Using alfalfa (Medicago sativa) to ameliorate salt-affected soils in Yingda irrigation district in Northwest China

Secondary salinization of soil is a major limiting factor of agricultural sustainability and recovery of functional environments in irrigated agriculture in arid and semi-arid regions. The ameliorating effect of planting alfalfa (Medicago sativa) on salt-affected soils was assessed in field experiments in the irrigated region of Qingwangchuan basin for 5 years. The results showed that salt content in the soil profile gradually decreased with duration of alfalfa cultivation. Soil EC in the layer of 0-20 cm decreased significantly. The concentrations of soluble anions were found to be in the order of Cl^- > SO₄^2- > HCO₃^- in the soil profile of the study area. After alfalfa planting, Cl^- concentration in the soil profile notably decreased. In contrast, HCO₃^- concentration was significantly higher in the topsoil planted to alfalfa than in unplanted soil, especially after the first and the second year of cultivation, but markedly decreased after 3 years of alfalfa growth. With the extension of cultivation ages, total N content in different soil layers gradually increased through N2 fixation. Organic matter content in the soil profile was not enhanced significantly until the later stages of alfalfa cultivation. Available P accumulated in the topsoil in dependence on the length of cultivation. Soil pH was significantly higher in the planted than unplanted treatment, but was gradually decreased with increased duration of cultivation, especially in topsoil. Significant differences in ash content of alfalfa shoot were found between the different cultivation ages. Alfalfa shoot Na concentration showed slightly decrease, whereas shoot Cl^- concentration decreased with the duration of cultivation. The ameliorating effect of alfalfa cultivation on salt-affected soil showed a spatial and temporal variability due to the interactions between soil and plants. This positive effect resulted in either the salt leaching from the root zone to below 80-cm depth by irrigation water or the removal of less salts through harvest of alfalfa shoots.     

Growth Dynamics of Salmonella enterica Strains on Alfalfa Sprouts and in Waste Seed Irrigation Water

Alfalfa sprouts and other seed sprouts have been implicated in numerous outbreaks of salmonellosis. The source of these epidemics appears to have been low-level contamination of seeds by Salmonella bacteria that developed into clinically significant populations during the seed germination process. To test the possibility that Salmonella enterica strains carry host range determinants that allow them to grow on alfalfa, strains isolated from alfalfa or other sources were surveyed for their ability to grow on germinating alfalfa seeds. An S. enterica serovar Cubana strain originally isolated from contaminated alfalfa sprouts multiplied most rapidly during the initial 24 h of the seed germination process. Germinating alfalfa seeds supported the multiplication of S. enterica cells prior to the emergence of the root radicle at 72 h. Thereafter, much lower rates of multiplication were apparent. The ability of S. enterica to grow on germinating alfalfa seeds was independent of the serovar, isolation source, or virulence of the strain. Isolates obtained from alfalfa attained population levels similar to those observed for strains isolated from contaminated meat products or stools. Each of the strains could be detected in the waste irrigation water, with populations being strongly correlated with those detected on the germinating alfalfa seeds. The S. enterica strains were capable of utilizing the waste irrigation water as a sole carbon and nitrogen source. S. enterica strains thus appear to grow saprophytically on soluble organics released from seeds during early phases of germination. The ability to detect S. enterica in the waste irrigation water early in the germination process indicates that this method may be used as a simple way to monitor the contamination of sprouts during commercial operations.     

Nutritional quality and yield of seedling alfalfa established with a barley companion crop and weeds

