Alfalfa (Medicago sativa L.) is a major forage crop in Argentina with an estimated cultivated area of 4 million ha in the 2009–2010 season, which constitutes a primary component for the animal production chain. In early summer of 2010, alfalfa plants showing virus-like symptoms were identified in 20 commercial fields in La Pampa Province with 95% disease prevalence. Diseased plants had shortened internodes, a bushy appearance, deformations, puckering, epinasty of leaflet blades, vein enations, and varying sized papillae on the adaxial leaflet surfaces. Similar symptoms were observed in alfalfa crops in Buenos Aires, Cordoba, Santa Fe, and Santiago del Estero provinces. Electron microscopy (EM) and molecular assays were performed on leaf tissue from one asymptomatic and two symptomatic plants. EM of ultrathin sections revealed membrane-bound bullet-shaped particles associated with the endoplasmic reticulum of phloem cells from symptomatic plants only. Total RNA was extracted from symptomatic and asymptomatic plants with the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany) for a template in one-step reverse transcription (RT)-PCR assays with the Access RT-PCR Kit (Promega, Madison, WI). RT-PCR assays employed degenerate primers targeting conserved regions of plant rhabdovirus polymerase (L) genes (2). An amplicon of approximately 1 kilobase pairs (detected only from symptomatic plants) was gel purified with the Wizard SV Gel and PCR Clean-Up System (Promega), cloned into pGEM-T Easy Vector System (Promega), and sequenced. Three independents clones were sequenced in both directions at Macrogen Inc. (Korea Republic) to generate a consensus sequence (GenBank Accession No. HQ380230) and compared to sequences of other plant rhabdoviruses available on GenBank. The partial L gene sequence of the alfalfa-infecting rhabdovirus shared highest nucleotide (68.0%) and amino acid (76.5%) sequence identity with the cytorhabdovirus Strawberry crinkle virus (Accession No. AY331390). A phylogenetic tree based on partial amino acid sequences of the polymerase gene indicated the alfalfa-infecting virus was more closely related to cytorhabdoviruses than to nucleorhabdoviruses. Symptoms observed resembled those reported for alfalfa plants infected with a plant rhabdovirus named Alfalfa enation virus (1), which has never been fully characterized. Collectively, the data implicate the observed rhabdovirus as the etiological agent. To our knowledge, this is the first report in Argentina (and South America) of a rhabdovirus infecting alfalfa. Additional field surveys and monitoring of vector/s and yield losses need to be conducted. References: (1) B. Alliot and P. A. Signoret. Phytopathol. Z. 74:69, 1972. (2) R. L. Lamprecht et al. Eur. J. Plant Pathol. 123:105, 2009.

The size and heterogeneity of world germplasm collections often have hindered their evaluation and utilization. Most of the diversity of germplasm collections could be represented by core collections (or core subsets), which are representative samples of the genetic diversity of a crop species and its relatives. Individual accessions not included in the core are retained as reserve subsets. The objectives of this research were to evaluate selection procedures for designating a core collection of plant introduction accessions (P.I.s) and to designate U.S.P.I. core collection for alfalfa (Medicago sativa L. sensu lato). About 1100 perennial Medicago P.I.s collected from 47 countries were classified into 18 geographical groups based on passport data from the Germplasm Resources Information Network (GRIN) System. data file was developed for 50 agronomic, forage quality, root and crown morphololD,, pest resistance, and stress tolerance traits. Eight methods for developing a 200-entry core were compared by nonparametric procedures with the original P.L collection. The methods included multivariate procedures, random and/or directed selection of entries, and a totally randomly selected core. The sign test was used to compare the means and the variances for 38 traits having the most complete data sets among the cores developed by the eight methods. None of the methods changed the trait means; but nearly all methods, with the exception of the randomly selected core, significantly increased the variance for most traits. Two methods were the best for designating a core collection. One method combined cluster analysis based on principal components within each geographical group with random selection of entries within each cluster (Method 3), the other method was direct selection of entries within each geographical group (Method 8). Method 3 needs a complete data set and extensive computer facilities. Method 8 can utilize incomplete data sets and does not require computer facilities. Method 8 was chosen for designating the core collection for perennial Medicago spp. P.l.s because it retained the greatest variability for all traits. This 200-entry core was one of the first designated for any crop in the GRIN System. F IRANKEL AND BROWN (1984) distinguished three phases of genetic resource activities during the last 60 yr. The first emphasized biogeography, taxonomy, and evolution. The second emphasized conservation. The third phase is beginning and emphasizes utilization of diverse germplasm. As a consequence of the first two phases, many germplasm collections became so large and diffuse that they discouraged effective evaluation of the entries, and thus hindered germplasm utilization. As a solution to the problem, Frankel and Brown (1984) suggested that a germplasm collection could be represented by what they termed a core collection (also called core subset). They defined a core as a "representation, with a minimum of repetitiveness, of the genetic diversity of a crop species and its relatives." Those individual

