Transcript analysis in two alfalfa salt tolerance selected breeding populations relative to a non-tolerant population

With the growing limitations on arable land, alfalfa (a widely cultivated, low-input forage) is now being selected to extend cultivation into saline lands for low-cost biofeedstock purposes. Here, minerals and transcriptome profiles were compared between two new salinity-tolerant North American alfalfa breeding populations and a more salinity-sensitive western Canadian alfalfa population grown under hydroponic saline conditions. All three populations accumulated two-fold higher sodium in roots than shoots as a function of increased electrical conductivity. At least 50% of differentially expressed genes (p < 0.05) were down-regulated in the salt-sensitive population growing under high salinity, while expression remained unchanged in the saline-tolerant populations. In particular, most reduction in transcript levels in the salt-sensitive population was observed in genes specifying cell wall structural components, lipids, secondary metabolism, auxin and ethylene hormones, development, transport, signalling, heat shock, proteolysis, pathogenesis-response, abiotic stress, RNA processing, and protein metabolism. Transcript diversity for transcription factors, protein modification, and protein degradation genes was also more strongly affected in salt-tolerant CW064027 than in salt-tolerant Bridgeview and salt-sensitive Rangelander, while both saline-tolerant populations showed more substantial up-regulation in redox-related genes and B-ZIP transcripts. The report highlights the first use of bulked genotypes as replicated samples to compare the transcriptomes of obligate out-cross breeding populations in alfalfa.

Screening of condensed tannins from Canadian prairie forages for anti-Escherichia coli O157:H7 with an emphasis on purple prairie clover (Dalea purpurea Vent)

Tannins from forages grown (n = 10) on the Canadian prairie, as well as from Quebracho, Rhus semialata, and brown seaweed (Ascophyllum nodosum), were screened for anti-Escherichia coli O157:H7 activity against E. coli O157:H7 strain 3081 at a concentration of 400 μg/ml for each tannin type, except for brown seaweed, which was at 50 μg/ml. Growth of the bacteria was assessed by measuring the optical density at 600 nm over 24 h. Tannin from seaweed at a concentration of 50 μg/ml inhibited growth of strain 3081. Among the terrestrial forages, only condensed tannins (CT) from purple prairie clover (Dalea purpurea Vent; PPC) increased (P < 0.05) the lag time and reduced (P < 0.05) the growth rate of E. coli O157:H7. The anti-E. coli O157:H7 activity of PPC CT was further assessed by culturing E. coli strain ATCC 25922 and eight strains of E. coli O157:H7 with PPC CT at 0, 25, 50, 100, or 200 μg/ml. Selected strains were enumerated after 0, 6, and 24 h of incubation, and fatty acid composition was determined after 24 h of incubation. E. coli strain 25922 was cultured with 0, 50, or 200 μg of CT per ml and harvested during the exponential growth phase for examination by transmission electron microscopy. Increasing CT concentration linearly increased (P < 0.001) the lag times of seven strains and linearly reduced (P < 0.001) the growth rates of eight E. coli O157:H7 strains. Proportions of unsaturated fatty acids in the total fatty acids were decreased (P < 0.01) by CT at 50 μg/ml. Transmission electron microscopy showed that CT disrupted the outer membrane structure. Anti-E. coli O157:H7 activity of PPC CT at levels of up to 200 μg/ml was bacteriostatic rather than bactericidal, and the mechanism of anti-E. coli activity may involve alteration in the fatty acid composition and disruption of the outer membrane of the cell.

Ruminal degradability and whole-tract digestibility of protein and fibre fractions in fenugreek haylage

