Alfalfa Cultivars Research Articles

Dry matter yield and nutritive quality of alfalfa (Medicago sativaL.) cultivars grown in sub-humid areas in Ethiopia

Alfalfa (Medicago sativa L.) is one of the most important perennial forage legumes with high nutritional quality. Four alfalfa cultivars were sown in randomized block design with four replications to evaluate their dry matter yield and nutritional quality under rain-fed conditions during 2016–2017 at Masha, southwest Ethiopia. Percentage of plot cover, plant height, leaf to stem ratio, dry matter yield, crude protein yield, and dry matter (DM), ash, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) were measured. The combined analysis revealed that days to 50% flowering were significantly (P < 0.01) influenced by cultivar and cropping year. Dry matter yield was significantly affected by cultivar and cultivar vs year interaction. Hairy Peruvian scored the highest plot cover percentage followed by Pioneer 00407, Hunter River, and Magna 788. The overall mean for days to 50% flowering indicated that Hunter River reached more lately than others. We observed that leaf-to-stem ratio and plant height were insignificant among the cultivars. Hairy Peruvian gave a higher dry matter yield (15.0 t ha−1) followed by Pioneer 00407 (12.1 t ha−1), Magna 788 (11.5 t ha−1), and Hunter River (10.5 t ha−1). The chemical compositions did not vary significantly (P > 0.05) due to cultivar differences. It could be concluded that, of the tested cultivars, Hairy Peruvian is an appropriate cultivar for biomass production potential under rain-fed conditions for sub-humid areas of southwest Ethiopia.

New Insights into the Life History Changes Can Enhance Control Strategies for Therioaphis trifolii

The spotted alfalfa aphid (SAA), Therioaphis trifolii, is a phloem-feeding pest with a complex life history, and it causes a tremendous global loss of crop yields. A large number of previous studies focused only on few-generation life tables, whereas multi-generation life tables could explore aphid adaptation processes that are poorly understood. In this study, we investigated the effects of physical characters of alfalfa on SAA growth and development and used life-table parameters to evaluate the transgenerational effects of SAA populations on highly resistant (HA-3) and highly susceptible (Hu) alfalfa cultivars. The results indicated that alfalfa waxy content, anatomical structure of vegetative organs, and density and length of leaf hairs were significantly positively correlated with resistance to the SAA. In terms of the developmental time of total preoviposition period (TPOP), no significant differences were observed between two populations; compared to the HA-3 population, the G2-G8 Hu populations were markedly lower and G9-G10 Hu populations were visibly higher. Meanwhile, the reproductive days, mean longevity, and fecundity (offspring) of the HA-3 population were obviously higher than those of the Hu group after G5. Furthermore, the finite rate of increase (λ) and intrinsic rate of increase (r) of HA-3 were significantly higher than for the Hu population after G7. Meanwhile, the net reproductive rate (R0) and mean generation time (T) of HA-3 were significantly higher than for the Hu population after G5. On the whole, the SAA had a high survival rate, strong reproductive capacity, long life span, and high population growth parameters on Hu in the early stage, while the SAA had better growth and development on HA-3 in the late stage. The physical characteristics of alfalfa leaves could be used as one of the indicators of aphid resistance. However, the coevolutionary coupling was broken with the gradual adaptation of SAA, which provides an empirical basis for further exploring the mechanisms of alfalfa resistance to aphids and the integrated control of pests.

Leaf transcriptome analysis of Medicago ruthenica revealed its response and adaptive strategy to drought and drought recovery

