Genetic variations in the digestibility in sheep of selected whole-crop cereals used as silages

Whole-plant winter cereals could be of great interest if used as silages for ruminant feeding as opposed to summer crops in that they would spare water resources or valorize low-input management. This study aimed to compare the feeding value of rye, barley, wheat (two genotypes) and triticale (six genotypes). The cereals were sown in October and harvested as silage in June. Forages were offered to Texel castrated sheep in order to evaluate the organic matter digestibility (OMd). The OMd of the wheat cultivars was higher (61.6%, P<0.05) than those of barley (57.2%) and rye (54.7%) but no different from that of triticale (60.6%). Within the triticale genotypes, OMd ranged from 54.7 to 62.3%. The presence of rough barbs should explain the relatively low intake of the cereals with the exception of wheat. Winter cereals provide good-quality forage for feeding ruminants. Wheat has a higher nutritional value than barley and rye and a wide variability for digestibility seems to exist within the triticale cultivars. Such variability in a species known for its ability to be cropped under limiting conditions should be explored in much greater depth as it could result in providing farmers with genotypes of good quality with an acceptable yield at a lower cost.     

An Early Indicator of Resistance in Barley to Russian Wheat Aphid

During early stages of infestation by Russian wheat aphids (Diuraphis noxia [Mordvilko]; RWAs), barley (Hordeum vulgare L.) leaf cells collapsed and showed autofluorescence in the mesophyll and bundle sheath adjacent to the RWA stylet sheath. The response was visually similar to the hypersensitive cell death response, typical of resistance to microbial pathogens. Resistant barley produced significantly more collapsed, autofluorescent cells (CAC) than did susceptible barley. RWA stylet entry sites and sheath paths also fluoresced, making them easy to observe in whole leaf sections. The number of CAC increased with the number of RWAs and with the number of days of feeding in resistant plants. The CAC could be observed 1 d following infestation, making this the most rapid plant response toward the RWAs known to date. The response may be useful in screening for resistant plants and may provide insight into resistance mechanisms in barley.     

Cover crop, rye residue and in-furrow treatment effects on thrips

Abstract:  Thrips and thrips damage to cotton and peanut plants were compared in plots with in-furrow treatments of aldicarb, phorate and diammonium phosphate (DAP) fertilizer under two tillage regimes with a winter cover of crimson clover and under different levels of rye residue ground cover. Adult and larval thrips numbers were significantly lower in cotton plots following winter crimson clover cultivation compared with no-cover plots in all 3 years. Thrips numbers did not differ with respect to the in-furrow treatments in the clover plots, but in the no-cover plots, they were significantly higher in the untreated control and DAP treatments compared with the aldicarb treatment. Thrips damage was higher in the no-cover than the clover plots except in the aldicarb treatments. Within the cover crop plots, thrips damage was highest in the control and phorate treatments and similar in the DAP and aldicarb treatments. There was an inverse relationship between the amount of rye residue ground cover and thrips density and thrips damage in cotton and peanuts. There was also an inverse relationship between the density of rye residue and damage to peanuts from Bunyaviridae tospovirus. Cotton yield was reduced in the cover crop plots and was not measured in the rye residue and peanut plots. These results suggest that ground cover alone decreases thrips numbers and thrips damage in both cotton and peanuts and that a winter crimson clover cover and an in-furrow treatment of DAP enhanced plant protection from thrips in cotton.     

Differential response of rye,triticale, bread and durum wheats to zinc deficiency in calcareous soils

