Alfalfa (Medicago sativa L.)/Crops intercropping provides a feasible way to improve productivity under environmental constraints

The growing threats facing both food security and the environment require a sustainable development. The need for sustainable agricultural alternative systems is prompted by economic, environmental and biological perspectives. Producers require cultivation methods that minimize environmental damage while simultaneously preserving and improving farm profitability. One of the key solutions is intercropping. Which is a cropping system where the crop can coexist in the same soil and can be irrigated simultaneously at the same time. It is used to improve crop yields, land use rates, as well as to reduce the barriers towards sustainable cultivation and the development of disease and insect pests as well as control weed growth. Besides, intercropping of legumes in a cropping system provides advantages for non-legumes due to improved nutrient distribution, to improved soil biology and to enhanced use of available resources. The biological fixation of nitrogen by legume crops makes intercropping legumes, especially alfalfa, a cost-effective solution to the problem of using artificial fertilizers. Alfalfa intercropping does not only meet the requirements of food security and forage needs, but also preserves the eco-environment, which has made this cultivation model a very promising one for agricultural development under environmental constraints

Influence of drought and heat stresses in fodder legumes productivity and nutritive value

Plants are often subjected to several environmental constraints in the field, often simultaneously, which significantly affect their productivity. Among these constraints, water deficit and heat stress are the main constraints limiting plant yield in the arid regions of the Mediterranean basin. Both of these abiotic factors are exacerbated by climate change. Fodder legumes provide a rich resource of plant nutrition to human diets, and are vital for food security and sustainable cropping. Numerous biochemical, molecular, and physiological responses are evoked by drought and heat stresses, influencing the fodder crop yield and nutritional value. When plants are water stressed, they are unable to maintain good growth and produce high yields. Drought also reduces the protein content of the plants, which can lead to a decrease in forage quality. Heat can negatively affect the productivity of forage legumes. High temperatures can cause heat stress which can lead to decreased photosynthesis and reduced productivity. In addition, high temperatures can result in decreased forage quality and increased nutrient losses. Exposure to combined water stress and heat can reduce the protein, fiber and mineral content of forage legumes and can also reduce their digestibility. This review summarizes the current status of the effects of drought and heat stresses on forage crops productivity and fodder quality

Morphological and physiological behaviour of sea barley (Hordeum marinum ssp marinum) genotypes originating from Soliman Sebkha under increasing salinity

Evaluation of germplasm in salt stress environment may help identifying salt-tolerant genotypes. In this study, we analyzed the genetic diversity of Hordeum marinum, genotypes originated from Soliman Sebkha in response to salinity (0, 250 and 400 mM) by measuring a set of parameters related to growth, water statue and photosynthetic activity. Results of ANOVA showed that variability of measured parameters was explained by the effects genotypes, treatment and their interaction, with treatment factor recorded the highest values. Salinity significantly reduced the photosynthetic rate and related parameters, including stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration (E). Several indices for salt tolerance indices comprising tolerance index (TOL), stress tolerance index (STI) and Salt Tolerance (ST) were calculated based on drought biomass (ADW) under non-stressed and under stress conditions. Results showed that lower values of TOL and higher values of ST and STI indicate the superiority of the genotypes having enough plasticity to respond to extreme conditions. Principal Component Analysis clustered genotypes into sensitive (21.43%), moderately tolerant (50%), and highly tolerant (28.57%) groups, depending on their relative potential to sustain good growth under high salinity. Results indicating sufficient genetic variability for salinity tolerance among the studied genotypes, hence tolerant genotypes can be good candidates in future breeding programs

Analysis of salinity tolerance in two varieties of Medicago sativa at the vegetative stage.

