Forage Legumes Research Articles

Effect of seeding ratio and time of planting of cowpea (Vigna unguiculata) intercropping with maize (Zea mays) on agronomic parameters, forage biomass and grain yield of maize

The study was conducted at Adami Tulu and Dugda districts of Oromia regional state, Ethiopia to determine the optimum level of seeding ratio and planting time of cowpea under maize for optimum forage biomass production and maize grain yield. Combinations of four levels of cowpea seeding ratios and four different cowpea planting dates were laid out in a randomized complete block design in factorial arrangement with three replications. The levels of seeding ratios were 100%, 75%, 50%, 25%, 0% (sole maize) for the two districts. The four planting dates for cowpea were simultaneously planting with maize, 10 days after maize planting (DAMP), 20 DAMP and 30 DAMP. The results indicated that increasing seeding ratio of cowpea from 25% to the highest level (100%) resulted in significantly increased cowpea forage biomass yield. Time of cowpea planting in maize also influenced the plant height and biomass yield of cowpea. The highest forage biomass yield was recorded from simultaneously planting of the two crops. On the other hand, seeding ratio of cowpea has significantly influenced the grain yield of maize. It was also indicated that the time of cowpea planting in maize have significantly affected the grain yield of maize with simultaneously planting resulting in the lowest grain yield. The total LER in most of the intercropping system was more than one showing that intercropping of forage legumes with maize is more advantageous than sole cropping of maize. The optimum forage legume biomass yield (1.78 t/ha) was obtained from the combination of seeding ratio of 75% with 10 DAMP without significantly (p>0.05) reducing the grain yield of maize. Hence this combination was recommended for production of cowpea forage and maize grain from intercropping of the two crops in the study areas. From these results, it can be concluded that additional forage can be produced by intercropping cowpea with maize at their appropriate seeding ratio and planting time with a little or no sacrifice in maize grain yield. Moreover, it is important to further demonstrate and promote the recommended maize-cowpea intercropping practices for the end users of the study areas and similar agro-ecologies.

Combining crop diversification practices can benefit cereal production in temperate climates

Diversifying cropping systems by increasing the number of cash and cover crops in crop rotation plays an important role in improving resource use efficiency and in promoting synergy between ecosystem processes. The objective of this study was to understand how the combination of crop diversification practices influences the performance of arable crop sequences in terms of crop grain yield, crop and weed biomass, and nitrogen acquisition in a temperate climate. Two field experiments were carried out. The first was a 3-year crop sequence with cereal or grain legume as the first crops, with and without undersown forage legumes and forage legume-grass crops, followed by a cereal crop. The second experiment was a 2-year crop sequence with cereal or legume as the first crops, a legume cover crop, and a subsequent cereal crop. For the first time, crop diversification practices were combined to identify plant-plant interactions in spatial and temporal scales. The results partly confirm the positive effect of diversifying cereal-based cropping systems by including grain legumes and cover crops in the crop sequence. Legume cover crops had a positive effect on subsequent cereal grain yield in one of the experiments. Using faba beans as the first crop in the crop sequence had both a positive and no effect on crop biomass and N acquisition of the subsequent cereal. In cover crops composed of a forage legume-grass mixture, the grass biomass and N acquisition were consistently increased after the grain legume, compared to the cereal-preceding crop. However, differences in the proportion of legume to grass in mixture did not influence crop yield or N acquisition in the subsequent cereal. In conclusion, these results support that increased crop diversity across spatial and temporal scales can contribute to resource-efficient production and enhance the delivery of services, contributing to more sustainable cropping systems.

Investigating the Drought and Salinity Effect on the Redox Components of Sulla Coronaria (L.) Medik.