Alfalfa (Medicago sativa L.) was established with barley (Hordeum vulgare L.) and weeds to determine the effect of weed management treatments on yield and nutritional quality of alfalfa and companion crop and weeds. Alfalfa+barley and alfalfa+wild oat (Avena fatua L.) had much higher yields in August of the first year than alfalfa alone. Total yields for the first three harvests were similar for alfalfa established weed free, with broad leaf weeds, wild oat or green foxtail (Setaria viridis L.). Protein contents in forage from the August harvest were 228, 196, 117 and 181 g/kg dry matter (DM) in weed free alfalfa, alfalfa plus broadleaf weeds, alfalfa plus wild oat, and alfalfa plus green foxtail, respectively. Alfalfa+barley had higher total in vitro gas production than pure alfalfa, which is correlated with the digestibility of the forage. Total in vitro gas production indicated that alfalfa+barley+weeds had slightly lower digestibility than weed free alfalfa+barley. However, alfalfa with a high percentage of redroot pigweed (Amaranthus retroflexus L.), wild oat or green foxtail had similar or higher in vitro gas production than pure alfalfa. The results from this experiment support a previous economic study that indicated herbicide application for weed control in seedling alfalfa was not necessary.     

Alfalfa Carbon and Nitrogen Sequestration Patterns and Effects of Temperature and Precipitation in Three Agro-Pastoral Ecotones of Northern China

Alfalfa (Medicago sativa L.) is a primary and widely cultivated forage crop in China. As a perennial leguminous grass, continuous planted alfalfa may influence carbon and nitrogen sequestration in soils. We evaluated the effect of alfalfa, planted for different lengths of time, and temperature and precipitation on soil organic carbon (SOC) and total nitrogen (TN) contents, and estimated soil SOC and TN inventories from 0–60 cm in three agro-pastoral ecotones of northern China. Alfalfa SOC and TN storage patterns were significantly different with increasing soil depths between the three regions of northern China. Continuous alfalfa grassland planted had a positive effect on accumulation of both SOC and TN in the Northwest region, whereas SOC storage peaked 6–7 years after planting in the Northeast and North region. Moreover, relatively higher TN storage appeared 7 years after planting in the Northeast and North regions. This study controlled as many factors as possible, but we caution that such temporal inferences could be artifacts of site selection. The regression analysis indicated that SOC and TN accumulation was mainly dependent on temperature (≥10°C of effective total accumulated temperature) in the North region. Precipitation in the growing season was the main limiting factor for SOC storage in the Northwest region and TN accumulation in the North regions. Therefore, the different climate factors affecting SOC and TN sequestration in alfalfa occurred at a regional scale.     

Alfalfa as a single dietary source for molt induction in laying hens

Molting is a process by which a hen's reproductive tract is rejuvenated prior to the beginning of a laying cycle. This process is often artificially induced in commercial settings in order to extend the productive life of a flock of hens. The most common method for the induction of molt is feed withdrawal for a period of several days. It has been noted that feed withdrawal, while effective in inducing molt and allowing an adequate reproductive rest period for the hen, may cause deleterious effects on the animal. This has prompted the investigation of alternatives to feed deprivation for the induction of molt in commercial laying hens. This study involved feeding alfalfa to hens to assess its ability to induce molt. Results show that alfalfa meal and alfalfa pelleted diets were equally effective as feed withdrawal in causing ovary weight regression in birds. Molted hens induced by alfalfa diets exhibited postmolt levels of egg production over a twelve week period that were similar to that of hens molted by feed withdrawal. The postmolt eggs laid by hens molted by alfalfa were of comparable quality to eggs from feed deprived hens. Alfalfa, a fibrous feed with low metabolizable energy, may be provided to hens on an ad libitum basis for an effective molt induction that retains comparable egg quality and production.     

Occurrence of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) populations along roadsides in southern Manitoba,Canada and their potential role in intraspecific gene flow