In this study, we analyzed salt tolerance in two varieties of Medicago sativa at the vegetative stage. Gabès2355 and Californian varieties of M. sativa were cultivated under control treatment and under a range of salt concentrations (50 mM, 100 mM, 150 mM, and 200 mM NaCl) in a greenhouse. At harvest, ten quantitative characters related to aerial and root growth were measured for plants of both varieties. Results from ANOVA showed that the variation of the traits measured is explained by the effects of variety, treatment and the interaction of variety x treatment. The treatment factor represents the most pronounced effect. While the Californian variety was more sensitive than the Gabès variety under 50 mM NaCl, it was the most tolerant under higher concentrations of NaCl. Specific correlations between measured traits were noted under control treatment and salt stress. Further work is needed to evaluate the agronomic performances of both varieties in the field under salinity constraint

Variability in Responses to Phoma medicaginis Infection in a Tunisian Collection of Three Annual Medicago Species

Spring black stem and leaf spot, caused by Phoma medicaginis, is an issue in annual Medicago species. Therefore, in this study, we analyzed the response to P. medicaginis infection in a collection of 46 lines of three annual Medicago species (M. truncatula, M. ciliaris, and M. polymorpha) showing different geographic distribution in Tunisia. The reaction in the host to the disease is explained by the effects based on plant species, lines nested within species, treatment, the interaction of species × treatment, and the interaction of lines nested within species × treatment. Medicago ciliaris was the least affected for aerial growth under infection. Furthermore, the largest variation within species was found for M. truncatula under both conditions. Principal component analysis and hierarchical classification showed that M. ciliaris lines formed a separate group under control treatment and P. medicaginis infection and they are the most vigorous in growth. These results indicate that M. ciliaris is the least susceptible in response to P. medicaginis infection among the three Medicago species investigated here, which can be used as a good candidate in crop rotation to reduce disease pressure in the field and as a source of P. medicaginis resistance for the improvement of forage legumes

Identification of genetic basis of agronomic traits in alfalfa (Medicago sativa subsp. sativa) using Genome Wide Association Studies

Alfalfa (Medicago sativa L.) is one of the most widely cultivated forage crops due to its high yield, value of nutrients, and adaptation to diverse environments. However, many of the desired agronomic traits in alfalfa are quantitative, and therefore improving them under abiotic and biotic stresses becomes an important goal in alfalfa breeding. One way to achieve such a goal is identification of loci that contribute to variation in complex traits. Genome Wide Association Studies (GWAS) provide advanced tools to identify genetic loci associated with traits of interest using high-density markers throughout the genome. In M. sativa, previous studies indicated that GWAS could identify numerous candidate single nucleotide polymorphism (SNP) markers for quantitative traits, including biomass, yield, forage quality, and drought/salt tolerance. Furthermore, mapping SNP markers against the M. sativa reference genome revealed many putative candidate genes which are associated with several cell wall-related traits. In this review, we summarize Genome Wide Association (GWAS) in alfalfa from concept to application and the identification and characterization of candidate genes for traits of interest

Harnessing the potential of endophytes: Sustainable solutions for enhancing forage crop resilience and soil fertility

Environmental changes pose significant challenges to sustainable agriculture, adversely affecting crop production and soil fertility. Factors such as drought, salinity, pathogens, and soil type exert their influence on the behavior of fodder crops by altering their morphological, biochemical, and molecular mechanisms, ultimately leading to reduced yields and productivity. Consequently, there is a pressing need to develop mitigation strategies aimed at enhancing the tolerance of forage crops to both biotic and abiotic stresses, addressing a critical challenge in sustaining their growth. In recent times, the use of biofertilizers has emerged as an environmentally friendly alternative to chemical fertilizers, holding promise for sustainable horticultural, agricultural, and forestry production systems. Notably, endophytic microorganisms play a pivotal role in promoting plant growth through direct or indirect mechanisms. Additionally, endophytic bacteria actively regulate gene expression responsible for the production of antioxidant enzymes, various phytohormones, siderophores, and ROS scavenging enzymes, all of which contribute to supporting the growth of host plants even in extreme environments. Consequently, there is a growing focus on understanding and validating the mechanisms through which beneficial plant endophytes interact to combat both biotic and abiotic stresses. This review emphasizes the potential of endophytes as biofertilizers, biocontrol agents, and contributors to the mitigation of abiotic and biotic stresses, all of which play crucial roles in maintaining the development of forage crops and soil fertility

