Effects of mildew on the growth and yield of spring barley: 1969-72

Mildew decreased grain yield by decreasing ear number and grain size (but not grain number/ear), the damage depending on the earliness and severity of mildew. In 1971 when mildew was early and severe, ethirimol seed dressings at 0.22 kg a.i./ha, which gave only early protection, increased yield more than did ethirimol sprays applied to protect the flag leaf and ear. In 1972 sprays were better than seed dressings at this rate because mildew was less severe during the seedling stages.     

Effects of Mildew and Nitrogen on Grain Yield of Barley Artifically Infected in the Field

Powdery mildew was artificially introduced into field plotsof barley given two amounts of nitrogen fertilizer. In Tyraand Triumph, grain dry matter and nitrogen yield of healthyplots increased in response to nitrogen fertilizer. In mildewedplots increases in response to nitrogen did not occur in Triumph,despite low levels of mildew infection. Mildew reduced grainyield and nitrogen content at both levels of nitrogen in bothvarieties. Hordewm vulgare L., barley, Erysiphe graminis, powdery mildew, nitrogen fertilizer, grain yield     

Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.     

Effects of barley mildew on green leaf area and grain yield in field and greenhouse experiments

In 1980 the relationships between mildew severity, green leaf area (GLA) and grain yield of spring barley were examined using greenhouse-grown plants and plants grown in micro-plots in the field. Mildew, by causing premature senescence, reduced GLA and grain yield was strongly correlated with GLA integrated from growth stages 2–10.5 on the Feekes scale. Early mildew attack reduced all yield components (including grain size) even when fungicidal control had eliminated mildew by anthesis. Analyses of culms at anthesis and harvest supported the view that the smaller grain size associated with early mildew attack resulted from a deficiency in carbohydrate stored in culms before anthesis and available for retranslocation to the developing grain. Amounts of total soluble carbohydrate at anthesis and the amounts lost beween anthesis and harvest were both strongly correlated with GLA up to anthesis.     

A survey of foliar diseases of spring barley in England and Wales in 1967

A total of 5,250 acres of spring barley was sampled in proportion to the barley acreage in each of eight regions. The percentage leaf area ‘affected’ by each disease was recorded for the first (flag) and second leaves at a growth stage when the grain was milky ripe. The operation was automated by punching the data directly on to computer paper tape and a programme was written to analyse the results. Mildew was found to be the most important disease, causing an average loss in yield of approximately 18 %, followed in descending order by brown rust 3%, leaf blotch 1 %, yellow rust 1 %, halo spot 1 %. The total loss due to foliar diseases was estimated to be 20–25% of the national barley yield. Diseases were more severe in the southern than northern regions, e.g. mildew severity was three times higher because of the greater popularity of mildew-susceptible varieties, and the prevalence of weather more conducive to mildew development. Disease severity was not related to previous cropping, and in general the February-sown crops had more mildew than the April-sown crops.     

Interactions between fungicide, plant growth regulator, nitrogen fertiliser applications, foliar disease and yield of winter barley

Leaf size and foliar disease in winter barley increased with increasing total amounts of nitrogen applied to the crop: flag leaf areas increased at an average of 10% per 35 kg N ha^-1 Nitrogen top dressing applied in mid-March (G.S. 31) resulted in larger leaves, more foliar disease, more straw, delayed ear emergence, fewer grains ear^-1 and less grain yield than nitrogen applied in mid-April (G.S. 31). Application of chlormequat at G.S. 30 gave a variable response, but overall it increased fertile stems m-² and crop yield and decreased crop height but had no significant effect on straw yield. Fungicide treatments suppressed foliar disease and improved yield. Yield responses were greater when plant growth regulator and mid-March nitrogen had been applied at sites where more disease prevailed than with April-applied nitrogen. In one of the field experiments, on cv. Sonja, delaying the main nitrogen application until April, without fungicide treatment, gave a similar yield to that provided by nitrogen in March with two or three fungicide sprays.     

Growth, yield and grain quality of barley (Hordeum vulgare L.) in response to nitrogen uptake. II. Plant development and rate of germination

A nutrient culture system supporting stands of barley was used to examine the effect of nitrogen supply on plant development and germination rate. Two contrasting cultivars of barley were grown for two seasons with nitrogen supplied at an optimal rate and at one-third that rate. Mature grain was dissected from ears by grain position; stored until out of dormancy, weighed, and the time from inhibition to germination estimated for different ear positions. A parallel set of samples was analysed for grain nitrogen concentrations. A systematic increase in germination time was observed from the bottom to the top of the ear. This effect was in addition to and of the same order as the effect of grain size on germination time. Although there was significant variation in nitrogen concentration by grain position, these effects were smaller than the variations in grain weight within the ear and were not related to germination rate. These results are discussed in relation to plant development and events at the onset of germination.Keywords: Barley, germination, grain size, ear position, nitrogen.      

