Actinomycete complexes in the rhizosphere of winter rye on soddy podzolic soil

The structure of actinomycete complexes in the rhizosphere of winter rye (Secale cereale L.) varieties originating from different ecosystems and geographical zones was studied in field experiments on soddy podzolic soil. In addition to streptomycetes, the complexes studied contained actinomycetes of the genera Micromonospora and Streptosporangium, represented at high occurrence and comparable abundance rates. The rhizosphere of most of the studied rye varieties was dominated by micromonosporas. The antifungal potential of mycelial prokaryotes associated with winter rye was assessed. The taxonomic and functional structure of actinomycete complexes was shown to be similar in rye varieties originating from the nonchernozem zone of Russia. However, the actinomycete complex proved to be much different in the rye variety that developed in the steppe zone of the lower Volga region.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 271–277.Original Russian Text Copyright © 2005 by Shirokikh, Merzaeva.     

Actinomycete complexes in the rhizosphere of winter rye on soddy podzolic soil

The structure of actinomycete complexes in the rhizosphere of winter rye (Secale cereale L.) varieties originating from different ecosystems and geographical zones was studied in field experiments on soddy podzolic soil. In addition to streptomycetes, the complexes studied contained actinomycetes of the genera Micromonospora and Streptosporangium, represented at high occurrence and comparable abundance rates. The rhizosphere of most of the studied rye varieties was dominated by micromonosporas. The antifungal potential of mycelial prokaryotes associated with winter rye was assessed. The taxonomic and functional structure of actinomycete complexes was shown to be similar in rye varieties originating from the nonchernozem zone of Russia. However, the actinomycete complex proved to be much different in the rye variety that developed in the steppe zone of the lower Volga region.     

Antifreeze proteins in winter rye leaves form oligomeric complexes

Antifreeze proteins (AFPs) similar to three pathogenesis-related proteins, a glucanase-like protein (GLP), a chitinase-like protein (CLP), and a thaumatin-like protein (TLP), accumulate during cold acclimation in winter rye (Secale cereale) leaves, where they are thought to modify the growth of intercellular ice during freezing. The objective of this study was to characterize the rye AFPs in their native forms, and our results show that these proteins form oligomeric complexes in vivo. Nine proteins were separated by native-polyacrylamide gel electrophoresis from apoplastic extracts of cold-acclimated winter rye leaves. Seven of these proteins exhibited multiple polypeptides when denatured and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After isolation of the individual proteins, six were shown by immunoblotting to contain various combinations of GLP, CLP, and TLP in addition to other unidentified proteins. Antisera produced against individual cold-induced winter rye GLP, CLP, and TLP all dramatically inhibited glucanase activity in apoplastic extracts from cold-acclimated winter rye leaves, and each antiserum precipitated all three proteins. These results indicate that each of the polypeptides may be exposed on the surface of the protein complexes. By forming oligomeric complexes, AFPs may form larger surfaces to interact with ice, or they may simply increase the mass of the protein bound to ice. In either case, the complexes of AFPs may inhibit ice growth and recrystallization more effectively than the individual polypeptides.     

Abundance,biomass, structure,and activity of the microbial complexes of minerotrophic and ombrotrophic peatlands

A very large microbial biomass was revealed in peat bogs by means of fluorescence microscopy. In ombrotrophic peatlands, the pool of the dry-weight microbial biomass in the 1.5-m layer constituted 3–4 t/ha and was twice as high as in the minerotrophic peat bogs. Fungal biomass was predominant (55–99%) in ombrotrophic peatlands, while bacterial biomass predominated (55–86%) in minerotrophic peatlands. In ombrotrophic peatlands, the microbial biomass was concentrated in the upper layers, while in minerotrophic peatlands, it was uniformly distributed in the bulk. After drainage, the microbial pool in the ombrotrophic peatlands increased twofold; that in the minerotrophic peatlands remained at the same level. The potential activity of nitrogen fixation and denitrification was revealed across the whole profile of the peatlands. The average values of these potential activities were five times higher in the minerotrophic peatlands, where bacterial biomass predominated.     

