Grassland Science最新文献

Livestock excretions are crucial for nutrient cycling in pasture ecosystems. However, conventional methods based on field observations require significant human power and are time-consuming. This study developed a model, ‘Dung Detector (DD)’, for detecting cattle dung in pastures from drone images using the You Only Look Once (YOLO) v5 algorithm. The DD model was trained using our custom dataset including 1,504 split images from drone orthomosaic images in five paddocks: Obihiro (OBH), Shintoku (STK), Minokamo (MNO), Miyota (MYT), and Yatsugatake (YGK). The detection accuracy was evaluated using ground-truth data acquired in two quadrats within paddocks. The DD model performed well for OBH and STK (F-score = 0.861 and 0.835) paddocks with simple grass species and low surface sward height (SSH). Although the MNO and MYT, with complex vegetation and high SSH, showed few false positives (precision >0.9), some cattle dung pats were undetectable, presumably due to grass height (Recall = 0.500 and 0.276).

The objective of this study was to evaluate the effects of different potassium (K) fertilization levels and defoliation intensities on performance of “BRS Zuri” guineagrass Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L Jacobs (syn. Panicum maximum Jacq.). Treatments were the factorial arrangement of three K fertilization levels: 0 (control), 40, 80 kg K₂O/ha/harvest) and two defoliation intensities (10- and 20-cm stubble heights), distributed in a completely randomized design with five replications. The experiment was conducted in Araguaina, TO, Brazil, from October to January, 2020–2021 and 2021–2022. Plots were harvested four times per year with 21-day regrowth interval. The 40 and 80 kg K₂O/ha/harvest fertilization levels had greater HA than the control (5490 vs. 3,440 kg DM/ha, respectively). There was a K fertilization level × stubble height interaction on tiller population. There was greater tiller population at 20- than 10-cm stubble height at 40 kg K₂O/ha/harvest; however, no effect of stubble height was detected at 0 and 80 kg K₂O/ha/harvest. Plots fertilized with 80 kg K₂O/ha/harvest had greater tiller population than 40 kg K₂O/ha/harvest, which was greater than control. Forage harvested at 10 cm had greater crude protein (CP) than 20-cm stubble height (mean = 11.4% vs. 10.8%). Tissue K concentration increased from control to 40 kg K₂O/ha/harvest, but there was no difference between 40 and 80 kg K₂O/ha/harvest (mean = 1.1% vs. 3.5%). The combination of 40 kg K₂O/ha/harvest and 20-cm stubble height may be a desirable management strategy to promote Zuri guineagrass productivity in tropical regions.

Plant size is a critical component of agricultural productivity as larger plants produce more biomass. To identify genes related to plant size, we grouped C₄ grasses into small and large and used OrthoFinder to find orthologous genes present in large but absent in small grasses. Three such genes were identified from sorghum (Sorghum bicolor [L.] Moench) by phylogenomic approach, and they encode nitrate transporter (Sobic.007G213200), oxysterol binding protein (SbRio.01G578800) and thioredoxin reductase (SbRio.05G168300), respectively. Overexpression of all three genes driven by the maize ubiquitin promoter in Setaria viridis (L.) Beauv. indicates that they all affected plant size as measured by plant height and tiller number. Both nitrate transporter and oxysterol binding protein increased plant height and tiller number, and thioredoxin reductase significantly decreased tiller number but had minimal effect on plant height. In rice (Oryza sativa L.), all three constructs reduced plant height significantly. The only commonality between the transgenic species was that nitrate transporter and oxysterol binding protein increased tiller number in both S. viridis and rice. Overall, we have demonstrated that phytogenomic approach can be used to identify genes responsible for large plant size in the grasses.

Sainfoin (Onobrychis viciaefolia) is an important legume forage. This study aims to explore the response mechanisms of sainfoin germplasm resource accessions to drought stress, which provides the theoretical basis for tolerant breeding of sainfoin. In this study, 20 sainfoin germplasm resource accessions were used as the test materials, and the effects of drought stress on morphological and physiological characteristics were determined under simulated levels of drought (−0.5, −1.0, −1.5 and −2.0 MPa) × exposure times (7 days) in pots. The results showed that leaf area, leaf relative water content, root-shoot ratio, root length, root surface area, root volume, root diameter, root tip number, chlorophyll a content, chlorophyll b content and catalase activity decreased with increasing drought stress. In contrast, proline, soluble sugar, soluble protein and malondialdehyde contents increased in response to drought. Root activity, superoxide dismutase and peroxidase activities increased first and then decreased and reached the maximum at −1.0 MPa. Cluster analysis showed that 20 sainfoin germplasm resources could be divided into three categories, of which four accessions were high tolerance types, and three accessions were low tolerance type. These findings will help provide some theoretical basis for cultivating new varieties.

