Medicago Polymorpha Research Articles

Effect of weed management methods on weeds and wheat (Triticum aestivum L.) yield

An experiment was conducted at Holetta Agricultural Research Center to study the effect of weed management practices on weeds and yield of wheat (Triticum aestivum L.) during 2010 to 2011 crop seasons in randomized complete block design with three replications. The experiment comprised of twelve weed management practices as treatments. The crop was infested with Avena fatua L. Cynodon dactlylon (L) Pers, Digitaria abbisinica (A. Rich) Stapt and Phalaris paradoxa L. among grass weeds and Amaranthus spinosus L., Caylusea abyssinica (Feresen.) fisch and May, C. trigyna L., Conolvulus arvenesis L., Chenopodium album L., Chenopodom nobile L., Corrigoala capensis Willd., Galinsoga parviflora Cov. Guizotia scabra (Vis.) Chiov., Medicago polymorpha L., Oxalis latifolia H.B.K., Polygonum nepalense L., Plantago lanceolata L., Raphanus raphanistrum L., Spergula arvensis L. and Tagetes minuta L. were among broad leaf weeds. The results showed that broadleaved, grass and total weed density as well as dry weight were significantly influenced by weed management practices. Hand weeding + 15 cm row spacing followed isoproturon at 1.5 kg ha-1 + 15 cm row spacing significantly reduced density and dry weight of weeds. Among herbicides, isoproturon + 15 cm row spacing provided better control of broadleaved and total weeds, whereas; clodinafop-propargyl + 15 cm row spacing proved better than isoproturon at 1.50 kg ha-1and hand weeding + 15 cm row spacing in controlling grass weeds. Highest grain yield (2289.4 kg ha-1) in was recorded in hand weeding + 15 cm row spacing followed by isoproturon at 1.50 kg ha-1 + 15 cm row spacing (2177.3 kg ha-1). Maximum N uptake was also recorded in these treatments. Uncontrolled weed growth throughout the crop growth caused a yield reduction 57.6 to 73.2%. Post emergence herbicides (isoproturon at 1.50 kg/ha) and /or hand weeding and hoeing at tillering + narrow spacing (15 cm) can further enhance the weed suppressive effect of the crop. Key words: Wheat, weeds, weed management methods, yield loss.

Genome sequence of the Medicago-nodulating Ensifer meliloti commercial inoculant strain RRI128.

Ensifer meliloti strain RRI128 is an aerobic, motile, Gram-negative, non-spore-forming rod. RRI128 was isolated from a nodule recovered from the roots of barrel medic (Medicago truncatula) grown in the greenhouse and inoculated with soil collected from Victoria, Australia. The strain is used in commercial inoculants in Australia. RRI128 nodulates and forms an effective symbiosis with a diverse range of lucerne cultivars (Medicago sativa) and several species of annual medic (M. truncatula, Medicago littoralis and Medicago tornata), but forms an ineffective symbiosis with Medicago polymorpha. Here we describe the features of E. meliloti strain RRI128, together with genome sequence information and annotation. The 6,900,273 bp draft genome is arranged into 156 scaffolds of 157 contigs, contains 6,683 protein-coding genes and 87 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.

Assessment of Plant and Chemical Poisoning In Livestock in Central Ethiopia

The survey was conducted with the objective of assessing potentially poisonous plants and chemicals in and around Adama town, Central Ethiopia. Three types of structured questionnaires were developed and 118 individuals (93 livestock owners, 11 animal health practitioners and 14 factories managers) were interviewed on voluntary basis. The result of this assessment indicated that 71(76.3%) of livestock owners and 10(90.9%) of animal health practitioner complained presence of plant poisoning on livestock in the study area. Similarly 31 plants were identified as having poisoning effect on livestock among which Rhizophoraceae, Sorghum bicolar, Parthenium hysterophorus, and Medicago polymorpha had the highest botanical frequency. On the other hand, 22(23.7%) livestock owners and 1(9.1%) animal health practitioners observed chemical toxicosis, respectively. About two individuals of (14.2%) interviewed factories managers received complaints of chemical toxicosis of livestock due to inappropriate disposal of their wastes. Food shortage 48%, nutritional deficiency 10.4% and due to excess consumption 8.1% were identified as major risk factors which predispose livestock in and around Adama town to poisonous plants and toxic chemicals. Therefore, further study on complained poisonous plants and toxic chemicals in the study area, and institution of pertaining control and prevention method is strongly recommended.

