Medicago Polymorpha Research Articles

Utilization of phosphorus by pasture plants supplied with myo-inositol hexaphosphate is enhanced by the presence of soil micro-organisms

A range of pasture grass (Danthonia richardsonii and Phalaris aquatica) and legume (Medicago polymorpha, M. sativa, Trifolium repens and T. subterraneum) species showed limited capacity to obtain phosphorus (P) from inositol hexaphosphate (IHP), when grown in either sterile agar (pH 5.0 or 5.5) or sand-vermiculite media (pH 5.0). The total P content of shoots from IHP-supplied plants grown in agar was between 20% and 34% of that for seedlings supplied with an equivalent amount of P as inorganic phosphate (Pi), while in sand-vermiculite, the total P content of IHP-grown plants was between 5 and 10% of control plants. The poor ability of plants to utilize P from IHP resulted in significantly lower tissue P concentrations and, in general, reduced plant dry weight accumulation. In contrast, the P nutrition of plants supplied with IHP was significantly improved by inoculating media with either a cultured population of total soil micro-organisms or with a specific isolate of Pseudomonas sp., selected for its ability to release phosphate from IHP (strain CCAR59; Richardson and Hadobas, 1997 Can. J. Micro. 43, 509-516). In agar and sand-vermiculite media, respectively, the P content of IHP-grown plants increased with inoculation by up to 3.9- and 6.8-fold, such that the dry weight and P content of the plant material were equivalent to those observed for control plants supplied with Pi. However, the response to inoculation was dependent on the growth medium and the source of micro-organisms used. In sand-vermiculite, the cultured population of soil micro-organisms was effective when IHP was supplied at an equivalent level of Pi required for maximum plant growth. By comparison, inoculation of plants with the Pseudomonas strain was only effective at very high levels of IHP supply (×36), whereas in agar a response to inoculation occurred at all levels of IHP. The ability of pasture plants to acquire P from phytate was, therefore, influenced by the availability of IHP substrate, which was further affected by the presence of soil micro-organisms. Our results show that in addition to having an effect on the sorption characteristics of the growth media, soil micro-organisms also provided a source of phytase for the dephosphorylation of phytate for subsequent utilization of Pi by plants.

Comparative soil water, pasture production, and crop yields in phase farming systems with lucerne and annual pasture in Western Australia

Two field experiments in the Great Southern region of Western Australia compared the soil water content under lucerne (Medicago sativa) with subterranean clover (Trifolium subterranean) and annual medic (Medicago polymorpha) over a 2-year period. Lucerne depleted soil water (10–150 cm) between 40 and 100 mm at Borden and 20 and 60 mm at Pingrup compared with annual pasture. There was also less stored soil water after wheat (Triticum aestivum) and canola (Brassica napus) phases which followed the lucerne and annual pasture treatments, 30 and 48 mm after wheat, 49 and 29 mm after canola at Borden and Pingrup, respectively. Lucerne plant densities declined over 2 seasons from 35 to 25 plants/m2 (Borden) and from 56 to 42 plants/m2 (Pingrup), although it produced herbage quantities similar to or greater than clover/medic pastures. The lucerne pasture also had a reduced weed component. Wheat yield at Borden was higher after lucerne (4.7 t/ha) than after annual pasture (4.0 t/ha), whereas at Pingrup yields were similar (2 t/ha) but grain protein was higher (13.7% compared with 12.6%) . There was no yield response to applied nitrogen after lucerne or annual pasture at either site, but it increased grain protein at both sites. There was no pasture treatment effect on canola yield or oil content at Borden (2 t/ha, 46% oil). However, at Pingrup yield was higher (1.5 t/ha compared to 1.3 t/ha) and oil content was similar (41%) following lucerne–wheat. The results show that lucerne provides an opportunity to develop farming systems with greater water-use in the wheatbelt of Western Australia, and that at least 2 crops can be grown after 3 years of lucerne before soil water returns to the level found after annual pasture.