Field and greenhouse experiments were carried out to study the response of rye (Secale cereale L. cv. Aslim), triticale (× Triticosecale Wittmark. cv. Presto), two bread wheats (Triticum aestivum L, cvs. Bezostaja-1 and Atay-85) and two durum wheats (Triticum durum L. cvs. Kunduru-1149 and C-1252) to zinc (Zn) deficiency and Zn fertilization in severely Zn-deficient calcareus soils (DTPA-Zn=0.09 mg kg^-1 soil). The first visible symptom of Zn deficiency was a reduction in shoot elongation followed by the appearance of whitish-brown necrotic patches on the leaf blades. These symptoms were either absent or only slight in rye and triticale, but occurred more rapidly and severely in wheats, particularly in durum wheats. The same was true for the decrease in shoot dry matter production and grain yield. For example, in field experiments at the milk stage, decreases in shoot dry matter production due to Zn deficiency were absent in rye, and were on average 5% in triticale, 34% in bread wheats and 70%, in durum wheats. Zinc fertilization had no effect on grain yield in rye but enhanced grain yield of the other cereals. Zinc efficiency of cereals, expressed as the ratio of yield (shoot dry matter or grain) produced under Zn deficiency compared to Zn fertilization were, on average, 99% for rye, 74% for triticale, 59% for bread wheats and 25% for durum wheats.These distinct differences among and within the cereal species in susceptibility to Zn deficiency were closely related to the total amount (content) of Zn per shoot, but not with the Zn concentrations in shoot dry matter. For example, the most Zn-efficient rye and the Zn-inefficient durum wheat cultivar C-1252 did not differ in shoot Zn concentration under Zn deficiency, but the total amount of Zn per whole shoot was approximately 6-fold higher in rye than the durum wheat. When Zn was applied, rye and triticale accumulated markedly more Zn both per whole shoot and per unit shoot dry matter in comparison to wheats.The results demonstrate an exceptionally high Zn efficiency of rye and show that among the cereals studied Zn efficiency declines in the order rye>triticale>bread wheat>durum wheat. The differences in expression of Zn efficiency are possibly related to a greater capacity of efficient genotypes to acquire Zn from the soil compared to inefficient genotypes.     

Host range,mating type and population structure of Magnaporthe sp. of a single barley field in São Paulo state,Brazil

Brazil is blast disease hot spot because severe epidemics have occurred among wheat, triticale, rye, barley and oat crops. Although the first outbreak of barley blast appeared in 1998, little information is available. Therefore, this study aimed to examine host range, mating type composition and population structure of Magnaporthe sp. from a single barley field in São Paulo, Brazil. To examine pathogenicity, 25 Magnaporthe isolates were inoculated on five, three, two and two cultivars of barley, wheat, oat and rice, respectively, and one cultivar each of rye, corn, sorghum, triticale and certain weeds (Cenchrus echinatus, Setaria geniculata, Brachiaria plantaginea and Eleusine indica). Mating type distribution of 33 isolates was investigated by molecular tools. The genotypic divergence of 41 barley and five wheat isolates was investigated by 15 random amplified polymorphic DNA primers and unweighted pair group method with arithmetic mean. The host range of the barley blast pathogen included wheat, oat, rye and triticale but not rice and weeds. Sexual reproduction appeared to not be involved in the high genotypic diversity because only a single isolate, MAT1‐2, was identified. The majority of barley isolates clustered together with wheat blast, except for four, suggesting a different origin.     

Predatory effect of Coccinella septempunctata on Thrips tabaci and Trialeurodes vaporariorum

Abstract:  The predatory effect of adult ladybird Coccinella septempunctata L. on adults of thrips, Thrips tabaci Lindeman, and whiteflies, Trialeurodes vaporariorum (Westwood), was examined in controlled environment chambers, on tomato leaves, in transparent small plastic cages at proportions of 1/(10 + 10), 1/(20 + 20), 1/(30 + 30) and 1/(40 + 40) predator/number of thrips and whiteflies. We conclude that C. septempunctata could be used with success for the biological control of thrips and whiteflies in greenhouse crops, with almost the same effectiveness as for aphids, at predator/prey proportions near 1 : 30. Additionally, it was found a prey preference for T. tabaci in comparison with T. vaporariorum . According to the model used, effective predation is correlated with predator/prey ratio rather than to prey preference.     

Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Content and Activity in Wheat, Rye and Triticale

Photosynthetic parameters were measured in triticale and its parents wheat and rye. Soluble protein content in leaves, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content per fresh mass, total chlorophyll content, biomass yield, leaf area, leaf mass and specific leaf mass were higher but Rubisco content expressed as percentage of soluble protein, carboxylase activity, photosynthetic rate and stomatal conductance were significantly lower in rye than in wheat. Native-PAGE of Rubisco revealed that rye carboxylase was different from that of wheat. The difference was not related to either the small or large subunit of Rubisco but, may be, to the ionic and/or other properties of the Rubisco protein moiety. Triticale Rubisco was similar to wheat. For most of the studied physiological parameters, triticale showed much more similarity with wheat than with rye.     

Biology,host preferences and fitness of <Emphasis Type="Italic">Oulema melanopus</Emphasis> (Coleoptera: Chrysomelidae), a recent invasive pest in Western Canada

The developmental parameters and fitness of a recent invasive insect pest of cereals in western Canada, the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), were compared on live plants and excised leaves of commercial cultivars of potential cereal hosts including wheat (winter and spring), oats, barley, corn, rye and triticale. Host preference and utilization within the fundamental host range of O. melanopus differed. The biological parameters differed significantly when the larvae were reared on excised tissues versus on live host plants. In both studies, wheat (winter and spring), oat (cv. Morgan) and barley were the most preferred hosts in terms of development, survivorship, adult weights and fecundity. Prolonged development with low fitness gains was noted on corn. Although the development on hosts such as rye and triticale was prolonged and adult fitness was low, the survivorship was high on these hosts. Hence, these crops can act as secondary hosts for the beetle in its new eco-region. Larvae fed foliage of Waldern, a local oat cultivar, had increased developmental time and lower survivorship compared with other cereal hosts. Despite differences in fitness gains among hosts, similar numbers of eggs were laid on all hosts. Hence, the oviposition choice of O. melanopus may not be driven by fitness gains alone and it may indicate adaptive strategy to hosts in newer environments.     

Impact of straw mulch on populations of onion thrips (Thysanoptera: Thripidae) in onion

Development of insecticide resistance in onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), populations in onion (Allium spp.) fields and the incidence of the T. tabaci transmitted Iris yellow spot virus have stimulated interest in evaluating alternative management tactics. Effects of straw mulch applied in commercial onion fields in muck areas of western New York were assessed in 2006 and 2007 as a possible onion thrips management strategy. In trials in which no insecticides were applied for thrips control, straw mulch-treated plots supported significantly lower T. tabaci populations compared with control plots. In both years, the action thresholds of one or three larvae per leaf were reached in straw mulch treatments between 7 and 14 d later than in the control. Ground predatory fauna, as evaluated by pitfall trapping, was not increased by straw mulch in 2006; however, populations of the common predatory thrips Aeolothrips fasciatus (L.) (Thysanoptera: Aeolothripidae) were significantly lower in straw mulch plots in both years. Interference of straw mulch in the pupation and emergence of T. tabaci was investigated in the lab and their emergence was reduced by 54% compared with bare soil. In the field the overall yield of onions was not affected by the straw mulch treatment; however, the presence of jumbo grade onions (>77 mm) was increased in 2006, but not in 2007. These results indicate that populations of T. tabaci adults and larvae can be significantly reduced by the use of straw mulch without compromising overall onion yield. The use of this cultural practice in an onion integrated pest management program seems promising.     

Yield stability of hybrids versus lines in wheat,barley, and triticale

Key message

We present experimental data for wheat, barley, and triticale suggesting that hybrids manifest on average higher yield stability than inbred lines.

Abstract

Yield stability is assumed to be higher for hybrids than for inbred lines, but experimental data proving this hypothesis is scarce for autogamous cereals. We used multi-location grain yield trials and compared the yield stability of hybrids versus lines for wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and triticale (×Triticosecale Wittmack). Our study comprised three phenotypic data sets of 1,749 wheat, 96 barley, and 130 triticale genotypes, which were evaluated for grain yield in up to five contrasting locations. Yield stability of the group of hybrids was compared with that of the group of inbred lines estimating the stability variance. For all three crops we observed a significantly (P < 0.05) higher yield stability of hybrids compared to lines. The enhanced yield stability of hybrids as compared to lines represents a major step forward, facilitating coping with the increasing abiotic stress expected from the predicted climate change.     