Mapping QTL controlling yield and yield components in a spring barley (Hordeum vulgare L.) cross using marker regression

An RFLP map constructed from 99 doubled haploid lines of a cross between two spring barley varieties (Blenheim × Kym) was used to localize quantitative trait loci (QTL) controlling grain yield and yield components by marker regression and single-marker analysis. Trials were conducted over three years. Genotype-by-year interaction was detected for plant grain weight and ear grain weight so they were analysed separately for each year. None was detected for thousand-grain weight and ear grain number so data were pooled over years. A total of eleven QTL were detected for plant grain weight over two years and fourteen for ear grain weight over three years. Seven QTL were detected for plot yield. The locus with the largest effect was on chromosome 2(2H)L and accounted for 19% of the variation in the progeny. Eight QTL were detected for thousand-grain weight and five for ear grain number. Many of the QTL detected were in comparable positions in each year. Yield and yield components were only partly correlated. Comparisons based on common RFLP markers showed that some QTL were found in positions similar to those identified in other studies. For a number of QTL the identification of linked markers provided suitable opportunities for marker-assisted selection and improvement of barley and reference markers with which to analyse the homoeologous chromosome regions of wheat and other cereals.     

Economic evaluation of the effects of planting date and application rate of imidacloprid for management of cereal aphids and barley yellow dwarf in winter wheat

The effects of planting date and application rate of imidacloprid for control of Schizaphis graminum Rondani, Rhopalosiphum padi L. (Homoptera: Aphididae), and barley yellow dwarf virus (BYDV) in hard red winter wheat were studied. The first experiment was conducted from 1997 to 1999 at two locations and consisted of three planting dates and four rates of imidacloprid-treated seed. The second experiment was conducted from 2001 to 2002 in Stillwater, OK, and consisted of two varieties of hard red winter wheat seed and four rates of imidacloprid. Aphid densities, occurrence of BYDV, yield components, and final grain yield were measured, and yield differences were used to estimate the economic return obtained from using imidacloprid. In the first study, aphid populations responded to insecticide rate in the early and middle plantings, but the response was reduced in the late planting. Yields increased as insecticide rate increased but did not always result in a positive economic return. In the second study, imidacloprid seed treatments reduced aphid numbers and BYD occurrence, protected yield, and resulted in a positive economic return. The presence of aphids and BYDV lowered yield by reducing fertile head density, total kernel weight, and test weight. Whereas the application of imidacloprid seed treatments often provided positive yield protection, it did not did not consistently provide a positive economic return. A positive economic return was consistently obtained if the cereal aphid was carrying and transmitting BYDV and was more likely to occur if wheat was treated with a low rate if imidacloprid and planted in a "dual purpose" planting date window.     

Physiological Causes of Differences in Grain Yield between Varieties of Barley

In a field experiment on barley at Rothamsted with the highmean yield of 49 cwt. of grain per acre, the varieties Proctorand Herta produced 10—15 per cent, more grain than Plumage-Archeron plots that received no nitrogenous fertilizer. When nitrogenwas applied the difference was increased to about 30 per cent.,because the higher nitrogen supply caused the Plumage-Archercrop to lodge and did not increase its yield, while Proctorand Herta remained standing. The three varieties did not differ in leaf-area index nor innet assimilation rate before ear emergence, so that all hadthe same total dry weight. After ear emergence, the leaf-areaindices of Proctor and Plumage-Archer were nearly equal, butthat of Herta was smaller. Assuming that the photosyntheticefficiency of the leaves continued to be the same in all varieties,the higher grain yields of Proctor and Herta cannot be attributedto greater production of dry matter by the leaves, either beforeor after ear emergence. A pot experiment on plants with shadedears confirmed that the dry matter contributed to grain yieldby unit leaf area was nearly equal in all the varieties. The higher grain yield of Proctor and Herta than of Plumage-Archermust therefore have come from additional photosynthesis in partsof the plant other than the leaves, i.e. in the ears themselves.An attempt to demonstrate this directly in a pot experiment,by comparing the grain yields of plants with shaded or withunshaded ears, was unsuccessful because the varieties behaveddifferently in pots; Proctor and Herta produced only about 6per cent, more grain yield than Plumage-Archer, and though thedecrease in grain yield by shading the ears was slightly greaterfor Proctor and Herta, the differences were not significant. The sum of ear sizes (estimated from length and breadth measurements)per m.1 in the field experiment was greater for Proctor andHerta than for Plumage-Archer. Also the distribution of drymatter between developing ears and shoots apparently differedwith variety, so that at ear emergence the dry weight of earsper m.² was greater in the two higher yielding varieties. Theincreased amount of photosynthetic tissue in the ears of Proctorand Herta, as measured by size or weight, may not wholly explaintheir greater dry-matter production; ears of Herta may alsohave a higher photosynthetic efficiency. No differences in nutrient uptake that could account for thevarietal differences in grain yield were found. Plumage-Archerabsorbed more potassium, and Herta less phosphorus than theother varieties. About a quarter of the final content of nitrogen,and a third of the phosphorus, was absorbed after ear emergence,but the potassium content was nearly maximal at ear emergenceand later decreased. The pot experiment showed that, on the average of all varieties,26 per cent. of the dry matter in the grain at harvest originatedfrom photosynthesis in the ears, including 10 per cent, fromthe awns; 59 per cent, came from photosynthesis in the flag-leaflamina and sheath and peduncle, and 15 per cent, from partsof the shoot below the flag leaf.     