Genome sequence of Ensifer medicae strain WSM1115; an acid-tolerant Medicago-nodulating microsymbiont from Samothraki, Greece.

Ensifer medicae strain WSM1115 forms effective nitrogen fixing symbioses with a range of annual Medicago species and is used in commercial inoculants in Australia. WSM1115 is an aerobic, motile, Gram-negative, non-spore-forming rod. It was isolated from a nodule recovered from the root of burr medic (Medicago polymorpha) collected on the Greek Island of Samothraki. WSM1115 has a broad host range for nodulation and N2 fixation capacity within the genus Medicago, although this does not extend to all medic species. WSM1115 is considered saprophytically competent in moderately acid soils (pH(CaCl2) 5.0), but it has failed to persist at field sites where soil salinity exceeded 10 ECe (dS/m). Here we describe the features of E. medicae strain WSM1115, together with genome sequence information and its annotation. The 6,861,065 bp high-quality-draft genome is arranged into 7 scaffolds of 28 contigs, contains 6,789 protein-coding genes and 83 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.

Ethnobotanical appraisal and cultural values of medicinally important wild edible vegetables of Lesser Himalayas-Pakistan

BackgroundThe association among food and health is momentous as consumers now demand healthy, tasty and natural functional foods. Knowledge of such food is mainly transmitted through the contribution of individuals of households. Throughout the world the traditions of using wild edible plants as food and medicine are at risk of disappearing, hence present appraisal was conducted to explore ethnomedicinal and cultural importance of wild edible vegetables used by the populace of Lesser Himalayas-Pakistan.MethodsData was collected through informed consent semi-structured interviews, questionnaires, market survey and focus group conversation with key respondents of the study sites including 45 female, 30 children and 25 males. Cultural significance of each species was calculated based on use report.ResultsA total of 45 wild edible vegetables belonging to 38 genera and 24 families were used for the treatment of various diseases and consumed. Asteraceae and Papilionoideae were found dominating families with (6 spp. each), followed by Amaranthaceae and Polygonaceae. Vegetables were cooked in water (51%) followed by diluted milk (42%) and both in water and diluted milk (7%). Leaves were among highly utilized plant parts (70%) in medicines followed by seeds (10%), roots (6%), latex (4%), bark, bulb, flowers, tubers and rhizomes (2% each). Modes of preparation fall into seven categories like paste (29%), decoction (24%), powder (14%), eaten fresh (12%), extract (10%), cooked vegetable (8%) and juice (4%). Ficus carica was found most cited species with in top ten vegetables followed by Ficus palmata, Bauhinia variegata, Solanum nigrum, Amaranthus viridis, Medicago polymorpha, Chenopodium album, Cichorium intybus, Amaranthus hybridus and Vicia faba.ConclusionsPatterns of wild edible plant usage depend mainly on socio-economic factors compare to climatic conditions or wealth of flora but during past few decades have harshly eroded due to change in the life style of the inhabitants. Use reports verified common cultural heritage and cultural worth of quoted taxa is analogous. Phytochemical analysis, antioxidant activities, pharmacological applications; skill training in farming and biotechnological techniques to improve the yield are important feature prospective regarding of wild edible vegetables.

Phenological and growth response of legume cover crops to shading

SUMMARYAnnual medics and clovers have distinct properties in terms of usage as cover crops in Mediterranean orchards, but little is known of their capacity to adapt to the level of shading encountered on an orchard floor. A 2-year field experiment was conducted in South–Eastern Sicily to investigate the effects of withholding 0·50 of sunlight on the phenology and growth pattern of four medic and five clover accessions, focusing on traits known to be important for cover cropping. Shading delayed both seedling emergence and the onset of flowering (by up to 5 and 9 days, respectively), while it extended both the growth period and the overall life-cycle duration (by up to 5 and 11 days, respectively). It also induced an increase in cover crop height (from 34 to 38 cm) and crop light use (from 0·60 to 0·94 g DW/m2/MJ), but a reduction in soil coverage, above-ground dry biomass, maximum growth rate and maximum relative growth rate (by up to 13, 18, 21 and 7%, respectively), so compromising the competitiveness of cover crops against weeds. The responses to shading varied between genotypes. Medicago polymorpha ecotype S. Rosalia, Medicago rugosa ecotype Piano Lauro and ecotype Zappulla were the strongest competitors against weeds, whereas Trifolium tomentosum ecotype Bucampello was interesting in terms of its biomass yield and crop light use. The performance was unstable over seasons, so any future attempt to improve the species’ performances under shade by breeding will need to focus on reseeding capacity.