Economic injury levels for western flower thrips (Thysanoptera: Thripidae) on greenhouse cucumber

Low, medium and high densities of western flower thrips, Frankliniella occidentalis (Pergande), were established in three greenhouses at the Greenhouse and Processing Crops Research Centre, Ontario, Canada, in 1996 and 1998 to develop economic injury levels for thrips on greenhouse cucumber. Thrips densities were monitored weekly using yellow sticky traps and flower counts. Fruit was harvested twice a week, graded for size, weighed, and rated for thrips damage using three damage categories. Significant yield reduction was detected 4 wk after severe fruit damage was observed in the high and medium thrips density treatments in 1996 and 7 wk in 1998. Percentage of severe damaged fruit (P(F3)) has significant linear relationships with the adult thrips density (x) that was sampled by sticky traps 1 wk before harvest (P(F3) = -0.2533 + 0.0828x) and that was sampled by flower counts 2 wk before harvest (P(F3) = -0.2025 + 0.5490x). Based on the regression equations, economic injury levels, expressed as adult thrips per sticky trap per day or adult thrips per flower, were calculated for various combinations of control costs, yield potential and fruit prices. The economic injury levels for F. occidentalis ranged from 20 to 50 adults per sticky trap per day or 3 to 7.5 per flower as determined under average greenhouse production conditions in Ontario, Canada.     

Transferability of SSR markers among wheat,rye, and triticale

Simple sequence repeat (SSR) markers are a valuable tool for many purposes, such as mapping, fingerprinting, and breeding. However, they are only available in some economically important crops because of the high cost and labor intensity involved in their development. Comparative mapping reveals a high degree of colinearity between closely related species, which allows the exchange of markers between them. Our objective was to examine the transferability of SSR markers among wheat (Triticum aestivum L.), rye (Secale cereale L.), and triticale (X Triticosecale Wittmack). One hundred forty-eight wheat and 28 rye SSR markers were used to amplify genomic DNA extracted from five lines each of wheat, rye, and triticale. Transferability of wheat SSR markers to rye was 17%, whereas 25% of rye markers were amplifiable in wheat. In triticale, 58% and 39% transferability was achieved for wheat and rye markers, respectively. Wheat markers gave an average of 2.6, 2.7, and 2.4 polymorphic bands in wheat, rye, and triticale, respectively, while rye markers gave an average of 2.0 in rye and none in wheat and triticale. These transferable markers can now be exploited for further genetic and breeding studies in these species.Nebraska Agricultural Research Division, Journal Series No. 14243Communicated by B. Friebe     

Comparison of structural damage caused by Russian wheat aphid (Diuraphis noxia) and Bird cherry-oat aphid (Rhopalosiphum padi) in a susceptible barley cultivar, Hordeum vulgare cv. Clipper

The Russian wheat aphid (RWA, ( Diuraphis noxia ) and the Bird cherry-oat aphid (BCA, ( Rhopalosiphum padi L.) cause severe damage to grain crops, including barley. An investigation of the effects of these aphids on a susceptible cultivar revealed that BCA-infested barley plants remained healthy looking for 2 weeks after feeding commenced. In contrast, signs of stress and damage, including chlorosis and leaf necrosis were evident in RWA-infested plants. Our study suggests that damage to the vascular tissue because of sustained feeding by BCA was not as extensive as that caused by RWA. In addition, there is a marked difference in the salivary secretion pattern within xylem elements punctured by aphids tapping the xylem for water. RWA deposit electron-dense, amorphous to smooth saliva, which completely encases the inner walls of affected elements, and saliva encases pit membranes between xylem elements, and between xylem vessels and xylem parenchyma. Xylem tapped by BCA contained more granular saliva, which apparently does not occlude vessel wall apertures or the pit membranes to the same extent, as was observed with RWA. Damage to phloem tissue, including phloem parenchyma elements, sieve tube–companion cell (CC–ST) complexes as well as thick-walled ST, was extensive. Plasmodesmata between phloem parenchyma elements as well as pore plasmodesmata between the CC and ST were occluded by callose. We conclude that severe, perhaps permanent damage to conducting elements in RWA-infested leaves may be responsible for the detrimental chlorosis and necrosis symptoms. These symptoms are absent in BCA-infested plants.     