BackgroundDrought is one of the main causes of losses in forage crop yield and animal production. Medicago ruthenica (L.) cv. Zhilixing is a high-yielding alfalfa cultivar also known for its high tolerance to drought. We analyzed the transcriptome profile of this cultivar throughout drought stress and recovery and we were able to describe its phased response through the expression profiles of overlapping gene networks and drought-specific genes.ResultsThe ABA and auxin signal transduction pathways are overlapping pathways in response to drought and drought recovery in forage crops. Medicago ruthenica (L.) cv. Zhilixing adopts different strategies at different degrees of drought stress. On the 9th day of drought, transcriptional regulations related to osmoregulation are enhanced mainly through increased activities of carbohydrate and amino acid metabolism, while photosynthetic activities were reduced to slow down growth. With drought prolonging, on the 12th day of drought, the synthesis of proline and other stored organic substances was suppressed in general. After recovery, Medicago ruthenica synthesizes flavonoids through the flavonoid biosynthesis pathway to remove accumulated ROS and repair the oxidative damage from water stress. In addition, the regulation of circadian rhythm seems to accelerate the drought recovery process.ConclusionsMedicago ruthenica adapts to drought by regulating the osmoregulatory system and photosynthesis, which appears to involve the ABA and auxin signaling pathways as key regulators. Furthermore, the synthesis of flavonoids and the regulation of the circadian rhythm can accelerate the recovery process. These results enriched our knowledge of molecular responses to drought and drought recovery in Medicago ruthenica and provide useful information for the development of new legume forage grass varieties with improved adaptability to drought stress.

Determination of Hay Yield and Quality Traits of Some Alfalfa Cultivars

Bu araştırma, Bursa ekolojik koşullarında bazı yonca çeşitlerinin ot verimi ve kalite özelliklerini belirlemek &#x0D; amacıyla 2015-2017 yılları arasında yürütülmüştür. Denemede Alsancak, Bilensoy-80, Diane, İside, Özpınar ve Prosementi çeşitleri ele alınmıştır. Çalışmada yonca çeşitlerinde ana sap uzunluğu, ana sap çapı, kuru ot verimi, ham protein oranı, ham protein verimi, ADF ve NDF içeriği gibi özellikler incelenmiştir. Araştırmadan elde edilen sonuçlara göre; denemenin ikinci ve üçüncü yıllarında en yüksek kuru ot verimleri sırasıyla 1830.6 kg da-1 ve 1559.2 kg da-1 ile İside çeşidinden elde edilmiştir. Denemede kullanılan bu çeşidin ham protein verimleri de aynı yıllarda diğer çeşitlerden daha yüksek olmuştur. Araştırma elde edilen sonuçlara göre, yüksek verim ve kalite açısından Bursa ve benzer ekolojik koşullarda İside, Bilensoy-80 ve Alsancak çeşitlerinin yetiştirilebileceği belirlenmiştir.

CaO and Graphene Oxide Enhances Drought Stress from Callus Tissues of Medicago Sativa L. Cultivars

Drought stress can be described as multidimensional stress factors affecting plants’ growth, development, and productivity. In order to reduce the adverse impact of drought stress, a plethora of attempts have been employed. Among those attempts, nano-engineered particles have gained a remarkable attention. Of the relevant particles, calcium oxide (CaO) and graphene oxide (GO) have been well-documented to positively regulate and mediate the plant growth system through shifting physiological biochemical and molecular aspects of the plant. The solo impacts of the nanoparticles are well-known but their interactions were not assayed for Medicago sativa L. cultivars. For that reason, the present study investigates the impact of CaO NPs and GO on the response and regulation of the defensive mechanism in alfalfa (Medicago sativa L.) callus in drought stress-suffered cultivars. The activation of CaO-GO can be induced with mannitol in the callus of alfalfa cultivars. Dry and fresh weight values were determined in callus samples. There were significant differences between cultivars and concentration. In terms of MDA, H2O2, proline content, it was observed that the Ca2+ NPs application was important, and it showed a strong link with the resistance degree of cultivars. Erzurum cultivar was observed for better proline content with 1.5 ppm GO. MDA activities demonstrated an increasing trend concerning concentrations of mannitol and nanoparticles. The MDA highest activity was observed with 1/2 ppm CaO+0.5/1.5 ppm GO (0.1849 mg/g FW) in the Erzurum. However, the Erzurum cultivar responded with better H2O2 content with 100 mM mannitol +0.5 ppm (0.1017 mg/g FW). This result has presented, under in vitro conditions, that the supplementation of CaO and GO can importantly reduce the negative impacts of drought stress on alfalfa callus; additionally, it has been seen that the dosages of nanoparticle and mannitol are also important.