Evaluation of Low-rate Herbicides to Supplement Methyl Bromide Alternative Fumigants to Control Weeds in Strawberry

Methyl bromide has been the foundation of chemical weed control in strawberry (Fragaria ×ananassa) in California for over 40 years. The impending phaseout of methyl bromide may leave strawberry producers dependent on less efficacious alternative fumigants for weed control. The use of herbicides to supplement fumigants is a potential weed control strategy for strawberry. A 2-year field study was conducted in California to evaluate 10 herbicides as possible supplements for methyl bromide alternative fumigants. Herbicides were applied immediately after transplanting (immediate posttransplant), and 3 weeks after transplanting (delayed posttransplant). Napropamide applied immediate posttransplant was included as a commercial standard. Immediate posttransplant treatments that were safe in strawberry include carfentrazone at 0.075 and 0.15 lb/acre (0.084 and 0.168 kg·ha-1), flumioxazin at 0.063 lb/acre (0.071 kg·ha-1) and sulfentrazone at 0.175 and 0.25 lb/acre (0.196 and 0.28 kg·ha-1). Triflusulfuron at 0.016 lb/acre (0.017 kg·ha-1) was the only delayed posttransplant treatment with acceptable selectivity. Among the selective herbicides applied immediate posttransplant, flumioxazin and napropamide provided the most consistent control of bur clover (Medicago polymorpha) and shepherd's purse (Capsella bursa-pastoris). Triflusulfuron applied delayed posttransplant did not significantly reduce bur clover densities, but did reduce shepherd's purse densities.

Suppressing spread of alfalfa mosaic virus in grazed legume pasture swards using insecticides and admixture with grass, and effects of insecticides on numbers of aphids and three other pasture pests

SummaryField experiments were sown with alfalfa mosaic virus (AMV)‐infected or healthy seed of burr medic (Medicago polymorpha) and grazed by sheep. Seed‐infected plants acted as primary sources for virus spread by naturally occurring aphids. Admixture with annual ryegrass (Lolium rigidum), a non‐host of AMV, and different insecticides were used in attempts to suppress virus spread. Sowing swards to provide the ratios 1: 4 and 1: 13 of medic:ryegrass plants diminished AMV spread in medic plants by 23% and 45% respectively. Applications of organophosphorus (demeton‐s‐methyl), carbamate (pirimicarb) and newer generation synthetic pyrethroid (alpha‐cypermethrin) insecticides, all significantly decreased final AMV incidence. Alpha‐cypermethrin was the most effective, suppressing AMV incidence by 87% (two sprays), 79% (one late spray) and 65% (one early spray). Two sprays of demeton‐s‐methyl decreased incidence by only 36%, while two and 2 weekly applications of pirimicarb diminished it by 29–65% and 35–70% respectively. AMV infection of medic seed harvested decreased by up to 76% in sprayed plots. Insecticide treatment did not prevent winged aphids from landing but numbers of wingless Acyrthosiphon kondoi colonising swards were suppressed by up to 92% by spraying with pirimicarb and up to 96% by alpha‐cypermethrin. A. kondoi were much slower to recover with alpha‐cypermethrin than with pirimicarb, the former still significantly diminishing its numbers 35 days after spraying. Alpha‐cypermethrin was also very effective at suppressing Halotydeus destructor and Penthaleus major but not Sminthurus viridis. Greater effectiveness of insecticides in controlling spread of AMV in pasture than has been found previously with non‐persistently aphid‐transmitted viruses in annual crops seems due to the key role played by wingless aphids as virus vectors.

Determining ‘threshold’ levels for seed-borne virus infection in seed stocks

There have been many advances in testing procedures to detect seed-borne virus infection in seed samples. However, scant attention has been given to the implications of improved test results in terms of the economic losses resulting from sowing seed stocks with different amounts of infection. For agricultural and horticultural industries to use the results of tests on representative samples, defined ‘threshold’ values for percentage seed infection are required that identify acceptable levels of risk of economic losses resulting from sowing the virus-infected seed stocks. Such information is provided by field experiments in which infected seed is sown and the consequences are followed in terms of virus spread, yield losses and infection of newly produced seed. These field experiments need to continue over several years at diverse sites so that they represent a wide range of infection scenarios. Extensive surveys to determine seed-borne virus occurrence in different regions are also required to define areas of greater or lesser risk of economic losses. In this paper, an example is described of how field experiments and surveys were used to define ‘threshold’ values of seed-borne Cucumber mosaic virus infection in an annual crop (lupin: Lupinus angustifolius) and two such examples are given for pasture species: Cucumber mosaic virus in subterranean clover (Trifolium subterraneum), and Alfalfa mosaic virus in annual burr medic ( Medicago polymorpha). The aim of this paper is to encourage others to address the urgent need for similar ‘threshold’ information with other economically important combinations of seed-borne viruses and host plant.