Doepel, L., Montgomery, J. E., Beauchemin, K. A., King, J. R. and Acharya, S. N. 2012. Ruminal degradability and whole-tract digestibility of protein and fibre fractions in fenugreek haylage. Can. J. Anim. Sci. 92: 211–217. The purpose of this study was to evaluate the digestibility of fenugreek forage compared with alfalfa in dairy cows. Alfalfa and two genotypes of fenugreek, Quatro and F70, were harvested and prepared as plastic-wrapped high-moisture bales. Fourteen weeks after baling, forage samples were obtained for determination of ruminal degradation and whole-tract digestibility. To determine ruminal degradation, forage samples were placed in polyester bags and incubated in the rumen for various time points (up to 168 h) in lactating Holstein cows. Digestibility in the rumen, intestine and the whole digestive tract was estimated by incubating samples in the rumen, followed by measurements of intestinal digestibility using the mobile bag technique in two non-lactating Holstein cows. Effective ruminal degradability of DM was lower for F70 than for alfalfa, while for ADF and NDF it was equivalent in all forages. Whole-tract disappearance of DM, CP, ADF and NDF was lower for F70 than Quatro. In general, Quatro and alfalfa were similar in terms of ruminal degradation and digestion in the rumen, intestine and whole-tract, while F70 tended to be of lower quality.

Biological Control of Blossom Blight of Alfalfa Caused by Botrytis cinerea Under Environmentally Controlled and Field Conditions

Fungal and bacterial antagonists were tested for their inhibition of sporulation of Botrytis cinerea on detached alfalfa florets. Clonostachys rosea, Gliocladium catenulatum, and Trichoderma atroviride were evaluated for protecting young blossoms and pods of alfalfa from infection by B. cinerea in vitro. C. rosea was further tested to control pod rot and seed rot caused by B. cinerea under field conditions. The results showed that four of the tested antagonists, C. rosea, G. catenulatum, T. atroviride, and Trichothecium roseum, could inhibit sporulation by B. cinerea on detached alfalfa florets. Both C. rosea and G. catenulatum were effective in suppression of infection of alfalfa pods by B. cinerea when inoculated on fresh petals of alfalfa at the anthesis stage, and their efficacy was greater than that of Trichoderma atroviride. A significant suppression of B. cinerea by C. rosea and G. catenulatum on pods and seed of alfalfa was observed when they were inoculated on senescent petals at the pod-development stage. Results of a field trial indicated that C. rosea applied to upper parts of alfalfa plants significantly suppressed pod rot and seed rot caused by B. cinerea, and significantly increased seed production of alfalfa in each of 3 years. These studies show that C. rosea has potential as a biocontrol agent for control of alfalfa blossom blight caused by B. cinerea.

Sensitivity of Ulocladium atrum, Coniothyrium minitans, and Sclerotinia sclerotiorum to benomyl and vinclozolin

Assays on mycelial growth and spore germination were carried out to determine the sensitivity of the biocontrol agents Ulocladium atrum and Coniothyrium minitans and the plant pathogen Sclerotinia sclerotiorum to benomyl and vinclozolin. Ulocladium atrum was more tolerant to these fungicides than C. minitans and S. sclerotiorum. The 50% effective concentration (EC50) of U. atrum based on the mycelial growth inhibition was 1467.3 µg active ingredient (a.i.)/mL for benomyl and 12.6 µg a.i./mL for vinclozolin, and the maximum inhibition concentration was higher than 4000 µg a.i./mL for both fungicides. For C. minitans and S. sclerotiorum, however, the EC50 based on mycelial growth inhibition was lower than 1 µg a.i./mL. After incubation for 24 h at 20°C, the germination rate of U. atrum conidia was 90–99% on potato dextrose agar (PDA) amended with benomyl at 100–500 µg a.i./mL or vinclozolin at 10–500 µg a.i./mL. At these concentrations, germ tubes of U. atrum developed into long, branched hyphae in benomyl treatments, but they remained short and clustered in vinclozolin treatments. Pycnidiospores of C. minitans and ascospores of S. sclerotiorum germinated on PDA amended with benomyl at 100–500 µg a.i./mL, but the germ tubes did not grow further. Spore germination of C. minitans and S. sclerotiorum was less than 3.2% on PDA amended with vinclozolin at 10–500 µg a.i./mL after 24 h. This is the first report on the sensitivity of U. atrum and C. minitans to benomyl and vinclozolin. The results suggest that it is possible to control S. sclerotiorum using a combination of U. atrum and benomyl or vinclozolin.Key words: fungicides, mycelial growth, spore germination, integrated pest management.