A Pan-Transcriptome Analysis Indicates Efficient Downregulation of the FIB Genes Plays a Critical Role in the Response of Alfalfa to Cold Stress.

Alfalfa (Medicago sativa L.) is a perennial forage legume that is widely distributed throughout the world, and cold stress is an important environmental factor limiting the growth and production of alfalfa in cold regions. However, little is known of the molecular mechanisms regarding cold tolerance in alfalfa. Here, we conducted physiological metabolism assays and pan-transcriptome sequencing on eight cultivars of alfalfa under cold stress conditions. The results of the RNA-seq analysis showed that the genes are "oxidoreductase activity" and "transcription regulator activity", suggesting that genes with such functions are more likely to play important roles in the response to cold stress by alfalfa. In addition, to identify specific gene modules and hub genes in response to alfalfa cold stress, we applied weighted gene co-expression network (WGCNA) analyses to the RNA-seq data. Our results indicate that the modules of genes that focus on the ATPase complex, ribosome biogenesis, are more likely to be involved in the alfalfa response to cold stress. It is important to note that we identified two fibronectin (FIB) genes as hub genes in alfalfa in response to cold stress and that they negatively regulate alfalfa response to chilling stress, and it is possible that dormant alfalfa is more effective at down-regulating FIB expression and therefore more resistant to cold stress.

Lipid composition remodeling and storage lipid conversion play a critical role in salt tolerance in alfalfa (Medicago sativa L.) leaves

Alfalfa is the most important forage internationally due to its high yield and nutritional value, but its production is severely limited by soil salinization. A better understanding of alfalfa’s salt response mechanism is needed to provide guidance for breeding salt tolerant varieties. Lipidomic profiling of the salt-tolerant alfalfa cultivar Medicago sativa cv. Zhongmu-4 was performed after salt treatment. Of the 275 molecular species of lipid identified, 171 had altered levels after salt treatment. The levels of phospholipids, glycolipids, fatty acids, and sphingolipids decreased whereas lysophospholipids and glycerides accumulated in the salt treated plants. Specifically, higher PC/PE and DGDG/MGDG ratios and increased levels of FA 18:3 were observed, suggesting that changes in bilayer membrane structure integrity and fluidity maintenance occur in alfalfa leaves during salt stress. An accumulation of DAG (36:6, 36:5) and TAG (54:8, 54:9, 54:7, 54:6, 52:5, 52:6) was found, consistent with their potential role as storage substrates for membrane regeneration under salt stress. Changes in PI, LPC (16:0, 18:3, 18:2, 18:0), LPE (16:0, 18:2), and Cer (42:1;4 O, 34:1;4 O, 40:1;4 O) suggest these compounds may play a role in signal transduction under salt stress. The levels of PE, DGDG, and TAG were highly correlated (r＞0.8) with changes in salt-related physiological parameters. In addition, the apparent remodeling of lipid profiles was supported by complementary changes in gene expression, including DGD2, SQD2, FAD2, DGK, DGAT, and TAGL, that can be important candidate genes for alfalfa salt tolerance improvement. The detailed description of the changes occurring in lipid profiles and gene expression in alfalfa under salt stress provided by this study implicate lipid remodeling as an important feature of the salt-stress response, and provides a basis for the genetic improvement of alfalfa salt tolerance.