The alfalfa (Medicago sativa L.) crown is an important morphological structure because of its association with regrowth, yield, and persistence. The objectives of this research were to evaluate variability for crown morphological traits among 1067 plant introductions (P.I.s) and 110 North American cultivars, to determine the association between crown morphological traits and germplasm sources, and to compare the association between crown morphological traits and fall dormancy classes for North American alfalfa cultivars. The P.I.s and the cultivars were grown in separate field studies at Rosemount, MN, during 1989 and 1990, respectively. Plots consisted of one 3.5‐m‐long row for P.I.s, and one 1.8‐m‐long row for cultivars. They were seeded in May and the plants were dug in October. Plants were individually evaluated for crown depth, crown width, number of crown stems, crown stem width, and number of crown buds. Variation was observed among both P.I.s and North American cultivars for all crown traits. Discriminant analysis of crown traits was effective at separating germplasm sources from diverse geographic origins. The crown traits of germplasm sources from less diverse origins appeared similar. Discriminant analysis of crown traits separated highly dormant (fall dormancy = 1) cultivars more effectively than semi‐dormant and non‐dormant cultivars. Only number of crown buds had a meaningful correlation (−) with fall growth. Variation observed for crown traits among alfalfa germplasm sources indicated that selection for specific crown modifications could be effective.

A novel process for the production of transgenic alfalfa varieties. Numerous species of legumes, including alfalfa, are critical factors for agroecosystems due to their ability to grow without nitrogen fertilizers derived from non-renewable fossil fuels, their contribution of organic nitrogen to the soil, and their increased nutritional value. Alfalfa is the main source of vegetable proteins in meat and milk production systems worldwide. Despite the economic and ecological importance of this autotetraploid and allogamous forage crop, little progress has been made in the incorporation of transgenic traits into commercial alfalfa. This is mainly due to the unusually strong transgene silencing and complex reproductive behavior of alfalfa, which limit the production of events with high transgene expression and the introgression of selected events within heterogeneous synthetic populations, respectively. In this report, we describe a novel procedure, called supertransgene process, where a glufosinate-tolerant alfalfa variety was developed using a single event containing the BAR transgene associated with an inversion. This approach can be used to maximize the expression of transgenic traits into elite alfalfa germplasm and to reduce the cost of production of transgenic alfalfa cultivars, contributing to the public improvement of this legume forage and other polyploid and outcrossing crop species.

Alfalfa (Medicago sativa L.) selection for stress-prone regions has high priority for sustainable crop-livestock systems. This study assessed the genomic selection (GS) ability to predict alfalfa breeding values for drought-prone agricultural sites of Algeria, Morocco, and Argentina; managed-stress (MS) environments of Italy featuring moderate or intense drought; and one Tunisian site irrigated with moderately saline water. Additional aims were to investigate genotype × environment interaction (GEI) patterns and the effect on GS predictions of three single-nucleotide polymorphism (SNP) calling procedures, 12 statistical models that exclude or incorporate GEI, and allele dosage information. Our study included 127 genotypes from a Mediterranean reference population originated from three geographically contrasting populations, genotyped via genotyping-by-sequencing and phenotyped based on multi-year biomass dry matter yield of their dense-planted half-sib progenies. The GEI was very large, as shown by 27-fold greater additive genetic variance × environment interaction relative to the additive genetic variance and low genetic correlation for progeny yield responses across environments. The predictive ability of GS (using