Developmental Responses to Temperature and Photoperiod in Ecotypes of Medicago polymorpha L. Collected Along an Environmental Gradient in Central Chile

The phenological development of nine Chilean accessions of Medicago polymorpha, collected along a north–south aridity gradient, and of two commercial cultivars of the same species, were compared in 12 sequential outdoor sowings at Cauquenes (35°58′S, 72°17′W, elev. 177m), in the sub-humid Mediterranean climate zone of Chile. A glasshouse experiment was also conducted to evaluate the effect of photoperiod on phenophase timing. There was a clear gradient in precocity among the Chilean accessions in both experiments: accessions MPO-9-88 and MPO-7-88, from the arid zone, were the earliest-flowering accessions, whereas MPO-36-88 from the humid Mediterranean zone was the latest. Both experiments revealed significant variation among the Chilean accessions in the response of flowering time to variation in photoperiod regime. Differences in days to flowering between the least- (8 h) and the most- (16 h) inductive photoperiods were lower in precocious accessions from arid and semi-arid zones, than in late-flowering accessions from more humid zones. Rate of progress to flowering, defined as the inverse of time from emergence to first flower appearance (1/ f), was related to mean diurnal temperature, or to both mean diurnal temperature and mean photoperiod. In two early-flowering accessions from the arid zone, and in the Australian cultivar ‘Circle Valley’, 1/ f was affected significantly (P<0.05) by both temperature and photoperiod. In the remaining accessions, no significant responses to temperatures were detected; 1/ f was influenced significantly by photoperiod only.

Fitness effects of two facultative endosymbiotic bacteria on the pea aphid, Acyrthosiphon pisum, and the blue alfalfa aphid, A. kondoi

AbstractThe effects of two bacterial endosymbionts, designated PASS and PAR, were evaluated on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera:Aphididae), in which they occur facultatively, and on the blue alfalfa aphid, A. kondoi Shinji, in which these bacteria have not been found in natural populations. Subclones of pea aphids and blue alfalfa aphids, derived from parent aphid clones that did not contain PASS or PAR, were infected with one or both bacteria, generating PASS‐ and/or PAR‐positive subclones with minimal genetic differences from the parent clones. Under laboratory conditions at 20 °C, PAR consistently reduced the fecundity (by between 19 and 60%) of subclones derived from three different parent pea aphid clones on bur clover, Medicago hispida Gaertn. PAR had intermediate effects on pea aphids reared on sweet pea, Lathyrus odoratus L., and had no significant effect on pea aphids on alfalfa, Medicago sativa L. The effect of PASS was either neutral or negative, depending on parent clone as well as host plant. Also at 20 °C, PASS reduced fecundity (70–77%) and longevity (40–48%), and increased the age of first reproduction (by up to 1.5 days) of blue alfalfa aphid reared on alfalfa and clover. PAR had a less dramatic effect (e.g., 30–39% reduction in fecundity) on these traits of blue alfalfa aphid. In contrast, PAR and PASS increased the fitness of pea aphid subclones of one parent clone reared for three generations at 25 °C on each of the three test plants. Without facultative bacteria, fecundity of the parent clone was reduced to a mean total of &lt; 6 offspring per adult at this elevated temperature, but with PASS or PAR, mean total fecundity of its subclones was &gt; 35. However, this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived subclones. Alate production in pea aphids was significantly increased in large populations of two PASS‐ and PAR‐positive subclones relative to their parent clones. Attempts to transmit PASS or PAR horizontally, i.e., from aphid to aphid via feeding on host plants (bur clover), were unsuccessful.

Cover Crops for Saline Soils

A 3-year study was conducted in the Central Valley of California to evaluate 125 prospective winter-growing cover crops for growth and nitrogen productivity in saline soils. Soil saturation paste electrical conductivities (ECes) in the surface 15 cm averaged 7dS m -1 at fall planting and 5.3 dS m -1 at spring harvest dates of each experiment. Species evaluated varied substantially in plant height. In general, the tallest plants were the Brassica species, which consistently grew to over 1.4m. Annual grasses (barley, rye, triticale and wheat) averaged about 1.0-1.3 m in each year. Of the legume species screened, heights were greatest for Hedysarum coronarium, Trifolium alexandrium, Vicia spp., and Medicago polymorpha and truncatula, averaging 59, 47, 39, 38 and 37 cm, respectively, over all experiments. About one third of the species screened produced crop cover in excess of 90% in each year. Groups of plants with consistently high crop cover percentages included various species/accessions of Brassica, Hedysarum, annual grasses, cool-season annual medics, Medicago polymorpha and Medicago truncatula, and two annual clovers, Trifolium alexandrium cv 'Multicut' and rose clover, Trifolium hirtum cv 'Hykon.' Total above-ground plant dry weights were highest for Brassica spp., which produced twice as much biomass as the annual grass species, and roughly four times as much dry matter as any of the legume species. Hedysarum, Lana and Namoi woolypod vetch, purple vetch, berseem clover, and several of the annual medic species consistently had the highest biomass among the legumes.