The response of alfalfa cultivars to mobile aluminum toxicity

AbstractAlfalfa (Medicago sativa L.) as a perennial forage grass is widely adapted to favorable environmental conditions with wide range of soils including acid soils. The productivity traits of alfalfa in the soil without and with 1.8–14.7 mgAl/kg concentration of mobile Al were investigated. The study site was conducted at the Vėžaičiai Branch of the Lithuanian Research Centre for Agriculture and Forestry, 55°70 N lat., 21°49 E long. The experiment featuring 19 cultivars was established on a Balthygleyic Dystric Retisol in 2018. In 2019 and 2020, the productivity traits were evaluated: spring regrowth, plant height before flowering, stem number, seed yield, and fresh and dry matter yield. The mobile Al negatively influenced productivity traits of alfalfa in 2019 and 2020. Several cultivars of alfalfa were distinguished by tolerance to mobile Al and will be used for further selection for breeding. In 2020, the cultivar Europe from France was distinguished by spring regrowth, number of stems and fresh matter yield in the soil with mobile Al. The cultivar Ludelis from France differed by spring regrowth and height before flowering time in the soil with mobile Al in 2019–2020. The cultivar Skriveru from Latvia was the most yielding by seed yield in the soil without and with mobile Al in 2019. The Lithuanian cultivar Antanė was yielding by dry matter yield in the soil with and without mobile Al in 2019. The cultivar Žydrūnė from Lithuania was yielding by fresh and dry matter yield in the soil with and without mobile Al in 2020. This study on acid soils with and without mobile Al concentrations has revealed the differences of productivity traits under different environmental conditions of experimental years. Results of this study are important not only for Lithuania but also for the other lands of Europe where Retisol are prevails.

Effect of Sodium Chloride Salt on Germination, Growth, and Elemental Composition of Alfalfa Cultivars with Different Tolerances to Salinity

The aim of this study was to evaluate physiological responses and elemental composition of three salt tolerant alfalfa (Medicagosativa L.) cultivars, ‘Halo’, ‘Bridgeview’, ‘Rugged’, and two intolerant cultivars ‘Rangelander’ and ‘Vernal’ under five salinity levels (0 dSm−1, 4 dSm−1, 8 dSm−1, 12 dSm−1 and 16 dSm−1) in a sand based hydroponic system in the greenhouse. The germination percentage among the cultivars was highest for ‘Halo’ under salt stress. ‘Rugged’ and ‘Halo’ had higher seed vigor than the other cultivars in 16 dSm−1 EC. Among the alfalfa cultivars, ‘Rugged’ had the highest chlorophyll content at 0–12 dSm−1 EC. There was variation for root (p = 0.01) and shoot (p = 0.03) biomass among the alfalfa cultivars. Salt stress reduced (p &lt; 0.001) plant height and shoot biomass, with 4.2% and 7.9% reduction for each 1 dS m−1 increase, respectively. Shoot biomass showed a positive correlation with plant height (p &lt; 0.001, r = 0.80), chlorophyll content (p &lt; 0.001, r = 0.56), root biomass (p &lt; 0.001, r = 0.51), but was not correlated with seed vigor. This study demonstrated that seed vigor in the germination stage can not be used to predict salt tolerance of alfalfa at mature growth stages, however plant height and leaf chlorophyll content can serve as physiological markers for high shoot biomass selection at mature growth stages under salt stress.

Fine-Tuned Immune Antagonism and Nodule-Specific Cysteine-Rich Peptides Govern the Symbiotic Specificity Between Alfalfa Cultivars and Ensifer meliloti

