Grassland Science最新文献

Genetic relatedness and diversity of 62 cultivars and breeding lines of tetraploid Italian ryegrass (Lolium multiflorum Lam.; 39 accessions) and its interspecific hybrids, Festulolium (18 accessions), and hybrid ryegrass (Lolium × hybridum Hausskn.; 5 accessions), mainly from Japan, were revealed based on 2,824 genome-wide allele frequencies obtained by the genotyping by random amplicon sequencing-direct (GRAS-Di) method using bulk genomic DNA testing. Genomic composition of each accession was estimated according to the occurrence of 77,373 unique GRAS-Di sequences in the reference population consisting of diploid Italian ryegrass, meadow fescue (Festuca pratensis Huds.), and perennial ryegrass (Lolium perenne L.). The high correlation coefficient (0.98) between the fescue-specific reads ratio and the previously obtained f-ratio of genomic in situ hybridization in Festulolium cultivars suggests the usefulness of this simple method. Both cluster analysis based on Nei's standard genetic distance (D_ST) and principal component analysis (PCA) showed that groups were formed largely by species. However, the complex heritage of Lolium-Festuca (Festulolium) materials could not be determined by species registration or breeding history alone. Some Festulolium accessions were closely related to Italian ryegrass, whereas some defined as Italian ryegrass may actually be interspecific hybrids. The high genetic diversity of Festulolium compared to Italian ryegrass and hybrid ryegrass revealed by PCA seems due to the wide range of fescue-specific read ratios (0.04–33.0%). Tetraploid Italian ryegrass did not show clear structural differentiation, but some genetic relationships attributable to breeding history were demonstrated. Mean pairwise D_ST of tetraploid Italian ryegrass cultivars was significantly lower than that of diploids. Tetraploids and diploids could be separated by PCA plot. Although mean expected heterozygosities of tetraploid and diploid cultivars were not significantly different, the results suggest that the utilization of diploid genetic resources is effective in maintaining and increasing the genetic diversity of breeding populations of tetraploid Italian ryegrass.

This study aimed to investigate the effect of a soil ammonia-oxidizing bacterial (AOB) strain on Italian ryegrass (Lolium multiflorum Lam.) regrowth. Potted Italian ryegrass was used as test material. We isolated and screened an AOB strain from the soil for use in inoculation of other soils to increase nitrification. The sequence of the two isolated and screened AOB strains (S2_8_1 and S2_7_25) were 100% similar to that of Ensifer sesbaniae and Acinetobacter pittii. The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) was also added to the soil to inhibit nitrification. The experimental design involving the inoculation of the soils with the AOB strain included seven treatments: (1) regrowth without any additives, (2) regrowth with blank enrichment medium added to the soil, (3) regrowth with S2_8_1 strain inoculation, (4) regrowth with S2_7_25 strain inoculation, (5) regrowth with DMPP added to the soil, (6) regrowth with DMPP added to the soil and with S2_8_1 strain inoculation, and (7) regrowth with DMPP added to the soil and with S2_7_25 strain inoculation. Compared with regrowth treatment without any additives, the regrowth treatment with S2_8_1 and S2_7_25 inoculations significantly increased leaf biomass by 23.5–48.6%, the leaf net photosynthetic rate by 27.9–48.5%, the rhizosphere soil nitrification rate by 43.0–144.2%, leaf cytokinin concentrations by 23.7–24.9%, and xylem sap cytokinin concentrations by 32.5–43.2%. The increase of nitrate nitrogen content in rhizosphere soil induced by S2_8_1 and S2_7_25 promoted the transfers of cytokinin from roots to leaves, resulting in the increase of cytokinin concentration in leaves. This increase in leaf cytokinin concentrations improved Italian ryegrass regrowth. However, the S2_8_1 and S2_7_25-induced increases in the nonrhizosphere soil nitrification rate were not closely related to Italian ryegrass regrowth. The tested AOB strains have considerable potential to increase Italian ryegrass regrowth.

Low temperature is one of the abiotic factors that limit the biomass of Medicago ruthenica (L.), and carbon and nitrogen have important roles in the plant's growth and development. However, the information on the distribution of carbon and nitrogen under low temperature conditions is limited. In this study, we investigated the influence of carbon and nitrogen distribution on M. ruthenica (L.) Trautv. cv. ‘Zhilixing’ based on ¹³C and ¹⁵N isotope tracers in two temperature-controlled chambers (4–10°C and 25°C, respectively) for 30 days. Results showed that under low temperature, plant height significantly decreased by 22.74%, whereas the ratio of underground to aboveground biomass considerably increased by 146.31% compared to the control plants at 30 days. Moreover, low temperature stress significantly increased the activities of sucrose synthase and glutamine synthase in leaves, shoots and roots. The total carbon content and the abundance of ¹⁵N increased in leaves, shoots and roots under low temperature, with a greater level of increase in shoots than in leaves and roots. The weight of leaves, shoots and roots was correlated with δ¹⁵N. Hence, low temperature inhibited growth and promoted the transport of carbon and nitrogen.