Identification of Ensifer strains isolated from root nodules of Medicago hispida grown in association with Zea mays in the Quechua region of the Peruvian Andes

Peasants of the Quechua region of the Peruvian Andes use chacras to grow maize (Zea mays) in innate association with bur clover (Medicago hispida). From a total of 25 bacterial strains isolated from root nodules of bur clover grown in soils from chacras in Allpas (Acobamba, Peru) 7 clustered into 6 Repetitive extragenic palindromic-polymerase chain reactions (REP–PCR) groups. The nearly complete 16S rRNA gene sequence from the representative strains AP1, AP15, AP28, AP29, AP37, and AP70 showed they were closely related to members of the genus Ensifer of the Alphaproteobacteria. Sequencing of the housekeeping atpD, glnII, and recA and the symbiotic nodC genes from each of the six strains revealed they all were similar to those of strains included in Ensifer medicae. The remaining 18 strains were distributed into 8 REP–PCR groups and analyses of the 16S rRNA gene sequences showed that the isolates belong to several phylogenetic groups, being closely related to species of genera Kaistia, Pseudomonas, Achromobacter, Stenotrophomonas, Xanthomonas, Sphyngopyxis, Duganella, and Rheinheimera.

Seed Persistence in Soil of Five Medic Cultivars in Southeastern Wyoming

ABSTRACTThe success of annual medic pastures in ley farming systems is largely due to their ability to establish and maintain a viable seed bank from which these pastures can annually regenerate. A medic pod burial study was conducted to evaluate seed bank persistence of a range of commercially available and experimental annual medic lines under field conditions in southeastern Wyoming. The Medicago rigidula (L.) All. (tifton burclover) cultivar Laramie had the highest proportion of hard seed throughout the study period (1997–2001). After 5 yr of pod burial, this cultivar retained 56% of the original seed bank as hard seed within 5 cm of the soil profile depth. In contrast, the best of the Australian‐developed cultivars Santiago (burr medic [Medicago polymorpha L.]) maintained 48% hard seeds within 5 cm soil depth after 3 yr of pod burial. The remaining Australia developed cultivars maintained at least half the seed bank for just 1 yr at either the surface or 5 cm depth. Our results demonstrated that Laramie annual medic has the ability to produce a large and viable seed bank capable of persisting for an extended period in southeastern Wyoming ley farming systems.

Nickel, lead and manganese content of forages irrigated with different sewage water treatments: A case study of a semiarid region (Sargodha) in Pakistan

The use of sewage water for agricultural purpose has tremendously increased during the last few years due to shortage of water availability, especially in semi-arid regions. Despite of many nutrients recycling advantages of sewage water, farmers are not fully aware of its harmful chemical composition. Heavy metals toxicity in soil and crops results from the long term use of sewage effluent for irrigation purposes. The present study was conducted to assess effect of sewage water on the uptake of Ni, Pb and Mn in different forage species with respect to the nutrient requirement of the grazing ruminants inSargodha,Punjab,Pakistan. Five samples each of six fodder species viz., Trifolium alexandrinum, Cichorium intybus, Avena sativa, Medicago polymorpha, Brassica campestris and Medicago sativa were collected from three fields irrigated with canal water, mix water (canal plus sewage water) and sewage water respectively. Pb, Ni and Mn concentration in the forage species during different treatments varied from 0.624 to1.672 mg/g, 7.364 to 10.17 mg/g and 5.136 to 12.422 mg/kg respectively. High value of Pb and Mn concentrations was observed during sewage water treatment. Lead is a non-essential element and is a very toxic metal. But in the present investigation Ni and Pb level in forages were below the toxic level, so the ruminants feeding on these forage species had no chance of Pb and Ni toxicity. On the other hand, Mn concentration in the forage species under observation was below the critical level. So the grazing animals at this location need continued mineral supplementation of Mn to prevent diseases caused by Mn deficiency, and to support optimum animal productivity. The objective of this study was to examine the potential for forage analysis as indicators of likely mineral deficiencies or excesses of grazing livestock during different sewage water treatments.