Alfalfa expresses significantly distinct sets of genes in response to infection with different rhizobial strains at the below species level (i.e., biotype or strain). However, differences in the transcriptomic profiles of two alfalfa cultivars nodulated by a single rhizobium strain have been largely unexamined. In this study, comparative RNA-seq analysis of two alfalfa cultivars, Medicago sativa cv. Gannong No. 3 (G3) and cv. Gannong No. 9 (G9) inoculated with one Ensifer meliloti strain LL2, with varying symbiotic performance, was conducted, followed by hub gene interaction network construction based on weighted gene co-expression network analysis (WGCNA). The G9-LL2 symbiotic system showed better nodule formation, nitrogen fixation, and growth characteristics than the G3-LL2 system. Compared with the non-inoculated control, the LL2-inoculated G9 plants (10,053) produced more differentially expressed genes (DEGs) than the LL2-inoculated G3 plants (7112). A group of 227 genes displayed completely distinguished expression in G9 (6.63 < log2(FC) < 15.45) and G3 (‒ 3.05 < log2(FC) < 12.05), which are primarily involved in encoding nodule-specific cysteine-rich peptides (NCRs), nodulin, and leghemoglobin. Although genes with predicted roles in nitrogen metabolism were primarily upregulated and almost all of those in ubiquitin-mediated proteolysis and plant–pathogen interaction were suppressed, interestingly, a consistently higher expression level measured by log2(FC) was observed in G9 plants. Hub gene interaction networks showed that NCRs, late nodulin, and genes related to plant immunity (TIR-NBS-LRR, defensin, thioredoxin, thionine, and polygalacturonase) regulate other genes at the source node positions. After successful initiation of nodulation in both alfalfa cultivars G3 and G9 by E. meliloti strain LL2, G9 achieved preferable outcomes of rhizobia–alfalfa symbiosis by equilibrating the antagonism and compatibility of plant immunity. It elevated PTI, suppressed defense and ETI, and enhanced nitrogen fixation and utilization efficiency by inducing the expression of genes encoding NIN, NFH1, LysM-RLK, LRP, NCRs, nodulin, and leghemoglobin. Hub genes were predominantly associated with highly specific rhizobia–alfalfa symbiosis positively governed by NCRs and fine-tuned immune antagonism, comprising NCRs, late nodulin, and TIR-NBS-LRR. These findings provide insights into the genetic mechanisms underlying the modification and efficient utilization of semi-compatible and incompatible rhizobial resources.

Differentially expressed genes related to plant height and yield in two alfalfa cultivars based on RNA-seq.

BackgroundAlfalfa (Medicago sativa L.) is a kind of forage with high relative feeding value in farming and livestock breeding, and is of great significance to the development of animal husbandry. The growth of the aboveground part of alfalfa is an important factor that limits crop yield. Clarifying the molecular mechanisms that maintain vigorous growth in alfalfa may contribute to the development of molecular breeding for this crop.MethodsHere, we evaluated the growth phenotypes of five cultivars of alfalfa (WL 712, WL 525HQ, Victoria, Knight 2, and Aohan). Then RNA-seq was performed on the stems of WL 712, chosen as a fast growing cultivar, and Aohan, chosen as a slow growing cultivar. GO enrichment analysis was conducted on all differentially expressed genes (DEGs).ResultAmong the differentially expressed genes that were up-regulated in the fast growing cultivar, GO analysis revealed enrichment in the following seven categories: formation of water-conducting tissue in vascular plants, biosynthesis and degradation of lignin, formation of the primary or secondary cell wall, cell enlargement and plant growth, cell division and shoot initiation, stem growth and induced germination, and cell elongation. KEGG analysis showed that differentially expressed genes were annotated as being involved in plant hormone signal transduction, photosynthesis, and phenylpropanoid biosynthesis. KEGG analysis also showed that up-regulated in the fast growing cultivar were members of the WRKY family of transcription factors related to plant growth and development, members of the NAC and MYB gene families related to the synthesis of cellulose and hemicellulose, and the development of secondary cell wall fibres, and finally, MYB family members that are involved in plant growth regulation. Our research results not only enrich the transcriptome database of alfalfa, but also provide valuable information for explaining the molecular mechanism of fast growth, and can provide reference for the production of alfalfa.

Application of machine learning to explore the genomic prediction accuracy of fall dormancy in autotetraploid alfalfa.

Fall dormancy (FD) is an essential trait to overcome winter damage and for alfalfa (Medicago sativa) cultivar selection. The plant regrowth height after autumn clipping is an indirect way to evaluate FD. Transcriptomics, proteomics, and quantitative trait locus mapping have revealed crucial genes correlated with FD; however, these genes cannot predict alfalfa FD very well. Here, we conducted genomic prediction of FD using whole-genome SNP markers based on machine learning-related methods, including support vector machine (SVM) regression, and regularization-related methods, such as Lasso and ridge regression. The results showed that using SVM regression with linear kernel and the top 3000 genome-wide association study (GWAS)-associated markers achieved the highest prediction accuracy for FD of 64.1%. For plant regrowth height, the prediction accuracy was 59.0% using the 3000 GWAS-associated markers and the SVM linear model. This was better than the results using whole-genome markers (25.0%). Therefore, the method we explored for alfalfa FD prediction outperformed the other models, such as Lasso and ElasticNet. The study suggests the feasibility of using machine learning to predict FD with GWAS-associated markers, and the GWAS-associated markers combined with machine learning would benefit FD-related traits as well. Application of the methodology may provide potential targets for FD selection, which would accelerate genetic research and molecular breeding of alfalfa with optimized FD.