Abundance, biomass, structure, and activity of the microbial complexes of minerotrophic and ombrotrophic peatlands

Very large microbial biomass was revealed in peat bogs by means of fluorescence microscopy. In ombrotrophic peatlands, the pool of the dry-weight microbial biomass in the 1.5-m layer constituted 3-4 t/ha and was twice as high as in the minerotrophic peat bogs. Fungal biomass was predominant (55-99%) in ombrotrophic peatlands, while bacterial biomass predominated in minerotrophic peatlands (55-86%). In ombrotrophic peatlands, the microbial biomass was concentrated in the upper layers, while in minerotrophic peatlands, it was uniformly distributed in the bulk. After drainage, the microbial pool in the ombrotrophic peatlands increased twofold; that in the minerotrophic peatlands remained at the same level. The potential activity of nitrogen fixation and denitrification was revealed across the whole profile of the peatlands. The average values of these potential activities were five times higher in the minerotrophic peatlands, where bacterial biomass predominated.     

The occurrence and effects of red clover necrotic mosaic virus in red clover (Trffbliumpratense)

In 1976, red clover necrotic mosaic virus (RCNMV) was identified in red clover variety trials at the Scottish Colleges of Agriculture and at the trial centres of the National Institute of Agricultural Botany (NIAB) in Northumberland, Dyfed, Devon and Cambridge. In 1977, RCNMV was also found in two commercial crops of red clover in South Wales. The only previous finding of this virus in Britain was in 1971.
In red clover leaves RCNMV causes veinal chlorosis, often followed by severe necrosis and deformation; the plants become stunted. All cultivars tested were infected either in field or glasshouse experiments and three of the four most susceptible cultivars were tetraploids. Yield losses in cv. Hungaropoly averaged 57% over three cuts. RCNMV was transmitted manually but not through seed or by aphids {Acyrthosiphon pisum and Myzus persicae) or weevils (Apion spp. and Sitona lineatus). Seedlings became infected when grown in pots containing RCNMV-infected plants or soil from infected sites, and the roots of infected test seedlings contained an Olpidium sp. which may be the vector.
White clover mosaic virus (WCMV), also common in red clover at some sites, was less damaging than RCNMV and in a glasshouse experiment decreased yield by only 22%. An unidentified seed-borne virus with spherical particles c. 33 nm in diameter was the only virus detected in clover seedlings screened for RCNMV.     

Permeability of the suberized mestome sheath in winter rye

Mestome sheath cells of winter rye (Secale cereale L. cv Puma) deposit suberized lamellae in their secondary cell walls. Histochemical tests including acid digestion and staining with Sudan IV and Chelidonium majus root extract were used to detect the presence of suberin in the primary cell wall. There was no evidence of a Casparian band between adjacent mestome sheath cells. Fluorescent dye techniques were used to trace solute movement through the rye leaf apoplast. Calcofluor white M2R, a fluorescent dye which binds to cell walls as it moves apoplastically, proved to be too limited in its mobility in leaves to test mestome sheath permeability. Trisodium 3-hydroxy-5,8,10 pyrene trisulfonate, a fluorescent dye which is mobile in the apoplast, moved easily up the vascular bundles in the transpiration stream, and diffused outward from the veins to the epidermal cell walls within minutes of reaching a particular level in the leaf. We conclude that the suberized mestome sheath of rye leaves is freely permeable to solutes moving apoplastically through radial primary cell walls.     

Leaf area index, canopy structure and photosynthesis of red clover (Trifolium pratense L.)

Abstract. The influence of leaf age, total leaf area and its dispersion in space on canopy photosynthesis were studied using microswards of red clover ( Trifolium pratense L.) which were established in the greenhouse. Two varieties, Renova (flowering) and Molstad (non-flowering), were sown in separate plastic boxes at densities of 225, 400 and 625 plants per m².
Vertical distribution of photosynthetically active radiation (PAR), leaf area, leaf age and ¹⁴CO₂-fixation were determined periodically. Net photosynthesis and dark respiration of canopies were measured. Maximum photosynthetic capacity of individual leaves was measured on plants taken from the intact canopy or from plants where shading of the growing leaves had been prevented.
Net photosynthetic rate of canopies increased linearly with leaf area index (LAI) up to an LAI of 3.5 and then declined at higher LAI, independent of variety and sowing density. Below the optimum LAI, net photosynthesis depended mainly on interception of PAR. Decrease in canopy photosynthesis above the optimum LAI was due to a higher proportion of old leaves with decreased photosynthetic capacity, and not to an increase in respiring plant parts. It is concluded that LAI and position of leaf age categories in the canopy are more important than vertical distribution of leaf area in determining canopy photosynthesis of red clover.     