Trophic consequences of a biological invasion: do plant invasions increase predator abundance?

As invasive species become integrated into existing communities, they engage in a wide variety of trophic interactions with other community members. Many of these interactions are direct (e.g. predator–prey interactions or interference competition), but invasive species also can affect native community members indirectly, by influencing the abundances of intermediary species in trophic webs. Observational studies suggest that invasive plant species affect herbivorous arthropod communities and that these effects may flow up trophic webs to influence the abundance of predators. However, few studies have experimentally manipulated the presence of invasive plants to quantify the effects of plant invasion on higher trophic levels. Here, I use comparisons across sites that have or have not been invaded by the invasive plant Medicago polymorpha, combined with experimental removals of Medicago and insect herbivores, to investigate how a plant invasion affects the abundance of predators. Both manipulative and observational experiments showed that Medicago increased the abundance of the exotic herbivore Hypera and predatory spiders, suggesting positive bottom–up effects of plant invasions on higher trophic levels. Path analyses conducted on data from natural habitats revealed that Medicago primarily increased spider abundance through herbivore‐mediated indirect pathways. Specifically, Medicago density was positively correlated with the abundance of the dominant herbivore Hypera, and increased Hypera densities were correlated with increased spider abundance. Smaller‐scale experimental studies confirmed that Medicago may increase spider abundance through herbivore‐mediated indirect pathways, but also showed that the effects of Medicago varied across sites, including having no effect or having direct effects on spider abundance. If effects of invasive species commonly flow through trophic webs, then invasive species have the potential to affect numerous species throughout the community, especially those species whose dynamics are tightly connected to highly‐impacted community members through trophic linkages.

Tillage and weed control effects on productivity of a dry seeded rice–wheat system on a Vertisol in Central India

A 3-year (2006–2007 to 2008–2009) field study was conducted to evaluate the effect of four tillage systems {zero tillage (ZT) in rice (Oryza sativa L.) and wheat (Triticum aestivum L.), conventional tillage (CT) in rice and wheat, and two rotational tillage sequences that alternated between CT and ZT} with three weed management levels (weedy check, recommended herbicide and herbicide+1 hand weeding) in rice–wheat cropping system on a clay-loam soil. Continuous ZT increased the population density of awnless barnyard grass [Echinochloa colona (L.) Link] and rice flat sedge (Cyperus iria L.) in rice but reduced the population of wild oats [Avena ludoviciana (L.) Dur.] and common lambsquarters (Chenopodium album L.) in subsequent wheat. Pendimethalin (1.0kga.i.ha−1) fb 2,4-D (0.50kga.i.ha−1) significantly reduced the population density of E. colona, C. iria and sessile joyweed [Alternanthera sessilis (L.) D.C.], but did not control pink node flower (Caesulia axillaris Roxb.) in rice. In wheat, clodinafop propargyl (0.06kga.i.ha−1) fb 2,4-D (0.50kga.i.ha−1) significantly reduced the population of A. ludoviciana, but had no effect on toothed burclover (Medicago hispida Gaertn.). Continuous ZT resulted in significantly higher yield of rice (2.94Mgha−1), wheat (4.45Mgha−1) and rice–wheat system (7.39Mgha−1) compared to continuous CT (2.35, 3.86 and 6.21Mgha−1, respectively). For the total soil depth sampled (0–20cm), weed seed population was significantly greater under continuous ZT (165 weeds 500g−1 soil) and CT (101 weeds 500g−1 soil), compared to rotational tillage (71–85 weeds 500g−1 soil). Rotational tillage systems significantly reduced the seed density of C. iria, A. ludoviciana and M. hispida compared to continuous ZT or CT. Total weed seed density was 66% lower in herbicide treated than in untreated plots. Continuous ZT with effective weed management using recommended herbicide+1 hand weeding was more remunerative and energy efficient. These results suggest that conventional till-based rice–wheat system could be replaced with zero-till-based crop establishment method with effective weed control to save labor and energy in Vertisols of Central India.