Comparative Transcriptome and Anatomic Characteristics of Stems in Two Alfalfa Genotypes.

Stems are more important to forage quality than leaves in alfalfa. To understand lignin formation at different stages in alfalfa, lignin distribution, anatomical characteristics and transcriptome profile were employed using two alfalfa cultivars. The results showed that the in vitro true digestibility (IVTD) of stems in WL168 was significantly higher than that of Zhungeer, along with the significantly lower neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin contents. In addition, Zhungeer exhibited increased staining of the xylem areas in the stems of different developmental stages compared to WL168. Interestingly, the stems of WL168 appeared intracellular space from the stage 3, while Zhungeer did not. The comparative transcriptome analysis showed that a total of 1993 genes were differentially expressed in the stem between the cultivars, with a higher number of expressed genes in the stage 4. Of the differentially expressed genes, starch and sucrose metabolism as well as phenylpropanoid biosynthesis pathways were the most significantly enriched pathways. Furthermore, expression of genes involved in lignin biosynthesis such as PAL, 4CL, HCT, CAD, COMT and POD coincides with the anatomic characteristics and lignin accumulation. These results may help elucidate the regulatory mechanisms of lignin biosynthesis and improve forage quality in alfalfa.

Compatibility of new sainfoin populations as forage mixtures with alfalfa and orchardgrass in Alberta

Sainfoin is a highly nutritious non-bloating leguminous forage crop of temperate regions. Despite non-bloating properties, its use in pastures was limited due to low dry matter yield (DMY), lack of persistence in the mixed pasture, and slow regrowth. The paradigm then shifted when new sainfoin cultivars planted in mixtures with alfalfa reduced 98% bloat incidence in ruminants. Two experiments were conducted to determine the compatibility of sainfoin with grass and alfalfa. Experiment (Exp.) I was established by drilling alfalfa cv. Longview and orchardgrass cv. Kayak with new sainfoin populations in alternate or cross-seeding rows under irrigated and unirrigated conditions in Lethbridge, AB. Exp. II was established by drilling sainfoin populations in mixture with alfalfa cultivars in alternate rows under irrigation. DMY and botanical composition (dry matter basis) were observed for both experiments. In Exp. I, monoculture orchardgrass produced the least DMY compared with the mixtures under both growing conditions and over all growing seasons. Alfalfa–sainfoin mixture yielded higher under irrigatated and less under unirrigated conditions relative to alfalfa monoculture. The percentage DMY contribution of sainfoin in alfalfa–sainfoin mixtures decreased but increased in sainfoin–orchardgrass mixtures over successive harvests under both environments. In Exp. II, we observed that new sainfoin populations mixed with alfalfa cvs. Beaver and Longview yielded greater ( P &lt; 0.05) than their corresponding monocultures and this increase was not associated with the proportion of the species in the mixture suggesting new sainfoin populations are as productive as alfalfa.

Occurrence and Nutrition Indicators of Alfalfa withLeptosphaerulina in Chifeng, Inner Mongolia