For the Mediterranean region, climate models predict an acceleration of desertification processes, thus threatening agriculture. The present work aimed to investigate the effect of drought and salinity on Sulla coronaria (L.) Medik., a Mediterranean forage legume, for understanding plant defence systems activated by these stressors. In detail, we focused our attention on the variations on the plant redox status. Plants were subjected to suboptimal watering and irrigation with sodium chloride (NaCl) solutions. The same salt treatment was applied for in vitro tests on seedlings. Water content did not change after treatments. Salt negatively influenced seed germination and seedling development, but it did not affect photosynthesis parameters, contrary to what was observed in adult plants. Proline concentration increased in all samples, while abscisic acid level increased exclusively in seedlings. NaCl caused accumulation of superoxide anion in plants and seedlings and hydrogen peroxide only in seedlings; nevertheless, lipid peroxidation was not detected. Total phenolics, glutathione, expression level, and activity of antioxidant enzymes were assayed, revealing a complex antiradical molecular response, depending on the type of stress and development stage. Our results confirm Sulla as a drought- and salt-tolerant species and highlight its ability to counteract oxidative stress. This evidence suggests a key role for the redox components, as signal transduction messengers, in Sulla acclimation to desertification. Finally, plants and seedlings showed different acclimation capacity to salinity, revealing a greater genomic plasticity for seedlings.

Water footprint, herbage, and livestock responses for nitrogen‐fertilized grass and grass–legume grazing systems

AbstractReplacing N fertilizer with forage legumes may increase sustainability of grazing systems. The objectives were to evaluate herbage and animal responses and to quantify the water footprint associated with beef production in N‐fertilized grass or grass–legume systems during 4 yr under continuous stocking. The three year‐round forage systems were: Grass+N which included N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer which was overseeded with N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter; Grass+Clover included bahiagrass without N fertilizer during summer which was overseeded with rye, oat, and a mixture of clovers (Trifolium spp.) during winter; and Grass+Clover+RP included rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture during summer which was overseeded with a similar rye–oat–clover mixture as for Grass+Clover. Clover inclusion improved uniformity of herbage distribution throughout the winter. Including rhizoma peanut increased cattle average daily gain (ADG) by 74% during summer. The ADG in Grass+Clover+RP was 0.61 kg d−1 compared with 0.35 kg d−1 on Grass+N and Grass+Clover. The water footprint during summer was less in Grass+Clover+RP than Grass+Clover (18 and 25 m3 kg−1 bodyweight, respectively). Gain per area (GPA) was similar across all treatments through the year, indicating similar productivity in grass–legume and N‐fertilized grass systems. The N‐fertilizer inputs were reduced from 224 to 34 kg N ha−1 yr−1 in Grass+Clover+RP, compared to Grass+N. Inclusion of rhizoma peanut and clovers contributes to developing sustainable grazing systems with reduced levels of off‐farm inputs.

Nutrient excretion from cattle grazing nitrogen‐fertilized grass or grass–legume pastures

AbstractNutrient cycling via livestock excreta is an important grassland ecosystem service. This study was conducted in 2016 and 2017 and determined nutrient excretion from cattle grazing three systems: (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) overseeded with rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N), (b) unfertilized bahiagrass overseeded with rye–oat–clover (Trifolium sp.) mixture (Grass+clover), and (c) rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture overseeded with a rye–oat–clover mixture (Grass+CL+RP). Urinary volume excreted in the warm season ranged from 122 to 182 L ha−1d−1, more than double that in the cool season (56–70 L ha−1 d−1). Urinary N concentration during the warm season was greater in Grass+CL+RP compared with Grass+N (4.4 vs. 3.1 g kg−1, respectively). In addition, fecal dry matter and organic matter output was greater for Grass+N than for steers grazing Grass+CL+RP during the warm season (3.8 and 3.2 vs. 2.8 and 2.2 kg hd−1 d−1, respectively). Total annual feces excretion concentrations of P, K, Mg, and N were greater in the Grass+N than in Grass+CL+RP system. The introduction of legumes increased the proportion of N returning via urine. However, when summed across seasons, total N excretion (feces and urine) was greater in Grass+N than in Grass+CL+RP (89 vs. 71 kg ha−1 yr−1), mainly due to the greater stocking rate in the former. Grass–legume systems receiving 34 kg N ha−1 yr−1 recycled 80% of the N recycled in the grass system receiving 224 kg N ha−1 yr−1, indicating the potential of forage legumes to add N to grasslands.