Endophytic microbes modulate plant responses to abiotic stresses: a review

Many groups of microorganisms have been studied for their benefits towards humankind due to their capacity to produce natural compounds that can be valorized in many economic sectors such as agriculture. Due to the extensive use of chemicals pesticides and fertilizers, current agriculture systems facing several major problems such as emergence of resistant in pathogens and pests, soil infertility and bioaccumulation of toxic residues in the environment and particularly in foods which negatively affects human health. The use of natural products harmless to plants, humans and biodegradable constitute a promising way to overcome these problems. Modern agriculture systems are moving toward the use of beneficial microorganisms isolated from the soil, plant surfaces and inside tissues for developing eco-friendly products such as biofertilizers and biopesticides. Recent literatures show that colonization of plants by endophytes is the rule in nature and endophyte-free plant is a rare exception. Endophytes are microbes living inside plant tissues and supporting them in growth and development, as well as stresses tolerance without causing any apparent disease symptom. Abiotic stresses have a great impact on growth, production and health of plants. Many literatures show the role of endophytes in abiotic stress tolerance as well as mechanisms involved to cope with these constraints via the induction of stress-related genes and molecules. This review provides a summary of literature on how endophytes modulate plant growth and responses to abiotic stresses which may help to better understand their role in plant adaptation to environmental constraints and valorize their use in agriculture

Effects of salt stress on the germination of two contrasting Medicago sativa varieties.

Selection strategies for increased salt tolerance in Medicago sativa must involve several growth stages, with the germination stage as a particularly important stage. At this stage, M. sativa is known to be more sensitive to salt than later growth stages. Cultivars differ significantly in their capacity to germinate under saline conditions. For this consideration and in order to analyze the response to salinity, initial screening at the germination stage for two varieties of M. sativa was undertaken. Seeds were germinated in Petri dishes under control treatment (0 mM NaCl) and four concentrations of NaCl (100, 150, 200 and 250 mM). Results from ANOVA showed that variation in root length (RL), fresh root weight (RFW) and shoot fresh weight (SFW) was explained by variety effect. The variation in hypocotyl length, (HL) SFW and RL was explained by the interaction of variety x treatment. Under salt stress, there was a major reduction (46, 66%) in final germination rate (GR) when seeds were geminated in 250 mM NaCl. The RL and HL were affected by salt stress and their respective values were reduced by more than 40% in 200 mM NaCl. The Californian variety was lesser affected by salt stress for RL and RFW while the local variety from El Hemma showed the lowest reduction for SFW. Further work is needed to asses these effects in later growth stages and in field conditions under salt stress

Variation of Medicago sativa varieties tolerance to Phoma medicaginis infection.

Due to its very important agronomic value and nutritional quality, Medicago sativa L. is considered as the queen of fodder and the first cultivated forage crop in the world. In field conditions, M. sativa is exposed to several biotic and/or abiotic constraints that affect its quality. In this regard, research is still underway to improve M. sativa resistance to many biotic stresses and, in this context, we analyzed the responses of a core collection of 10 varieties of M. sativa to Phoma medicaginis infection. Results from ANOVA showed that most growth parameters exhibited significant differences between the studied varieties. Nevertheless, only the number of healthy leaves among infection parameters varied significantly between the varieties. The local variety Gabès2355 exhibited the highest biomass. Positive correlations were found between the measured parameters. PCA based on the traits showing significant differences among the studied lines showed that the Gabès variety formed a separate group. Cluster analysis revealed that the studied varieties are classified into three major groups. The first group is formed by Gabès2353, the second group is composed of the Californian and El Hamma varieties, and the third group is constituted of the seven remaining varieties. Gabès2355 was the most tolerant to the Pm8 strain of P. medicaginis while Magna601 variety was the most susceptible. These two varieties will be useful to analyze the physiological and genetic determinants for M. sativa tolerance to P. medicaginis infection