The methods used to evaluate kinetic parameters of ruminant feeds can be in situ and in vitro. For both methods, it is necessary to maintain cannulated animals in order to collect the inoculum from the rumen, which has been under strong pressure from society, in terms of animal welfare policies, to avoid this type of practices. This work aimed to evaluate the estimation of in vitro digestibility and fermentation of elephant grass forage by near infrared reflectance spectroscopy (NIRS), as a fast and noninvasive alternative to the in vitro method. The experimental design was in randomized blocks with three repetitions. The treatments were arranged in a split-plot scheme, with 13 genotypes in the plot and 15 regrowth ages in the subplot. Crude protein (CP) and neutral detergent fiber (NDF) contents; in vitro dry matter (IVDMD) and NDF (IVNDFD) digestibilities; and total volume (V_t), gas production rate (μ) and half-life conventional analyses were determined for pre-dried elephant grass forage samples. For the evaluation of NIRS models performance, coefficient of determination (R²cv) and standard error of cross validation (SECV) were used. As the regrowth age advanced, there was a linear increase in the NDF content and a linear reduction in the IVDMD, IVNDFD and V_t values. The NIRS estimates proved to be adequate for IVDMD (R²cv = .95), IVNDFD (R²cv = .85), V_t (R²cv = .81) and gas production at 48 (R²cv = .82), 72 (R²cv = .85) and 96 h (R²cv = .84), confirming as an alternative to the in vitro methods that dispense with the use of cannulated animals.

This study aimed to determine the fermentation quality, nutritive value and in vitro ruminal digestion of silages produced with mixtures of Napier grass (NG) and sugarcane top (ST) in five different ratios of fresh matter: 100:0 (N100), 75:25 (N75), 50:50 (N50), 25:75 (N25) and 0:100 (N0) with or without lactic acid bacteria (LAB) and formic acid (FA). The NG contained a higher crude protein (CP) content and buffering capacity, but lower dry matter (DM), organic matter, neutral detergent fiber, acid detergent fiber and water-soluble carbohydrates contents than ST. The N25 silage fermented well, with a significantly higher lactic acid (LA) content (p < .05) and lower pH and NH₃-N concentration than those of other mixed silages (p < .05). The FA addition resulted in the highest CP content and lowest pH, LA, acetic acid (AA) and NH₃-N contents, while LAB addition resulted in the highest LA content compared with other treatments. Although in vitro DM digestibility (IVDMD) did not significantly differ among the mixed silages (p > .05), mixing with ST and adding LAB or FA increased the IVDMD. Gas production (GP) and AA content of N25 silages were significantly higher than those of other silages (p < .05). The LAB- or FA-treated silages had higher IVDMD, GP, total volatile fatty acid and AA contents (p < .05) but lower pH compared with the control silage (p < .05). These results demonstrated that NG utilization improved upon mixing with ST due to the enhanced fermentation during ensiling, and the optimum mixing ratio for NG and ST was 25:75 on FM basis. Using LAB and FA as additives during ensiling can improve silage fermentation quality and in vitro ruminal digestion.

Satisfying the animals feed demand from the forage supply by grasslands remains a major challenge in the grassland–livestock ecosystem. To provide an alternative forage sources, this study conducted two feeding trials in the summer of 2015 and 2016 to compare the nutritive value, digestibility and nutrients utilization of native pasture (NH) and oat forage (OT) fed to Tibetan sheep (Ovis aries). Twelve Tibetan sheep with a mean body weight of 39.11 ± 3.66 kg in 2015 and 27.97 ± 2.69 kg in 2016 were use in this study. The experiment was 2 (year: 2015 and 2016) by 2 (forage: NH and OT) factorial. Data on proximate analysis, fiber fraction and nutrients digestibility were collected and analyzed using general linear model. However, the crude protein (CP) and water-soluble carbohydrates contents in OT were higher (P < .001) than those in NH by 7.81–8.93% and 46.40–47.05%, respectively. In contrast, the neutral detergent fiber (NDF) and acid detergent fiber contents were higher (P < .001) in NH by 14.28–15.78% and 15.62–18.00%, respectively. The dry matter digestibility coefficient in OT (0.82 in 2015 and 0.79 in 2016) was significantly higher than that in NH (0.68 in both years). In addition, the OT diet had higher (P < .001) organic matter, NDF and CP digestibilities. Animals fed OT retained significantly more nitrogen (2.66 g/day in 2015 and 1.93 g/day in 2016) than those fed NH (0.96 g/day in 2015 and 0.42 g/day in 2016). The digestible energy and metabolizable energy were higher (P < .001) in OT than in NH. Our data indicated that Tibetan sheep urinary N excretion increased by 0.726 g with increase of 1 g in the nitrogen intake. Conclusively, the OT had higher nutritive value than NH and could therefore use to satisfy livestock demand and reduce the grazing pressure on grasslands.