Evaluation of Yield Production and Chemical Composition of Three Types of Forage Legumes at Different Cutting Intervals and Cutting Times to Assess Their Benefits as Ruminant Animal Feed

The purpose of this study was to evaluate the potential of yield production and chemical composition response to cutting intervals of three forage legumes over a 5 month period of the dry season in Sa Kaeo province for use as an alternative forage for farmers. The experiment was conducted in a factorial arrangement in randomized complete block design. The first factor was the types of forage legumes, including alfalfa, hamata and stylo ‘Tha pra’ and the second factor was the cutting intervals at 30, 45, 60 and 75 days. The results for stylo ‘Tha pra’ showed that the average height, total weight per area, fresh weight (FW) and dry weight (DW) per plant were the highest (P <0.001). The cutting interval at 75 days provided the highest average height, FW and DW in all legume forage types. The FW and DW increased with increases in the cutting times (number of cuts) at all cutting intervals for all three forage legume types. The three different types of forage legumes and the different cutting intervals resulted in different chemical compositions (P <0.001) except for dry matter (DM) for which there was only a difference from the cutting interval. Each chemical composition showed an unequal response to the increase in cutting times. Keywords: Chemical composition, Cutting intervals, Cutting times, Forage legumes, Ruminant feed, Yield production

Prospects for Trifolium Improvement Through Germplasm Characterisation and Pre-breeding in New Zealand and Beyond.

Trifolium is the most used pastoral legume genus in temperate grassland systems, and a common feature in meadows and open space areas in cities and parks. Breeding of Trifolium spp. for pastoral production has been going on for over a century. However, the breeding targets have changed over the decades in response to different environmental and production pressures. Relatively small gains have been made in Trifolium breeding progress. Trifolium breeding programmes aim to maintain a broad genetic base to maximise variation. New Zealand is a global hub in Trifolium breeding, utilising exotic germplasm imported by the Margot Forde Germplasm Centre. This article describes the history of Trifolium breeding in New Zealand as well as the role and past successes of utilising genebanks in forage breeding. The impact of germplasm characterisation and evaluation in breeding programmes is also discussed. The history and challenges of Trifolium breeding and its effect on genetic gain can be used to inform future pre-breeding decisions in this genus, as well as being a model for other forage legumes.

Salt stress on Lotus tenuis triggers cell wall polysaccharide changes affecting their digestibility by ruminants

Lotus tenuis is a glycophytic forage legume (Fabaceae) used in feeding ruminants that can grow under salinity and waterlogging stresses. Plants obtained in controlled conditions were affected negatively in their growth by the effect of salt. Results from sequential extraction of plant cell wall polysaccharides and chemical characterization were related to those from nutritional parameters used to assess ruminants feedstuffs (Van Soest detergent system). Shoots and leaves were analyzed, and the most important differences were found for shoots. The salt-stressed shoots gave lower values of neutral detergent fiber and acid detergent fiber; they produced higher amounts of reserve α-glucans, and hemicelluloses (xyloglucans and glucuronoxylans from primary and secondary cell walls, respectively) and pectins, leaving less material resistant to extraction. This effect was clearly confirmed by an in vitro gas production assay. In addition, observations by light microcopy (LM) and transmission electron microscopy (TEM), showed in some tissues thicker walls and more opened cell wall structures in regard to control samples, which could allow easier access of degrading enzymes in the rumen. Although the plant biomass of Lotus tenuis produced under salt stress was lower, its quality as forage improved due to production of increased quantities of more digestible polysaccharides.