Alfalfa is a highly outcrossing perennial species that can be noticed in roadsides as feral populations. There remains little information available on the extent of feral alfalfa populations in western Canadian prairies and their role in gene flow. The main objectives of this study were (a) to document the occurrence of feral alfalfa populations, and (b) to estimate the levels of outcrossing facilitated by feral populations. A roadside survey confirmed widespread occurrence of feral alfalfa populations, particularly in alfalfa growing regions. The feral populations were dynamic and their frequency ranged from 0.2 to 1.7 populations km⁻¹. In many cases, the nearest feral alfalfa population from alfalfa production field was located within a distance sufficient for outcrossing in alfalfa. The gene flow study confirmed that genes can move back and forth between feral and cultivated alfalfa populations. In this study, the estimated outcrossing levels were 62% (seed fields to feral), 78% (feral to seed fields), 82% (hay fields to feral) and 85% (feral to feral). Overall, the results show that feral alfalfa plants are prevalent in alfalfa producing regions in western Canada and they can serve as bridges for gene flow at landscape level. Management of feral populations should be considered, if gene flow is a concern. Emphasis on preventing seed spill/escapes and intentional roadside planting of alfalfa cultivars will be particularly helpful. Further, realistic and pragmatic threshold levels should be established for markets sensitive to the presence of GE traits.     

Ethanol synthesis and loss from flooded roots of Medicago sativa L. and Lotus corniculatus L.

Abstract Field flooding of established alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) for up to 12 d resulted in a significant increase in alcohol dehydrogenase activity (ADH) and an increase in the K_m of ADH in both species. Root concentration of ethanol increased throughout the flooding regime in alfalfa roots. No ethanol was detected in any trefoil root samples. Alfalfa plants which had shoots removed 5 d prior to flooding accumulated significantly higher levels of root ethanol and showed flooding injury sooner, indicating a significant effect of shoots on development of flooding injury. Alfalfa and trefoil plants grown in the greenhouse were flooded and ethanol in the transpiration effluent was trapped and measured. Alfalfa transpired measurable quantities of ethanol which peaked just prior to development of shoot injury symptoms. No ethanol was detected in the transpiration effluent from trefoil shoots. Flooded roots of both alfalfa and trefoil excreted ethanol but alfalfa roots synthesized more total ethanol and retained a larger proportion in the roots than did trefoil. While the ethanol accumulation response in alfalfa and trefoil are consistent with the ethanol ‘self-poisoning’ hypothesis of flooding injury, the very small quantities of ethanol found in these roots still raises questions as to its absolute effect in the plant.     

Using mixed silages of sweet sorghum and alfalfa in total mixed rations to improve growth performance,nutrient digestibility,carcass traits and meat quality of sheep

Combining sweet sorghum (SS) with alfalfa for ensiling has the potential to make a high-quality silage with relatively a better nutrient balance. However, the existing data are insufficient about how changes in ratios of SS to alfalfa in different silage mixtures affect animal performance and meat quality. Therefore, the objective of this study was to determine the effect of feeding total mixed rations containing mixed silages of SS and alfalfa on growth performance, nutrient digestibility, carcass traits and meat quality of Karakul sheep. Five total mixed rations were formulated with different SS proportions at 100%, 80%, 60%, 40%, and 20% on a fresh weight basis. Thirty 4-month old male Karakul sheep with 25.5 ± 1.4 kg BW were randomly allocated into five treatment groups, each with six lambs for this experiment. The results indicated that the Karakul sheep consuming total mixed rations containing SS-Alfalfa (SS-AF) silage mixtures with a lower proportion of SS tended to increase nutrient digestibility, growth performance, carcass traits, and meat quality. Feeding diets with SS at 40% and 20% inclusion rate showed a significant linear increase in the apparent digestibility of DM, CP and NDF, as well as subcutaneous fat thickness and water holding capacity (P < 0.5). Moreover, reduction in SS inclusion rate in these diets caused significant (P < 0.05) linear and quadratic increases in DM intake, final BW, average daily gain, carcass weight, and the amino acid contents of meat (P < 0.05). Conversely, feeding diet with lower SS inclusion rate led to decrease in feed conversion ratio and shear force significantly (P < 0.05) for these sheep. It appears that 40% inclusion of SS was the optimal rate in making the SS-AF silage mixture for lambs to achieve a superior production performance and high-quality meat products in Karakul sheep. However, further research is needed to investigate the effect of feeding SS-AF silage mixtures alongside contrasting ingredients on rumen function, ruminal microorganisms and digestive enzyme activity of sheep and other ruminant animals.     