Effects of foliar application of BAP on source and sink strength in four six-rowed barley (Hordeum vulgare L.) cultivars

A field experiment was conducted to investigate the effects of foliar application of a synthetic cytokinin (BAP) on source and sink strength of four different six-rowed barley (Hordeum vulgare L.) cultivars. Different spraying treatments consisting of spraying on whole plant, spraying only on leaves and spraying only on ears started at anthesis and continued for 7 days. One additional spraying was carried out on late period of grain filling. Results showed that spraying only on leaves did not affect ear weight, grain yield and 1,000-grain weight, while the two other treatments increased all above mentioned traits. Neither of treatments affected stem weight, biological yield and contribution of stem reserves in grain filling. Exogenous cytokinin did not increase photosynthetic rate and chlorophyll content in treated leaves until late period of grain filling, although there was no significant increase in final grain weight due to late application of BAP. Our results suggested that effects of foliar application of BAP were mostly due to increased sink size soon after anthesis and increased sink demand probably met by current photosynthesis of organs other than leaves, like ear green tissues. An erratum to this article is available at .     

Grain Yield in Two Contrasting Varieties of Spring Wheat

To investigate factors determining grain yield in spring wheattwo contrasting varieties of high (Jufy I) and low (Peko) yieldingcapacity were grown in field and glasshouse experiments. In a field trial Jufy I yielded approximately 14 per cent moregrain than Peko on both control and nitrogen-treated plots.In another field trial employing small plots, although for bothvarieties doubling the seed-rate did not affect grain yield,the two varieties differed in their response to the increasein density. In Peko the yield level remained unaffected becausedoubling the seed-rate halved the number of fertile tillersper plant, whereas for Jufy I in addition to a shift in tillernumber per plant there were changes in the number of grainsper ear. In both varieties the weight per seed remained constant. When the two varieties were grown alone or as a 1: 1 mixtureat the same seed-rate the grain yields were similar. In themixture, Peko, compared with Jufy I, produced a greater numberof fertile tillers and consequently a greater contribution tothe total grain yield. In glasshouse experiments the grain yield per tiller and theorder of leaf area duration per tiller for the period from earemergence to grain ripening were both higher for Jufy I. Onthe other hand, there was no varietal difference for the netassimilation rate estimated during the vegetative phase, butexcluding the roots. Additional nitrogen primarily stimulated tiller production inboth varieties. Shading either the upper or lower parts of the plant demonstratedthat the ear and flag leaf and its sheath are important sourcesof assimilates for grain formation, whereas the lower partsare relatively unimportant in this respect. There were indicationsthat the response between varieties differed.     

Control of pearl millet downy mildew by seed treatment with metalaxyl*

Three formulations of the systemic fungicide metalaxyl were tested in various seed treatments for the control of pearl millet downy mildew in three field experiments with downy mildew-susceptible pearl millet hybrid NHB-3. Uniform, high levels of sporangial inoculum of the causal fungus, Sclerospora graminicola, were provided throughout the growth of the test crops from inoculated infector rows of NHB-3, planted earlier between the test plots. Significant reductions in downy mildew were obtained with all fungicide treatments. Best control was obtained when seed was soaked in a 0.5% aqueous solution of a liquid formulation (mean infection index of 9.8% compared with 94.8% in the untreated check). The degree of control with the wettable powder formulations was directly related to fungicide dosage, and there were no significant effects of application method. Simple dusting of seed at 2 g a.i./kg, a rapid and simple operation requiring small quantities of fungicide and no special application equipment, gave a high level of control (infection index of 12.6% compared with 78.9% in the untreated check). In two experiments grain yields from all the treated plots were significantly greater than from the untreated plots (means of 1234 and 1534 kg/ha for treated plots compared with 485 and 743 kg/ha, respectively), and in the third, the treatment with the least downy mildew gave significantly more grain than the untreated check (1228 compared with 727 kg/ha).     