Perennial forage legume cultivation and their above-ground mass management methods for weed suppression in arable organic cropping systems

BackgroundIn organic crop farms, growing crop yields are limited by insufficient nitrogen supply to plants and crop weediness. In such farms, legume swards are proposed as a service crop to improve nitrogen cycling. However, a positive effect of nitrogen is not only on cereals but also on weeds. In crop rotation, legume swards can stimulate the competition of cereals using the above-ground mass of legume to control the spread of weeds.The effects of the following methods for weeds control were analyzed: (i) forage legumes (Trifolium pratense L. and T. repens) undersown in cereals, (ii) forage legumes (T. pratense L., Medicago sativa L.) and their mixture with festulolium (x Festuliolium) and their above-ground mass management methods, and (iii) plant-based fertilizers (red clover above-ground mass fermented and composted).ResultsOat with red clover undersown reduced weediness more than red clover monocrops, pea, and their mixture with oats. Incorporated undersown white clover mass increased spring barley competitiveness with weeds. When growing legume swards for a longer period of time (green fallow), red clover and their mixture with festulolium are the most suitable for this purpose. The lowest weed dry weight (average 34%, compared with the removal from the field) was obtained while using the mixed management. The cultivation of cereals after forage legumes and their mixtures with festulolium (as a preceding crop) increases its grain yield and competitive ability against weeds. Fermented red clover and fermented pea and spring wheat mixture mass, as a manure, did not increase weediness.ConclusionsIt was concluded that the effectiveness of the perennial forage legumes is determined by the uses of the above-ground mass: soil cover, mulching, application of green manure, and intensity of mass mineralization. Type of activity of forage legumes on weeds were competition for environmental resources, disruption/promotion of germination, destruction of above-ground mass, reduction of the amount of matured seeds, creation of a physical barrier (mulch), and increase of competitiveness of cereals. Growing forage legumes in pure crops usually leads to a loss of marketable production.Graphic abstract

Dynamics of Germination Behaviour, Protein Secondary Structure, Technofunctional Properties, Antinutrients, Antioxidant Capacity and Mineral Elements in Germinated Dhaincha.

SUMMARYResearch backgroundDhaincha (Sesbania aculeata) is a forage legume primarily used for green manuring and animal feed. Good nutritional profile of dhaincha makes it a potential alternative legume in human nutrition. However, the presence of high amount of antinutrients poses a problem in its utilisation for food applications. The present investigation intends to germinate dhaincha seeds at different time-temperature regimes and to evaluate the process of germination to ascertain optimal conditions and improve its potential for utilisation.Experimental approachDhaincha seeds were germinated at 24, 28 and 32 °C for 24, 48 and 72 h. Germination characteristics and germination loss, spectral characteristics, technofunctionality, antinutrients, bioactive constituents, antioxidant capacity and mineral element content of germinated dhaincha were evaluated. Optimal balance of technobiofunctionality of germinated dhaincha seeds was validated by principal component analysis.Results and conclusionsSprout length and germination loss increased with the higher germination temperature and prolonged germination time. Seeds showed similar germination rate at 28 and 32 °C and it was markedly higher than at 24 °C. Germination for 24 h resulted in mild conformational changes in the secondary structure of proteins, whereas germination for 48 and 72 h exhibited major conformational changes in the β-sheets, resulting in the improvement in the hydration and foaming properties. Progression of germination (72 h) caused the decrease of tannin (24.47%), phytic acid (16.38%) and saponin (24.58%) mass fractions, and of trypsin inhibitor (40.33%) and lectin activity (62.50%). Slight decrease of DPPH˙ (3.7%) and ABTS˙+ (18.5%) values was also observed, whereas total flavonoid content (36.14%) and metal chelating activity (26.76%) increased. Total phenolics, FRAP, and reducing power decreased after 24 h, followed by a gradual increase. Zinc extractability increased drastically with germination. Germination at 28 °C for 72 h resulted in higher reduction of antinutrients with optimal retention of antioxidant activity and better functional characteristics, as validated by principal component analysis.Novelty and scientific contributionDhaincha is an unknown crop in Europe, and even in Asia it is predominantly used as green manure and animal feed. This research demonstrated that the intervention in germination can transform dhaincha into a promising crop for food industry. Germinated dhaincha exhibited enhanced technobiofunctionality for utilisation in various food formulations.

High diversity of responses among Medicago truncatula lines to Phoma medicaginis infection.