Integrated production systems have been an alternative for diversifying agricultural production, and therefore, it is necessary to study tropical forage grasses that can impact both straw production and soil organic matter, as well as benefit animal production. The objective of this work was to evaluate the productive characteristics and accumulation of nutrients in the biomass of grasses of the genus Panicum grown in the off-season, in Cerrado biome soil as cover plants for use in integrated production systems. It evaluated different grasses of Panicum maximum: Aruana, Tamani, and Massai guinea grasses, distributed in a randomized block design with four replications of each grass. The productive characteristics, mineral accumulation, and carbon/nitrogen (C/N) ratio in the biomass of the cultivars were evaluated. No cultivar effect was observed for forage mass (3997.4 kg/ha DM). However, the largest (p = 0.0077) leaf blade masses were observed in the Massai and Tamani guinea grasses. On the contrary, the Aruana guinea grass exhibited the highest value (p = 0.0001) for stem mass, reflected in a higher (p = 0.0001) leaf/stalk ratio in the Massai and Tamani guinea grasses. No effect (p > 0.05) of the cultivar on micronutrients, magnesium, and phosphorus concentrations was observed. However, the Aruana guinea grass presented higher concentrations of calcium and sulfur; on the other hand, potassium values were higher in the Massai and Tamani guinea grasses. The Massai guinea grass exhibited a higher (p = 0.0214) C/N ratio, while the Aruana guinea grass recorded lower values, with no significant differences between these cultivars and Tamani guinea grass. The Tamani and Massai guinea grasses stand out as recommended choices for cultivation during the off-season in Cerrado biome soils as cover crops in integrated production systems.

Our study area, Ejina, is located in the southern Gobi Desert, Inner Mongolia, China, where the annual precipitation is <50 mm and the annual potential evaporation is >3,600 mm. The Heihe River flows from the Qilian Range through the study area, and the desert landscape along the river includes oases formed by forests and grasslands. We established a survey area of approximately 1.5 ha in grassland facing a seasonal swamp, a branch of the Heihe River. We posed the following questions in this desert grassland: (1) how do soil water content (SWC) and salinity change with distance from the riverbank? (2) How do vegetation, aboveground biomass, and species richness change with distance from the riverbank? (3) How much can be supplied to grazing animals, and how many animals can be grazed? Our results indicated that (1) the SWC is high within 20 m of the riverbank and low beyond 20 m, the standing biomass is positively correlated with SWC, but there was no evidence of a correlation between salinity and distance to water; the electrical conductivity was high both inland and adjacent to the riparian swamp. (2) Vegetation could be classified to six classes, following a gradient from the riverbank (swamp margin) to the dry inland area beyond 20 m from the riverbank. Species richness and aboveground biomass were highly correlated. Classification result led us to recommend that generalist species tolerant of the distinct moisture gradient in the site be used in restoration efforts. (3) Per-hectare aboveground biomass was 478.93 dry weight (dw) kg, 321.2 ha of equivalent grassland would be required to graze 100 goats annually.

Drought is a major factor limiting plant growth. Plants cope with stress via morphophysiological responses. Rhizosphere-related bacteria, fungi and other microorganisms can help plants cope with drought via various mechanisms. We conducted a pot experiment on Cyperus esculentus wherein we subjected it to various drought levels and analyzed the functional traits of its aboveground and belowground organs. High-throughput sequencing was used to study the structure and diversity of the microbial community in the rhizosphere. Drought stress substantially lowered the densities of the leaves, stems, roots and seeds relative to the untreated control. Drought stress inhibited the growth and reduced the yield of C. esculentus. The leaves and seeds have higher water content and are more sensitive to drought stress than the roots. With the aggravation of drought stress, the plant height of C. esculentus decreased significantly, the root:shoot ratio increased and the specific leaf weight had no significant difference. Change in shoot height was the most evident response of C. esculentus to drought stress. Plants under drought stress reduced their leaf area and assumed a specific leaf weight to maintain photosynthetic performance. Rhizosphere fungi were more sensitive to drought stress than rhizosphere bacteria. Drought stress increased the relative abundances of Bacteroidetes, Verrucomicrobia, Patescibacteria, Actinobacteria and Nitrospirae. Drought-stressed C. esculentus maintained their photosynthetic performance by reducing shoot height and leaf area while assuming a stable specific leaf weight. Drought stress exerted a significantly stronger negative impact on rhizosphere fungi than rhizosphere bacteria. The results clarified the response strategies of functional traits and rhizosphere microorganisms of C. esculentus to drought stress.