Water-Soluble Polysaccharides of Alfalfa (Medicago sativa (Fabaceae)) of Flora of Krasnoyarsk Krai

Alfalfa is a very high-quality perennial leguminous grass with a long history of cultivation and application in traditional medicine in Russia. In addition, alfalfa is a valuable forage representative of the legume family, its acreage in Russia reaches 2.3–2.5 million ha. The polysaccharide complex (PSC) was isolated from the aerial part of alfalfa by aqueous extraction (pH = 9) and characterized by physicochemical methods. The content of uronic acids was 13.1 ± 0.9%, the quantitative content of impurity substances such as protein was 4.25 ± 0.28%, nucleic acids 0.0056 ± 0.0003%, and mineral impurities (ash content) 3.45 ± 0.18%. The PSC was studied by IR spectroscopy. The monomeric composition of PSC was characterized by chromatography-mass spectrometry (major monosugars arabinose, glucose and galacturonic acid). The molecular weight distribution of PSC was studied by the high-pressure exclusion chromatography method. Data demonstrated that the polysaccharide complex of the aerial part of alfalfa consists of three components with molecular weights of 1100 ± 60, 16 ± 2 and 7 ± 1 kDa. The fact that PSC is a mixture of seven polysaccharides was demonstrated by the column ion-exchange chromatography method.

     

Phytoremediation Efficiency of a PCP-Contaminated Soil using Four Plant Species as Mono- and Mixed Cultures

Bioremediation of soil polluted by pentachlorophenol (PCP) is of great importance due to the persistence and carcinogenic properties of PCP. Phytoremediation has long been recognized as a promising approach for removal of PCP from soil. The present study was conducted to investigate the capability of four plant species; white clover, ryegrass, alfalfa, and rapeseed grown alone and in combination to remediate pentachlorophenol contaminated soil. After 60 days cultivation, white clover, raygrass, alfalfa, and rapeseed all significantly enhanced the degradation of PCP in soils. Alfalfa showed highest efficiency for the removal of PCP in single cropping flowed by rapeseed and ryegrass. Mixed cropping significantly enhanced the remediation efficiencies as compared to single cropping; about 89.84% of PCP was removed by mixed cropping of rapeseed and alfalfa, and 72.01% of PCP by mixed cropping of rape and white clover. Mixed cropping of rapeseed with alfalfa was however far better for the remediation of soil PCP than single cropping. An evaluation of soil biological activities as a monitoring mechanism for the bioremediation process of a PCP-contaminated soil was made using measurements of microbial counts and dehydrogenase activity.     

Allelopathic interference of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) genotypes to annual ryegrass (<Emphasis Type="Italic">Lolium rigidum</Emphasis>)

Alfalfa (Medicago sativa L.) genotypes at varying densities were investigated for allelopathic impact using annual ryegrass (Lolium rigidum) as the target species in a laboratory bioassay. Three densities (15, 30, and 50 seedlings/beaker) and 40 alfalfa genotypes were evaluated by the equal compartment agar method (ECAM). Alfalfa genotypes displayed a range of allelopathic interference in ryegrass seedlings, reducing root length from 5 to 65%. The growth of ryegrass decreased in response to increasing density of alfalfa seedlings. At the lowest density, Q75 and Titan9 were the least allelopathic genotypes. An overall inhibition index was calculated to rank each alfalfa genotype. Reduction in seed germination of annual ryegrass occurred in the presence of several alfalfa genotypes including Force 10, Haymaster7 and SARDI Five. A comprehensive metabolomic analysis using Quadruple Time of Flight (Q-TOF), was conducted to compare six alfalfa genotypes. Variation in chemical compounds was found between alfalfa root extracts and exudates and also between genotypes. Further individual compound assessments and quantitative study at greater chemical concentrations are needed to clarify the allelopathic activity. Considerable genetic variation exists among alfalfa genotypes for allelopathic activity creating the opportunity for its use in weed suppression through selection.     