Medicago truncatula is an omni-Mediterranean species grown as an annual forage legume. In addition to its small genome size and simple genetics, M. truncatula harbors several attributes, which make it an attractive model forage plant. In this study, we investigated the variation of responses in ten parental lines of M. truncatula to Phoma medicaginis infection. Plants were cultivated in the growth chamber under controlled conditions and were inoculated after two months with P. medicaginis. At harvest, 13 quantitative traits of growth and pathogenicity were measured. Results from ANOVA showed that the variation of analyzed parameters was explained by the effect of line. All measured parameters, except the root fresh weight, showed significant difference among the 10 studied lines. Most tolerant lines are those with the lowest ratios of the number of infected and dead leaves. Studied lines were clustered into three groups according to their responses to P. medicaginis infection. The most resistant TN6.18 line and most sensitive F83005.5 to P. medicaginis are useful for the exploration of physiological mechanisms and genetic determinants for M. truncatula tolerance to this constraint.

Methane mitigating options with forages fed to ruminants

AbstractNutritional strategies, including feed management measures, are promising methods for CH4 and overall GHG reduction. Evidence from literature is reviewed in this article in relation to the effects of forage quality (digestible organic matter, DOM) and forage type (grasses vs. legumes, and maize). The major determinants of forage quality are botanical composition and phenological stage, i.e., at advanced growth stages of plants, the fibre content increases while DOM decreases. Methane yield (g/kg DMI) decreases with increased digestibility of forages in both dairy cattle and sheep, and also CH4 intensity (g/kg milk) decreases with increased digestibility of forages for dairy cattle. Using forage legumes in ruminant feeding systems can reduce overall GHG emissions due to decreased N fertilizer use and related emissions. Recommended dietary mitigation measures are often related to a reduction in N excretion such as better matching of dietary protein to animal needs, shifting N excretion from urine to faeces (by tannin inclusion at low levels) and reducing the amount of excreted fermentable organic matter. Methane decreases with increasing intake of forage legumes rich in tannins and there is a shift of N partition from urinary N towards faecal N. Reduced CH4 emissions from ruminants fed on forage‐based diets will decrease the carbon footprint of livestock and agriculture and improve the efficiency of productive ruminants in both developing and developed countries. Likewise, estimations of net CH4 output should account for enteric CH4 emissions and soil carbon (C) sequestration of land used for feed production (i.e., grasslands and croplands).

Effects of Autotoxicity on Alfalfa (Medicago sativa): Seed Germination, Oxidative Damage and Lipid Peroxidation of Seedlings

Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively.

Forage Species Identity Shapes Soil Biota in a Temperate Agroecosystem

Increasing plant diversity in the perennial phase of pasture-crop rotations is predicted to positively affect belowground productivity and microbial communities and, in turn, augment belowground agroecosystem services including soil health and carbon storage. Using two grass and one legume forage species grown as monocultures and combined in four intercropped combinations, we evaluated how species identity and richness influence belowground productivity, soil microbial communities, and soil C pools. Though grass-legume intercrops demonstrated higher aboveground productivity than component species grown in monoculture, higher species richness was not associated with increased productivity belowground. Root biomass was greatest in tall fescue (Festuca arundinacea Schreb.) monoculture, and intercrops including this species. Species identity was similarly associated with soil microbial community attributes. Orchardgrass (Dactylis glomerata L.) monoculture exhibited lower total microbial abundance and lower bacterial abundance than grass-legume intercrops. Bacterial abundance was also lower in orchardgrass compared to white clover (Trifolium repens L.) monoculture. A common indictor of soil function, the fungal:bacterial ratio, was higher in grass-only than clover-only stands. The prevalence of species-specific impacts on roots and microbial communities in this study suggests that species identity may have a stronger influence than species richness on belowground agroecosystem services from perennial forages in temperate regions.