The performance of seven Urochloa grass genotypes (three worldwide cultivars cv. Basilisk, cv. Piata, cv. Xaraes and four landrace cv. Adamaoua1, cv. Adamaoua2, cv. North1 and cv. North2) subjected to two cutting regimes (mid-June cut and mid-July cut) was evaluated for regrowth characteristics, seed yields, seed quality and herbage production in 2020 and 2021 cropping seasons at Wakwa, Ngaoundere, Cameroon. This divergence in harvesting practices raises concerns regarding the effectiveness and efficiency of forage utilization, as well as the potential impact on livestock productivity and sustainable farming systems. A split plot design with five replications and a 1-year-old sward was used for the study. In both years, genotypes were significantly different for plant height and tiller numbers at 12 weeks after cutting (P ≤ 0.007). In 2020, the dry matter yield (DMY) ranged between 8.78 t/ha (cv. Piata) and 12.75 t/ha (cv. Xaraes) for June cut regrowth and between 7.69 t/ha (cv. Piata) and 10.26 t/ha (cv. Xaraes) for July cut regrowth. In 2021, DMY ranged between 6.06 t/ha (Adamaoua2) and 13.95 t/ha (cv. Xaraes) for the June cut and between 6.55 t/ha (cv. Adamaoua2) and 10.47 t/ha (cv. Basilisk) for the July cut. For flowering behavior and seed yields, Basilisk flowered earliest while cv. Xaraes flowered latest. In 2020, seed yields were 74.80 kg/ha and 107.72 kg/ha for June cut and July cut regrowth, respectively, whereas in 2021, seed yields were 331 kg/ha and 431 kg/ha for June cut and July cut regrowth, respectively. cv. Adamaoua1 produced the highest seed yield in both years. The cutting regimes evaluated in this study were indifferent for DMY and seed yield.

Bahiagrass (Paspalum notatum Flügge) is a warm-season grass where high lignin content limits its forage quality, negatively affecting animal performance. To create a new breeding method by genome editing, isolation and characterization of lignin biosynthesis genes and identification of their molecular relationships are essential. The caffeic acid O-methyltransferase (COMT) and cinnamyl alcohol dehydrogenase (CAD) cDNA clones were isolated from bahiagrass, and their protein sequences showed high similarity to other C4 monocot species through phylogenetic analysis. Gene expression analysis of phenylalanine ammonia-lyase (PAL), COMT and CAD, involved in crucial stages of lignin biosynthesis and lignin content, was conducted at different plant developmental stages. The highest gene expression levels of these genes were observed in the vegetative (V) and early reproductive stages, while the lignin content increased until the middle reproductive stage and remained constant thereafter. Additionally, to further understand the molecular relationships in lignin biosynthesis, the effect of CAD downregulation was analyzed in transgenic bahiagrass lines introduced with sorghum CAD antisense and RNAi vector obtained from a previous report. This led to a reduced lignin content and affected the expression of PAL and COMT working upstream of CAD. In the V stage, PAL expression was lower in transgenic lines compared to wild type (WT), while COMT expression showed no significant differences. However, PAL and COMT expression of transgenic lines in the middle reproductive stage (R2) was significantly higher than in the WT. These findings suggest that the downregulation of CAD gene expression affects PAL and COMT expression and induces a feedback system in the R2 stage. Lignin content influenced the phenotype of the transgenic plants with significantly reduced lignin, exhibiting a dwarf phenotype with shorter plant heights. The findings of this study can be applied to genome editing for the development of practical new breeding materials with improved digestibility in bahiagrass.

The purpose of this study was to evaluate different methodologies used in the field in order to find the one that could most effectively relate to the morphophysiological condition of Brachiaria decumbens cv. Basilisk (syn. Urochloa decumbens cv. Basilisk Stapf R.D. Webster). Two light interception frequencies (LI, 85% and 95%) and two defoliation intensities were adopted as targets for the residual leaf area index (RLAI 1.3 and 1.8). The treatments consisted of evaluating different methods of measuring the canopy height (CH) through its ability to correlate with the morphophysiological variables of species B. decumbens cv. Basilisk. High correlations between the methods CH, compressed height (CHe), weighted height 1 (WH₁) and weighted height 8 (WH₈) were observed mainly with the variables total forage biomass (TFB) and leaf area index (LAI) in both residual and pre-grazing conditions. The path analysis showed degrees of multicollinearity, which determined the use of the “k” constants in order to correct the distortions of the diagonal elements of the correlation matrix X'X. Path analysis provided direct cause/effect indexes on TFB using LAI = 0.1435, photosynthesis (A) = −0.1061, CH = 0.1616, CHe = 0.0913, WH₁ = 0.1386 and WH₈ = 0.0575; on LAI using CH = 0.2404, CHe = 0.2164, WH₁ = 0.2307 and WH₈ = 0.2183; and on photosynthesis rate (A) using LAI = 0.2895, CH = 0.0203, CHe = −0.1170, WH₁ = 0.0352 and WH₈ = 0.0937. Similarity was observed between intercepts and slope coefficients for TFB prediction using CH, CHe, WH₁ and WH₈, providing mean values of 1069.57 and 204.06, respectively. Methods CH and WH₁ presented a significant correlation with most morphophysiological variables and can be used to quantify TFB and LAI, while CH and WH₈ can be used only for TFB.