Factors affecting ambulatory dispersal in the predaceous mite Neoseiulus californicus (Acari: Phytoseiidae)

Experiments conducted in the laboratory showed that different biotic and abiotic factors affected the ambulatory dispersal behaviour of Neoseiulus californicus. The experimental set-up comprised dwarf alfalfa (Medicago polymorpha) infested or unifested by Tetranychus urticae. Temperatures were measured with thermocouples. Trials were performed at three temperatures, three prey densities, three light intensities, two relative humidities (RHs) and two vegetative states of alfalfa plants, turgid and withered. Deutonymphs were the most dispersive followed by young ovipositional females. High temperatures (35°C), high light intensities (40 000 lux) and drought-stressed alfalfa increased the dispersal of N. californicus. The availability of food in the environment and high moisture (80% RH) slowed down dispersion. The main factors which seem to elicit dispersal behaviour are the deprivation of food and high temperatures which result in an increase in the walking speed of the mite. In addition, other factors tested either increase or reduce the ambulatory dispersal of N. californicus. According to our results, individuals could move from ground cover into apple trees before spring. © Rapid Science Ltd. 1998

Inheritance of Pod Type, Stem Color, and Dwarf Growth Habit in Medicago polymorpha

Identification of marker traits in annual Medicago species (medics) would assist plant breeders in cultivar development. The objective of this research was to determine the inheritance of pod type, stem color, and dwarf growth habit in Medicago polymorpha L., a diploid species. Progeny from each of three crosses were evaluated in the F1, F2, and F3 generations. Results indicate that pod type was controlled by a single gene with a dominant allele for spiny pods. We propose the gene symbol Sp1 for the pod type trait. Stem color also was controlled by a single gene, with a dominant allele for red stems. We propose Rs1 as the gene symbol for this trait. The dwarf trait was not present in the parents or the F1 generation, but was observed in the F2 generation of one of the crosses. Dwarf plants had much shorter stems, internodes, and leaf petioles than normal plants, and they also had smaller, puckered leaves. The trait appeared to be controlled by two genes with partial recessive epistasis. We propose the gene symbols Dwl and Dw2 for this trait. Results indicated that the genes for pod type and stem color segregated independently and were not linked.

Medic Planting Date Effect on Dry Matter and Nitrogen Accumulation When Clear‐Seeded or Intercropped with Corn

AbstractIntercropping annual forage legumes with row crops has been proposed as a strategy to control erosion, suppress weeds, and contribute biological N to companion or subsequent crops. This experiment evaluated the effect of planting date of two annual medic species [burr and snail medic, Medicago polymorpha L. and M. scutellata (L.) Mill.] on yield and N accumulation of both medic and interseeded corn (Zea mays L.). Medics were either clear‐seeded (i.e., monocropped) or interseeded into corn at five planting dates from 7 May to 13 July in each of two years at East Lansing, MI, on a Capac loam (fine‐loamy, mixed, mesic Aerie Endoaqualf). Clear‐seeded medic produced up to 3 Mg ha−1 of dry matter at 60 d after planting. In the interseeding system, medic dry matter yields were only 50% of yield in a clearseeded system. Average aboveground medic N concentration was 50 and 20 kg ha−1 in clear‐seeded and interseeded systems, respectively. Interseeding at corn planting produced the greatest medic dry matter, but also was associated with the greatest reduction in corn yield. Corn yields were not reduced by interseeding medic 28 d after com planting. Interseeding medic into corn was associated with a positive yield response (3–25%) of subsequent corn grain. Medics reduced fertilizer needs of corn in the subsequent year by 37 kg N ha−1.

RAPD analysis reveals a low rate of outcrossing in burr medic (Medicago polymorpha L.)