Evaluation of yield formation and nutritive value of forage legumes and herbs with potential for diverse grasslands due to their concentration in plant specialized metabolites

The use of forage legumes and herbs in temporary grassland swards is a promising strategy to enhance productivity, protein supply, herbage quality and species diversity in forage-based low input dairy production. Species containing plant specialized metabolites (PSM; e.g. tannins or polyphenol oxidase) are associated with positive effects on ruminants’ health, performance and nitrogen use efficiency. However, plant growth characteristics and the occurrence of PSMs with potential for improved nutritive value vary greatly depending on species and environment and to date, few species have been exploited agronomically. Thus, the current study aims to screen a range of forage species that are abundant in low input and semi-natural grasslands, in terms of productivity and forage quality for dairy cows under limited nitrogen availability in a ley system. Pure stands of eight legumes, six herbs and perennial ryegrass as reference, were established in a field experiment and sampled over two years (2010 and 2013) in their first full production year. Freeze-dried plant material was analysed for crude protein (CP), enzyme soluble organic matter (ESOM), fibre parameters (ADF, NDF), total phenolics (TP) and condensed tannins (CT). The species variation was significant for each parameter (P < 0.001). In comparison to high yielding legumes, herbage production of investigated alternative species was generally low, but for Cichorium intybus and Plantago lanceolata comparable or even higher than for Lolium perenne. Differences existed in yield development throughout the year, thus exhibiting temporal asynchrony for improved performance if grown in mixtures. Apart from Onobrychis viciifolia, the CP concentration in legume species was highest while ESOM was outstandingly high in herbs (except Plantago lanceolata). TP concentration was generally higher in herbs but in Onobrychis viciifolia and Lotus corniculatus the concentration of condensed tannins exceeded 10 g kg−1 DM. The results indicate that alternative forage species exist with high forage quality and potentially promising PSM concentrations, thus making them interesting additions for temperate grasslands.

Forage legumes from the Mediterranean Fynbos biome of South Africa with potential for domestication: slope aspect affects tissue fibre and mineral composition

Fabaceae plants contribute greatly to a high quality of pasture in rangelands, because of high levels of protein in their tissues. Despite this established importance, only a few southern African legumes have been evaluated for nutritional value and domestication. The Overberg renosterveld vegetation of the Fynbos biome occupies undulating landscapes that have multiple slope aspects, creating variable microclimatic conditions affecting nutrient dynamics, species richness and plant chemical compositions. We assessed the effect of slope aspect on fiber and mineral composition of forage species present to provide information on the importance of slope for species characterization and nutritional value for domestication. Tissue samples from six replicates of the same species occurring on opposing aspects were collected for nutritional assessment. Results on the data showed that fibre and mineral composition differed in species occurring on different slopes, albeit with few exceptions. The concentrations of P, K and Mg in some species were significantly higher on the cooler and wetter south facing slopes relative to north facing slopes. Nutrient elements in soil samples collected from each site varied with slope aspects and elements. It is recommended that topography should be considered when studying forage nutritional assessments as part of future domestication programs.

The genome of a wild Medicago species provides insights into the tolerant mechanisms of legume forage to environmental stress

BackgroundMedicago ruthenica, a wild and perennial legume forage widely distributed in semi-arid grasslands, is distinguished by its outstanding tolerance to environmental stress. It is a close relative of commonly cultivated forage of alfalfa (Medicago sativa). The high tolerance of M. ruthenica to environmental stress makes this species a valuable genetic resource for understanding and improving traits associated with tolerance to harsh environments.ResultsWe sequenced and assembled genome of M. ruthenica using an integrated approach, including PacBio, Illumina, 10×Genomics, and Hi-C. The assembled genome was 904.13 Mb with scaffold N50 of 99.39 Mb, and 50,162 protein-coding genes were annotated. Comparative genomics and transcriptomic analyses were used to elucidate mechanisms underlying its tolerance to environmental stress. The expanded FHY3/FAR1 family was identified to be involved in tolerance of M. ruthenica to drought stress. Many genes involved in tolerance to abiotic stress were retained in M. ruthenica compared to other cultivated Medicago species. Hundreds of candidate genes associated with drought tolerance were identified by analyzing variations in single nucleotide polymorphism using accessions of M. ruthenica with varying tolerance to drought. Transcriptomic data demonstrated the involvements of genes related to transcriptional regulation, stress response, and metabolic regulation in tolerance of M. ruthenica.ConclusionsWe present a high-quality genome assembly and identification of drought-related genes in the wild species of M. ruthenica, providing a valuable resource for genomic studies on perennial legume forages.