Potential of alfalfa as an alternative molt induction diet for laying hens: egg quality and consumer acceptability

Dietary molt induction to initiate additional egg laying cycles in commercial laying hen flocks is a wide spread practice in the United States. Feed deprivation is the most commonly used method but this practice has generated several concerns which has lead to research for viable alternative approaches. From a management standpoint a single ingredient molting diet consisting of high fiber-low energy represents an easily adaptable diet for large laying hen production units. Alfalfa meal is readily available in most commercial locations and possesses many of the desirable properties of an ideal laying hen molt diet. In the current study hens at a commercial laying facility were molted by both alfalfa and feed deprivation. After the hens had reentered post-molt commercial egg production, eggs were examined for egg quality performance. Egg shell strength, albumen height, yolk height, weight, length, and yolk color were all tested using various mechanical techniques. The eggs were also sampled for testing by consumer sensory panels that assessed the desirability of the eggs' color and flavor/texture. Eggs laid by hens molted by alfalfa had a significantly lower (p<0.05) "a*" level of colorimetry. Eggs laid by hens molted with alfalfa also exhibited significantly higher (p<0.05) egg weights and length. In the consumer sensory test, there was no significant difference (p>0.05) in color or flavor/texture scores in eggs from either feed deprived or alfalfa molted hens. The consumer sensory and mechanical quality attributes indicates that alfalfa shows promise as an alternative molt induction diet by providing a single diet option for extending egg production into a second egg laying cycle.     

Effect of alfalfa and dietary fiber on the growth performance of weanling rabbits

The addition of 10%, 20%, 30%, and 40% sun-cured alfalfa meal to a high-energy, low-fiber, basal diet for weanling rabbits gave increased average daily gains as compared to gain on the basal diet. Deaths from enteritis complex occurred only at the 0% and 10% alfalfa levels. When 2.5%, 5%, 7.5%, and 10% alfalfa meal were used, the average daily gains were numerically higher for all alfalfa-fed groups than for the basal diet. Maximum gains were achieved at the 20% alfalfa level. Alfalfa extracted with 95% ethanol retained its growth-stimulating effect when added to the basal diet. Feed preference trials gave conflicting results. In one trial, the basal diet was preferred over all alfalfa diets in a two-choice feed preference test, while in a second trial, all alfalfa diets were preferred over the basal diet. It was concluded that the growth of weaning rabbits fed a high energy diet was improved by the addition of alfalfa meal.     

High genetic differentiation among wild populations of alien Medicago sativa in Lithuania

Alfalfa (Medicago sativa; =M. sativa ssp. sativa) in Lithuania is sown as albuminous forage for cattle due to favourable climatic condition. Over many generations, alfalfa plants have escaped from cultivation fields into natural ecosystems and established wild populations. We collected and analyzed individuals from seventeen wild populations of M. sativa. Using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) analyses, 117 RAPD and 64 ISSR reproducible and highly polymorphic (90.8% for RAPD and 86.3% for ISSR) loci were established. AMOVA showed a high genetic differentiation of M. sativa populations for both types of DNA markers utilized. According to RAPD markers, the genetic variability among populations was 63.1% and 57.0% when ISSR markers were used. Taken together, these results demonstrate that wild populations of M. sativa possess a high potential of genetic variability, that could potentially result in colonization of natural ecosystems. The UPGMA cluster analysis also showed that the DNA markers discovered in this study can distinguish between M. sativa and M. falcata (=M. sativa ssp. falcata) populations and therefore may be used to study the genetic impact of M. sativa on the native populations of M. falcata.     