Although burr medic (Medicago polymorpha L.) is commonly considered a self-pollinating species, intrapopulational variation for morphological, biochemical and molecular markers is relatively high. To investigate whether part of this variation is the result of outcrossing, we designed RAPD analysis experiments to reveal both inter- and intra-accession crossing. No cases of inter-accession hybrids were documented, but an intra-accessional crossing rate of 0 to 4% was estimated for one of the four accessions studied. Therefore, a rare outcrossing event between local individuals and migrating genotypes may contribute to high genetic variability observed in natural M. polymorpha. A better understanding of the factors which influence outcrossing in M. polymorpha is pertinent both for medic breeding programmes and for assessing risks associated with releasing transgenic herbicide-resistant crops.

Application of non-selective herbicides during flowering of pasture legumes can reduce seed yield and alter seed characteristics

Summary. Spraytopping, the application of a low rate of non-selective herbicide (usually glyphosate or paraquat) to annual grass seed heads in the spring or early summer for seed set control is widely practised throughout Australia. While grasses are the targets of the spray treatment, annual pasture legumes may also be damaged by spraytopping, particularly if the legumes are flowering at the time of application. The effect of applying glyphosate (90, 112 or 162 g a.i./ha), paraquat (100 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) to subterranean clover (Trifolium subterraneum L. cv. Dalkeith) and annual medic (Medicago polymorpha L. cvv. Serena, Santiago and Circle Valley) pastures at various times during flowering was investigated during the spring of 1993 and 1994. Experiments were located at Tincurrin and Tenindewa, Western Australia. Subterranean clover seed yield was most affected by applications of glyphosate (90 and 162 g a.i./ha) and glyphosate plus MCPA (90 + 150 g a.i./ha) during early–mid flowering. Seed yield was reduced by as much as 88% following application of glyphosate plus MCPA when 20% of the subterranean clover plants were flowering. Treatment with paraquat (100 g a.i./ha) during mid–late flowering reduced seed yield of subterranean clover by 25–50% in experiment 1 only. Medic seed yield was reduced up to 90% depending on cultivar when glyphosate (112 g a.i./ha) was applied during early–mid flowering. In addition to seed yield, the level of hard seed was assessed. Treatment of subterranean clover during early–mid flowering with glyphosate (90 and 162 g a.i./ha) significantly reduced the quantity of hard seed produced. Thirty–forty percent of subterranean clover seed was germinable soon after seed set, compared with 7–17% germinable for the seed from untreated plants. Treatment with glyphosate (112 g a.i./ha) reduced the proportion of hard seed in the medics when applied during mid flowering. Treatment with paraquat had little effect on the proportion of hard seed formed. This work demonstrates that using a spraytopping technique for control of seed set in annual grasses may dramatically reduce seed yield in pasture legumes. Spraytopping can further reduce the ability of legumes to persist in cropping rotations by reducing the amount of hard seed formed. Implications for practical farming systems are outlined.

Factors affecting soil acidification under legumes. II. Effect of phosphorus supply

Phosphorus deficiency is common in crop production. This pot experiment examined whether the supply of Ca(H2PO4)2 affected acid production by N2-fixing plants of 5 grain and 4 pasture legume species grown in a P-deficient sandy soil for 60-64 days. The legume species differed greatly in their response to P application. Lupinus albus, L. luteus, and Biserrula pelecinus were less responsive to P supply than Cicer arietinum, Vicia faba, Medicago polymorpha, Ornithopus sativus, and Trifolium subterraneum, which in turn were less reponsive than L. angustifolius. Increasing P supply up to moderately deficient levels increased the amount of acid production per unit shoot biomass (specific acid production), and further increasing P decreased specific acid production. The effect of species on acid production was greater than the effect of P supply. Among the species, C. arietinum had the highest specific acid production and B. pelecinus the lowest. Specific acid production was correlated with concentrations of excess cations and ash alkalinity as well as Ca and Mg but not P in shoot. There was a very good agreement between total acid production and total content of excess cations in the whole plant, irrespective of P supply and plant species. The results suggest that acid production by legumes under various P supplies is related to the imbalance of cation and anion uptake.

Observation of Vesicular-Arbuscular Mycorrhizal Formation in the Roots of Some Seasonal Weeds Proliferated in Citrus Orchards.