Can Mass Trapping Reduce Thrips Damage and Is It Economically Viable? Management of the Western Flower Thrips in Strawberry

The western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a cosmopolitan, polyphagous insect pest that causes bronzing to fruit of strawberry (Fragaria x ananassa). The main aim of this study was to test whether mass trapping could reduce damage and to predict whether this approach would be economically viable. In semi-protected strawberry crops, mass trapping of F. occidentalis using blue sticky roller traps reduced adult thrips numbers per flower by 61% and fruit bronzing by 55%. The addition of the F. occidentalis aggregation pheromone, neryl (S)-2-methylbutanoate, to the traps doubled the trap catch, reduced adult thrips numbers per flower by 73% and fruit bronzing by 68%. The factors affecting trapping efficiency through the season are discussed. Damage that would result in downgrading of fruit to a cheaper price occurred when bronzing affected about 10% of the red fruit surface. Cost-benefit analysis using this threshold showed that mass trapping of thrips using blue sticky roller traps can be cost-effective in high-value crops. The addition of blue sticky roller traps to an integrated pest management programme maintained thrips numbers below the damage threshold and increased grower returns by a conservative estimate of £2.2k per hectare. Further work is required to develop the F. occidentalis aggregation pheromone for mass trapping and to determine the best timing for trap deployment. Mass trapping of thrips is likely to be cost-effective in other countries and other high-value crops affected by F. occidentalis damage, such as cucumber and cut flowers.     

Economic thresholds for Aphis gossypii (Hemiptera: Aphididae) on Citrus clementina

Different levels of Aphis gossypii Glover were maintained on clementine trees by means of isolation inside mesh cages. Clementine yield loss was correlated with the number of aphids per square meter of canopy, obtaining the corresponding formula. Starting from this formula, the economic injury level (EIL) was calculated as follows: [218,333C + 11,130.6 VP0K]/[57.08 VP0K - 100C] = EIL (aphids/m2), where C = total insecticide cost per hectare, V = fruit price per kilogram, P0 = yield per hectare of a minimum pest level orchard, and K = reduction of injury due to treatment. Starting from the EIL, the economic threshold, the environmental EIL, and the environmental economic threshold were obtained. Formulae relating the number of aphids per square meter with other simpler indices expressing these thresholds (percentage of infested shoots, infested shoots per 0.25 m2 ring, index of infestation, percentage of occupied rings, and number of weekly captured aphids in a yellow trap) also were calculated.     

Infestation of transgenic powdery mildew-resistant wheat by naturally occurring insect herbivores under different environmental conditions

A concern associated with the growing of genetically modified (GM) crops is that they could adversely affect non-target organisms. We assessed the impact of several transgenic powdery mildew-resistant spring wheat lines on insect herbivores. The GM lines carried either the Pm3b gene from hexaploid wheat, which confers race-specific resistance to powdery mildew, or the less specific anti-fungal barley seed chitinase and β-1,3-glucanase. In addition to the non-transformed control lines, several conventional spring wheat varieties and barley and triticale were included for comparison. During two consecutive growing seasons, powdery mildew infection and the abundance of and damage by naturally occurring herbivores were estimated under semi-field conditions in a convertible glasshouse and in the field. Mildew was reduced on the Pm3b-transgenic lines but not on the chitinase/glucanase-expressing lines. Abundance of aphids was negatively correlated with powdery mildew in the convertible glasshouse, with Pm3b wheat plants hosting significantly more aphids than their mildew-susceptible controls. In contrast, aphid densities did not differ between GM plants and their non-transformed controls in the field, probably because of low mildew and aphid pressure at this location. Likewise, the GM wheat lines did not affect the abundance of or damage by the herbivores Oulema melanopus (L.) and Chlorops pumilionis Bjerk. Although a previous study has revealed that some of the GM wheat lines show pleiotropic effects under field conditions, their effect on herbivorous insects appears to be low.     