Comparison of the ruminal metabolism of nitrogen from 15N-labeled alfalfa preserved as hay or as silage

Alfalfa (Medicago sativa L. cv. AC Blue J) was labeled with 15N during growth in a greenhouse, harvested at early bloom, and preserved as silage (19% dry matter) or as sun-cured hay. The labeled silage and hay were given as single-pulse doses to two lactating Holstein cows fed diets comprising 30% concentrate and 70% alfalfa forage (preserved either as silage or as hay). Labeled forage and ruminal content samples collected for 72 h after dosing were partitioned into N fractions and analyzed for 15N-enrichment. Pool sizes of N compartments and kinetics in the rumen were derived by isotope dilution and by gravimetric measurements. The rate of outflow of total N, determined gravimetrically, was 21% higher with the silage diet than with the hay diet. On both diets, the largest individual flux was associated with the nonprotein, nonammonia, nonmicrobial nitrogen (NPAM-N) pool. As related to the flux of 15N through the acid detergent insoluble N pool, less tracer passed through the solid-phase nonfiber N and the soluble protein-N pools, and more passed through the NPAM-N pool, with silage than with hay. The solid-phase nonfiber N pool, which includes readily available feed N and adherent bacterial- and protozoal-N, constituted the largest N entity in the rumen, followed by the NPAM-N pool. When the forage component of the diet was alfalfa silage, N flux through the NPAM-N pool was remarkably high, and with both methods of preserving alfalfa forage, the exchange of tracer was most intensive through this pool.

Replication-dependent early meiotic requirement for Spo11 and Rad50

Spo11 and the Rad50-Mre11 complex have been indirectly implicated in processes associated with DNA replication. These proteins also have been shown to have early meiotic roles essential for the formation of a programmed DNA double-strand break known in Saccharomyces cerevisiae to initiate meiotic recombination. In both S. cerevisiae and the basidiomycete Coprinus cinereus, spo11 and rad50 mutants are defective in chromosome synapsis during meiosis. Here we demonstrate that a partial restoration of synapsis occurs in C. cinereus spo11 and rad50 mutants if premeiotic DNA replication is prevented. Double mutants were constructed with spo11-1 or rad50-4 and another mutant, spo22-1, which does not undergo premeiotic DNA replication. In both cases, we observed an increase in the percentage of nuclei containing synaptonemal complex (SC) structures, with concomitant decreases in the percentage of nuclei containing axial elements (AE) only or no structures. Both types of double mutants demonstrated significant increases in the average numbers of AE and SC, although SC-containing nuclei did not on average contain more AE than did nuclei showing no synapsis. Our results show that Spo11-induced recombination is not absolutely required for synapsis in C. cinereus, and that the early meiotic role of both Spo11 and Rad50 in SC formation partially depends on premeiotic S phase. This dependency likely reflects either a requirement for these proteins imposed by the premeiotic replication process itself or a requirement for these proteins in synapsis when a sister chromatid (the outcome of DNA replication) is present.

Shearing force of alfalfa stems: Effects of genotype and year interactions

Shearing force of alfalfa (Medicago sativa L.) stems was measured to evaluate genotype-by-year interactions. Based on mean shearing force for each stem segment and genotype clustering criteria, several genotypes had similarly shearing forces among years. Therefore, selecting genotypes with desirable shearing force characteristics to improve digestibility or intake potential of forages may be possible. Key words: Genotype, environment, shearing force, cell wall chemical constituents

Comparison of alfalfa and fenugreek (Trigonella foenum-graecum) silages supplemented with barley grain on performance of growing steers

