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.

The nutritional quality of lucerne (alfalfa, Medicago sativa L.) plants correlates positively with the presence of multifoliolate (MF) leaves. Using phenotypic recurrent selection, we developed populations with an increased percentage of MF expression from 6.7% in the original population (C0) to 77.7% in the fourth cycle (C4). The effect of selection on genetic diversity within and among populations was evaluated. The populations C0 and C4 were represented by 40 plants genotyped by using 25 simple sequence repeats (SSR). The number of alleles per locus was large in both C0 and C4, averaging 6.28. The within-population genetic diversity (HE) overall estimation was 0.723 for C0 and 0.726 for C4, the absence of significant difference between the two populations indicating that the genetic diversity was as large in C4 as in C0. The Nei’s population differentiation (GST) overall estimation was 0.013, meaning that only 1.3% of the total genetic diversity was between populations and 98.7% was within populations. An efficient selection process was conducted without any increase in inbreeding or genetic drift.

Most major crops are polyploid species and the production of genetically engineered cultivars normally requires the introgression of transgenic or gene-edited traits into elite germplasm. Thus, a main goal of plant research is the search of systems to identify dominant mutations. In this article, we show that the Tnt1 element can be used to identify dominant mutations in allogamous tetraploid cultivated alfalfa. Specifically, we show that a single allelic mutation in the MsNAC39 gene produces multifoliate leaves (mfl) alfalfa plants, a pivot trait of breeding programs of this forage species. Finally, we discuss the potential application of a combination of preliminary screening of beneficial dominant mutants using Tnt1 mutant libraries and genome editing via the CRISPR/Cas9 system to identify target genes and to rapidly improve both autogamous and allogamous polyploid crops.

El aumento del número de raíces laterales a través del mejoramiento puede ser importante para reducir el daño provocado por el complejo de gorgojos de la alfalfa. El objetivo fue evaluar, en cuatro ambientes (siembras de otoño y primavera con y sin riego), el comportamiento de 10 poblaciones seleccionadas por alto número de raíces laterales. Los caracteres evaluados fueron: categoría (Cat) de daño de gorgojos (de 1 = sin daño a 5 = daño severo), rendimiento promedio de forraje (BP), número de raíces secundarias (NRLR) y diámetro de raíces laterales (DRLR). Las poblaciones s755, s545 y s614 presentaron los mayores valores de DRLR y NRLR, el menor daño de gorgojos (Cat 2+3) y la mayor variabilidad para los caracteres estudiados. Las poblaciones s545 y s616 exhibieron el mayor DRLR y el menor NRLR, respectivamente. Las condiciones de riego propiciaron un menor daño, y fueron menos afectadas en estos ambientes las poblaciones s545, s614 y s617; por el contrario, las poblaciones s461, s755, s463 resultaron las más afectadas. Los daños más severos (Cat4+5) se observaron en secano y las poblaciones s618 y s616 fueron las más afectadas; sólo bajo estas condiciones el mayor daño se correlacionó con menor BP.

Evaluación de la virosis del achaparramiento de la alfalfa (Medicago sativa L.) en dos ambientes contrastantes de ArgentinaOdorizzi, A. S., Cornacchione, M. V., Arolfo, V., Basigalup, D. H., Mijoevich, M. L. y Balzarini, M. resumenEn los últimos años se vienen observando daños crecientes de una enfermedad viral que afecta la producción y la persistencia del cultivo de alfalfa en Argentina. El objetivo de este trabajo fue comparar la incidencia y severidad de la sintomatología de la enfermedad y explorar las relaciones de su dinámica con respecto a precipitaciones (pp) y temperaturas (T) ambientales en seis cultivares comerciales de alfalfa durante el período 2010-2014. Los cultivares CW1010, WL1058, Traful PV INTA, WL903, Monarca SP INTA y LPS8500 fueron evaluados en los campos experimentales de la Estación Experimental Agropecuaria (EEA) Manfredi del Instituto Nacional de Tecnología Agropecuaria (INTA) y de la EEA Santiago del Estero-INTA. En ambos ensayos se registraron incidencias medias entre 50% y 80%, con importante variabilidad interanual y diferencias entre cultivares. La severidad fue mayor para los cultivares evaluados en Santiago del Estero. Los cultivares WL903 y WL1058 presentaron menor severidad, mientras que LPS8500 y Monarca SP INTA presentaron los mayores valores. De las variables climáticas utilizadas para este análisis, la pp (pp + riego en Santiago del Estero) y la T máxima fueron las de mayor peso para explicar la incidencia de la enfermedad. Con respecto a la severidad, la variable que mayor explica su incremento es la T media. EEA Santiago del Estero-INTA. In both trials, mean incidences between 50% and 80% were recorded, with significant interannual variability and differences among cultivars. The severity was higher for the cultivars evaluated in Santiago del Estero. Cultivars WL903 and WL1058 presented the lowest severity, while LPS8500 and Monarca SP INTA showed the highest values. As for the climatic variables used for this analysis, pp (pp + irrigation in Santiago del Estero) and maximum T were the variables that mostly determined the incidence of the disease. Mean T was the most important variable regarding severity.