Weeds were collected from citrus orchards in April and July to investigate vesicular-arbuscular mycorrhizal (VAM) infection. The infection was found to be high in the roots of spring weeds : Rumex acetosa L., Agropyron tsukuhiense (Honda) Ohwi var. transiens (Hack.) Ohwi, Stellaria media Villars., Vicia cracca L., Lamium amplexicaule L., and Medicago polymorpha L., and in the roots of summer weeds : Erigeron canadensis L., Amaranthus lividus L., Cynodon dactylon (L.) Pers., Beckmannia syzigachne (Steud.) Fern., Commelina communis L., Oxalis corniculata L., and Digitaria adscendens Henr. Spore formation was mostly found in the roots of spring weed : Stellaria media, Vicia cracca, and Lamium amplexicaule ; no VAM infection was observed in the roots of Rumex japonicus Houtt., Equisetum arvense L., and Polygonum blumei Meisn.

Genetic variability organisation and gene flow in natural populations of Medicago polymorpha L. prospected in Tunisia

Genetic variability organisation and gene flow in natural populations of Medicago polymorpha L. prospected in Tunisia

Genetic variability organisation and gene flow in natural populations of Medicago polymorpha L. prospected in Tunisia

Pour identifier les ressources phytogenetique utiles et leur integration dans des programmes de sauvegarde et de conservation, seize accessions de germophasm Tunisien de Medicago polymorpha L., sont caracterisees pour leur diversite enzymatique. Les extraits proteiques des populations de cette espece sont analyses par electrophorese pour estimer la variation isoenzymatique. Deux systemes enzymatiques revelant six alleles ont ete retenus, parmi les six systemes testes par electrophorese sur gel d'amidon, pour leur profil electrophoretique polymorphe. Les analyses statistiques ont montre une importante variabilite entre les populations etudiees indiquant un potentiel genetique interessant pour la selection. L'heterogeneite interpopulation est elevee, un tel resultat est en accord avec le systeme de reproduction strictement autogame de ce taxon. Les donnees isoenzymatiques suggerent que le flux genique entre les populations de cette espece est faible. La derive genetique est sans doute responsable de la differenciation entre les populations. Par ailleurs, aucun parametre eco-geographique (distance et altitude) ne semble influencer leur structuration genotypique. Les marqueurs isoenzymatiques ainsi reveles sont tres utiles dans des schemas de selection pour une meilleure efficacite d'amelioration.

3-22 Differentiation of Local Populations of Medicago polymorpha L. in Symbiotic Association with Rhizobium meliloti

3-22 Differentiation of Local Populations of Medicago polymorpha L. in Symbiotic Association with Rhizobium meliloti

Allelopathic effect of Cistus ladanifer on seed germination

1. The allelopathic effect of the exudate secreted by Cistus ladanifer leaves was tested on different plant species. Cynodon dactylon and Rumex crispus, species absent from C. ladanifer scrub (jarales), were clearly inhibited by the exudate. 2. Species present in the jarales, Medicago polymorpha and Lolium rigidum, showed no direct inhibition of germination, but the process this was delayed, and cotyledon and root size was diminished. This implies inhibition of seedling growth, and may explain the low abundance of these species inside the jarales. 3. The active constituents in the inhibition of germination are low molecular weight phenolic compounds. The flavonoids appear to exert no direct effect on germination of the species tested, but do provoke a reduction in cotyledon and root size, and could thereby inhibit subsequent seedling development.

The Effects of Cutting at Different Phenological Stages to Shoot and Root Development and Forage Yield of Annual Medics

This research, was conducted in the experimental fiels of Agronomy Department, Faculty of Agriculture, Ankara University, Turkey in 1989 and 1992 and in the greenhouse of Plant Science Department, Nova Scotia Agricultural College, Canada in 1991. The experiment was arranged in a split-plot design with four replications. Three annual medic species (Medicago polymorpha L. var. brevispina (Benth.) Heyn, Medicago scutellata (L.) Mill. and Medicago ciliaris (L.) Willd.) were the main plot units and cutting stages (a) beginning of flowering, b) %50 flowering, and c) end of flowering) were the sub-plot units. The highest stem development, root development and forage yields were taken from M. scutellata, however, M. polymorpha var. brevispina had the lowest values in both field and greenhouse experiments. The effects of cutting at different phenological stages and stem and root development and forage yields of annual medics were numerically higher in the greenhouse experiments than the field experiments. According to the progressive cutting stages, stem and root development and forage yields of annual medics were increased in the greenhouse experiment. Nodulation was occured in the field experiments, indicating the presence of native rhizobia. In the second greenhouse trial, seeds were inoculated commercial strain of Rhizobium meliloti for nodulation. But, only the nodules of M. scutellata were active for fixing nitrogen which was found by acetylene reduction assay.