Mechanisms underlying the effects of fall dormancy on the cold acclimation and winter hard- iness of Medicago sativa

As a global planting forage legume, alfalfa (Medicago sativa) is a valuable material to study the evolutionary and ecological mechanisms on plant adaptation to freezing due to their contrasting winter hardiness induced by fall dormancy (FD). This paper reveals that FD is an important growth characteristic that is adaptative to short-day and reducing temperature in late autumn, followed by a higher overwintering rate. Alfalfa cultivars are grouped into 11 FD ratings (numbered from 1 to 11), and this phenomenon is related to the extensive spread and cultivation for thousands of years in the globe. Alfalfa cultivars are under different climate habitats for a long time, leading to FD adaptive evolution, which provides rich genetic resources for human. In general, adaptative process associated with cold acclimation and winter hardiness in alfalfa is affected by FD, thus differences in winter hardiness exist among alfalfa cultivars. So far, regulation of FD by light and temperature and effects of FD on physiological and ecological processes involved in cold acclimation have been reported largely. However, signal transduction and the regulatory network associated with gene expression, especially the molecular mechanisms by which antifreeze proteins function in cold adaptation, are still poorly understood. Several scientific problems that need to be addressed in the future studies are highlighted in this review.     

Detection of new viruses in alfalfa,weeds and cultivated plants growing adjacent to alfalfa fields in Saudi Arabia

A total of 1368 symptomatic plant samples showing different virus-like symptoms such as mottling, chlorosis, mosaic, yellow mosaic, vein clearing and stunting were collected from alfalfa, weed and cultivated plant species growing in vicinity of alfalfa fields in five principal regions of alfalfa production in Saudi Arabia. DAS-ELISA test indicated occurrence of 11 different viruses in these samples, 10 of which were detected for the first time in Saudi Arabia. Eighty percent of the alfalfa samples and 97.5% of the weed and cultivated plants samples were found to be infected with one or more of these viruses. Nine weed plant species were found to harbor these viruses namely, Sonchus oleraceus, Chenopodium spp., Hibiscus spp., Cichorium intybus, Convolvulus arvensis, Malva parviflora, Rubus fruticosus, Hippuris vulgaris, and Flaveria trinervia. These viruses were also detected in seven cultivated crop plants growing adjacent to the alfalfa fields including Vigna unguiculata, Solanum tuberosum, Solanum melongena, Phaseolus vulgaris, Cucurbita maxima, Capsicum annuum, and Vicia faba. The newly reported viruses together with their respective percent of detection in alfalfa, and in both weeds and cultivated crop plant species together were as follows: Bean leaf roll virus (BLRV) {12.5 and 4.5%}, Lucerne transient streak virus (LTSV) {2.9 and 3.5%}, Bean yellow mosaic virus (BYMV) {1.4 and 4.5%}, Bean common mosaic virus (BCMV) {1.2 and 4.5%}, Red clover vein mosaic virus (RCVMV) {1.2 and 4%}, White clover mosaic virus (WCIMV) {1.0 and 5%}, Cucumber mosaic virus (CMV) {0.8 and 3%}, Pea streak virus (PeSV) {0.4 and 4.5%} and Tobacco streak virus (TSV) {0.3 and 2.5%}. Alfalfa mosaic virus (AMV), the previously reported virus in alfalfa, had the highest percentage of detection in alfalfa accounting for 58.4% and 62.8% in the weeds and cultivated plants. Peanut stunt virus (PSV) was also detected for the first time in Saudi Arabia with a 66.7% of infection in 90 alfalfa samples collected from the surveyed regions during the last visit that tested negative to all the previously detected viruses.     

紫花苜蓿秋眠性对低温驯化过程与越冬耐寒适应的作用机理

紫花苜蓿(Medicago sativa)是全球性的栽培牧草, 因其秋眠性强弱而导致的抗寒性差异为深刻解析植物耐寒适应的进化生态学机制提供了一个很好的研究模式。作为多年生豆科植物, 秋眠性是紫花苜蓿适应晚秋日照缩短、温度降低, 以及提高越冬存活率的一种生长特性。秋眠性的形成与几千年来紫花苜蓿在全球的传播扩展和栽培利用有关, 长期处于不同的气候生境, 导致秋眠性的适应进化, 这为人类利用提供了丰富的遗传资源。根据秋眠性的强弱, 学术界目前将之分为11个等级。一般而言, 秋眠性的强弱影响了紫花苜蓿的低温驯化与越冬耐寒适应等过程, 导致不同品种间的抗寒性存在差异。迄今, 关于秋眠性的光温调控, 以及秋眠性影响低温驯化的生理生态过程研究较多, 而对相关的细胞信号转导与基因表达调控途径, 尤其是对秋眠性如何影响越冬紫花苜蓿抗冻蛋白作用等耐寒适应的分子机制, 尚知之甚少。针对目前研究中存在的问题, 该文提出了未来需要重点关注的科学问题。     