Earlier onset of DNA fragmentation in leaves of wheat compared to barley and rye

We have found extensive nucleosomal fragmentation of native DNA extracted from leaves of healthy cereal plants, as indicated by ladder patterns on agarose gels and TUNEL staining. The time of first appearance of fragmentation differed among cereals. Native DNA from the first leaf of 10-day-old plants formed a clear ladder pattern of multiples of 180 bp fragments in wheat and triticale but not in barley and oats. In one cultivar of rye a weak ladder pattern occurred but not in another. Freezing and thawing of samples before DNA extraction resulted in much more extensive DNA fragmentation in wheat but not in rye and barley, indicating that DNA-degrading enzymes are present in the cytoplasm of wheat, but not in barley and rye, at this stage. In barley, nucleosomal fragmentation was first detected in 25-day-old plants. These results indicate that programmed cell death takes place in developing leaves of young cereal plants, but that the time of onset differs among cereal species.     

Salt Tolerance in the Triticeae: Ion Discrimination in Rye and Triticale

When rye and triticale accessions were grown in saline hydroponicculture they exhibited the low Na and high K concentrationsin their leaves which are characteristic of the enhanced K/Nadiscrimination trait originally found in the D genome of wheat.This trait was not consistently improved by the presence ofthe D genome in octaploid triticale or in D genome substitutionlines of hexaploid triticale. The presence of the rye genomedid not significantly affect anion concentrations within theleaves. At high salt concentrations (250 mol m^–3 NaCl+12.5mol m^–3 CaCl₂) the triticales were more tolerant thanthe rye accessions or a DDRR-genome tetraploid, with two triticalelines being almost as salt-tolerant as barley. Key words: Salt, ion transport, R genome, rye (Secale cereale L.)     

Effect of sowing date and straw mulch on virus incidence and aphid infestation in organically grown faba beans (Vicia faba)

The effect of sowing date on aphid infestation and the incidence of aphid-transmitted viruses were investigated in organically managed, small-scale field experiments with two faba bean cultivars over 3 years (2002–04). As an additional factor, straw mulch was applied in 2 of the 3 years shortly before the start of vector activity in May. Virus incidence was determined using enzyme-linked immunosorbent assay and immunoelectron microscopy. Aphid flight activity was monitored using standard yellow water traps. Bean colonising aphids were assessed throughout the vegetation period by counting the number of plants infested with Acyrthosiphon pisum , Megoura viciae and Aphis fabae . Pea enation mosaic virus and bean yellow mosaic virus were the most abundant aphid-transmitted viruses, being detected in 22–54% and 9–69%, respectively, of the total number of virus-infected plants analysed per year. Further aphid-transmitted viruses found in faba bean were bean leaf roll virus, beet western yellows virus, clover yellow vein virus (in 2002) and soybean dwarf virus (in 2004). A. pisum was the predominant aphid species colonising faba bean plants. Early sowing compared with late sowing led to a significant reduction of the total virus incidence in faba bean in all 3 years. However, significantly decreased levels of A. pisum colonisation as a result of early sowing were observed only in 1 year and one cultivar. Irrespective of sowing date, straw mulching had no significant effects on virus incidence and aphid colonisation. Compared with late sowing, early sowing significantly increased bean yield in all 3 years and kernel weight in 2 years, whereas straw mulching had no effect on yield.     

Molecular characterization and functional analysis of elite genes in wheat and its related species

The tribe Triticeae includes major cereal crops (bread wheat, durum wheat, triticale, barley and rye), as well as abundant forage and lawn grasses. Wheat and its wild related species possess numerous favourable genes for yield improvement, grain quality enhancement, biotic and abiotic stress resistance, and constitute a giant gene pool for wheat improvement. In recent years, significant progress on molecular characterization and functional analysis of elite genes in wheat and its related species have been achieved. In this paper, we review the cloned functional genes correlated with grain quality, biotic and abiotic stress resistance, photosystem and nutrition utilization in wheat and its related species.