To compare nutritive value of alfalfa and fenugreek silages for weaned back-grounding feedlot steers, isonitrogenous diets of alfalfa or fenugreek silage, supplemented with three levels of steam-rolled barley (0, 15 and 30% DM) were fed ad libitum to 60 steers (initial weight of 237 ± 18 kg). The study was conducted in individual pens for 105 d using a 2 × 3 factorial experiment. Fenugreek was cut 17 wk after seeding while the alfalfa was cut at mid-bloom. Both fenugreek and alfalfa silages were prepared in plastic tube silos after wilting to 38 and 35% DM, respectively. After ensiling for 40 d, silage tubes were opened and a feeding trial was conducted. Alfalfa and fenugreek silage contained similar levels of CP (18.0 and 17.2%, respectively) while fenugreek silage contained a lower level of NDF (38.2%) than alfalfa silage (40.4%). Dry matter intake (DMI) and average daily gain (ADG) of steers increased (P < 0.001) and feed efficiency (FE) improved linearly (P < 0.001) with increasing grain level in the diet. Dry matter intake (6.4 vs. 6.2 kg d−1), ADG (0.82 vs. 0.84 kg d−1), FE (8.1 vs. 7.8), total rumen volatile fatty acids (103.4 vs. 105.3 mM), rumen fluid pH (6.9 vs. 6.9) and rumen ammonia concentration (9.6 vs. 10.4 mg dL−1) in steers were similar for both alfalfa- and fenugreek-silage-based diets, respectively. Although in vitro rate of gas production was different at 12.6 and 17.4% h−1 for alfalfa and fenugreek diets, respectively, potential gas production at the end of 72 h of fermentation was similar (21.6 vs. 22.3 mL 100 mg−1 DM). The presence of steroidal saponins in fenugreek plants did not affect steer performance or hormonal status when fed as silage. Results from this study indicate that the nutritive value of fenugreek silage is comparable to that of mid-bloom alfalfa silage, and that fenugreek, a high-DM yielding annual legume, has potential to be a valuable forage in feedlot diets. Key words: Alfalfa silage, fenugreek silage, annual legume, feedlot, steer, barley

Nutrient composition, in vitro gas production and digestibility of fenugreek (Trigonella foenum-graecum) and alfalfa forages

Nutritive value of forage from the annual legume fenugreek (Trigonella foenum-graecum L.) was evaluated by comparing its chemical composition, in vitro dry matter disappearance (IVDMD) and in vitro gas production with that of alfalfa. Samples of forage grown in a greenhouse or in field plots under irrigation were collected 9, 15, and 19 wk postseeding and nutritive quality was compared with alfalfa harvested at early-bloom. Greenhouse grown fenugreek-9 contained more ash than alfalfa cut at early-bloom, yet the IVDMD of fenugreek-9 was greater than that of the alfalfa. Total in vitro gas production was generally greater for alfalfa than fenugreek; however, lag time prior to initiation of gas production was shorter for alfalfa than fenugreek. Greenhouse grown fenugreek-15 or -19 contained less CP than alfalfa, while the NDF content of fenugreek-19 was highest. The IVDMD of fenugreek-15 and -19 were greater (P < 0.05) than for alfalfa. Total in vitro gas production was similar for all forages. The rate of gas production was slower (P < 0.05) for fenugreek-19 than for alfalfa. Fenugreek-9 harvested from field plots contained higher (P < 0.05) CP than fenugreek-15 and -19 and alfalfa. Protein content of fenugreek-19 was similar to that of early-bloom alfalfa (P > 0.05), while NDF and ADF contents of fenugreek-9 and -15 were lower (P < 0.05) than alfalfa. Total in vitro gas production of fenugreek-19 was similar to that of alfalfa even though the rate of gas production was slower for fenugreek-19 than for alfalfa. Volatile fatty acids production and composition were generally similar for fenugreek-15 or -19 and early-bloom alfalfa. The estimated DM yield of fenugreek-19 from plots was approximately 10.4 t ha−1. These results suggest that the nutritive value of fenugreek biomass regardless of its stage of growth, is at least comparable to that of early-bloom alfalfa and so it has potential as a forage crop. Feeding trials with cattle are still required to determine intake and utilization potential of this crop. Key words: Alfalfa, fenugreek, IVDMD, in vitro gas production

Effect of stage of maturity and growth cycle on shearing force and cell wall chemical constituents of alfalfa stems