Sex pheromone of the red clover casebearer moth,Coleophora deauratella,an invasive pest of clover in Canada

The red clover casebearer, Coleophora deauratella Lienig & Zeller (Lepidoptera: Coleophoridae), is an invasive pest of Trifolium species (Fabaceae) in Canada. We identified candidate sex pheromone components from female pheromone gland extracts using coupled gas chromatographic–electroantennographic analysis detection. Three compounds elicited an electrophysiological response from antennae and were identified as: (Z)‐7‐dodecenyl acetate, (Z)‐5‐dodecenyl acetate, and (Z)‐7‐dodecen‐1‐ol. Field tests of the candidate pheromone components revealed that males were attracted to a binary mixture of (Z)‐7‐dodecenyl acetate and (Z)‐5‐dodecenyl acetate. Male moth trap capture was greatest in traps baited with lures containing 100:10 or 100:20 ratios of these pheromone components, respectively. Trap capture was reduced when (Z)‐5‐dodecenyl acetate was present below 10 or above 20% of (Z)‐7‐dodecenyl acetate. Equal numbers of male moths were captured in traps baited with 10, 100, and 1 000 μg of the attractive binary mixture. These findings allow for the development of a pheromone‐based monitoring system for this invasive pest of clover in Canada.     

The effects of phenotypic plasticity on photosynthetic performance in winter rye, winter wheat and Brassica napus

The contributions of phenotypic plasticity to photosynthetic performance in winter (cv Musketeer, cv Norstar) and spring (cv SR4A, cv Katepwa) rye (Secale cereale) and wheat (Triticum aestivum) cultivars grown at either 20°C [non‐acclimated (NA)] or 5°C [cold acclimated (CA)] were assessed. The 22–40% increase in light‐saturated rates of CO₂ assimilation in CA vs NA winter cereals were accounted for by phenotypic plasticity as indicated by the dwarf phenotype and increased specific leaf weight. However, phenotypic plasticity could not account for (1) the differential temperature sensitivity of CO₂ assimilation and photosynthetic electron transport, (2) the increased efficiency and light‐saturated rates of photosynthetic electron transport or (3) the decreased light sensitivity of excitation pressure and non‐photochemical quenching between NA and NA winter cultivars. Cold acclimation decreased photosynthetic performance of spring relative to winter cultivars. However, the differences in photosynthetic performances between CA winter and spring cultivars were dependent upon the basis on which photosynthetic performance was expressed. Overexpression of BNCBF17 in Brassica napus generally decreased the low temperature sensitivity (Q₁₀) of CO₂ assimilation and photosynthetic electron transport even though the latter had not been exposed to low temperature. Photosynthetic performance in wild type compared to the BNCBF17‐overexpressing transgenic B. napus indicated that CBFs/DREBs regulate not only freezing tolerance but also govern plant architecture, leaf anatomy and photosynthetic performance. The apparent positive and negative effects of cold acclimation on photosynthetic performance are discussed in terms of the apparent costs and benefits of phenotypic plasticity, winter survival and reproductive fitness.     

Phyto-oestrogens in herbage and milk from cows grazing white clover, red clover, lucerne or chicory-rich pastures

A grazing experiment was carried out to study the concentration of phyto-oestrogens in herbage for cattle and in milk during two periods (May and June). Forty-eight Danish Holstein cows were divided into four groups with four treatment diets; white clover, red clover, lucerne and chicory-rich pastures. Each experimental period lasted 15 days. Herbage samples from the first day and individual milk samples from the last day of the experimental period were analysed for phyto-oestrogens using LC-MS technique. The total concentration of phyto-oestrogens was 21 399 mg/kg dry matter (DM) for red clover and 238 to 466 mg/kg DM for the other three herbages mainly due to a much higher concentration of biochanin A, formononetin and glycitein in red clover. In the milk, the total concentration of phyto-oestrogens was 253 to 397 μg/l for red clover milk and 56 to 91 μg/l in the milk from the other three treatments. This was especially due to a higher concentration of equol, daidzein and formononetin in the red clover milk. The concentration of biochanin A was significantly higher in milk from the red clover treatment in May while no differences were observed in June. Enterodiol was similar across treatments while the concentration of enterolactone was significantly lower for red clover milk compared with the other treatments. Of the tested pastures, red clover appears to have the highest concentration and to be the best source of phyto-oestrogens, especially equol, in bovine milk.     