The effect of powdery mildew (Erysiphe graminis f.sp. avenae) on yield, yield components and grain quality of spring oats

Yield components and grain quality were investigated on eight cultivars of spring oats with known differences in adult plant resistance to mildew and with different fungicide treatments. Losses in grain yield caused by mildew could be accounted for mainly by reductions in numbers of fertile panicles and thousand grain weights. The proportion of grain yield to total biomass, (harvest index) was also reduced. There were no effects of treatment on the concentration of fatty acids in the grain, the proportions of the component fatty acids, the percentage content of grain protein or the specific weights. However, correlation analysis of the data revealed that percentage protein contents and specific weights were negatively correlated with levels of mildew. There were significant genetic differences between cultivars in all of the yield and quality characteristics but no fungicide treatment/cultivar interactions.     

Arbuscular mycorrhiza increased the activity of a biotrophic leaf pathogen – is a compensation possible?

Arbuscular mycorrhizal barley-plants were more susceptible to the obligate biotrophic shoot pathogen Erysiphe graminis f. sp. hordei. In experiments under greenhouse and open-air conditions on leaves of mycorrhizal plants, the sporulation rate of the mildew fungus was more than twice that on control plants. However, mycorrhizal plants suffered less than non-mycorrhizal plants in terms of grain number, ear yield and thousand-grain weight. Disease-yield-relationship analysis showed that the symbiosis neutralised the positive correlation between disease severity and yield loss (up to 25% infected leaf area tested). After mildew infection, nitrogen in ears of non-mycorrhizal barley was higher because of an impaired starch accumulation during grain filling. In mycorrhizal plants, leaf disease did not impair either the quantity or quality of grain yield. This improved compensation in mycorrhizal plants was related to maintained photosynthetic capacity and a delay in pathogen-induced senescence. Thus filling of long-term storage pools (fructans in internodes) and consequently reallocation of these reserves during grain filling was improved. The results suggest that higher availability of energy and material during grain formation, together with longer physiological activity, were the basis of yield maintenance and, therefore, expression of mycorrhiza-induced tolerance towards the pathogen.     

Analysis of Growth and Yield of Winter and Spring Wheats

In a field experiment to investigate the physiological causesof variation in yield between autumn- and spring-sown wheatand between old and new varieties, the grain yields of the winterwheats were 3-15 per cent, greater than of the spring ones andthe new varieties Cappelle-Desprez and Jufy I yielded 40-70per cent, more than Squarehead's Master and Atle. Nitrogen fertilizerincreased the yields of Cappelle-Desprez and Jufy I more thanof Atle, and decreased the yield of Squarehead's Master by makingit lodge. Until ear emergence the winter varieties had greater leaf-areaindices (L) and dry weights, but smaller net assimilation rates(E), than the spring varieties. Square-head's Master had greaterL but smaller E, and similar dry weight to Cappelle-Desprez.Jufy I had similar E to Atlc, but greater L and dry weight.Nitrogen increased L and dry weight, but decreased E. All thedifferences in E between varieties and nitrogen treatments couldbe explained by the opposite effects on L, that is to say, thedifferences in E were caused by variation in mutual shadingarising from the differences in L and not by changes in leafphysiology. L of winter wheat reached its maximum at the end of May, butL of spring wheat continued to increase until ear emergence.Afterwards Ldecreased more rapidly for winter than for springwheat, so that eventually spring wheat had the greater L. Thesedifferences in the time changes of L partially compensated forthe shorter growth period of spring wheat, and tended to equalizethe grain yield from winter and spring sowings. After ear emergence total dry weight of winter varieties continuedto be greater than of spring ones, but the difference in dryweight of ears was much smaller because ear: shoot dry-weightratio was greater for the spring varieties. Total dry weight,ear dry weight and ear: shoot ratio were all greater in thenew than in the old varieties. Leaf area duration (D) afterear emergence was slightly greater for the winter than for thespring varieties and similar for old and new. The apparent efficiencyof this leaf area in grain production, measured by the grainleaf ratio (ratio of grain dry weight to D), was similar forwinter and spring varieties but greater for new than for old.This suggests that Cappelle-Desprez and Jufy I have higher grainyields because their ears photosynthesize more than do the earsof Squarehead's Master and Atle. Before ear emergence winter varieties had more shoots than springones, and old varieties more than new. After ear emergence therewere only small differences in numbers of ears; percentage survivalwas greater for spring than for winter and for new than forold varieties. Differences in dry weight between varieties were not causedby differences in nitrogen uptake.     