Two experiments were conducted to assess whether stage of maturity and growth cycle affected shearing force of alfalfa (Medicago sativa L.) stems. In both experiments, stem shearing force, diameter and weight were measured at several segments on the stem. In exp. 1, Anchor, Barrier and Vernal alfalfa, at the second and third regrowth were harvested at the early bud stage. Stem weight and diameter were larger at the second regrowth for all stem segments. A numeric trend for lower stem diameter in Vernal compared to Anchor and Barrier was observed. For all stem segments, shearing forces for Anchor and Barrier were lower than for Vernal and shearing force was highest for second regrowth. Vernal had higher NDF, ADF, hemicellulose and cellulose content than other cultivars and ADL was highest at the second regrowth (P < 0.01). In exp. 2, Anchor, Barrier and Vernal alfalfa, in the second production year, were harvested at four stages of maturity, early bud, early flower, late flower and early seed pod. A significant stage of maturity × stem segment effect was observed for shearing force, diameter, and weight. Shearing force, stem diameter and weight measurements generally increased as the plants aged for all stem segments. Quadratic relationships (P < 0.0001) for shearing force stem diameter and weight were observed with increasing stage of maturity for all stem segments. Generally, hemicellulose and lignin contents increased as the plants matured, while cellulose concentrations were variable. Both stage of maturity and growth cycle affected shearing force of alfalfa stems and this was associated with changes in stem diameter, weight and its cell wall chemical constituents. Key words: Alfalfa, stage of maturity, growth cycle, shearing force, cell wall chemical constituents

Feasibility of using cattle to disperse cicer milkvetch (Astragalus cicer L.) seed in pastures

The passage of cicer milkvetch (Astragalus cicer L.) through the digestive tract of cattle was examined in relation to recovery, germination, and establishment. About 86% of seed ingested was recovered over a 4-d period. Most seed was excreted 24–48 h after ingestion and soft seed was reduced by about 3% for every 24-h period spent in the digestive tract. However, the field observation of 20 established plants indicates low efficiency of this method for dispersal of cicer milkvetch. Key words:Astragalus cicer, digestion, germination, soft seed, establishment, cattle

Assessment of stem shearing force for three alfalfa cultivars grown under dryland and irrigated conditions

The Ottawa Texture Measuring System was used to assess the shearing force of three alfalfa cultivars at similar physiological maturity. Shearing force of stems varied among growing conditions and shearing locations. A significant positive relationship was observed between shearing force and stem diameter. Shearing force may indicate stem fragility and provide a rationale for differences in forage breakdown during mastication. Key words: Alfalfa, Ottawa Texture Measuring System, Warner-Bratzler blade, physical property, shearing force

Genetic basis of dormancy and differential response to sodium azide in Avena fatua seeds

Seven crosses, involving either nondormant × dormant or dormant × dormant pure lines of wild oats (Avena fatua L.), were made. Selfing of the hybrid and further hybridization were carried out to produce the F2 and reciprocal backcross generations. The seed germination time-course curves of the parents, their F1, and segregating generations over a 20-week period were studied. Differences in time course of germination in these generations were interpreted in terms of a minimum of three interacting loci. Two pure lines, AN51 and MO73, differed in their response to sodium azide, a respiratory inhibitor, with the former being more responsive. In crosses between these lines, the F1 seeds were also more responsive when AN51 was used as the maternal parent. This differential response of two dormant pure lines and their reciprocal F1s suggests maternal influence in germination response to sodium azide.

OUTCROSSING RATES IN BARLEY POPULATIONS IN THE CANADIAN PRAIRIES

Using three morphological markers, the magnitude of natural cross-fertilization in three successive generations, F3, F4 and F5 of four single crosses of barley (Hordeum vulgare L.) was estimated under dryland conditions of the Canadian Prairies. The average frequency of outcrossing was very low (0.35%). Somewhat higher rates of outcrossing were observed in a highly variable composite cross population of barley (CC XXI). CC XXI showed an overall outcrossing rate of 0.80%, when propagated under irrigated conditions, but only 0.47% under rainfed conditions. Outcrossing was significantly influenced by three components of the environment: temperature, precipitation and relative humidity during the flowering period. Temperature was most important when moisture was not limiting, whereas precipitation was the most important factor under field level drought. The overall frequency of outcrossing in CC XXI was not only considerably lower in the Prairies than in California or Scotland, but decreased progressively with advancing generations, in contrast to results in California.

Dormancy studies in seed of Avena fatua. 10. On the inheritance of germination behaviour

Breeding experiments were performed with pure lines of Avena fatua differing characteristically in duration of primary seed dormancy. The results indicate that the parental lines differ for at least three genes controlling rate of afterripening. It is evident that at least two of these genes influence the rate of afterripening at different periods after seed maturation.