Economic damage by Limothrips denticornis in rye, triticale and winter barley

Abstract:  Limothrips denticornis is a common thrips infesting rye, triticale and winter barley in Sweden. Field experiments with insecticides were carried out 1983–1996 in farmers' fields to investigate the damage to the plant and to evaluate the relationship between thrips density and crop yield losses. The total number of experiments was 99 in rye, 41 in triticale and nine in winter barley. The mean number of thrips per leaf sheath was around 8 in all three crops. The highest number found was 27 thrips per leaf sheath. The population density in the leaf sheath was correlated with the damage observed on the leaf sheath as percentage damaged surface. The effect on the leaf sheath alone contributed to a significant proportion of the yield loss. Thrips in the ear and aphids also contributed to the damage but with multiple regression methods it was possible to estimate the damage done solely by L. denticornis . The yield loss caused by L. denticornis was about the same in all three crops, with a variation between 21 and 26 kg per thrips per leaf sheath and hectare. Compared with the yield loss for aphids, which is about 40 kg per aphid per tiller and hectare, this is considerably lower. The economic injury level was found to be about 14 thrips per straw. The economic threshold for L. denticornis has to be decided when the females are flying into the crop and it was found to be 0.5 females per straw at earing. Economic damage by L. denticornis alone was estimated to be 20% of the total number of experiments for all three crops but economic damage for the three pests together was estimated at 40% of the total number of experiments.     

Temperature responses of membrane-associated activities from spring and winter oats

Abstract Two-week old, glasshouse-grown seedlings of spring and winter oats (Avena sativa cv. Margam and Pennal respectively) were transferred to growth rooms where the daylength was 8 h and the temperature was either 20° or 5°C. Leaves from the 20°C treatment were harvested 1 week after transfer and those from the 5°C treatment after 3 weeks. Measurements were made, at temperatures in the range 5–20°C, of the rate of senescence of excised leaf sections; the rate of in vivo tetrazolium (TTC) reduction; the NADH-MTT tetrazolium diaphorase (NMD) activity of a membrane preparation isolated by sucrose gradient centri-fugation; and Hill activity of isolated chloroplasts. Data from these experiments, either untransformed or plotted in accordance with the Arrhenius equation, were analysed by the method of maximum likelihood for the occurrence of rate-temperature discontinuities. Distinct breakpoints at 14.2–16.3°C were detected for senescence, TTC reduction and NMD in winter oat leaves from the 20°C treatment, but spring oats grown at the same temperature gave a significant discontinuity only in the rate of senescent yellowing. After the hardening treatment, 3 weeks at 5°C, senescence and TTC reduction in winter oats exhibited breakpoints at 10.1–12.4°C and spring oats gave breaks at 11.8–17.3°C. No breakpoint was observed for Hill activity from either variety under either temperature treatment. The use of this approach in studies of growth at chilling temperatures and its potential as a screening method are discussed.     

The interrelationship of growth and frost tolerance in winter rye

The reduction in growth of winter cereals that occurs in the fall is thought to be required for the development of frost resistance. In the present study, the interrelationship of freezing tolerance and growth was examined by raising winter rye ( Secale cereale cv. Puma) plants at 20/16°C (day/night) and at 5/3°C under 8-, 16- and 24-h daylengths to vary growth rates and frost tolerance. Temperature and irradiance were quantified as thermal time, photothermal time and photosynthetic photon flux and examined by multiple linear regression in order to determine their effects on growth and frost tolerance of rye shoots. At low temperature, both growth and frost tolerance were markedly influenced by daylength and irradiance. Plants grown at 5/3°C with a short daylength accumulated shoot dry weight and increased frost tolerance at a greater rate per unit photothermal time or photon flux than plants grown at longer daylengths. Moreover, 5/3°C plants grown with a 16-h day grew more slowly and were less frost tolerant than plants grown with a 24-h day. We conclude that the interrelationship between growth and frost tolerance is a quantitative one. Frost tolerance is induced only by low temperature, but the development of forst tolerance is dependent upon both irradiance, which affects the amount of photoassimilate available, and daylength, which may affect the partitioning of photoassimilates between growth and frost tolerance.