Effects of variation in ear temperature on growth and yield of spring wheat

Wheat plants were kept in a growth room at 15 ^oC from 7 days after an-thesis until maturity and their ears were warmed to 20 or 25 ^oC for various periods. Continuous warming initially increased the growth rate of the ear and decreased that of the stem, but hastened senescence of the ear and decreased final grain yield by decreasing dry weight per grain. Warming the ears increased the movement of ¹⁴C and nitrogen to them from the leaves and stem during the early stages of grain growth but decreased it later. Warming the ears for only the first 10 or 20 days also hastened ear senescence; grain yield decreased progressively with increase in duration of the warm period. All effects were greater at 25 than at 20 ^oC. The effects of changing ear temperature from 15 to 20 ^oC were independent of the temperature of the rest of the plant. Altering the humidity of the air around the ears by 4–7 mb at constant temperature had no effect on ear growth or senescence. Warming all of the plant except the ears from 15 to 20 ^oC increased ear growth slightly during early grain growth and decreased it later, irrespective of ear temperature: stem dry weight, leaf area and net photosynthetic rate of flag leaves and green stems were decreased and dark respiration rate of stems was increased.     

Effects of fungicides and insecticides applied to spring barley sown on different dates in 1976-79

Factorial experiments in 1976–1979 investigated the effects of sowing date, fungicides (ethirimol seed treatments and tridemorph sprays) and insecticides (phorate applied to the soil, and menazon or dimethoate sprays) on powdery mildew, aphids, barley yellow dwarf virus (BYDV) and grain yield of spring barley (cv. Julia in 1976 and 1977; cv. Wing in 1978 and 1979). Late sowing usually increased the severity of powdery mildew, numbers of aphids and incidence of BYDV and generally decreased yield. Responses to pesticides were commonly greater on the late-sown than on the early-sown barley. Response to fungicides are principally attributed to the control of powdery mildew (Erysiphe graminis f. sp. hordei; the target species) but responses to insecticides cannot be attributed to virus control and seem unlikely to be due solely to control of aphids, whose numbers were relatively small. There were some effects of fungicides on aphids and insecticides on mildew, but they were inconsistent and too small to affect crop protection strategies.     

Influence of Chlorocholine Chloride on Grain Growth of Winter Barley (Hordeum distichon L. cv. Igri) in the Field

Green, C. F., Dawkins, T. C. K. and McDonald, H. G. 1985. Influenceof chlorocholine chloride on grain growth of winter barley (Hordeumdistichon L. cv. Igri) in the field.–J. exp. Bot. 36:1126–1133. Chlorocholine chloride was applied to winter barley either inthe Spring or Autumn. It increased grain number per unit croparea. Rates of incorporation of dry matter into the grain weredecreased, but the period of growth was extended by the treatments.Overall the final mean grain weight was reduced so that no advantagesin terms of yield resulted from the increased grain numbers. Key words: —Chlormequat, chlorocholine chloride, CCC, Hordeum distichon L., barley, grain growth, grain weight, senescence, grain yield     

Photosynthesis of Ears and Flag Leaves of Wheat and Barley

Immediately after anthesis ears of spring wheat absorbed lessthan 0.5 mg CO₂, per hour in daylight and later evolved CO₂,in the light and in the dark. The rate of apparent photosynthesisof the combined flag-leaf lamina and sheath and peduncle (collectivelycalled flag leaf) of two spring wheat varieties, Atle and JufyI, was 3–4 mg per hour; the rates of the flag leaf andthe ear of two spring barleys, Plumage Archer and Proctor, wereeach about 1 mg per hour. The gas exchange of ears and flag leaves between ear emergenceand maturity accounted for most of the final grain dry weight.The CO₂, fixed by the wheat ear was equivalent to between 17and 30 per cent of the grain weight, but more than this waslost by respiration, so assimilation in the flag leaf was equivalentto 110–20 per cent of the final grain weight. In barley,photosynthesis in the flag leaf and the net CO₂ uptake by theear each provided about half of the carbohydrate in the grain. Barley ears photosynthesized more than wheat ears because oftheir greater surface, and flag leaves of wheat photosynthesizedmore than those of barley because they had more surface anda slightly greater rate of photosynthesis per dm².