Alfalfa Leptosphaerulina leaf spot is a common disease of alfalfa, while its effect on alfalfa quality has not been reported. The present study aimed to investigate the alfalfa Leptosphaerulina leaf spot in Chifeng City, Inner Mongolia, China and determine the quality of alfalfa plants and leaves with different scales. The incidence and disease index of nine alfalfa cultivars ranged from 12.1% to 59.8% and 10.0 to 51.0, respectively. The incidence of the Optimus cultivar and the disease index of the WL168 cultivar were significantly higher than those of the other cultivars. Therefore, different scales (0–4) of the alfalfa WL168 plant and leaves were used to determine their nutritional levels. Compared with healthy plants and leaves, the severity of alfalfa leaf spot on a scale of 4 decreased by 3.7% to 29.4% or 1.7% to 40.7%, respectively, in 18 nutrients; and increased by 12.0% to 14.5% or 17.8% to 26.9% in the Rumen protein (RUP), acid detergent fiber (ADF) and neutral detergent fiber (NDF), respectively. In addition, the crude protein (CP) content of alfalfa plants or leaves based on a severity scale of 4 decreased by 16.7% and 6.2%, respectively. Correlation analysis revealed a strong negative correlation between 18 nutritional contents and disease severity, except for NDF, ADF and RUP. Conclusively, alfalfa Leptosphaerulina leaf spot strongly influences the plant and the leaves’ nutrient content in the plant.

Metabolomic changes in crown of alfalfa (Medicago sativa L.) during de-acclimation

Alfalfa is a high-quality forage legume species that is widely cultivated at high latitudes worldwide. However, a decrease in cold tolerance in early spring seriously affects regrowth and persistence of alfalfa. There has been limited research on the metabolomic changes that occur during de-acclimation. In this study, a liquid chromatography–mass spectrometry system was used to compare the metabolites in two alfalfa cultivars during a simulated overwintering treatment. In four pairwise comparisons, 367 differential metabolites were identified, of which 31 were annotated according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Many of these metabolites were peptides, carbohydrates, and lipids. At the subclass level, 17 major pathways were revealed to be significantly enriched (P < 0.05). The main differential metabolites included amino acids, peptides and analogs, carbohydrates, and glycerol phosphocholines. A metabolomic analysis showed that the up-regulation of unsaturated fatty acids and amino acids as well as the enhancement of the related metabolic pathways might be an effective strategy for increasing alfalfa cold tolerance. Furthermore, glycerophospholipid metabolism affects alfalfa cold tolerance in early spring. Study results provide new insights about the changes in alfalfa metabolites that occur during de-acclimation, with potential implications for the selection and breeding of cold-tolerant cultivars.

Distinct rhizosphere soil responses to nitrogen in relation to microbial biomass and community composition at initial flowering stages of alfalfa cultivars.

In the long-term growth process, alfalfa rhizosphere forms specific microbiome to provide nutrition for its growth and development. However, the effects of different perennial alfalfa cultivars on changes in the rhizosphere soil characteristics and microbiome are not well understood. In this study, 12 perennial alfalfa cultivars were grown continuously for eight years. Rhizosphere samples were tested using Illumina sequencing of the 16S rRNA gene coupled with co-occurrence network analysis to explore the relationship between alfalfa (biomass and crude protein content), soil properties, and the microbial composition and diversity. Redundancy analysis showed SOC and pH had the greatest impact on the composition of the rhizosphere microbial community. Moreover, microbial diversity also contributes to microbial composition. Soil properties (AP, EC, SOC and pH) exhibited a significant positive correlation with soil bacterial communities, which was attributed to the differences between plant cultivars. Partial least squares path modeling (PLS-PM) revealed that microbial biomass and community composition rather than diversity, are the dominant determinants in the rhizosphere soil nitrogen content of perennial alfalfa. Our findings demonstrate that the soil microbial biomass and composition of rhizosphere bacterial communities are strongly affected by cultivar, driving the changes in soil nitrogen content, and variances in the selective capacities of plants.

The Characterization and the Biological Activity of Phytotoxin Produced by Paraphoma radicina.