Salinity Stress Alters the Secondary Metabolic Profile of M. sativa, M. arborea and Their Hybrid (Alborea).

Increased soil salinity, and therefore accumulation of ions, is one of the major abiotic stresses of cultivated plants that negatively affect their growth and yield. Among Medicago species, only Medicago truncatula, which is a model plant, has been extensively studied, while research regarding salinity responses of two important forage legumes of Medicago sativa (M. sativa) and Medicago arborea (M. arborea) has been limited. In the present work, differences between M. arborea, M. sativa and their hybrid Alborea were studied regarding growth parameters and metabolomic responses. The entries were subjected to three different treatments: (1) no NaCl application (control plants), (2) continuous application of 100 mM NaCl (acute stress) and (3) gradual application of NaCl at concentrations of 50-75-150 mM by increasing NaCl concentration every 10 days. According to the results, M. arborea maintained steady growth in all three treatments and appeared to be more resistant to salinity. Furthermore, results clearly demonstrated that M. arborea presented a different metabolic profile from that of M. sativa and their hybrid. In general, it was found that under acute and gradual stress, M. sativa overexpressed saponins in the shoots while M. arborea overexpressed saponins in the roots, which is the part of the plant where most of the saponins are produced and overexpressed. Alborea did not perform well, as more metabolites were downregulated than upregulated when subjected to salinity stress. Finally, saponins and hydroxycinnamic acids were key players of increased salinity tolerance.

A 3-year field study to assess winter cover crops as nitrogen sources for an organic maize crop in Mediterranean Portugal

Current environmental concerns, the rising economic and environmental costs of mineral fertilizers and the need to respond to the limitations of N fertilization in organic farming motivate the search for alternative sources of N in maize cropping. Forage legumes used as winter cover crops may improve soil N fertility and offer benefits to the environment. The aim of this study was to examine the effects, in a factorial field experiment, of two sowing dates (SD) and nine different cover crop treatments (balansa clover, crimson clover, gland clover, arrowleaf clover, French serradella, yellow lupin, Italian ryegrass, a cover mixture and a weedy fallow) as a potential alternative N source in an organically managed maize crop. The experiment was conducted at Viseu (Portugal) for three years (2007/2008, 2008/2009 and 2011/12), in the same field. Results showed that maize grain yield was not influenced by cover crop species but was affected by SD and the higher dry matter (DM) aboveground biomass production was observed in early SD (6.1 t ha−1). The cover crops revealed their importance in maize N uptake: yellow lupin of earlier SD had the highest N uptake (83.6 kg N ha−1), but this was not significantly different from balansa clover (83.2 kg N ha−1). Ryegrass was the most efficient in depleting soil mineral N but values were just significantly lower than yellow lupin.Lupin was the least efficient, leaving more mineral N in the soil than the others cover crops, immediately before the period when the risk of leaching is high. It was concluded that, under the edaphoclimatic conditions tested, most of the tested cover crops were efficient in supplying N to maize, and balansa clover had the best performance.

Genetic diversity and population structure analysis in a large collection of white clover (Trifolium repens L.) germplasm worldwide.

White clover is an important temperate legume forage with high nutrition. In the present study, 448 worldwide accessions were evaluated for the genetic variation and polymorphisms using 22 simple sequence repeat (SSR) markers. All the markers were highly informative, a total of 341 scored bands were amplified, out of which 337 (98.83%) were polymorphic. The PIC values ranged from 0.89 to 0.97 with an average of 0.95. For the AMOVA analysis, 98% of the variance was due to differences within the population and the remaining 2% was due to differences among populations. The white clover accessions were divided into different groups or subgroups based on PCoA, UPGMA, and STRUCTURE analyses. The existence of genetic differentiation between the originally natural and introduced areas according to the PCoA analysis of the global white clover accessions. There was a weak correlation between genetic relationships and geographic distribution according to UPGMA and STRUCTURE analyses. The results of the present study will provide the foundation for future breeding programs, genetic improvement, core germplasm collection establishment for white clover.