostly on data generated under experimental conditions, but these studies do not necessarily reflect the full range of innovation or practical limitations that are part of commercial agriculture. The analysis we present here offers a new perspective, based on organic yield data collected from over 10,000 organic farmers representing nearly 800,000 hectares of organic farmland. We used publicly available data from the United States Department of Agriculture to estimate yield differences between organic and conventional production methods for the 2014 production year. Similar to previous work, organic crop yields in our analysis were lower than conventional crop yields for most crops. Averaged across all crops, organic yield averaged 80% of conventional yield. However, several crops had no significant difference in yields between organic and conventional production, and organic yields surpassed conventional yields for some hay crops. The organic to conventional yield ratio varied widely among crops, and in some cases, among locations within a crop. For soybean (Glycine max) and potato (Solanum tuberosum), organic yield was more similar to conventional yield in states where conventional yield was greatest. The opposite trend was observed for barley (Hordeum vulgare), wheat (Triticum aestevum), and hay crops, however, suggesting the geographical yield potential has an inconsistent effect on the organic yield gap.     

Damage potential of grasshoppers (Orthoptera: Acrididae) on early growth stages of small-grains and canola under subarctic conditions

We characterized the type and extent of grasshopper injury to above- and below-ground plant parts for four crops [barley (Hordeum vulgare L.), oats (Avena sativa L.), wheat (Triticum aestivum L.), and canola (Brassica campestris L.)] commonly grown, or with potential to grow, in central Alaska. Cages were placed on 48 pots containing plants in second to third leaf stages and stocked with 0, 2, 4, and 6 first-instar Melanoplus sanguinipes F. pot(-1). Plants were harvested 22 d after planting. Stem growth of barley and oats was not affected except at the highest grasshopper treatment. In canola, stem biomass was reduced at the medium and high grasshopper treatments, when most of the leaves had been consumed. The highest grasshopper treatment reduced leaf area in barley and oats by approximately 55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41-72%). Wheat and canola plants were smaller than barley and oats across all treatments and, at the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley and oats were reduced by 20-28% again at the highest grasshopper density, whereas the reduction for wheat and canola ranged from 50 to 90%. There was little or no difference among all grasshopper densities for C-N ratio in leaf and stem tissues of all crops. The results suggest that wheat and canola are more susceptible than barley and oats and that densities > or = 2 pot(-1) (approximately > or = 50 m(-2)) of even very small grasshoppers could cause significant damage in small-grain and oilseed crop production.     

Seed treatments with Vitavax for the control of loose smut of wheat and barley

Seed dressings with Vitavax—75 % w.p.—eliminated Ustilago nuda in spring barley seeds and greatly reduced infection due to U. tritici in winter wheat. Emergence and yield of these crops were not adversely affected. Seed soak treatments including 0·2 % aqueous Vitavax for 6 h at 30 °C (wheat and barley), 0·2% thiram for 24 h at 30 °C (barley) and 0·2% Vitavax for 1 h at 30 °C (barley) also rid the seeds of infection. In other tests with barley 2 h soaks in 0·2 % aqueous suspensions of Vitavax at 30 °C gave equivalent control to 12 h soaks in 0·2% thiram at 30 °C.     

The effects of solar ultraviolet-B radiation on the growth and yield of barley are accompanied by increased DNA damage and antioxidant responses

There is limited information on the impacts of present-day solar ultraviolet-B radiation (UV-B) on biomass and grain yield of field crops and on the mechanisms that confer tolerance to UV-B radiation under field conditions. We investigated the effects of solar UV-B on aspects of the biochemistry, growth and yield of barley crops using replicated field plots and two barley strains, a catalase (CAT)-deficient mutant (RPr 79/4) and its wild-type mother line (Maris Mink). Solar UV-B reduced biomass accumulation and grain yield in both strains. The effects on crop biomass accumulation tended to be more severe in RPr 79/4 (≈ 32% reduction) than in the mother line (≈ 20% reduction). Solar UV-B caused measurable DNA damage in leaf tissue, in spite of inducing a significant increase in UV-absorbing sunscreens in the two lines. Maris Mink responded to solar UV-B with increased CAT and ascorbate peroxidase (APx) activity. No effects of UV-B on total superoxide dismutase (SOD) activity were detected. Compared with the wild type, RPr 79/4 had lower CAT activity, as expected, but higher APx activity. Neither of these activities increased in response to UV-B in RPr 79/4. These results suggest that growth inhibition by solar UV-B involves DNA damage and oxidative stress, and that constitutive and UV-B-induced antioxidant capacity may play an important role in UV-B tolerance.     

Salicylic Acid-Mediated Regulation of Morpho-Physiological and Yield Attributes of Wheat and Barley Plants in Deferring Salinity Stress

Salinity has been observed to be a global problem that impede the physiological characteristics of plants. Salicylic acid (SA) as a phytohormone play multifaceted role in plants in terms of development as well as stress management. The current study was conducted to evaluate the effect of salinity and salicylic acid on the performance of wheat and barley plants under field experimentation followed by on-farm study to validate the results. This research was firstly conducted in a 4-year research barley field (2012–2013 and 2013–2014) and wheat (2014–2015 and 2015–2016) and subsequently in an on-farm research in four places (2017–2018). Results depicted that salinity decreased plant yield components and altered ion concentrations (Na⁺/K⁺) causing reduced grain and biological yield. However, SA foliar application induced yield components, especially grain number of plants in both years in non-saline and saline conditions. Exogenously SA application not only led to higher grain yield of barley and wheat but also significantly improved their salt tolerance. Our findings revealed that optimum SA concentrations for achieving highest barley yield were 0.85 and 0.78 mM under saline and non-saline conditions, respectively, while on-farm scale studies observed that foliar application of SA increased grain and biological yield of wheat in Ardakan, Ashkzar (saline soil and water) and Mehrabad (non-saline field) regions. There was no significant effect in Tijerd, a completely non-saline field. The grain yields were higher in SA-treated Ardakan, Ashkzar, and Mehrabad plants in field by 19, 16, and 15%, respectively. Based on present detailed studies, it was concluded that SA improved salinity tolerance and increased crop yield. So, optimum concentration (1.0–1.5 mM) with proper time application (double ridges), SA increased wheat and barley yields up to 20%. Therefore, SA priming could be used as a potent strategy to cope up salinity stress from plants.

     

Domestication and crop evolution of wheat andbarley: Genes,genomics, and future directions

Wheat and barley are two of the founder crops of the agricultural revolution that took place 10,000 years ago in the Fertile Crescent and both crops remain among the world's most important crops. Domestication of these crops from their wild ancestors required the evolution of traits useful to humans, rather than survival in their natural environment. Of these traits, grain retention and threshability, yield improvement, changes to photoperiod sensitivity and nutritional value are most pronounced between wild and domesticated forms. Knowledge about the geographical origins of these crops and the genes responsible for domestication traits largely pre-dates the era of nextgeneration sequencing, although sequencing will lead to new insights. Molecular markers were initially used to calculate distance(relatedness), genetic diversity and to generate genetic maps which were useful in cloning major domestication genes. Both crops are characterized by large,complex genomes which were long thought to be beyond the scope of whole-genome sequencing. However, advances in sequencing technologies have improved the state of genomic resources for both wheat and barley. The availability of reference genomes for wheat and some of its progenitors,as well as for barley, sets the stage for answering unresolved questions in domestication genomics of wheat and barley.