Identification of Alfalfa Mosaic Virus in Greek Alfalfa Crops

Alfalfa mosaic virus (AMV) was found to be the prevalent virus disease in alfalfa crops in Central and Northern Greece. The virus was identified on the basis of the host symptomatology, aphid and seed transmission, particle morphology and serological tests. AMV was largely detected in commercial seeds of local grown alfalfa cvs by ELISA. Infected seed lots appear to be the main source responsible for the widespread distribution of the virus in Greek alfalfa fields.     

Growth dynamics of Salmonella enterica strains on alfalfa sprouts and in waste seed irrigation water

Alfalfa sprouts and other seed sprouts have been implicated in numerous outbreaks of salmonellosis. The source of these epidemics appears to have been low-level contamination of seeds by Salmonella bacteria that developed into clinically significant populations during the seed germination process. To test the possibility that Salmonella enterica strains carry host range determinants that allow them to grow on alfalfa, strains isolated from alfalfa or other sources were surveyed for their ability to grow on germinating alfalfa seeds. An S. enterica serovar Cubana strain originally isolated from contaminated alfalfa sprouts multiplied most rapidly during the initial 24 h of the seed germination process. Germinating alfalfa seeds supported the multiplication of S. enterica cells prior to the emergence of the root radicle at 72 h. Thereafter, much lower rates of multiplication were apparent. The ability of S. enterica to grow on germinating alfalfa seeds was independent of the serovar, isolation source, or virulence of the strain. Isolates obtained from alfalfa attained population levels similar to those observed for strains isolated from contaminated meat products or stools. Each of the strains could be detected in the waste irrigation water, with populations being strongly correlated with those detected on the germinating alfalfa seeds. The S. enterica strains were capable of utilizing the waste irrigation water as a sole carbon and nitrogen source. S. enterica strains thus appear to grow saprophytically on soluble organics released from seeds during early phases of germination. The ability to detect S. enterica in the waste irrigation water early in the germination process indicates that this method may be used as a simple way to monitor the contamination of sprouts during commercial operations.     

The Biology and Ecology of Feral Alfalfa (Medicago sativa L.) and Its Implications for Novel Trait Confinement in North America

Alfalfa (Medicago sativa) is an important forage crop worldwide. Apart from cultivated fields, alfalfa is also found along roadsides and in natural and semi-natural habitats. However, little information is available on the establishment capabilities of alfalfa in noncultivated areas and the potential of these founding populations to become feral. Some crop species have not lost all their wild characteristics during the domestication process and with several inherent traits favoring weediness, alfalfa could be one among those that can become feral. There is great interest in the feral potential of alfalfa, particularly due to the concerns that feral plants could act as genetic bridges and facilitate novel trait movement at the landscape level. Alfalfa is the first perennial, insect-pollinated crop to be genetically engineered and approved for unconfined release into the environment. This review investigates and compiles information in the literature that reveals the life history components that can influence ferality in alfalfa. Characteristics that can contribute to ferality in alfalfa include high genetic diversity, perenniality, quick regrowth potential, persistence, symbiotic nitrogen fixation, deep tap root system, drought and cold tolerance, and seed dormancy. With these traits, alfalfa is equipped to invade and dominate unmanaged habitats. Feral alfalfa populations can and will act as bridges for long-distance gene flow and facilitate the adventitious presence of novel traits in the environment. As such, feral populations will become a potential barrier for achieving coexistence of transgenic and nontransgenic alfalfa fields. Implications of ferality, including gene flow and hybridization with compatible wild relatives are also discussed in detail. This review serves as a resource for environmental risk assessment for the release of alfalfa containing novel traits.