Inoculation of Phaseolus vulgaris, Medicago laciniata and Medicago polymorpha with Agrobacterium sp. strain 10C2 may enhance nodulation and shoot dry weight but does not affect host range specificity

The aim of this work was to assess the effect of inoculation with the non-symbiotic Agrobacterium strain 10C2, previously isolated from root nodules of Phaseolus vulgaris, on nodulation, effectiveness and host range specificity. Two rhizobial strains, Ensifer meliloti 2011 and Ensifer medicae A321, were used in this study on the basis of their differential sensitivity to the in vitro antagonistic activity exercised by Agrobacterium sp. 10C2. Three host legumes, P. vulgaris, Medicago laciniata and M. polymorpha, were also selected for this experiment on the basis of their variable symbiotic specificity towards strains 2011 and A321. Cross inoculation experiments were conducted with or without co-inoculation with Agrobacterium sp. 10C2. Results showed that both rhizobial strains induced ineffective nodules on P. vulgaris. Nevertheless, inoculation with Agrobacterium sp. 10C2 slightly increased shoot dry weight with both strains and enhanced nodule number with strain 2011 only. Inoculation of M. polymorpha with strain 10C2 significantly increased the nodule number induced by E. medicae A321 but did not affect biomass production. However, inoculation of M. laciniata by strain 10C2 enhanced nodule number and shoot dry weight with strain 2011 only. Agrobacterium sp. 10C2 did not affect the non-inoculated control, nor the contrasted host range of both rhizobial strains towards M. polymorpha and M. laciniata. The potential negative effect of the in vitro antagonistic activity of strain 10C2 on reduction of nodule number or symbiotic effectiveness was not proved. No evidence of symbiotic gene transfer from the rhizobial strains to Agrobacterium sp. 10C2 was also proved. The effect of strain 10C2 is probably mediated by nodules since no result was observed in the non-inoculated control or when the rhizobial strain failed to induce nodules. It would be interesting to investigate the implications on nodule functioning, mainly the impact on nitrogenase activity, antioxidant enzymes and nodule senescence.

Evolutionary indirect effects of biological invasions

Just as ecological indirect effects can have a wide range of consequences for community structure and ecosystem function, theory suggests that evolutionary indirect effects can also influence community dynamics and the outcome of species interactions. There is little empirical evidence documenting such effects, however. Here, I use a multi-generation selection experiment in the field to investigate: (1) how the exotic plant Medicago polymorpha and the exotic insect herbivore Hypera brunneipennis affect the evolution of anti-herbivore resistance traits in the native plant Lotus wrangelianus and (2) how observed Lotus evolutionary responses to Hypera alter interactions between Lotus and other members of the herbivore community. In one of two study populations, I document rapid evolutionary changes in Lotus resistance to Hypera in response to insecticide treatments that experimentally reduced Hypera abundance, and in response to Medicago-removal treatments that also reduced Hypera abundance. These evolutionary changes in response to Hypera result in reduced attack by aphids. Thus, an evolutionary change caused by one herbivore species alters interactions with other herbivore taxa, an example of an eco-evolutionary feedback. Given that many traits mediate interactions with multiple species, the effects of evolutionary changes in response to one key biotic selective agent may often cascade through interaction webs to influence additional community members.

ANNUAL SELF-RESEEDING LEGUMES AND THEIR APPLICATION INTO MEDITERRANEAN ORGANIC CROPPING SYSTEMS

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Organic Horticulture: Productivity and Sustainability ANNUAL SELF-RESEEDING LEGUMES AND THEIR APPLICATION INTO MEDITERRANEAN ORGANIC CROPPING SYSTEMS

Direct and indirect transgenerational effects alter plant-herbivore interactions

Theory suggests that environmental effects with transgenerational conse- quences, including rapid evolution and maternal effects, may affect the outcome of eco- logical interactions. However, indirect effects occur when interactions between two species are altered by the presence of a third species, and can make the consequences of trans- generational effects difficult to predict. We manipulated the presence of insect herbivores and the competitor Medicago polymorpha in replicated Lotus wrangelianus populations. After one generation, we used seeds from the surviving Lotus to initiate a reciprocal transplant experiment to measure how transgenerational effects altered ecological inter- actions between Lotus, Medicago, and insect herbivores. Herbivore leaf damage and Lotus fecundity were dependent on both parental and offspring environmental conditions. The presence of insect herbivores and Medicago in the parental environment resulted in transgenerational changes in herbivore resistance, but these effects were non-additive, likely as a result of indirect effects in the parental environment. Indirect transgenerational effects interacted with more immediate ecological indirect effects to affect Lotus fecundity. These results suggest that explanations of ecological patterns require an understanding of transgenerational effects and that these effects may be difficult to predict in species-rich, natural communities where indirect effects are prevalent.

