Flowering Distribution Pattern in White Clover Cultivars

A trial was carried out at Pergamino Agricultural Experimental Station to examine the distribution pattern and the profuseness of inflorescence production of white clover (Trifolium repens L.). The treatments were 16 cultivars (Churrinche, El Lucero MAG, Bayucuá, Estanzuela Zapicán, Lucero Plus Inta, Haifa, California, Ladino Gigante Lodigiano, Dubrava, Susi, Merwi, Blanca, Sonja, Espanso, Nora, S 184) of different origins and leaf size. The experimental design was a lattice with four replications. Southamerican cultivars showed a similar distribution pattern and had the highest inflorescence production. They also flowered earlier than foreign cultivars, except Haifa. Some of the cultivars evaluated did not have an acceptable inflorescence production. Some others produced seeds at the end of the season under bad weather conditions. Small-leaved varieties tended to have less inflorescence density. The spread of flowering during the reproductive cycle and the number of inflorescence per unit area are important characters that must be considered during breeding and before releasing introduced cultivars to the market

Evaluation and Utilization of a Tall Fescue Germplasm Collection at Pergamino INTA, Argentina

One hundred and fifty four accessions of tall fescue (Festuca arundinacea Schreb.) representing different types grown around the world were evaluated at Pergamino Inta Experimental Station. A multivariate analysis was carried out to evaluate individual and group variations. Three principal components (PCs) explained 70 % of the variation. Cluster analysis (Ward method) allowed the identification of 7 groups of populations. Plants from the most promising populations were selected in order to form a new breeding gene pool. The main objective of this study is to develop a new cultivar with improved winter herbage yield. Selected genotypes were mostly of Mediterranean origin

Genetic Characterization of Prairie Grass (\u3cem\u3eBromus Catharticus\u3c/em\u3e Vahl.) Natural Populations

Prairie grass, Bromus catharticus Vahl., is a winter annual or biennial grass, native of South America which is widely distributed in the Pampeana area of Argentina and also cultivated in temperate regions of the world. Morphophysiological traits are currently used to assess the variability from natural populations and cultivars of this species. Molecular markers, which are not influenced by the environment, allow a more accurate assessment of genetic variability. Previous results from our group (Puecher et al., 2001a) showed a narrow genetic basis for the prairie grass cultivars used in Argentina. On the other hand, we also observed that natural populations of this species collected in the typical area where prairie grass is cultivated in Argentina, showed a RAPD variability pattern similar to that previously observed for cultivars (Puecher et al., 2001b). The objective of this work was to establish, using RAPDs, the genetic relationships among prairie grass natural populations including accessions from the margins of the cultivation area of this species in Argentina

Conservación de germplasma ex situ revisada a la luz de mecanismos y métodos de genética

Los recursos genéticos vegetales para la alimentación y la agricultura se conservan ex situ en bancos de germoplasma como muestras (introducciones) de poblaciones naturales o naturalizadas ya sea como propágulos originales (mayoritariamente semillas) o sus multiplicaciones. Las premisas subyacentes son que (a) es la alternativa más segura y barata de preservación de germoplasma para futuras generaciones y (b) las introducciones son representativas de la diversidad genética que se encuentra en la naturaleza En las últimas décadas, se han presentado ideas, alternativas y consideraciones sobre el tema y se han elaborado protocolos para el muestreo, conservación y multiplicación de germoplasma. Sin embargo, organizaciones internacionales han señalado limitaciones en la eficiencia del manejo de los bancos de germoplasma. En nuestra opinión, se necesita revisar el funcionamiento y manejo de dichos bancos en general a la luz de los principios y métodos de Genética. Para tal fin, es necesario considerar la biología reproductiva de las plantas superiores -cuyas consecuencias genéticas a nivel de planta individual y de población no se comprenden en su totalidad o no se consideran al idear los protocolos -, las estructuras genéticas de poblaciones naturales y cultivadas, y el curso del material genético en las poblaciones. En este trabajo discutimos los tres temas y proveemos un ejemplo de un programa nacional de mejoramiento de forrajeras, desde las introducciones como germoplasma de origen hasta la obtención de cultivares comerciales. Finalmente, presentamos una propuesta como base de discusión entre curadores, investigadores y mejoradores.Plant genetic resources for food and agriculture are ex situ conserved in germplasm banks as samples (accessions) of natural or naturalized populations, either as the originally sampled propagules (mainly seeds) or their multiplications. The premises underlying ex situ conservation are that (a) it is the safest and cheapest alternative for germplasm preservation for future generations and (b) accessions are representative of the genetic diversity encountered in nature. In the past decades, ideas, alternatives and considerations have been put forward on the topic, and protocols have been devised for plant germplasm sampling, conservation and multiplication. However, limitations in the management efficiency of germplasm banks have been pointed out by international organizations. In our opinion, germplasm banks in general need to revise their functioning and management at the light of principles and methods of Genetics. To that end, it is necessary to consider the reproductive biology of higher plants -whose genetic consequences at both the individual plant and the population levels are not always either fully understood or taken into account in devising the protocols-, the genetic structures of wild and cultivated populations, and the course of the genetic material in the populations. In this paper, we discuss the three topics and provide an example of a national forage breeding program, from germplasm bank accessions as the germplasm of origin to the obtainment of commercial cultivars. Finally, we present a proposal as a base for discussion among curators, researchers and breeders.Fil: Camadro, Elsa Lucila. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Rimieri, P.. Instituto Nacional de Tecnología Agropecuaria; Argentin

Un programme coopératif français pour la gestion et l'utilisation des ressources génétiques du maïs.

This comprehensive genetic resource conservation and utilization programme depended upon the long-term cooperation between French public and private breeders. The important results included: the collection of a large number of populations of maize and their evaluation for agronomic molecular traits; the development of a restricted number of broad-based genetic pools, which facilitates the management and use of broad diversity; the improvement of some pools to stimulate their use and to broaden the genetic base of material used by breeders. The programme was also very informative concerning the methodology for the management and use of genetic resources. It was possible to classify the populations into groups, and to develop 'pools' useful for the breeders with the use of different types of data. RFLPs appeared to have a greater potential value than isoenzymes for the classification into groups and the prediction of within population variability for quantitative traits. The strategy that was used to prepare new material useful in the relatively short term for the plant breeder, i.e. development of pools after low selection intensity between populations and introgressing these pools by elite material seemed very efficient. However, it was clear that to make the maximum use of the genetic variability of such promising pools, several cycles of recurrent selection are necessary