Paraphoma radicina is a new pathogen that causes alfalfa paraphoma root rot (APRR), leading to alfalfa production losses. The resistance levels of 30 alfalfa cultivars to APRR have already been characterized. However, the pathogenic mechanism of P. radicina is still unclear. This study aimed to assess the effects of a crude toxin extracted from P. radicina cell-free culture filtrate (CFCF) on susceptible and resistant cultivars of alfalfa. Meanwhile, the crude toxin components were detected using gas chromatography-mass spectrometry (GC-MS) analysis. CFCF cultured in MEB medium for 14 days and crude toxin extracted by ethyl acetate induced significant phytotoxicity caused the average lesion areas of 5.8 and 3.9 mm2, respectively, on alfalfa leaves. The crude toxin exhibited resistance to high temperature, as shown by a lesion area of 3.6 mm2 when treated at 120 °C for 30 min. Different concentrations of the crude toxin in water and MS medium had different effects on susceptible and resistant cultivars. Moreover, the crude toxin affected the plasma membrane, mitochondria, and nuclear membranes of alfalfa root cortical cells. Further, it induced significant phytotoxicity on Sonchus oleraceus L., Capsella bursa-pastoris (Linn.) Medic, and Chenopodium album L. Agropyron cristatum L. (average lesion areas; 11.6, 15.8, 21.4, and 6.2 mm2, respectively), indicating that the crude toxin of P. radicina is a non-host-selective toxin. GC-MS analysis detected four possible active substances in the toxin (3-hydroxypyridine, 5-methylresorcinol, 3-Hydroxypropionic acid, and 4-Hydroxyphenylethanol). Therefore, this study may provide insight into the pathogenic mechanism of P. radicina to alfalfa.

The Physiological Role of Abscisic Acid in Regulating Root System Architecture of Alfalfa in Its Adaptation to Water Deficit

Alfalfa (Medicago sativa L.) is a perennial leguminous plant, with a strong tap root system that plays an important role in alfalfa’s adaptation to drought stress. However, a better understanding of root functional traits and how these root traits are related to whole plant responses in order to improve pasture productivity under water deficit. Two greenhouse experiments were conducted: Experiment 1 used three alfalfa cultivars and four levels of soil water content treatments to investigate herbage productivity, growth point density, residual shoot weight, and root weight. Experiment 2 assessed relationships among root-sourced abscisic acid (ABA), root system architecture and plant biomass in response to water deficit. The results demonstrated that root system was used as a useful tool to improve tolerant and adaptation when alfalfa copied with lower levels of soil water content. On average, maintaining 60–65% soil water-holding capacity alfalfa had the highest herbage accumulation (6.7 g DM pot-1), growing point density (46.5 pot-1), and residual shoot biomass (1.8 g DM pot-1). At the level of water stress, Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) tended to exhibit a herringbone branching pattern with less root tips, root forks, altitude, and magnitude than cv Golden empress (GE). Principal component analysis and structural equation modeling revealed that root-sourced ABA positively regulated the altitude and magnitude of root system architecture, root tips and root forks, and was closely associated with plant root biomass and herbage biomass. It was concluded that these findings can contribute to developing optimum irrigation strategies and help alfalfa breeders in the development of new cultivars with improved drought tolerance based on root system architecture, plant hormone, and plant growth.

Agronomical evaluation of low dormancy alfalfa populations selected by an indoor screening method

AbstractFall dormancy is a vital component of alfalfa (Medicago sativa L.) yield in northern climates, but selection for the trait is often done at the expense of winter survival. We performed one cycle of selection to reduce fall dormancy in two winter hardy cultivars (Yellowhead and Peace) using a new indoor screening method. We compared the reduced dormancy populations with their respective initial cultivars for fall dormancy, yield, and winter survival at four sites across Canada. During the establishment and the first production years, plants of the reduced dormancy populations were generally taller in the fall than their respective cultivar, which resulted in a one unit increase of their fall dormancy class. Under field conditions, plants of the reduced dormancy populations had a similar winter survival than those of the initial cultivars. Under simulated winter conditions, freezing tolerance was not affected by selection for reduced dormancy in Peace, whereas a decrease from −24.0 to −21.5 °C was observed in Yellowhead. However, in this cultivar, we noted a 37% yield increase under field conditions and a 40% more vigorous regrowth under simulated winter conditions in the reduced dormancy population. These results showed that the indoor selection method effectively reduced fall dormancy and that indirect responses for yield and winter survival were dependent on the genetic background used as selection material. This selection method could therefore be promising to develop alfalfa cultivars adapted to northern latitudes with high winter hardiness and improved late season yield.