Crop establishment, tillage and weed management techniques on weed dynamics and productivity of rice (Oryza sativa)-chickpea (Cicer arietinum) cropping system

A field study was conducted to study the effect of methods of rice establishment, tillage and weed management techniques in rice–chickpea cropping system. Treatments included four crop establishment techniques (transplanting, puddling and broadcasting sprouted rice seeds, i.e wet-seeding and dry seeding under conventional and zero tillage systems) in rice and two tillage (zero and conventional) and two weed control methods (weedy check and pendimethalin 1.0 kg/ha as pre-emergence + one hand weeding at 30 days after sowing) in succeeding chickpea. Rice field was infested with jungle rice [Echinochloa colona (L.) Link], Caesulia (Caesulia axillaris Roxb.), sessile joyweed [Alternanthera sessilis (L.) DC.], and rice flat sedge (Cyperus iria L.) and chickpea with wild oats (Avena ludoviciana Dur.) and toothed burclover (Medicago hispida Gaertn.). Results revealed that methods of rice establishment did influence the weed dynamics in rice– chickpea system. Mean yield of zero-till direct-seeded rice (3 262 kg/ha) was as good as that of puddle broadcast rice (3 343 kg/ha) and better than the transplanted rice (3 038 kg/ha). Effective weed control in preceding chickpea benefitted the succeeding rice crop. Methods of rice establishment and tillage did not influence the chickpea yield. Infestation of weeds caused 78.45% reduction in yield of chickpea. Maximum seed yield of chickpea (2 813 kg/ha) was noticed in pendimethalin followed by one HW under conventional tillage. Zero till direct-seeded rice followed by zero-till chickpea system was the best combination for maximizing system productivity, profitability and energy efficiency

Mutualism and adaptive divergence: co-invasion of a heterogeneous grassland by an exotic legume-rhizobium symbiosis.

Species interactions play a critical role in biological invasions. For example, exotic plant and microbe mutualists can facilitate each other's spread as they co-invade novel ranges. Environmental context may influence the effect of mutualisms on invasions in heterogeneous environments, however these effects are poorly understood. We examined the mutualism between the legume, Medicago polymorpha, and the rhizobium, Ensifer medicae, which have both invaded California grasslands. Many of these invaded grasslands are composed of a patchwork of harsh serpentine and relatively benign non-serpentine soils. We grew legume genotypes collected from serpentine or non-serpentine soil in both types of soil in combination with rhizobium genotypes from serpentine or non-serpentine soils and in the absence of rhizobia. Legumes invested more strongly in the mutualism in the home soil type and trends in fitness suggested that this ecotypic divergence was adaptive. Serpentine legumes had greater allocation to symbiotic root nodules in serpentine soil than did non-serpentine legumes and non-serpentine legumes had greater allocation to nodules in non-serpentine soil than did serpentine legumes. Therefore, this invasive legume has undergone the rapid evolution of divergence for soil-specific investment in the mutualism. Contrary to theoretical expectations, the mutualism was less beneficial for legumes grown on the stressful serpentine soil than on the non-serpentine soil, possibly due to the inhibitory effects of serpentine on the benefits derived from the interaction. The soil-specific ability to allocate to a robust microbial mutualism may be a critical, and previously overlooked, adaptation for plants adapting to heterogeneous environments during invasion.

Diversity of Salt Tolerance During Germination in Medicago ciliaris (L.) and Medicago polymorpha (L.)