Italian ryegrass (Lolium multiflorum Lam.) cultivars vary widely in their persistence; there are very early heading annual types as well as very late heading, summer-survival types that survive for 2 or 3 years. Hybrid cultivars that survive in summer temperatures are bred using genes of a similar species (Festuca) in combination with Lolium. It is hypothesized that commercial summer-survival cultivars of Italian ryegrass include Festuca genome fragments. In this report, we investigated the genomic constitution of five summer-survival cultivars using the genomic in situ hybridization technique. Two out of the five cultivars contained Festuca genome fragments, confirming that summer-survival cultivars may include Festuca genome fragments.

Identifying grass species in grasslands based on unmanned aerial vehicle hyperspectral remote sensing is the basis and premise of hyperspectral remote sensing when applied to grassland degradation monitoring and research. The small targets and mixed pixels involved grass species identification in grasslands creates problems, making identification cumbersome and classification accuracy difficult. This study involved the construction of an unmanned aerial vehicle hyperspectral remote sensing system using hyperspectral data of grass species in desert habitats that had been collected under natural light. A multi-resolution combined with a 1 × 1 feature map was formed by multiscale convolution, and grass species data were extracted from hyperspectral fine-grained feature data from grasslands. A recognition and classification model for degradation indicator species CNN was constructed using max pooling to retain the maximum amount of feature detail and up-sampling, reconstructing the feature space and feature fusion to smooth the edge texture of the data and enhance the weak data to alleviate the imbalance among samples. The results showed that the overall identification accuracy of the model for grassland species reached 98.78%, and the kappa coefficient reached 0.92, realizing the high-precision identification of grassland species, which laid the foundation for grassland species detection and research based on unmanned aerial vehicle hyperspectral imagery. In addition, the proposed degradation indicator species CNN model provides a useful reference for the identification and classification of small targets with mixed pixels.

The study aimed to determine the effect of fumaric and maleic acids on the ensiling process. The corn herbage was ensiled without additives (control silage) or with 0.25% fumaric acid (FA25), 0.50% fumaric acid (FA50), 0.25% maleic acid (MA25), 0.50% maleic acid (MA50), FA25 + MA25 (FA25MA25) and FA50 + MA50 (FA50MA50) (treatment silages) as wet basis. The starch contents of FA50 and MA50 silages were lower than the content of the control silage (p < .05). The lactic acid content of the FA50MA50 silage was lower than that of the control silage (p < .05). Percentages of linoleic acid of MA25 and MA50 silages were higher than that of the FA50 silage (p < .05). The in vitro methane production and metabolic energy (ME) value of FA50MA50 silage was lower than that of the control silage (p < .05). The in vitro organic matter digestion (OMD) values of FA25, MA25 and FA50MA50 silages were lower than that of control silage (p < .05). The molarities of acetic (AA), propionic (PA), butyric (BA), isovaleric (IVA), isobutyric (IBA) and total volatile fatty (TVFA) acids of the in vitro ruminal fermentation fluid for the FA50MA50 silage were lower than that of the control silage (p < .05). As a result, the addition of fumaric and maleic acids (0.25% alone and together, or 0.5% alone) in ensiling of corn herbage did not change the quality, acidity (except for propionic, butyric and isobutyric acids) and nutrient contents (except for non-fiber carbohydrates and starch) and in vitro ruminal fermentation values (gas–methane production and organic acids). The combined use of 0.5% fumaric plus 0.5% maleic acid harmed silage quality and in vitro ruminal fermentation values. However, 0.5% maleic acid was partially more effective than those other organic acid additions in preserving linoleic and α-linolenic acids in the silage material.