Variability of salt tolerance in eight wild populations of two annual Medicago species (Medicago ciliaris and Medicago polymorpha) was evaluated at germination stage using tree treatments of salinity: 50, 100 and 150 mM of NaCl. Results showed that germination is clearly affected by high salt stress; their germination rate doesn’t exceed 7% at 150 mM. The greatest variability in tolerance was observed at moderate salt stress (50 mM of NaCl) and the decrease in germination seems to be more accentuated in Medicago polymorpha than Medicago ciliaris. Whereas, the Tunisian population of Medicago ciliaris was the best tolerant in all ecotypes studied in this work. This population prospected on soils affected by salinity, exhibits a particular adaptability to salt environment, at least at this stage in the life cycle. This intra-specific variation in salt tolerance may be used to select genotypes particularly suitable for cultivation on lands relatively affected by salinity. On the other hand, when ungerminated seeds from NaCl treatments were transferred to distilled water, they recovered largely their germination at all the populations studied after only 2 days. This, indicate that the germination inhibition was related to osmotic stress rather than ion toxicity. In addition, seed germination in all populations tended to be extremely rapid than that observed in distilled water which indicate that this pretreatment raises dormancy.

Comparisons of annual pasture legumes in growth, ion regulation and root porosity demonstrate that Melilotus siculus has exceptional tolerance to combinations of salinity and waterlogging

Annual pasture legumes with high tolerance of combined salinity and waterlogging are needed for saline areas in many rain-fed agricultural regions. Melilotus siculus is an annual legume from saline marshy areas of the Mediterranean with potential use in saline pastures and, based on descriptions of its native habitat, was hypothesised to tolerate combined salinity and waterlogging. Experiments compared M. siculus to Trifolium michelianum and Medicago polymorpha, other annual pasture legumes with reported salt or waterlogging tolerances, with 0–450 mM NaCl in hydroponics or in sand culture. Tolerance to combined salinity and waterlogging was also evaluated at 150, 400 and 550 mM NaCl in a stagnant deoxygenated nutrient solution. M. siculus was substantially more salt tolerant than the other two species. At 450 mM NaCl, shoot DM of M. siculus was 30% of control, compared with only 15% for the other species. M. siculus was also the most tolerant species to combined salinity and stagnant treatment, and produced new leaves even after 14 d in stagnant nutrient solution with 550 mM NaCl (∼ sea water salinity). In comparison, T. michelianum and M. polymorpha only survived up to 5 d in stagnant solution with 400 mM NaCl. Even at only 150 mM NaCl in stagnant solution, shoot DM was just 30% of control for T. michelianum and M. polymorpha, compared to 60% for M. siculus. Tolerance to combined salinity and waterlogging was associated with higher root porosity and regulation of shoot Na + and Cl −, with the more tolerant M. siculus having similar shoot Na + and Cl − concentrations for both aerated-saline and stagnant-saline treatments. In summary, M. siculus is a pasture legume that can grow at high salinity (up to 550 mM) even when in combination with waterlogging, as root porosity and associated O 2 transport presumably enables continued regulation by the roots of Na + and Cl − entry under these dual stress conditions.

Effectiveness of Sinorhizobium Inoculants on Annual Medics

Annual medics (Medicago spp.) have potential to be important forage legumes in the southern Great Plains of the United States. Currently there are no commercial medic species‐specific rhizobia strains identified for their inoculation. However, commercially available alfalfa (Medicago sativa L.) inoculants may be effective at successfully nodulating annual medics. The objective of this study was to determine the relevant symbiotic rhizobial partner in association with seven annual medics. A greenhouse experiment arranged in three replications of a randomized complete block design quantified rhizobium effectiveness index and shoot and root dry matter (DM) of Medicago arabica (L.) Huds., Medicago lupulina L., Medicago minima (L.) Bartal., Medicago orbicularis (L.) Bartal., Medicago polymorpha L., Medicago rigidula (L.) All., and Medicago rigiduloides E. Small when inoculated with five Sinorhizobium spp. strains (M2, M49, Nitragin A, Nitragin N [a blend of three isolates], and WSM1115) and an untreated control (UTC). Strain M49 was the only strain that effectively nodulated M. rigiduloides, while Nitragin A commercial alfalfa strain was only effective on M. rigidula. Inoculants M2, Nitragin N, and WSM1115 were able to effectively nodulate M. polymorpha, M. arabica, M. minima, and M. orbicularis. To a lesser extent, M. lupulina, M. minima, and M. orbicularis were also effectively nodulated by Nitragin A alfalfa strain. These data indicate that there are differences in rhizobia specificity of annual medic species, and further research is warranted to improve nodulation of these legumes in the field.